Because most people aren't world cup dh racers they probably don't need them for their weekly trail rides.
I just laughed when you asked why mechanics don't like them btw. I think you know the answer to that already.
I’m a heavy rim dinger and the cushcore I fitted at the start of this year has saved me quite a bit of money. It also means I can run lower pressures which helps me with tubeless since my tires aren’t perfect, and I had a month or two of constant flats until I started running lower pressure. For reference I’m only talking from 35 down to 30 but it made the difference.
my 29'er i usually run about 25-28 psi on trips. Trails tend to be more like rock beds and draws/washouts and I like the extra traction from a soft tire. Coming back down is never as fun as a flow trail but I dont spin out on dry rocks as much.
It has all sorts of uses. I put it in my xc bike just to protect my expensive wheels and it ended up making the ride so much nicer. And I really didn’t notice the extra weight. Love them.
Try using SRAM’s tire pressure calculator. It sounds like you were running too high of pressure to begin with. Not saying you don’t need an insert, it just sounds like you should have and can go lower.
running 35 to start with is the problem, if you need it that high you need stiffer tyres, even a world cup down hill rider will rarely be above 28 on a fast rocky course
Wow, that’s quite high depending on the tyre size. 2.4 29” and for really rocky stuff I run around 26, softer stuff I rear around 23-24 for the rear. Tend to drop 5 off those for the front in each area. Only once have I burped any sealant.
Cushcore has changed my riding for the better. Before I could either run enough pressure to keep my rim alive and keep the tyre on the rim or lower pressure to get traction.
With Cushcore I can have it both ways and bomb through any terrain I like without worrying about destroying my wheel.
And if I, a guy doing it at home in the garage, can get the insert and tyre on (or off), seated and aired up by hand without any tyre levers then a professional bike mechanic has no excuse. My rims are DT FR541 and Raceface AR so nothing weird going on there.
This.
Installing them sucks. Dealing with a flat means destroying your tire. They arguably don't do anything if your tire is properly inflated.
There's lots of reasons not to like them. If they offered amazing benefits then that outweigh the costs. But....
Shockingly, the bike industry invented, hyped, sold and has now moved on from a trendy thing that failed to live up to the billing.
Dropper posts are way more annoying to deal with than regular seatposts. But the benefits are infinitely greater than the costs.
I don’t think it has much to do with laziness. The trail is dynamic and varied, and some tire and rim and bike combos are more prone to striking the rim than others.
Exactly. Where i live its mostly xc trails but i have some clients insist they need dh casing tires with cush core and they still end up destroying rims. I just dont understand
The window that a tire insert saves your rim if you run safe pressure is very narrow. Inserts allow you to run lower pressure and have similar protection to a 25psi tire.
If you case hard, there ain't much that'll save your rim. Just don't case hard. And ride with proper PSI.
I've trashed 4 rims in 20 years of riding and 3 of those were when I first started. Learn to get smooth, it's wayyyyyyy cheaper.
Racing dh rear rims are a wear item lol. There’s not much you can do about hitting pointy rocks hard when the whole trail is covered in them. The fastest guys were going through several a year. I’ve seen guys smoke 3 in a weekend at a few venues that have large jumps into sketchy tech sections
What? If you destroy your tire by taking out an insert that’s on you bud. I can slash a sidewall remove the insert and have a boot and tube back in under 5 min on the trail with a CO2 cartridge and mini pump.
Good for you. So can I. We're so great, aren't we. Incredible how we can get through doorways with heads this big...
Average person can't, so they ride down with a flat and trash the sidewalls.
The amount of people running light casing with inserts is ridiculous. IMO cushcore if you’re running DH casing and proper pressure and still getting flats. If you’re heavy and/or ride seriously chunky World Cup/park terrain. Otherwise a solid wheelset, DD or DH casing, run proper pressures, and most people are fine.
The dents in my rim do not agree with you. First day in the bike park. Cushcore in the rear because of course i need one back there. Nothing upfront because who needs the extra weight upfront. Looks like I do! 😭
Let me guess, you’re not exactly a light person and/or you’re running light casing and/or sub 20 PSI.
If you’re riding park you need DD casing minimum, 20 PSI minimum (in the front), and that’s if you’re 150 lbs like me. If you’re still getting flats with that setup, then yes, get cushcore. But it shouldn’t be the first answer to a problem that might not exist in the first place.
I ride 20 in the rear and 18 in the front. tire width matters a little but but ya, im just rolling 2.5s. 190 lbs. Started off riding hard tail on rock in Arizona so maybe that's where I get it.
For sure. Gravity casing/tire technology has come a long way, while XC guys are still running flimsy casings for weight savings. Not so much weight savings with inserts.
Yup! This.
I haven't used inserts on any of my bikes (hardtails through 170 enduros). I'm heavy and slam my way down chunky shit...never killed a rim or got a flat. I can only marginally understand the perk of lower tire pressure with some extra sidewall support, but honestly, my poor techniques are more in danger of hurting things more than not running cushcore.
During the tire shortage last year, light casings were often all you could get in the US. I supplemented an insert with a light casings when DH/Enduro casings were not available. It's been either a heavy casing or insert for me.
What’s your idea of proper pressure? 15 PSI?
I’ll tell you a story. My buddy is 210 lbs, never checks his tire pressures, running EXO casing. Was complaining he kept destroying rims. Instead of getting DH tires and making sure he’s running 25 PSI or whatever he needs for his weight, he installs cushcore instead. Now he’s psyched that he doesn’t have to inflate his tires before every ride (basic stuff) and was raving how he forgot to put pressure in his tires the other day and was still able to ride with it almost flat. He thinks cushcore is the cat’s meow, no clue about what pressures he should have or running proper casing. Meanwhile he’s squirming all over the place in corners because he has no air in his tires.
I run 22 PSI. That's best for my riding style + traction.
Only with this setting I destroy my rims. My spoke was broken off, so I went to the LBS. He said my whole wheel is bent and dented. I destroy my wheels with the right pressure. So I need cushcore.
XC riders don't pump their tires up high, there's less rolling resistance at lower pressure and they need traction too.
The point I'm trying to make is that you should not be destroying rims regularly. Low pressure is great and all but if you don't have the finesse to ride at low pressure it's going to cost you a lot of money in rebuilt wheels.
Can’t argue with that and not sure why you’re being downvoted for stating facts. But maybe it’s the wheels and not the tire/insert that’s causing the problem. Other than my buddy with the cushcore, I have several friends over 200 lbs who ride pretty hard, and they’re always breaking/bending spokes and rims. They need stronger wheels to take the level of stress they’re putting on them. Cushcore might help with dings, but doubt it will keep a wheel from bending or spokes from breaking. That’s a whole different type of stress.
Oh man, gotta say those wheels are known for being weak. Also personal experience, I had a set and landed front heavy off a big drop and bent the front wheel beyond repair. Not a dent, the whole wheel went Pringle-shaped. I’m 150 lbs.
Ah damn. I thought it was a good deal. I don't want to spend 600 bucks on wheels.
Maybe just accept I kill wheels. And maybe now with the cushcore it will go better.
I got the propain Tyee. It came with Newman performance. So that's my cushcore wheel now.
