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Carbon rims cutting tires

Old 07-17-22, 07:17 PM
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jayp410
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Carbon rims cutting tires

So last year I ordered some Light Bicycle WR38 rims, which I've been using this year. The rear rim has cut two Maxxis Rambler tires adjacent to the bead. After the first time it happend, I was willing to give it the benefit of the doubt that I might have mounted the tire incorrectly, but I was extra careful when mounting the replacement tire and kept it properly inflated.

I seem to be getting around 70 miles per tire before it cuts through. I can't feel anything sharp with my finger, but the carbon is quite thin, which could cut a tire even if it's not sharp to the touch. I'm thinking of sanding the edge to reduce the amount of lip overhang and make sure the profile is round..

This is partly an FYI, and partly I'm wondering if anyone has had similar experiences? Not sure if this is a design flaw or a QC problem. I'd hate to have to send it back to China, but at $1400 or so, I'd also hate to have them going unused hanging on the wall when I switch back to my alloy rims.

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Old 07-18-22, 06:40 AM
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I have two wheetsets from LB and both have been perfect. Mine came from the North American warehouse but regardless of where they were produced I know that LB has great customer service. Have you already contacted them?
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Old 07-18-22, 08:23 AM
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That's a bummer. No chance it was a tire issue?
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Old 07-18-22, 08:26 AM
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jayp410 : The two tires were identical make and model...Were they from the same batch? i.e., purchased around the same time?

I suggest trying a very different tire -- even an old used one that you've got around. That's an easy test to determine whether it's the rim or a tire defect.
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Old 07-18-22, 08:52 AM
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I have a set of 32mm wide hookless LB rims on my gravel bike and they have been great so far (1 year old / ~4000 miles with some very punishing terrain). In addition to what has already been suggested, maybe try some Liners?
What is your total rider+bike weight and what pressures are you running? Maybe check this out: SILCA TIRE PRESSURE CALCULATOR.
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Old 07-18-22, 09:12 AM
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These being carbon rims, I wonder if the hooks are part of the mold or if the area under the hooks is machined away after molding. The latter method could leave sharp edges.
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Old 07-18-22, 02:10 PM
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Originally Posted by Koyote
The two tires were identical make and model...Were they from the same batch? i.e., purchased around the same time?

I suggest trying a very different tire -- even an old used one that you've got around. That's an easy test to determine whether it's the rim or a tire defect.
Same make and model, but different variant. Not from the same batch. Both Maxxis Ramblers, but the first was Silk Shield and the second was Exo. I chose the Exo for the second tire because it was supposed to have additional protection against sidewall cuts.

Originally Posted by Clipped_in
In addition to what has already been suggested, maybe try some Liners?
These look interesting, although I have a concern that they would add weight, thus reducing the benefit of carbon rims. I didn't see the weight listed on that site.

Originally Posted by Clipped_in
What is your total rider+bike weight and what pressures are you running? Maybe check this out: SILCA TIRE PRESSURE CALCULATOR.
My combined rider/bike weight is around 235. Measured tire width is 43mm. According to that calculator, I should be running 33-38 PSI in the rear (depending on gravel type). I have been running 45 PSI rear, 43 PSI front. Not sure what to make of that. I could see how too much pressure could cause it to cut into the tire more quickly.
The front tire, at 43 PSI, has not had this issue so far, although it doesn't have as much weight on it, either.

Originally Posted by ThermionicScott
These being carbon rims, I wonder if the hooks are part of the mold or if the area under the hooks is machined away after molding. The latter method could leave sharp edges.
I have some experience hand fabricating CF parts (car parts, not bike parts). I suspect that the edge such as this would need to be machined / sanded, as it's where the carbon would exit the mold, and would have to be trimmed. However, carbon fibers are sharp by nature so if they are exiting the edge, they form kind of serrations like a knife. Maybe if sanding using very fine grit, the serrations could be eliminated. The faint gray line on my fingertip is from running my finger along the edge of a piece of CF while sanding, and it cut me deeply and left carbon dust in my flesh. It's kind of an unintentional tattoo.


Last edited by jayp410; 07-18-22 at 09:35 PM. Reason: fixed spelling: "Silk"
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Old 07-18-22, 02:47 PM
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Thanks for sharing. Unfortunately this is a known problem for hooked carbon rims (known in the industry if not with consumers like us).

It should not happen hookless (nor on a hooked aluminum rim)

Ya can't mold in a hook on a carbon rim. Somehow you have to have additional manufacturing steps to put that hook in, and that is where the problem comes from. carve it out too sharp, or expose some sharp fibers, and it will cut the tire.

