Do tire inserts mean it's time to rethink tire design?

Excellent question, David.

For those unfamiliar with tire inserts or CushCore, here's a primer: https://www.vitalmtb.com/features/Vital-MTB-Face-Off-The-Best-Tire-Insert-Systems,1841

Personally I don’t run inserts, I can’t see the point of buying a light tire and then going and buying an insert to protect it and adding the weight back to it. I just run super gravity magics Mary’s front and rear and only have the very odd problem. A tire filled with air is expensive enough never mind going and buying some super duper piece of foam after that.

Might be more beneficial to wrap your head around the understanding of how a tire is, or could be constructed. I am no expert on tire machines, but you might be asking more than the current machines can do.

I do find it rather odd that people are putting a ton of weight into carbon wheels with these inserts and ending up with larger rotational weights at a higher price. You are probably better off getting cheap alloy rims and smoking them on a regular basis.

This is definitely an interesting concept, especially for racing. Although personally, I've found just running an extra 3-4 PSI in my rear tire reduces my flats very significantly... Yeah I lose a bit of traction but for every day riding it's kind of worth it

Building a tire with an integrated insert/tube, making specific rims for those tires, and somehow forcing the two together...
Are we now basically talking about tubular mountain bike tires?

Really good post and a cool way to think about the evolution of an otherwise overlooked part of the bicycle system.

Spomer said it awhile ago, but the number of races over the years (and overal championships) decided by losing air out of a tire is far (far) too many. Its an obvious problem, and something that has more or less gone un-addressed.

Heck, we rarely even see tire companies playing with new casing, let alone something entirely new. Until the recent slew of inserts, there was really no development in this area.

As I posted in my wheel review, I expect to see a wheel that has some form of insert integrated from the factory. This will make for easier tire installs and the engineers to pull material where it really isn't needed.

Considering we are already seeing $100 tires, I'm not sure there is enough room in the market for an insert-based tire. EG: It'd just be too expensive for something you throw away in a month or two due to wear, but I could be wrong.

Oh, and to anyone that thinks the whole insert thing is just about keeping air in the tires, think again. Its the single most impressive thing I've put on my bike when it comes to improving ride quality and handling when really pushing my bike in rugged terrain...

I would assume that tyre companies are right now working on incorporating foam into the tyres (if not, they should be). And, like you say, reducing weight in the areas of the tyre that the foam will support. Of course, I've been waiting for this for several years, so it may not be happening at all!

Masjo wrote:

Building a tire with an integrated insert/tube, making specific rims for those tires, and somehow forcing the two together...
Are we now basically talking about tubular mountain bike tires?

Not really what I'm thinking, but I believe that I did see something along those lines in the coverage from one of the bike trade shows once.

My first post was pretty long so I'll see if I can clarify what I'm thinking and pull out some of the main points.

At the moment this is definitely a performance focused idea, something for racing and other mission critical applications were traction and keeping air the tire are the highest priority. One of the things that really got me thinking about this is the frustration of seeing races at the highest level of our sport being decided by flat tires. If I was going to list priorities they would be:

1. Keeping air in the tire air
2. Ride quality/traction (as a very close 2cnd)
3. Weight
4. Price

I know those aren't everybody's priority, but from a racing perspective it makes sense.

The insert and the tire would still separate elements from each other, but the tire would be a squirmy, undamped mess if you rode it at low pressures without the insert.

Essentially this a a thought exercise. All tires are currently designed with the notion that they should be able to perform at high level without an insert. The insert is a new and significant structural element that was never taken into account in the original design of any tire that is currently on the market.

I'm asking what might be possible if a tire was specifically designed with the knowledge that an insert would be a part of the overall system of the wheel/tire? Right now the tire designer has to come up with a tire that is able to offer a significant degree of sidewall support, ride damping, and pinch flat protection. If the tire doesn't have to deal with those roles because they are being handled by the insert would that free up resources -i.e. material constraints and hence weight- that could then be redirected towards keeping air in the tire?

There are already a variety of ballistic materials that are used in tire construction. If we reconsider the design brief of the tire based on the use of an insert could we come up with something that is significantly more slash and puncture proof, while also offering an improved ride quality?

“Its the single most impressive thing I've put on my bike when it comes to improving ride quality and handling when really pushing my bike in rugged terrain... ”

You have my attention. BUT these were my exact thoughts when I first used Maxxis DH casings.
So I have to ask, what tyres do you choose to run under said circumstances?
Genuinely curious here because I keep getting laughed at when I tell people how much of a difference the DH and DD tyres have made. I even think the weight aids stability as well as the damping characteristics. But it could all just be me. And I’m tryna figure that out...