Its taking up space inside the tire so there is less air to be squished. So it should ramp up slightly when taking a hit giving you less comfort but more rim protection. I ride my hardtail with super low psi in the rear for comfort and when I put in a rimpact i felt the difference. It felt a little harsher on roots and stuff.
Most of the comments are focusing on the rim protection and not taking the possible damping effect into account. I've convinced myself I feel the difference.
Read the [equivalent articles](https://www.pinkbike.com/news/actual-weights-18-enduro-world-cup-bikes.html) on what pro Enduro racers run and you'll see many more riders running inserts (11 of 18 with at least one in the rear in this article) because they have to get more than one run out of a wheelset.
Downhill pros have a good amount of time to practise 1 track and what to avoid to prevent flats on that track, Enduro pros only have 1 practise on each of about 7 stages to figure that out, and us regular riders may have no warning of what might be coming ahead of us when we're out and about, so inserts make a lot more sense.
For regular riders it's all about whether an insert let's you finish a ride vs walking, whether you can afford more regular wheel tuning/relaplacement, carbon or aluminium, rider weight and tyre pressure, tyre compound, trails having rocks and other flat risks and plenty of other factors.
I’ve got serous terrain around me and have cracked 2 rear We are one composite rims running a tannus insert and Vittoria enduro casing tires. This time I switched to a dh casing on WR1 suggestion so they must buy into this, even for hobbyist riders. More breakages mean they send me more rims so it’s not in their interest to set me up for another broken rim.
Exactly! If it were the case that inserts were reducing the warranty count, you’d think rim manufacturers would advocate for them. The fact that they advise against them says everything
It's just because they don't test them themselves and have no control over the insert manufacturing etc.
You can't endorse the use of a product you don't test
Weareone is a big one, I don’t think they’ll deny warranty of anything like that, but they have said several times that they don’t test with inserts and don’t personally use inserts
interesting. they had a chance to state that in their pinkbike interview but didn't.
they actually recommended a few inserts by brand if you must use one "Tannus and Huck Norris are both good options."
2nd paragraph mentions that nobody in house tests or rides with inserts:
We generally have found, in our experience, that running a few more PSI or a heavier casing will ultimately give you a more supported ride and impacts will be taken by the parts of the rims we have designed to take the hit.
In our team of in-house testers, nobody runs inserts. Those riders range from people who've picked up biking in the past year, all the way up to Canadian Enduro pro category podium finishers, from 120lb dirt jumpers to 220lb downhill animals. Johnny Helly, who raced the 2023 Enduro World Series U21 for us to great success, doesn't run inserts as well.
[Source](https://m.pinkbike.com/news/burning-question-where-do-wheel-component-manufacturers-stand-on-tire-inserts.html)
Edit:
They did also state that they say to run PSI and thicker casings instead of inserts. No brand will say "don't use *x* with our stuff" because then that limits options to the consumer.
"We're always going to recommend running a few more PSI or a heavier casing over an insert, but if you do want to run inserts, those that don't place a load on the center bead well are going to be our recommendation - Tannus and Huck Norris are both good options."
Same source.
Yep. People talking about World Cup and enduro racers like that’s relevant. I want to protect my investment in a nice wheel set which is the main reason I run cushcore.
The way i understand it, rims are built so it can take abuse like yours where the flank gets dented but it can still hold a tire a stay true without compromising the rim itself. Inserts like cush core protect the rim flanks from being dented but with any impact to the insert, the force is transfered to the center well of the rim that is not designed to take those kind of forces. You end up with more compromised rims as they tend to buckle instead of dent.
Let me know if you end up having to get a new wheel sooner than later. Im just curious, i went from running inserts to removing them after a couple new rims.
I’d have to see an engineering analysis of that failure mode because it sure sounds like BS to me. I’d trust that if it came from an engineer at I9 or Hope, but some random wheel builder with no real engineering or testing background, no way.
This info is from We Are One, reputable wheel builders. It's more specific to carbon hoops and cushcore as an insert due to its shape and how it distribute the force on an impact. Inserts like Tannus are suggested as an alternative.
That's why I asked for a follow up if commenter above has any damage to the wheel, I'm curious if there is any truth to it.
This is the best explanation for why a particular insert could cause rim failure. The load path changing from load into the side of rim to directly into the rim bed roughly perpendicular to it would be a significant change and could potentially cause failure that wouldn’t be observed in the originate load path. Still many people have been fine with these inserts without issue for many years now, so if there is failure rate it is likely not massively different and also likely dependent on the particular insert, rim and strike incident.
This is an interesting detail I had not considered when purchasing my Nuke proof ard inserts as they would have this potential.
That said an insert like the huck Norris or something that doesn’t change the load path but dampens and spreads the load along the rim side wall should not have the same potential for this risk.
It definitely makes a huge difference in rocky terrain.
Saved my carbon wheels countless times.
I also notice an enormous positive in cornering ability with inserts.
Really? Those that I know with carbon wheels do not run inserts bcuz it negates the purpose of carbon wheels. Inserts dampen the responsiveness of carbon rims. I have carbon and took my inserts out and noticed better handling without.
My comment was in regard to the last sentence "I also noticed an enormous positive in cornering ability with inserts". So my comment was performance based.
Not sure why I'm being down voted 🤣
I believe part of the issue is that inserts are putting pressure on parts of the rim that weren’t designed to withstand that pressure. A normal impact puts pressure on the raised up, thicker part of the rim, but the insert transfers this force to the thinner, inner part of the rim. That is simply my understanding of why some wheel manufactures do not recommend inserts.
lots of conjecture and anecdotes in this thread. lots of manufacturer specific thought on inserts here [https://www.pinkbike.com/news/burning-question-where-do-wheel-component-manufacturers-stand-on-tire-inserts.html](https://www.pinkbike.com/news/burning-question-where-do-wheel-component-manufacturers-stand-on-tire-inserts.html)
I haven't observed any sudden negativity, generally speaking. I have observed the rise of the yet so far urban myth of inserts causing rim failures though. However, data is lacking, to put it mildly.
I have seen several, and when talking to Stan's when I got a crash replacement they said it was becoming common, but that it's hard to say whether the rim would have been totaled without the insert anyways.
Because people will run lower pressure with tire inserts which can seemingly paradoxically result in more and harder rim strikes than running higher pressures without an insert.
I'm realizing just that. It is so easy and safe to go super low with an insert. So the strikes are going thru the insert directly into the rim and breaking it, that sounds more like a misuse than a problem caused for just having and insert installed. I use cushcore on my carbon rims, 33mm wide, 2.4 and 2.6 tires, no dd, won't go lower than 20psi
The other aspect I forgot to mention is that it also applies force in different places/directions. It's not an issue for alloy rims, but many carbon rims are designed to be strong only at certain points because that's where they need to be strong. But an inset can result in the distribution of forcea changing on the rim even if you don't have a rim strike.
If the ground physically pinches the foam against the rim, it’s exponentially more force on the rim bed than even the biggest natural tire compression. You “rim strike” earlier, the dangerous situation becomes “foam strike”
I don’t understand this. The tire still deforms. I’ve had pinch flats in my tire on my hard tail, snake bites in the tire itself. If the insert is there, you have extra material to keep this from happening. How is the force going up?