Sux it happened to you. Its a mfg defect, and should (ideally) be covered under warranty.

Originally Posted by ThermionicScott
These being carbon rims, I wonder if the hooks are part of the mold or if the area under the hooks is machined away after molding. The latter method could leave sharp edges.
unfortunately hooks can't be part of the mold (unlike aluminum). If they were, you wouldn't be able to release it from the mold.
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Old 07-18-22, 07:56 PM
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FWIW I have LB WR45 hookless rims on a tandem running Specialized Sawtooth 38c tires and have not had that problem. The only problem we had was a tire blowing off (not while riding) from being minimally over-inflated. I now run 55 psi and they have been great.
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Old 07-18-22, 11:13 PM
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(1) I would not modify the rims in any way.
(2) I'd contact the manufacturer about the problem first, not BF where you will get every OPINION under the sun.
(3) I'd try a different brand of tire and maybe a higher pressure. You state you keep it properly inflated but what is the tire width, your weight and the tire pressure you are running?
(4) I'd mark the spot on the rim where this happens and see if it happens again at the same place.
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Old 07-19-22, 12:12 AM
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Originally Posted by dwmckee
(1) I would not modify the rims in any way.
(2) I'd contact the manufacturer about the problem first, not BF where you will get every OPINION under the sun.
Yeah, I'm hesitant to sand the rims. That's why I'm posting here first.

I would trust BF member opinions more than manufacturer advice in general, as the manufacturer has a conflict of interest (profit margin). I probably will contact the manufacturer yet.

Originally Posted by dwmckee
(3) I'd try a different brand of tire and maybe a higher pressure. You state you keep it properly inflated but what is the tire width, your weight and the tire pressure you are running?
May try a different tire brand. These are my first gravel tires, and I have been otherwise happy with them. I'm not sure what might be better.

As stated above, total bike + rider weight around 235 lb. Nominal tire width: 40 mm, measured: 43 mm. I have been running 45 PSI rear, 43 front.

Not sure if higher or lower pressure would help. With higher PSI, I would think that the tire is pushing harder against the hook, so therefore may be more likely to be cut. On the other hand, with higher PSI, the tire would move less against the rim as the flexes, so may be less likely to be cut. Based on the calculator someone posted above, I may be running with pressures that are higher than recommended already.

(4) I'd mark the spot on the rim where this happens and see if it happens again at the same place.[/QUOTE]
Right. Unfortunately I didn't think to mark the location where it happened the first time, but will definitely note the location this time.
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Old 07-19-22, 07:23 AM
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I love ramblers. Great tire. While I have no problems with them, they are not heavy duty.

Some brands have extra rim protection to protect against pinch flats (often looks like a piece of cloth wrapped around the rim bead and going up ~5mm.

Leonard Zinn and/or Cycling tips have discussed this problem in the past. Part of the cost of hooked carbon rims is the extra machining, manual labor, and discard rate (due to problems like this) required when putting a hook in the rim.

If you are riding under 60psi, you probably don't need a hook. Certainly if you are going a lot over 80psi you do (but who here does that??).
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Old 07-19-22, 10:46 PM
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So I unmounted the tire and cleaned up the sealant. It's interesting that the cut (position marked with the blue painter's tape) is close to what appears to be a seam. There are 4 such seams at 90 degree angles, so it appears that the wheel (or at least the inner suface of it) may have been manufactured in quarters, then fused together, then more layers on the finished surface. It doesn't look or feel sharp, although there is a ridge where the seam is, that would give the tire bead a more narrow channel right there.

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Old 07-20-22, 09:24 AM
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My initial thought is to put a little something between the rim and tire.

FattyStripper Tubeless Fat Bike Solution and SkinnyStripper Tubeless CX & DH Solution <link rel="image_src" href="https://fattystripper.com/media/FattyStripper_Logo_320.jpg" / ><link rel="image_src" href="https://fattystripper.com/media/FattyStripper_L

These are minimal in price. Medium in installation difficulty. They also let your tubeless tires mount up better with fewer mystery leaks.

I think I heard that once trimmed on a gravel bike, the add less than 10g per wheel.

It ruins the stripper to remove a tire, but seeing how seldom I actually remove tubeless tires, it’s not an issue.

Understand this advice is from someone 100lbs your junior. So take it with a grain of salt.
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Old 07-20-22, 11:00 AM
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Originally Posted by jayp410
So I unmounted the tire and cleaned up the sealant. It's interesting that the cut (position marked with the blue painter's tape) is close to what appears to be a seam. There are 4 such seams at 90 degree angles, so it appears that the wheel (or at least the inner suface of it) may have been manufactured in quarters, then fused together, then more layers on the finished surface. It doesn't look or feel sharp, although there is a ridge where the seam is, that would give the tire bead a more narrow channel right there.
That is odd. you got me stumped.