ThomDawson wrote:

“Its the single most impressive thing I've put on my bike when it comes to improving ride quality and handling when really pushing my bike in rugged terrain... ”

You have my attention. BUT these were my exact thoughts when I first used Maxxis DH casings.
So I have to ask, what tyres do you choose to run under said circumstances?
Genuinely curious here because I keep getting laughed at when I tell people how much of a difference the DH and DD tyres have made. I even think the weight aids stability as well as the damping characteristics. But it could all just be me. And I’m tryna figure that out...

Used them with both DD and EXO casing. Have not used them with DH casing.

I could run my pressure as low as 18-19psi and still not get the tire to roll off the rim. To me that's amazing. Side note, I didn't actually run tire pressure that low, but it was cool to be able to play with it. I generally run 28-30psi-ish front and rear. 29" wheels. 30mm rim width. 2.4-2.5" tires.

With Cushcore I dropped to 23-26psi. YMMV


J

Edit: I'm 200lbs. And I hit shit. Hard.

DaddyFras wrote:

I would assume that tyre companies are right now working on incorporating foam into the tyres (if not, they should be). And, like you say, reducing weight in the areas of the tyre that the foam will support. Of course, I've been waiting for this for several years, so it may not be happening at all!

Tires have had anti-pinch inserts for over a decade. They are a material that wraps around the bead and up to about 20mm into the casing. They disappeared outside of DH tires as "tubeless make pinchflats a thing of the past(!!!)"

Maybe the cushcore type insert should have an integrated air bladder above it. That frees up the tire from holding air, it's just tread and abrasion resistant casing at that point with sidewall which doesn't inherently need to hold air. May be a good way to decouple abrasion/rock strikes from puncturing the air bladder internal to the tire.

_MK

The majority of the problems are pinching the tires. Sidewall tears but most of the time it’s a pinch in the tread casing. It’s the rim sidewall that’s the culprit. I’d like to see the rim have most of the material in the center and be flat across the top and then beadlock strips attached to the outside of that rim block. All at the same height. Fit the tire over the rim block then attach the beadlock side panels. Nothing to pinch if it’s flat across the top of the rim and beadlock panels. Add rim and beadlock panel softer density caps and tires with integrated inserts and no one will want what we have now. Different weights for different applications

grinch wrote:

The majority of the problems are pinching the tires. Sidewall tears but most of the time it’s a pinch in the tread casing. It’s the rim sidewall that’s the culprit. I’d like to see the rim have most of the material in the center and be flat across the top and then beadlock strips attached to the outside of that rim block. All at the same height. Fit the tire over the rim block then attach the beadlock side panels. Nothing to pinch if it’s flat across the top of the rim and beadlock panels. Add rim and beadlock panel softer density caps and tires with integrated inserts and no one will want what we have now. Different weights for different applications

...inserts basically fix this problem entirely.

I see a couple of issues:

- Carbon rims crack instead of bend

- Carbon rims are probably less elastic than aluminum and absorb less force

Inserts seem a temporary solution to a not fully mature technology. And a solution to the problem brought on by ourselves for putting on the carbon rims.

- The biggest issue I've seen are cut casings, pinches are rare compared to cuts.

I have to wonder if the bikes have become so good, and we can now ride so fast, that the tires are playing catch up in durability. I used to be able to ride 600g tires, but now have to run 900+g tires for durability (however the tires are bigger and 26 --> 27.5)

- Pro DHers do not ride like us

Perhaps to solve their issues, tire manufacturers make Pro-level tires that their pros won't rip off in competition. I would not want one, as it would probably ride like a brick for my level of riding. Not unlike the air spring rates the pros run are waaay beyond what we ride. Or maybe pros run moto style bead locks to keep their tires on.

What I want: a cut protected tire that is still supple.
The inserts solve issues I do not have.

Mr. P wrote:

I see a couple of issues:

- Carbon rims crack instead of bend

- Carbon rims are probably less elastic than aluminum and absorb less force

Inserts seem a temporary solution to a not fully mature technology. And a solution to the problem brought on by ourselves for putting on the carbon rims.

- The biggest issue I've seen are cut casings, pinches are rare compared to cuts.

I have to wonder if the bikes have become so good, and we can now ride so fast, that the tires are playing catch up in durability. I used to be able to ride 600g tires, but now have to run 900+g tires for durability (however the tires are bigger and 26 --> 27.5)

- Pro DHers do not ride like us

Perhaps to solve their issues, tire manufacturers make Pro-level tires that their pros won't rip off in competition. I would not want one, as it would probably ride like a brick for my level of riding. Not unlike the air spring rates the pros run are waaay beyond what we ride. Or maybe pros run moto style bead locks to keep their tires on.