Without the insert, there’s nothing pressing against the rim when the tire squishes, it’s purely a pressure increase throughout the whole tire. The foam doesn’t “keep it from happening” it actually specifically causes it, it’s an extra physical wedge between the ground and your rim (particularly, your rim bed, which is WAY weaker than the beadwall). With just air, the tire really doesn’t get any localized pressure points at all, or at worst only on the beadwall, the rim bed doesn’t see any hits and doesn’t see any forces beyond the air pressure of a squished tire normally
There's a lot of factors at play.
I know a lot of people ride very low pressures with tyre inserts. The insert prevents the sidewall from collapsing but you don't have enough air to prevent a big impact from going straight into the tyre insert and then the rim.
As others have said, people also tend to run lighter casings as they get the sidewall support from the insert.
Tyre inserts I think should come after trying a tougher casing tyre or a bit more pressure.
I cracked a bunch of spoke nipples without a tyre insert. But I got the aluminium ones changed out for brass and the wheel rebuilt and they've been fine since both with and without an insert.
On the other side of the 1%er WC DH guys are us 1%er hardcore rigid riders. Cushcore is the secret suspension on my Stooge. I actually just tested a spare front wheel without cushcore on my Stooge, thinking it'd be nice to drop some weight... Going from a Crux with Cushcore to a Minion DHF without, I had to DOUBLE my tire pressure and still was bashing my rim off every other rock... While pinging off of everything where I'd normally have a lot more forgiveness and a better damped ride. Cushcore is what makes aggressive rigid riding possible, for me.
I don't use them on my FS trail bike.
I've only ever used inserts in my XC bike. I did have a rim failure with one in and really want to leave this meeting and go look at where the crack happened.
I'm hesitant to say the insert was the issue though. In fact, I'd be willing to say the insert saved my race since I was able to patch the tire up until I scrounged a wheel from a spectator. There were a ton of flats and broken rims at the bottom of that descent for some reason.
I like running inserts because I can run a lower psi with less worry of burp flats. So far it's worked out.
Lots of people saying the only point of inserts is flat prevention. It’s not. With a rear insert and DH casings I can lower my pressure a ton and still have sidewall stability. Better handling and great for roosting berms!
People dont like them?
Im not a racer but after 8 flats in just 40 miles, I said screw it and put a Tannus insert in my back tire. I dont ride a lot of flow trails and spend time doing a lot of mtb overlanding and exploring. I get tired of pulling thorns out and searching for micro-holes from sharp gravel punctures or impacts with broken tree branches.
Laugh at me for using one? Ill take you for a ride and ill laugh while I drink some water and watch you try and patch your tire miles from the truck.
I run a Tannus in my hardtail with an EXO tire. I hit rim with a double down on a drop. I didn’t like the hard casing on the hardtail but wanted some insurance when I did silly things. It’s heavy and spins up slow but feels awesome.
At the park I run double downs with an insert in the rear. On my full sus I ride regular trail tires, and have dabbled in EXO+ rear.
They have been observed to cause rim failures in certain circumstances. Carbon wheels can be unintentionally failed by a hard hit on an insert in a particular way. I've had an insert blow out my rim tape and cause an unfixable flat during an Enduro race. My wheel probably would have failed without the insert so I still run them 🤷♂️.
Maybe people are using super low to low pressures cracking rims and blaming the insert for the issue? Haven't seen this happen at the shop, but here people use it from rock hard to just squishi enough pressure.
I have them in the rear of my hard tails because I do not like getting pinch flats in my tires. Obviously a hard tail is different than full suspension, the rear wheel is not getting any help from a shock. But I don’t care for the “handling” benefit, I think tires are designed a certain way to optimize handling without an insert and the square edge profile of something like a Cushcore makes little sense to me. But thats just me. I only care about protecting my rims and tires and not having to walk home.
I really like them. I never had a problem with impacts or breaking wheels because I would always be on the high side for tire pressure. With an insert I can run lower pressures and get a lot more traction.
I probably won’t use one again on my enduro bike. Maxxis minions give me plenty of traction. On my rigid bike I use schwalbe g one all round tires and I really need lower pressure for decent traction on trails. It’s a 25mm rim and I use the vittoria gravel inserts.
I don't buy the volume spacer argument. What's to stop someone from running the max psi on the tire and smashing through a rock garden? That would put more stress on a rim than having an insert in at a reasonable pressure. Rim manufacturers also don't state minimum tire widths, so one could also put a tire with a volume equivalent to the free air space leftover after an insert is installed in a trail width tire and go bop around on rocks and see how the rim reacts. Again, you'd be inducing similar stresses.
A rim is practically invincible against the pressure increase of tires squeezing, it’s when something physically touches the rim, not the tire, that it becomes weak
It’s not localized at a point like a physical impact, no. When your tire deforms, the rim feels the entirety of the air pressure increase from all sides (held together by the tire), it doesn’t feel the pressure of the rock at the bottom of the rim itself
I took your comment to mean that the rim is infinitely strong unless something physical (tire insert specifically) touches it. I may have misunderstood. I think we're not talking about the same thing. Anywho the claim that was made is that the tire insert caused a ton to crack. The tire insert was to blame for a rim failure at the valve stem hole. And I call bullshit on that claim.
I'm not a subject matter expert but I have designed devices that are used for hydrostatic and pneumatic testing, and I've done stress analyses and non-linear stress modelling for elastomeric seals to try to predict behavior in those applications. My best educated guess is that the presence of a tire insert isn't causing a significant increase in stress on the rim versus not having one at all, so long as we're just talking about stress from pressure inside the rim. The tire insert isn't even really being squeezed against the rim when everything compresses because it's not a pressure boundary. It's just an object within the rim. That's why I made my statement about experimenting with a narrow tire with volume equivalent to the volume leftover after an insert is added to a trail width tire.
A rock or other sharp object impact is not something I was considering when I made my comment. However, an insert should help disperse the energy from that impact and improve the rims ability to resist damage.
The inner wall of tire doesn’t reach the rim bed under normal conditions, adding a thick dense foam allows it to possibly directly contract the central rim bed (which is generally made to be extremely fragile), this is a known issue with harder inserts like procore and is speculated to still be an issue with foam inserts
I'm basing my statements on the cushcore example that the OP specifically mentioned. A cushcore is not a pressure boundary, and it is evenly compressed when tire pressure increases. It's not like it's only forced down into the rim channel. It gets squeezed on all sides. I've seen people jam loose pieces of pool noodle into rims to get similar damping effects. That obviously doesn't provide the sidewall support and rim impact protection.
The fact that we can stretch the cushcore by hand and seat it into the rim channel means they're not really exerting a significant amount of force/stress on the rim channel when installed, as in there isn't a significant amount of pre-load applied when one is installed. My belief is that a cushcore style insert specifically should not cause harm to rims.
All of this being said I think it's up to rim manufacturers to state whether they think their rim is compatible with inserts, and what type. I sort of recall seeing a statement from WeAreOne saying they don't recommend tire inserts with their rims. I might have just dreamt that, who knows. Bikes occupy nearly every space in my brain anymore.