If there is a manufacturer defect enough to hurt the tire, I'd think you would see and/or feel it there.

looking at the OP, it looks like the tire failed along a seam? We are looking at the inside - does it look like there was any abrasion on the tire itself? Odd that it happened twice on two different tires - that makes me think its not the tire.

Possibly the tire wasn't seated 100% correct all the way around? If for some reason it doesn't hook on that lip and bulges out a little there, it could stretch enough to cause that type of rip. I've done that in the past long long ago (with tubes). Pretty much gave me the type of tear you have in the original picture. Taught me to max out the PSI and check the tire was seated all the way around with no bulges and nothing where the bead had not popped on to the proper place.

if your bead is not seating properly at the spot where the rim is off/wavey, it could cause the tire to stretch and tear.
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Old 07-24-22, 11:47 PM
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Originally Posted by chas58
Thanks for sharing. Unfortunately this is a known problem for hooked carbon rims (known in the industry if not with consumers like us).

It should not happen hookless (nor on a hooked aluminum rim)

Ya can't mold in a hook on a carbon rim. Somehow you have to have additional manufacturing steps to put that hook in, and that is where the problem comes from. carve it out too sharp, or expose some sharp fibers, and it will cut the tire.

Sux it happened to you. Its a mfg defect, and should (ideally) be covered under warranty.


unfortunately hooks can't be part of the mold (unlike aluminum). If they were, you wouldn't be able to release it from the mold.
That’s not true according to Enve. See the Manufacturing Efficiency section at the following link and it says hooks *need* to be molded in:

https://www.gravelcyclist.com/bicycl...ve-composites/

I don’t think that applies to filament wound rims, but I honestly have no clear understanding of how that process is used to make CF rims…
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Old 07-25-22, 01:18 PM
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Originally Posted by chaadster
That’s not true according to Enve. See the Manufacturing Efficiency section at the following link and it says hooks *need* to be molded in:

https://www.gravelcyclist.com/bicycl...ve-composites/

I don’t think that applies to filament wound rims, but I honestly have no clear understanding of how that process is used to make CF rims…
Yeah, thanks for that. I did remember there are two ways to make carbon hookless - couldn't remember what the second way was - using a throwaway bladder.
Sounds like ENVE probably has a higher scrap rate for hooked carbon than LB does.
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Old 07-25-22, 04:28 PM
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Originally Posted by rosefarts
My initial thought is to put a little something between the rim and tire.

FattyStripper Tubeless Fat Bike Solution and SkinnyStripper Tubeless CX & DH Solution <link rel="image_src" href="https://fattystripper.com/media/FattyStripper_Logo_320.jpg" / ><link rel="image_src" href="https://fattystripper.com/media/FattyStripper_L

These are minimal in price. Medium in installation difficulty. They also let your tubeless tires mount up better with fewer mystery leaks.

I think I heard that once trimmed on a gravel bike, the add less than 10g per wheel.

It ruins the stripper to remove a tire, but seeing how seldom I actually remove tubeless tires, it’s not an issue.

Understand this advice is from someone 100lbs your junior. So take it with a grain of salt.
These look interesting. I'll definitely keep these in mind. I too was thinking about putting something, like a piece of electrical tape, between the hook and the tire.


Originally Posted by chas58
That is odd. you got me stumped.

If there is a manufacturer defect enough to hurt the tire, I'd think you would see and/or feel it there.

looking at the OP, it looks like the tire failed along a seam? We are looking at the inside - does it look like there was any abrasion on the tire itself? Odd that it happened twice on two different tires - that makes me think its not the tire.

Possibly the tire wasn't seated 100% correct all the way around? If for some reason it doesn't hook on that lip and bulges out a little there, it could stretch enough to cause that type of rip. I've done that in the past long long ago (with tubes). Pretty much gave me the type of tear you have in the original picture. Taught me to max out the PSI and check the tire was seated all the way around with no bulges and nothing where the bead had not popped on to the proper place.

if your bead is not seating properly at the spot where the rim is off/wavey, it could cause the tire to stretch and tear.
This is possible, that it wasn't seated evenly. Perhaps it could be due to that seam interfering with the profile of the tire just enough to make things uneven. I'm not ready to call this a manufacturer defect at this point... maybe it's more of a tire/wheel incompatibility.