What I want: a cut protected tire that is still supple.
The inserts solve issues I do not have.

"Carbon rims are probably less elastic than aluminum and absorb less force"

Not so sure I agree with the latter part of this statement, as its a bit too general for my liking. I have seen some carbon wheels that seem infinitely more durable than their alloy counterpart...

I don't disagree that we need some serious work on the tire front, especially with respect to casing durability. Cuts are very much a problem for all riders (pro or not). Still, with Double Downs, I do experience a much lower cut rate than I had in the past.

Most importantly...

"The inserts solve issues I do not have."

I don't agree with this. You are asking for a more supple tire. You can have this! Throw Cushcore into your tire/rim combo, run less pressure. Boom! You have what you are asking for. Nothing is going to be fully "cut protected" unless we ditch air all together, but something like Cushcore with a Double Down tire will be an improvement in everything except weight

grinch wrote:

The majority of the problems are pinching the tires. Sidewall tears but most of the time it’s a pinch in the tread casing. It’s the rim sidewall that’s the culprit. I’d like to see the rim have most of the material in the center and be flat across the top and then beadlock strips attached to the outside of that rim block. All at the same height. Fit the tire over the rim block then attach the beadlock side panels. Nothing to pinch if it’s flat across the top of the rim and beadlock panels. Add rim and beadlock panel softer density caps and tires with integrated inserts and no one will want what we have now. Different weights for different applications

jeff.brines wrote:

...inserts basically fix this problem entirely.

Have you inspected your inserts after a month? Rim sidewalls are an issue

grinch wrote:

Have you inspected your inserts after a month? Rim sidewalls are an issue

I have. Honestly, when running one of the burlier inserts and real tires, I am not having any problems with what you are describing. Maybe I need to smash harder or test longer, but on two sets of wheels I am yet to ping/pinch a tire. This, riding somewhere a bit on the rough side, racing at the "pro" level (only stated to show I'm "trying hard") and even running scary low pressure (just for testing - not for going fast).

MK_ wrote:

Maybe the cushcore type insert should have an integrated air bladder above it. That frees up the tire from holding air, it's just tread and abrasion resistant casing at that point with sidewall which doesn't inherently need to hold air. May be a good way to decouple abrasion/rock strikes from puncturing the air bladder internal to the tire.

_MK

You are just trolling right?
Integrated air bladder = innertube

JamesR_2026 wrote:

You are just trolling right?
Integrated air bladder = innertube

Ha ha. No. Bladder integrated into the cushcore type insert. I don't mean a tube placed on top of cushcore, half the tube material would be redundant and add unnecessary weight.

On a separate note, it seems that rim bead is the weakest link of any rim and the part which does the most tire and tube slicing. Maybe the rim should become just the support structure for the insert wrapped in tire with the beadlock attaching to the support to retain the tire. In effect, the rim would become totally beadless.

Spokes would lace up to the rim support, everything else would attach to it.

_MK

Enve appear to believe it's time to rethink rim design, adding an extra piece between the rim and tyre. Didn't seem to work so well for Minnaar though...
For me the issue isn't so much pinch flats or sidewall cuts, it is protecting the rims from damage.
I'm 92kg (200lbs) and race downhill. I generally run around 28psi in Maxxis DH casings front and rear on the DH rig
Main mode of flat tyres is rim damage causing the bead to leak, then the tyre gets trashed as the pressure goes down.
I recently added a DH spec Huck Norris to the rear tyre. I cased a 30' double in a race last weekend, landing on the log at the top of the downramp. Bent both pedals and exploded the bash guard/chain device but the rear wheel stayed inflated, round and straight. An insert definitely solves that problem for me and I'm happy to add 70g to the bike to do it!

So we are trying to get the lightest tires and rims and then putting ~300 grams of cheap foam inside, happy to pay a ton of money for it, reaching weights above the ones of a full DH tire/rim combo, and that's supposed to be called "groundbreaking"? Color me skeptical. As Mr. P said, anti-pinch butyl inserts were an early 2000s thing, and I wondered why the heck The Industry ™ decided to take them down ever since they did.