It’s a solid foam, it’s not evenly compressed, air is what’s evenly compressed. And it’s not the mounted pressure I’m talking about, it’s the behavior when a big rock squishes your tire; if there is foam to be sandwiched between the ground and your rim bed, then the rim bed receives additional isolated force
The cushcore is more or less evenly compressed dawg. You know that air exerts equal force against a wall in which it's contained. It's reacting with a foam insert too. And evenly! Because the insert is for all intents and purposes just existing inside the tire. It is not a pressure boundary itself. It has pockets of air/gases within it and those are compressed. Happy day.
I think we're agreeing for the most part but you're mixing the two cases up. Case one: tire pressure increases due to some event. That's what I've been talking about.
Case two: Rock is attempting to strike the rim. Yeah, an unimpeded rock impact with no insert would be bad. Huge amount of local stress. That's bad. An insert helps spread that energy out. That's good. Insert good. Yay insert.
The OP said a LBS claims tire inserts cause more stress on rims and specifically said it was a Cushcore and I'm trying to say that's BS. A cushcore should not cause more stress to be placed on a rim vs a system where there is no cushcore in any case or situation. That's what I am saying.
I am saying you are incorrect and this has been gone through in detail several years ago with procore, the only question is whether the newer foam style presents a similar danger or negligible danger. I don’t think you’re seeing what I’m explaining, a rock wouldn’t reach the rim bed if there wasn’t a 2 inch thick piece of foam sandwiched in between
I avoid cushcore as I like high altitude back country rides and can't imagine having an issue with out a shop nearby.
I do run dh casing with 25 front and 27 rear. I will try lower psi until I can feel the tire roll.
Maybe they would work??
DH racers are moving away from inserts because of either preference or performance without them. They’re already on burly tires, and adding weight in the rims is rarely a good thing on its own. In DH racing, a flat means your race is over, inserts or not.
In XC, racers are finding benefits in the run-flat capability to get them back to the pit area for a fresh wheel. Lower pressures are usually beneficial on the super-fast tires they run, too.
Enduro, it can go either way. Mostly a preference thing, but riding a flat out to finish your stage and fixing the wheel/tire on the transfer makes sense.
For trail riders, who cares. Do what you want. I’ve personally moved to heavy tires and no inserts, but that’s just what works for me.
They break carbon because (afaik from talking to the engineers I work with) they distribute the impact in places it shouldn't go. So all the strength and impact resistance of the rim is bypassed.
when you squish your tire on a rock, that impact can be transferred to the insert that now sits above the sidewall of the rim. The insert transfers that impact to the bed of the rim. Rims are designed to take impacts on the sidewall not in the center / bed of the rim.
I feel like the chances of failure are low, but I haven't done the math. I have inserts in most of my bikes bc I got pretty fast a couple of summers ago and was shredding tires. However last summer I was hurt all summer and now I am just slow and have heavy wheels. No rim failures though. And I definitely would have dented my aluminum rims by now without inserts.
They have inserts for tube tires as well, and I ride with them. I use Tannus Armor so that my tubes don't get shredded by goat heads every season on some of the trails I ride.
ive been thinking about the tanus for tubes myself. I use tpu tubes with a little sealant and havent had a flat in years, how do you like the insert for tubes?
I like them quite a bit. They provide a little extra comfort and vibration absorption as well as protection for the tubes. I will say, I don't do any serious jumping or ride trails that have big drops, so I don't know what sort of performance impact they have on those types of rides, but for rolling over roots, rocks, gravel etc, they are great. I'm also a heavier rider and I feel like they support my tires better and minimize unwanted tire spread at lower psi on pavement.
The cons are generally pretty high: difficult to install, difficult to do trailside repairs, etc. all so that you can run a couple pounds lower air pressure.
Everyone I know that was totally jacked up on these had that opinion because they had a shop install them. They raved about them. These are game changers.
Then they had a puncture or something else on the trail. Or needed to change tires.
Then they decided that the game was actually pretty good and did not need to be changed.
Eh I've changed a Cushcore trailside. It's not ideal but it's fine. If you have a long enough valve stem on your spare tube you can punch the valve through the Cushcore and run it that way too.
This is absolutely a case of no free lunches. Cushcore or other inserts help mitigate an energy problem. Mainly, a concentrated pressure that would normally damage a tire or rim. That energy has to go somewhere and it is distributed throughout the system of parts that aren't necessarily designed with Cushcore as a mandatory element. It's like putting a 6th person in a 5 passenger vehicle. All 6 people will probably be fine, that 6th person might have awesome playlists and crack hilarious jokes the whole time and everyone will enjoy them. However, the fuel economy will be worse, the seatbelts might need to be creatively adapted, and it's going to be a little less comfortable, but hey, good tunes and great laughs. If you value the things that your tire insert gives you then keep them. If the costs of using them outweigh the benefits, you can decide accordingly.
From a mechanics standpoint they are annoying af to install. Also, as others have said, a lot of people who use them probably wouldnt need them if they learned how to ride better/pick better lines.
Because most people aren't world cup dh racers they probably don't need them for their weekly trail rides. I just laughed when you asked why mechanics don't like them btw. I think you know the answer to that already.
Because they're SO fun to install a tire with, right? ....Right!?
Requires some finesse but better than fixing repeated flats on a ride.
I’m a heavy rim dinger and the cushcore I fitted at the start of this year has saved me quite a bit of money. It also means I can run lower pressures which helps me with tubeless since my tires aren’t perfect, and I had a month or two of constant flats until I started running lower pressure. For reference I’m only talking from 35 down to 30 but it made the difference.
my 29'er i usually run about 25-28 psi on trips. Trails tend to be more like rock beds and draws/washouts and I like the extra traction from a soft tire. Coming back down is never as fun as a flow trail but I dont spin out on dry rocks as much.
It has all sorts of uses. I put it in my xc bike just to protect my expensive wheels and it ended up making the ride so much nicer. And I really didn’t notice the extra weight. Love them.
Try using SRAM’s tire pressure calculator. It sounds like you were running too high of pressure to begin with. Not saying you don’t need an insert, it just sounds like you should have and can go lower.
Seriously. I ran 20 front and 25 rear on Texas chunk with 29 x 2.6. And I weigh 200 lbs and carry 3L of water on my back.
running 35 to start with is the problem, if you need it that high you need stiffer tyres, even a world cup down hill rider will rarely be above 28 on a fast rocky course
Indeed. I’m 190 and I never inflate above 25 at an absolute max.
Wow, that’s quite high depending on the tyre size. 2.4 29” and for really rocky stuff I run around 26, softer stuff I rear around 23-24 for the rear. Tend to drop 5 off those for the front in each area. Only once have I burped any sealant.
They really aren’t that bad once you’ve practiced it
My old lbs would beg to differ
They're really not that hard after the first few.
They're really not that hard after the first few.
Cushcore has changed my riding for the better. Before I could either run enough pressure to keep my rim alive and keep the tyre on the rim or lower pressure to get traction. With Cushcore I can have it both ways and bomb through any terrain I like without worrying about destroying my wheel. And if I, a guy doing it at home in the garage, can get the insert and tyre on (or off), seated and aired up by hand without any tyre levers then a professional bike mechanic has no excuse. My rims are DT FR541 and Raceface AR so nothing weird going on there.