I'm going in a bit of a weird direction to avoid / solve this.
1) Bought some Gravel King SK+ 38mm. (I wasn't sure the 43mm Gravel Kings would fit my bike). Was planning on putting them on the LB rims, but decided to put them on my alloy rims instead, just to have something bombproof to ride while I play around with these carbon rims. I was disappointed with the narrowness of the 38mm tires, after riding on the Maxxis that were 40mm nominal (43 measured). But I think I'm going to keep those 38's on the alloy rims, and have them as a spare or for smoother gravel.
2) The tire width disappointment got me thinking that I wanted to try some 650b rims with wide tires, to maximize the abilities of my bike, and the 700c LB rims weren't the final answer for that. So I ordered some Hunt Adventure Carbon 650b rims, which are hookless, so I shouldn't have a similar problem with those. So I'm going to put some 2.1" tires on those, to be my primary gravel wheels. Hunt is already shipping them... they are in stock, so that will be like 3 days vs. waiting 14 weeks for the LB wheels to be built last year.
3) I plan on using the LB wheels with road-specific 32mm tires, like maybe Conti GP4000S with tubes, to have some faster wheels for the road. Hopefully the LB rims will work out for that.

So I'll have road, wide gravel, and fast gravel wheelsets...
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Old 07-25-22, 04:51 PM
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Ooh, taking the N+1 to wheelsets, I like it. N+1 is always the answer*.


*until the spouse says it's not.
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Old 07-27-22, 09:47 AM
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Originally Posted by jayp410
These look interesting. I'll definitely keep these in mind. I too was thinking about putting something, like a piece of electrical tape, between the hook and the tire.
I've been using fatty strippers for about a decade, but I don't think they would do ya any good here. They are about the thickness of a latex balloon - and you cut them off basically at the lip of the rim.

Isn't the cut/tear just where the tire meets the rim (and not under/below the lip of the rim?)
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Old 07-27-22, 10:24 AM
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Thanks for posting. Looks like another thing to check when ordering new rims.
RATS... My list of things to check when ordering new parts is getting longer and longer...
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Old 07-28-22, 11:07 PM
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For the LB rims, ordered some 700 x 35c GravelKing Slick Plus as road tires.. will see how those do.

For now though, got the new 650b wheels (Hunt Adventure Carbon) w/ 2.1" tires mounted. These are so wide...halfway to being a fat bike, it seems. They barely fit my frame, with maybe 2 mm clearance to the drive-side chainstay. Looking forward to trying them this weekend.


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Old 07-29-22, 06:29 AM
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I just had a similar flat with one Bontrager tire I had put on a set of Aeolus 5 rims. Had put a few hundred miles on the tire. Mounted on the rear. Found it flat before a ride this week. Patched the tube but did not inspect the tire bead close. About an hour after the ride blame it went flat. Was running 75 psig for this 32mm tire. Then saw the damaged tire in the picture. I’ve run Conti GP4000 and GP5000 tires. Pressure for these 23 to 25mm from 85 to 115 psig. Never a bead issue. I think it was the tire and the extreme hook of the tubeless ready rim.

By pinky finger there is bead wear but not failed yet.



Oh the tire came off my Domane SL6 when I put on a set of GP5000s with tubes.
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Old 08-01-22, 09:48 AM
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I could be wrong, but its looking to me that these tires are not being mounted properly.

With tubeless wheels, mounting is much more critical and a PITA.

I've learned the hard way to:
- put soapy water on the bead when mounting
- pump the tires up to the maximum allowed pressure and let it sit for ~5 min
- look at the entire rim to ensure the tires have "popped" on the rim properly
- deflate, and reinflate (probably with the valve stem in this time).


If I don't do this, the tire often will not pop onto the rim properly. Looking closer I can see that most tires have a little extra layer of reinforcement at the bead. If I can not see this reinforcement all around the tire, that means the rim is against the sidewall of the tire, not against the reinforced bead strip, and problems will occur. And with hooked rims, I want to ensure the bead is evenly in the hook (it can be too low or too high, depending on wheel design)

Often I'll just put the tire on with a tube for a day or so, to ensure it is unfolded and in the right shape.
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Old 08-05-22, 07:13 PM
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FWIW I had a sidewall tear very similar in appearance and location to the one pictured above by biker128pedal. This was on a LB hookless rim running a Specialized Sawtooth 38c tire setup tubeless. I think it happened from running low pressure - which became unavoidable as we were in the middle of nowhere and I could not get the leak to stop and had the wrong size tubes with me. And this was the rear tire on a tandem, so lots of stress on the sidewall.
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