We might better concentrate on rethinking the rim profile, with better lateral support for the tire. Maybe creating an inner channel with tubular shape instead of the sharp hookless profiles we got used to see in the actual carbon craps these days would both improve lateral support and minimize the pinch flatting risk.

slimshady wrote:

So we are trying to get the lightest tires and rims and then putting ~300 grams of cheap foam inside, happy to pay a ton of money for it, reaching weights above the ones of a full DH tire/rim combo, and that's supposed to be called "groundbreaking"? Color me skeptical. As Mr. P said, anti-pinch butyl inserts were an early 2000s thing, and I wondered why the heck The Industry ™ decided to take them down ever since they did.

We might better concentrate on rethinking the rim profile, with better lateral support for the tire. Maybe creating an inner channel with tubular shape instead of the sharp hookless profiles we got used to see in the actual carbon craps these days would both improve lateral support and minimize the pinch flatting risk.

Maybe that wasn't directed at me. But for the love of God we need to start differentiating between a piece of foam floating in your system (Huck Norris) and a real insert system (Flat Tire Defender, Cushcore) that also changes how the tire rides

Nothing prior to these purpose built inserts has compared to what it can do to the overall feel of your tire interacting with the ground. Is it the end all be all? Heck no. But its the most groundbreaking thing I've tried with respect to actually keeping traction while not flatting in the last decade...

I personally thing the top notch wheel manufacturers have the rim profile thing pretty well dialed. Its all about adding an intermediate layer, tuning the volume of the tire and playing with casing technology that'll bring us the most gains in the shortest amount of time (and money)

But hey, be skeptical. I was!


EDIT: Put another way, a full DH tire can be compared to a heavy coilover. Its linear and offers no bottom out control.

An insert with a lighter tire is more like an air spring. It really isn't THAT much lighter (or any) than a good coil (dh tire) but it is more progressive, does have a different feel, and infinitely better when it comes to bottom out control...

This conversation seems very dh centric. If you can make the rim without a thin sidewall why wouldn’t you? Dh included. We’ve seen EWS bikes go from exo to dd weight tires to full dh tires and using full inserts(cushcore not huck Norris) all to prevent flats , for the most part(yes they ride better with inserts as well), and flats are still deciding races. No one I now rides a trail bike with dh tires and cushcore. I’ve settled on 1000g tires with huck Norris and a bit more air than I’d prefer. Huck Norris is cut to shit from the rim sidewall but it works. It’d probably be fine without the rim sidewall profile. I only use my set up as an example , it can be applied to lighter xc or heavier dh

Sorry about the harshness. It wasn't directed at you, but at the Industry as a whole. I'm still believing paper sidewalls and foam inserts can't be compared to a proper rim/tire interface and a meaty, supportive carcass. Many supposedly tubeless compatible tires out there sweat sealant when fist mounted, and that points out to not enough material in the sidewalls.

Heck, like someone said on Ridemonkey, the problem with properly designed tires is somebody will put them on a kitchen scale an bitch about them on the internet even before mounting them on their bikes.

EDIT: When talking about the rim profile, I was thinking of having it shaped like a toroid instead of being mostly laminar. That way you could still retain the vertical inner surface perpendicular to the rim bed -where the tire bead contacts the rim- while blending the outer surface of the rim in a semicircular way with it. It'll give the lower tire bead a greater surface to dissipate the impacts and from my limited knowledge in structural analysis I'm thinking it'll also increase the rim's strength, all without driving the weight through the roof.

jeff.brines wrote:

"Carbon rims are probably less elastic than aluminum and absorb less force"

Not so sure I agree with the latter part of this statement, as its a bit too general for my liking. I have seen some carbon wheels that seem infinitely more durable than their alloy counterpart...

I don't disagree that we need some serious work on the tire front, especially with respect to casing durability. Cuts are very much a problem for all riders (pro or not). Still, with Double Downs, I do experience a much lower cut rate than I had in the past.

Most importantly...

"The inserts solve issues I do not have."

I don't agree with this. You are asking for a more supple tire. You can have this! Throw Cushcore into your tire/rim combo, run less pressure. Boom! You have what you are asking for. Nothing is going to be fully "cut protected" unless we ditch air all together, but something like Cushcore with a Double Down tire will be an improvement in everything except weight

For what it is worth, I am running Maxxis Minnon 2.5 WT MaxTerra (3C/EXO/TR) on a 34i rim at 18f/23r psi and love it. I'm 190, but don't ride as hard as you, but do ride hard and in shale environments. What stops me from going lower psi is fold over when landing jumps/drops. I've found my sweet spot.

For me, hard trail riding, tires are just about there.

For pro competitive DH and Enduro (almost DH), tires seem to a have a ways to go. I hate to see races decided by a tire issue. But top level pros are so beyond how we are riding.