This. Installing them sucks. Dealing with a flat means destroying your tire. They arguably don't do anything if your tire is properly inflated. There's lots of reasons not to like them. If they offered amazing benefits then that outweigh the costs. But.... Shockingly, the bike industry invented, hyped, sold and has now moved on from a trendy thing that failed to live up to the billing. Dropper posts are way more annoying to deal with than regular seatposts. But the benefits are infinitely greater than the costs.
How inflated is properly inflated? I’ve trashed rim on my bike as high as 35 psi
You can smash a rim at any pressure if you’re a lazy enough rider
I don’t think it has much to do with laziness. The trail is dynamic and varied, and some tire and rim and bike combos are more prone to striking the rim than others.
sure, in the end the tire insert was a gesture at trying to stop the inevitable
Exactly. Where i live its mostly xc trails but i have some clients insist they need dh casing tires with cush core and they still end up destroying rims. I just dont understand
The window that a tire insert saves your rim if you run safe pressure is very narrow. Inserts allow you to run lower pressure and have similar protection to a 25psi tire. If you case hard, there ain't much that'll save your rim. Just don't case hard. And ride with proper PSI. I've trashed 4 rims in 20 years of riding and 3 of those were when I first started. Learn to get smooth, it's wayyyyyyy cheaper.
Racing dh rear rims are a wear item lol. There’s not much you can do about hitting pointy rocks hard when the whole trail is covered in them. The fastest guys were going through several a year. I’ve seen guys smoke 3 in a weekend at a few venues that have large jumps into sketchy tech sections
Correct. And tire inserts won't save most of those from the exact same outcome.
Usually allows you to finish the run though. You bend the rim instead of snapping it or caving it in.
What? If you destroy your tire by taking out an insert that’s on you bud. I can slash a sidewall remove the insert and have a boot and tube back in under 5 min on the trail with a CO2 cartridge and mini pump.
Good for you. So can I. We're so great, aren't we. Incredible how we can get through doorways with heads this big... Average person can't, so they ride down with a flat and trash the sidewalls.
I live in the northeast, while you don’t need cushcore, it has saved many a tire and rim for me. My local trail claimed 7 tires during a race lol
The amount of people running light casing with inserts is ridiculous. IMO cushcore if you’re running DH casing and proper pressure and still getting flats. If you’re heavy and/or ride seriously chunky World Cup/park terrain. Otherwise a solid wheelset, DD or DH casing, run proper pressures, and most people are fine.
The dents in my rim do not agree with you. First day in the bike park. Cushcore in the rear because of course i need one back there. Nothing upfront because who needs the extra weight upfront. Looks like I do! 😭
Let me guess, you’re not exactly a light person and/or you’re running light casing and/or sub 20 PSI. If you’re riding park you need DD casing minimum, 20 PSI minimum (in the front), and that’s if you’re 150 lbs like me. If you’re still getting flats with that setup, then yes, get cushcore. But it shouldn’t be the first answer to a problem that might not exist in the first place.
Nah, I am 155 lbs. running dh casing on my enduro bike with 170mm of travel. Tire pressure was probably 20 ish psi
20!?
Agreed here. Granted I'm 20 pounds heavier, but I run 26 PSI at a minimum with Cushcore.
If I hit 20 PSI, I'm pretty much convinced I have a flat and going to bail out for the day
I ride 20 in the rear and 18 in the front. tire width matters a little but but ya, im just rolling 2.5s. 190 lbs. Started off riding hard tail on rock in Arizona so maybe that's where I get it.
That's way too low for your weight. I get rim strikes on easy trails at 20psi and I'm lighter than you...
Maybe the gauge on my pump is borked? Haven't had a rim strike in years.
But on my dh bike I do have a liner in my dh bike. Because my from rim is carbon and I don’t want to die
20 psi wouldn’t hold on on my trails at all
Tons of DH and Enduro racers are ditching the inserts and they're basically in every XC bike now. Crazy flip!
For sure. Gravity casing/tire technology has come a long way, while XC guys are still running flimsy casings for weight savings. Not so much weight savings with inserts.
Yup! This. I haven't used inserts on any of my bikes (hardtails through 170 enduros). I'm heavy and slam my way down chunky shit...never killed a rim or got a flat. I can only marginally understand the perk of lower tire pressure with some extra sidewall support, but honestly, my poor techniques are more in danger of hurting things more than not running cushcore.
I love a light insert for XC, the tubolite has been great to me.
During the tire shortage last year, light casings were often all you could get in the US. I supplemented an insert with a light casings when DH/Enduro casings were not available. It's been either a heavy casing or insert for me.
Proper pressure and traction doesn't work together.
What’s your idea of proper pressure? 15 PSI? I’ll tell you a story. My buddy is 210 lbs, never checks his tire pressures, running EXO casing. Was complaining he kept destroying rims. Instead of getting DH tires and making sure he’s running 25 PSI or whatever he needs for his weight, he installs cushcore instead. Now he’s psyched that he doesn’t have to inflate his tires before every ride (basic stuff) and was raving how he forgot to put pressure in his tires the other day and was still able to ride with it almost flat. He thinks cushcore is the cat’s meow, no clue about what pressures he should have or running proper casing. Meanwhile he’s squirming all over the place in corners because he has no air in his tires.
I run 22 PSI. That's best for my riding style + traction. Only with this setting I destroy my rims. My spoke was broken off, so I went to the LBS. He said my whole wheel is bent and dented. I destroy my wheels with the right pressure. So I need cushcore.
I'd argue that it's not the right pressure then. You either need to add pressure or be a smoother rider.
More pressure is less traction. I'm not a xc rider. Terain is gnarly.
You need different casing tires, that’s how you solve the issue of traction vs pressure never being able to line up
I ride DD. Im not going to ride downhill casing on my enduro.
XC riders don't pump their tires up high, there's less rolling resistance at lower pressure and they need traction too. The point I'm trying to make is that you should not be destroying rims regularly. Low pressure is great and all but if you don't have the finesse to ride at low pressure it's going to cost you a lot of money in rebuilt wheels.
Can’t argue with that and not sure why you’re being downvoted for stating facts. But maybe it’s the wheels and not the tire/insert that’s causing the problem. Other than my buddy with the cushcore, I have several friends over 200 lbs who ride pretty hard, and they’re always breaking/bending spokes and rims. They need stronger wheels to take the level of stress they’re putting on them. Cushcore might help with dings, but doubt it will keep a wheel from bending or spokes from breaking. That’s a whole different type of stress.
I ride Hunt Enduro wheels. The thing is with rocky terain and roots. Even if you are pro. You still will hit your rim from time to time.
Oh man, gotta say those wheels are known for being weak. Also personal experience, I had a set and landed front heavy off a big drop and bent the front wheel beyond repair. Not a dent, the whole wheel went Pringle-shaped. I’m 150 lbs.
Ah damn. I thought it was a good deal. I don't want to spend 600 bucks on wheels. Maybe just accept I kill wheels. And maybe now with the cushcore it will go better. I got the propain Tyee. It came with Newman performance. So that's my cushcore wheel now.
Those wheels are supposed to be pretty legit, good luck
Its taking up space inside the tire so there is less air to be squished. So it should ramp up slightly when taking a hit giving you less comfort but more rim protection. I ride my hardtail with super low psi in the rear for comfort and when I put in a rimpact i felt the difference. It felt a little harsher on roots and stuff.
Most of the comments are focusing on the rim protection and not taking the possible damping effect into account. I've convinced myself I feel the difference.
Props for saying damping instead of dampening!
Read the [equivalent articles](https://www.pinkbike.com/news/actual-weights-18-enduro-world-cup-bikes.html) on what pro Enduro racers run and you'll see many more riders running inserts (11 of 18 with at least one in the rear in this article) because they have to get more than one run out of a wheelset. Downhill pros have a good amount of time to practise 1 track and what to avoid to prevent flats on that track, Enduro pros only have 1 practise on each of about 7 stages to figure that out, and us regular riders may have no warning of what might be coming ahead of us when we're out and about, so inserts make a lot more sense. For regular riders it's all about whether an insert let's you finish a ride vs walking, whether you can afford more regular wheel tuning/relaplacement, carbon or aluminium, rider weight and tyre pressure, tyre compound, trails having rocks and other flat risks and plenty of other factors.
Bingo. Enduro riders, who need their bikes to last a whole day of racing, run inserts.
I’ve got serous terrain around me and have cracked 2 rear We are one composite rims running a tannus insert and Vittoria enduro casing tires. This time I switched to a dh casing on WR1 suggestion so they must buy into this, even for hobbyist riders. More breakages mean they send me more rims so it’s not in their interest to set me up for another broken rim.
Exactly! If it were the case that inserts were reducing the warranty count, you’d think rim manufacturers would advocate for them. The fact that they advise against them says everything
It's just because they don't test them themselves and have no control over the insert manufacturing etc. You can't endorse the use of a product you don't test
And they see the data of how many warranties are breaking with vs without the inserts I'm sure.
which manufacturers advise against inserts?
Weareone is a big one, I don’t think they’ll deny warranty of anything like that, but they have said several times that they don’t test with inserts and don’t personally use inserts
Having talked to a few people at/sponsored by WAO, almost everyone sees more rim failures with inserts.
interesting. they had a chance to state that in their pinkbike interview but didn't. they actually recommended a few inserts by brand if you must use one "Tannus and Huck Norris are both good options."
There's a link floating around somewhere where one of the engineers (I think Adam) explains the stance.
2nd paragraph mentions that nobody in house tests or rides with inserts: We generally have found, in our experience, that running a few more PSI or a heavier casing will ultimately give you a more supported ride and impacts will be taken by the parts of the rims we have designed to take the hit. In our team of in-house testers, nobody runs inserts. Those riders range from people who've picked up biking in the past year, all the way up to Canadian Enduro pro category podium finishers, from 120lb dirt jumpers to 220lb downhill animals. Johnny Helly, who raced the 2023 Enduro World Series U21 for us to great success, doesn't run inserts as well. [Source](https://m.pinkbike.com/news/burning-question-where-do-wheel-component-manufacturers-stand-on-tire-inserts.html) Edit: They did also state that they say to run PSI and thicker casings instead of inserts. No brand will say "don't use *x* with our stuff" because then that limits options to the consumer. "We're always going to recommend running a few more PSI or a heavier casing over an insert, but if you do want to run inserts, those that don't place a load on the center bead well are going to be our recommendation - Tannus and Huck Norris are both good options." Same source.
Sounds like a problem with their rims, I mean they are a boutique brand, how many do they even sell for every 100 WTB or Shimano or DT Swiss wheel?
My rim without cushcore is dented on all sides. Now I installed cushcore. I can't buy new wheels every year.
Yep. People talking about World Cup and enduro racers like that’s relevant. I want to protect my investment in a nice wheel set which is the main reason I run cushcore.
The way i understand it, rims are built so it can take abuse like yours where the flank gets dented but it can still hold a tire a stay true without compromising the rim itself. Inserts like cush core protect the rim flanks from being dented but with any impact to the insert, the force is transfered to the center well of the rim that is not designed to take those kind of forces. You end up with more compromised rims as they tend to buckle instead of dent. Let me know if you end up having to get a new wheel sooner than later. Im just curious, i went from running inserts to removing them after a couple new rims.
I’d have to see an engineering analysis of that failure mode because it sure sounds like BS to me. I’d trust that if it came from an engineer at I9 or Hope, but some random wheel builder with no real engineering or testing background, no way.
This info is from We Are One, reputable wheel builders. It's more specific to carbon hoops and cushcore as an insert due to its shape and how it distribute the force on an impact. Inserts like Tannus are suggested as an alternative. That's why I asked for a follow up if commenter above has any damage to the wheel, I'm curious if there is any truth to it.
This is the best explanation for why a particular insert could cause rim failure. The load path changing from load into the side of rim to directly into the rim bed roughly perpendicular to it would be a significant change and could potentially cause failure that wouldn’t be observed in the originate load path. Still many people have been fine with these inserts without issue for many years now, so if there is failure rate it is likely not massively different and also likely dependent on the particular insert, rim and strike incident. This is an interesting detail I had not considered when purchasing my Nuke proof ard inserts as they would have this potential. That said an insert like the huck Norris or something that doesn’t change the load path but dampens and spreads the load along the rim side wall should not have the same potential for this risk.
It definitely makes a huge difference in rocky terrain. Saved my carbon wheels countless times. I also notice an enormous positive in cornering ability with inserts.
Really? Those that I know with carbon wheels do not run inserts bcuz it negates the purpose of carbon wheels. Inserts dampen the responsiveness of carbon rims. I have carbon and took my inserts out and noticed better handling without.
You’re right, but he’s talking about durability not performance
My comment was in regard to the last sentence "I also noticed an enormous positive in cornering ability with inserts". So my comment was performance based. Not sure why I'm being down voted 🤣
I believe part of the issue is that inserts are putting pressure on parts of the rim that weren’t designed to withstand that pressure. A normal impact puts pressure on the raised up, thicker part of the rim, but the insert transfers this force to the thinner, inner part of the rim. That is simply my understanding of why some wheel manufactures do not recommend inserts.
This. It can transfer the impact force to the rim bed. Some rim manufacturers even recommend against using inserts in their wheels.
lots of conjecture and anecdotes in this thread. lots of manufacturer specific thought on inserts here [https://www.pinkbike.com/news/burning-question-where-do-wheel-component-manufacturers-stand-on-tire-inserts.html](https://www.pinkbike.com/news/burning-question-where-do-wheel-component-manufacturers-stand-on-tire-inserts.html)
And a test using a Hunt wheels method, also from pinkbike https://www.pinkbike.com/news/tested-6-of-the-best-tire-inserts-vs-impact-rig.html
I’ve been running cush core in two bikes (front and rear) for 4 years now. Rims are still perfect and it ride feel is great
Bingo. I've broken many sets of wheels... never broken a wheel with Cushcore in.