Perhaps the trail tire, DH UCI pro tire conversation should be separated as they are really two separate issues. Reliability riding vs. finishing a pinned race with no tire issues.

slimshady wrote:

Sorry about the harshness. It wasn't directed at you, but at the Industry as a whole. I'm still believing paper sidewalls and foam inserts can't be compared to a proper rim/tire interface and a meaty, supportive carcass. Many supposedly tubeless compatible tires out there sweat sealant when fist mounted, and that points out to not enough material in the sidewalls.

Heck, like someone said on Ridemonkey, the problem with properly designed tires is somebody will put them on a kitchen scale an bitch about them on the internet even before mounting them on their bikes.

EDIT: When talking about the rim profile, I was thinking of having it shaped like a toroid instead of being mostly laminar. That way you could still retain the vertical inner surface perpendicular to the rim bed -where the tire bead contacts the rim- while blending the outer surface of the rim in a semicircular way with it. It'll give the lower tire bead a greater surface to dissipate the impacts and from my limited knowledge in structural analysis I'm thinking it'll also increase the rim's strength, all without driving the weight through the roof.

Didn’t see the ride monkey thread but I have to agree. For me if you’re riding for the downs then DH or DD tyres are by far superior to the exo (Xc) tyres. And it’s not just because they are more resilient, they squirm less and are way more damped. But everyone I tell just says “yeah but they’re 1300g a tyre”. It doesn’t matter, the benefits outweigh the extra weight
I’m interested how an exo tyre with an insert feels compared to a DH tyre with none, I just can’t imagine it being as good and for me at 62kg a DH tyre AND insert would be overkill.

Thanks for that analogy Jeff, interesting. I need to try myself before I can contribute more to the discussion.

jeff.brines wrote:

Maybe that wasn't directed at me. But for the love of God we need to start differentiating between a piece of foam floating in your system (Huck Norris) and a real insert system (Flat Tire Defender, Cushcore) that also changes how the tire rides

Nothing prior to these purpose built inserts has compared to what it can do to the overall feel of your tire interacting with the ground. Is it the end all be all? Heck no. But its the most groundbreaking thing I've tried with respect to actually keeping traction while not flatting in the last decade...

I personally thing the top notch wheel manufacturers have the rim profile thing pretty well dialed. Its all about adding an intermediate layer, tuning the volume of the tire and playing with casing technology that'll bring us the most gains in the shortest amount of time (and money)

But hey, be skeptical. I was!


EDIT: Put another way, a full DH tire can be compared to a heavy coilover. Its linear and offers no bottom out control.

An insert with a lighter tire is more like an air spring. It really isn't THAT much lighter (or any) than a good coil (dh tire) but it is more progressive, does have a different feel, and infinitely better when it comes to bottom out control...

spot on on the difference between the inserts... I have a huck norris and I think it just protects my rim if I flat.. it does not change any ride feeling... anyways I cut the crap and got alloy rear wheel with EX471 + DH tire for peace of mind and bombing down straight stupid lines...

I'm visiting my parents back home in Newfoundland so I get the feeling that I'm posting from a time zone a good bit east of most you. Anyhow, it's cool to have gotten up and see that a bit of discussion has sprung up. Too many interesting things have sprung up over night to respond to all of them, but to speak to a few of them...

I am looking at this from a Enduro and DH perspective, but I do wonder about whether this is something that could work for lighter duty tires as well. I know that CushCore are working on cyclocross insert as well, as someone that has raced cross bikes in the past that sounds like and epic idea and something that I would grab in a second if I was still racing.

My main point remains: If the tire designer doesn't need to focus on designing as much sidewall stability and damping into the casing of the tire, does this allow them to bring more resources to bear on making the tire cut and puncture proof?

I have no idea what these tire would weigh. I would hope for something between the weight of an exo tire and DD, but so long as the overall system offered a performance advantage I think there would be market even if it wasn't lighter. Tire and wheel tech has improved over the years, but I don't think its anywhere close to being all the way there yet.

If someone did manufacture a product along the lines of what I'm describing it might start as a race only product, but if it had merit it would filter down to general trail use for some riders. No, I definitely don't ride as hard a pro, but like Jeff I'm heavy (6'3, 195lbs), and I move pretty quick on a bike at times. To some extent I'm probably harder on my gear because I push hard, but I don't always have the skills to back it up all the way and I slam my wheels through chunder that I should be getting light and skipping over. Without a doubt racing pushes tech forward, there is a clear relation between the rise of enduro racing and the fact trail/enduro bikes, like the Transition Sentinel, hitting the market this year with head angles as slack as 64 degrees.