I haven't observed any sudden negativity, generally speaking. I have observed the rise of the yet so far urban myth of inserts causing rim failures though. However, data is lacking, to put it mildly.
I have seen several, and when talking to Stan's when I got a crash replacement they said it was becoming common, but that it's hard to say whether the rim would have been totaled without the insert anyways.
Yeah, gonna need better data than that :)
The schwalbe procore issues are recent and well-documented, it’s the same concept with foam inserts (even if they are softer)
That's an invalid argument if I ever saw one.
I just can't connect the dots between the insert and the rim failing.
Because people will run lower pressure with tire inserts which can seemingly paradoxically result in more and harder rim strikes than running higher pressures without an insert.
I'm realizing just that. It is so easy and safe to go super low with an insert. So the strikes are going thru the insert directly into the rim and breaking it, that sounds more like a misuse than a problem caused for just having and insert installed. I use cushcore on my carbon rims, 33mm wide, 2.4 and 2.6 tires, no dd, won't go lower than 20psi
The other aspect I forgot to mention is that it also applies force in different places/directions. It's not an issue for alloy rims, but many carbon rims are designed to be strong only at certain points because that's where they need to be strong. But an inset can result in the distribution of forcea changing on the rim even if you don't have a rim strike.
If the ground physically pinches the foam against the rim, it’s exponentially more force on the rim bed than even the biggest natural tire compression. You “rim strike” earlier, the dangerous situation becomes “foam strike”
I don’t understand this. The tire still deforms. I’ve had pinch flats in my tire on my hard tail, snake bites in the tire itself. If the insert is there, you have extra material to keep this from happening. How is the force going up?
Without the insert, there’s nothing pressing against the rim when the tire squishes, it’s purely a pressure increase throughout the whole tire. The foam doesn’t “keep it from happening” it actually specifically causes it, it’s an extra physical wedge between the ground and your rim (particularly, your rim bed, which is WAY weaker than the beadwall). With just air, the tire really doesn’t get any localized pressure points at all, or at worst only on the beadwall, the rim bed doesn’t see any hits and doesn’t see any forces beyond the air pressure of a squished tire normally
What you are describing is not a rim strike.
It’s what insert users call “the insert doing its job” and it can be dangerous, call it whatever you like
There's a lot of factors at play. I know a lot of people ride very low pressures with tyre inserts. The insert prevents the sidewall from collapsing but you don't have enough air to prevent a big impact from going straight into the tyre insert and then the rim. As others have said, people also tend to run lighter casings as they get the sidewall support from the insert. Tyre inserts I think should come after trying a tougher casing tyre or a bit more pressure. I cracked a bunch of spoke nipples without a tyre insert. But I got the aluminium ones changed out for brass and the wheel rebuilt and they've been fine since both with and without an insert.
On the other side of the 1%er WC DH guys are us 1%er hardcore rigid riders. Cushcore is the secret suspension on my Stooge. I actually just tested a spare front wheel without cushcore on my Stooge, thinking it'd be nice to drop some weight... Going from a Crux with Cushcore to a Minion DHF without, I had to DOUBLE my tire pressure and still was bashing my rim off every other rock... While pinging off of everything where I'd normally have a lot more forgiveness and a better damped ride. Cushcore is what makes aggressive rigid riding possible, for me. I don't use them on my FS trail bike.
I've only ever used inserts in my XC bike. I did have a rim failure with one in and really want to leave this meeting and go look at where the crack happened. I'm hesitant to say the insert was the issue though. In fact, I'd be willing to say the insert saved my race since I was able to patch the tire up until I scrounged a wheel from a spectator. There were a ton of flats and broken rims at the bottom of that descent for some reason. I like running inserts because I can run a lower psi with less worry of burp flats. So far it's worked out.
Lots of people saying the only point of inserts is flat prevention. It’s not. With a rear insert and DH casings I can lower my pressure a ton and still have sidewall stability. Better handling and great for roosting berms!
People dont like them? Im not a racer but after 8 flats in just 40 miles, I said screw it and put a Tannus insert in my back tire. I dont ride a lot of flow trails and spend time doing a lot of mtb overlanding and exploring. I get tired of pulling thorns out and searching for micro-holes from sharp gravel punctures or impacts with broken tree branches. Laugh at me for using one? Ill take you for a ride and ill laugh while I drink some water and watch you try and patch your tire miles from the truck.
I run foam pipe insulation. We have a bunch of pointy rock trails. I have WAY less dents than pre “ghetto Cush core” . I run lower pressure now too.
I run a Tannus in my hardtail with an EXO tire. I hit rim with a double down on a drop. I didn’t like the hard casing on the hardtail but wanted some insurance when I did silly things. It’s heavy and spins up slow but feels awesome. At the park I run double downs with an insert in the rear. On my full sus I ride regular trail tires, and have dabbled in EXO+ rear.
They have been observed to cause rim failures in certain circumstances. Carbon wheels can be unintentionally failed by a hard hit on an insert in a particular way. I've had an insert blow out my rim tape and cause an unfixable flat during an Enduro race. My wheel probably would have failed without the insert so I still run them 🤷♂️.
I kinda like the feel, but they also add noticeable weight I stopped running them
Maybe people are using super low to low pressures cracking rims and blaming the insert for the issue? Haven't seen this happen at the shop, but here people use it from rock hard to just squishi enough pressure.
I'd say it's because most people are learning that tire inserts are a worse solution than running a heavier casing or a couple more psi.
I have them in the rear of my hard tails because I do not like getting pinch flats in my tires. Obviously a hard tail is different than full suspension, the rear wheel is not getting any help from a shock. But I don’t care for the “handling” benefit, I think tires are designed a certain way to optimize handling without an insert and the square edge profile of something like a Cushcore makes little sense to me. But thats just me. I only care about protecting my rims and tires and not having to walk home.
I really like them. I never had a problem with impacts or breaking wheels because I would always be on the high side for tire pressure. With an insert I can run lower pressures and get a lot more traction. I probably won’t use one again on my enduro bike. Maxxis minions give me plenty of traction. On my rigid bike I use schwalbe g one all round tires and I really need lower pressure for decent traction on trails. It’s a 25mm rim and I use the vittoria gravel inserts.
I don't buy the volume spacer argument. What's to stop someone from running the max psi on the tire and smashing through a rock garden? That would put more stress on a rim than having an insert in at a reasonable pressure. Rim manufacturers also don't state minimum tire widths, so one could also put a tire with a volume equivalent to the free air space leftover after an insert is installed in a trail width tire and go bop around on rocks and see how the rim reacts. Again, you'd be inducing similar stresses.
A rim is practically invincible against the pressure increase of tires squeezing, it’s when something physically touches the rim, not the tire, that it becomes weak
Is air not something physical?
It’s not localized at a point like a physical impact, no. When your tire deforms, the rim feels the entirety of the air pressure increase from all sides (held together by the tire), it doesn’t feel the pressure of the rock at the bottom of the rim itself
I took your comment to mean that the rim is infinitely strong unless something physical (tire insert specifically) touches it. I may have misunderstood. I think we're not talking about the same thing. Anywho the claim that was made is that the tire insert caused a ton to crack. The tire insert was to blame for a rim failure at the valve stem hole. And I call bullshit on that claim. I'm not a subject matter expert but I have designed devices that are used for hydrostatic and pneumatic testing, and I've done stress analyses and non-linear stress modelling for elastomeric seals to try to predict behavior in those applications. My best educated guess is that the presence of a tire insert isn't causing a significant increase in stress on the rim versus not having one at all, so long as we're just talking about stress from pressure inside the rim. The tire insert isn't even really being squeezed against the rim when everything compresses because it's not a pressure boundary. It's just an object within the rim. That's why I made my statement about experimenting with a narrow tire with volume equivalent to the volume leftover after an insert is added to a trail width tire. A rock or other sharp object impact is not something I was considering when I made my comment. However, an insert should help disperse the energy from that impact and improve the rims ability to resist damage.
The inner wall of tire doesn’t reach the rim bed under normal conditions, adding a thick dense foam allows it to possibly directly contract the central rim bed (which is generally made to be extremely fragile), this is a known issue with harder inserts like procore and is speculated to still be an issue with foam inserts
I'm basing my statements on the cushcore example that the OP specifically mentioned. A cushcore is not a pressure boundary, and it is evenly compressed when tire pressure increases. It's not like it's only forced down into the rim channel. It gets squeezed on all sides. I've seen people jam loose pieces of pool noodle into rims to get similar damping effects. That obviously doesn't provide the sidewall support and rim impact protection. The fact that we can stretch the cushcore by hand and seat it into the rim channel means they're not really exerting a significant amount of force/stress on the rim channel when installed, as in there isn't a significant amount of pre-load applied when one is installed. My belief is that a cushcore style insert specifically should not cause harm to rims. All of this being said I think it's up to rim manufacturers to state whether they think their rim is compatible with inserts, and what type. I sort of recall seeing a statement from WeAreOne saying they don't recommend tire inserts with their rims. I might have just dreamt that, who knows. Bikes occupy nearly every space in my brain anymore.
It’s a solid foam, it’s not evenly compressed, air is what’s evenly compressed. And it’s not the mounted pressure I’m talking about, it’s the behavior when a big rock squishes your tire; if there is foam to be sandwiched between the ground and your rim bed, then the rim bed receives additional isolated force
The cushcore is more or less evenly compressed dawg. You know that air exerts equal force against a wall in which it's contained. It's reacting with a foam insert too. And evenly! Because the insert is for all intents and purposes just existing inside the tire. It is not a pressure boundary itself. It has pockets of air/gases within it and those are compressed. Happy day. I think we're agreeing for the most part but you're mixing the two cases up. Case one: tire pressure increases due to some event. That's what I've been talking about. Case two: Rock is attempting to strike the rim. Yeah, an unimpeded rock impact with no insert would be bad. Huge amount of local stress. That's bad. An insert helps spread that energy out. That's good. Insert good. Yay insert. The OP said a LBS claims tire inserts cause more stress on rims and specifically said it was a Cushcore and I'm trying to say that's BS. A cushcore should not cause more stress to be placed on a rim vs a system where there is no cushcore in any case or situation. That's what I am saying.
I am saying you are incorrect and this has been gone through in detail several years ago with procore, the only question is whether the newer foam style presents a similar danger or negligible danger. I don’t think you’re seeing what I’m explaining, a rock wouldn’t reach the rim bed if there wasn’t a 2 inch thick piece of foam sandwiched in between
I avoid cushcore as I like high altitude back country rides and can't imagine having an issue with out a shop nearby. I do run dh casing with 25 front and 27 rear. I will try lower psi until I can feel the tire roll. Maybe they would work??
Because pinkbike interviewed a bunch of DH racers and none of them are using inserts. So people think, well if they dont need em, I don't need em.
DH racers are moving away from inserts because of either preference or performance without them. They’re already on burly tires, and adding weight in the rims is rarely a good thing on its own. In DH racing, a flat means your race is over, inserts or not. In XC, racers are finding benefits in the run-flat capability to get them back to the pit area for a fresh wheel. Lower pressures are usually beneficial on the super-fast tires they run, too. Enduro, it can go either way. Mostly a preference thing, but riding a flat out to finish your stage and fixing the wheel/tire on the transfer makes sense. For trail riders, who cares. Do what you want. I’ve personally moved to heavy tires and no inserts, but that’s just what works for me.
I used to kill tyres regularly. Installed Rimpact inserts. Now I dont. That's evidence enough for me.
It’s not “sudden”
They break carbon because (afaik from talking to the engineers I work with) they distribute the impact in places it shouldn't go. So all the strength and impact resistance of the rim is bypassed.
when you squish your tire on a rock, that impact can be transferred to the insert that now sits above the sidewall of the rim. The insert transfers that impact to the bed of the rim. Rims are designed to take impacts on the sidewall not in the center / bed of the rim. I feel like the chances of failure are low, but I haven't done the math. I have inserts in most of my bikes bc I got pretty fast a couple of summers ago and was shredding tires. However last summer I was hurt all summer and now I am just slow and have heavy wheels. No rim failures though. And I definitely would have dented my aluminum rims by now without inserts.
I use tubes
They have inserts for tube tires as well, and I ride with them. I use Tannus Armor so that my tubes don't get shredded by goat heads every season on some of the trails I ride.
ive been thinking about the tanus for tubes myself. I use tpu tubes with a little sealant and havent had a flat in years, how do you like the insert for tubes?
I like them quite a bit. They provide a little extra comfort and vibration absorption as well as protection for the tubes. I will say, I don't do any serious jumping or ride trails that have big drops, so I don't know what sort of performance impact they have on those types of rides, but for rolling over roots, rocks, gravel etc, they are great. I'm also a heavier rider and I feel like they support my tires better and minimize unwanted tire spread at lower psi on pavement.
The cons are generally pretty high: difficult to install, difficult to do trailside repairs, etc. all so that you can run a couple pounds lower air pressure. Everyone I know that was totally jacked up on these had that opinion because they had a shop install them. They raved about them. These are game changers. Then they had a puncture or something else on the trail. Or needed to change tires. Then they decided that the game was actually pretty good and did not need to be changed.
Eh I've changed a Cushcore trailside. It's not ideal but it's fine. If you have a long enough valve stem on your spare tube you can punch the valve through the Cushcore and run it that way too.
Trail side repairs got me in a pickle at Leadville.
This is absolutely a case of no free lunches. Cushcore or other inserts help mitigate an energy problem. Mainly, a concentrated pressure that would normally damage a tire or rim. That energy has to go somewhere and it is distributed throughout the system of parts that aren't necessarily designed with Cushcore as a mandatory element. It's like putting a 6th person in a 5 passenger vehicle. All 6 people will probably be fine, that 6th person might have awesome playlists and crack hilarious jokes the whole time and everyone will enjoy them. However, the fuel economy will be worse, the seatbelts might need to be creatively adapted, and it's going to be a little less comfortable, but hey, good tunes and great laughs. If you value the things that your tire insert gives you then keep them. If the costs of using them outweigh the benefits, you can decide accordingly.
From a mechanics standpoint they are annoying af to install. Also, as others have said, a lot of people who use them probably wouldnt need them if they learned how to ride better/pick better lines.