Question about rim crack (repair)

Have a crack in my rim that I’ve been aware of for a while and riding on without any problems. Had to take the bike in to get suspension service and the tech is making it abundantly clear that they think I shouldn’t be riding this wheel.
Can I repair this myself. Was thinking some epoxy? Maybe some carbon fiber and epoxy? Where would I get a tiny amount of carbon fiber to use?

Looks like structural damage, not just superficial. Probably not a DIY job.


That looks like toast to me. I’d only ever consider repair from a qualified shop.

It’s new rim time from what I see.


Don’t even think about that! Your wheel is toast, no way I would ride that. The damage looks to be very deep, you can see ripped, exposed carbon fibers. I can’t quite tell how deep that is, but it might be that the rim is cracked all the way. That’s a serious accident waiting to happen.

Plus, I assume the employee in your LBS has seen their fair share of damaged carbon gear. So I’d heed their advice.

If you were to attempt a repair, then you should ask a qualified carbon repair service. Repairs of carbon frames and such can be done, but are not easy to do and not easy to do right. However, in this case, I am fairly certain that you wouldn’t find anyone who’d be willing to warranty the repair.


How much are you saving riding on this rim and is it more than the potential medical bills you are going to pay?

How long will you need to take off if you crash from a failure. Is the cost of a rim worth that risk?

You need to consider if the risk is worth it.

I was hoping at least one person would tell me to just glue it and go ride🤣
I guess I need a new wheel/rim. What should it cost to replace the rim? Smarter to buy a new wheelset I guess? I was looking into some anyway but planning on waiting a bit, oh well.

What brand rim? I broke a DTSwiss carbon rim and they replaced it for about $300. I de-laced the broken wheel, sent them my hub, and they built up a new wheel.

A requirement was that the hub was the original that came with the bike, and I was the original owner.

And to add - the crack in my rim was smaller than yours (maybe). I immediately bought a new wheel so I could continue riding (and a week or two later, started the above process with DTSwiss). There’s no way I’d ride a cracked wheel, especially one as bad as yours. Note: I often ride on rocky terrain with drops, where the wheel has to absorb impacts. I probably could have ridden on smooth dirt singletrack - slowly.


Yeah, no, way too much visible damage. Plus an opinion of an employee of your LBS. That’s a clear cut case.

A lot of manufacturers have a crash replacement policy, you should look into that. Usually that means you can buy a new wheel at a steep discount. However, usually that is limited to the first registered owner.

I think you’re confusing carbon fiber with Bondo.

Nah. Get a new rim. If you get exactly the same rim, you should be able to swap them out (either yourself, or a bike shop). The rim is the more expensive thing there.

If you can’t get a new same rim, but like the hub, you can re-build with a new rim and new spokes (spoke length is unlikely to be the same). It might be more fun to buy a new wheel instead though.

I am not the first owner, the lbs told me that specialized (it’s an epic) does offer a discount replacement but it has to be proof of purchase from first owner.
So I guess either rebuild at full price or a new wheel. This is a little older and the inner diameter is 21 I think so maybe an upgrade makes sense anyway.
Thanks for the feedback!


Just in time for Black Friday deals

1 Like

New rim time. You’ve cut all the super strong strings (Carbon) and cracked a bunch of the compression material (resin). Rims are cheap enough to warrant replacement here. It’s also not straight like a frame tube.

Spend $150 on a generic Carbon rim or buy an Amazon carbon wheel with the same dimensions as your current wheel and get it restrung.

Or get a quality aluminum rim. My sub-10 kg XC hardtail has Stans rims, which are excellent and evidently very light.

I disagree! AL Mtb rims hit the weight mark, are pretty durable, and a bit more economical. A cheap carbon rim is 25% more over a quality AL rim. It will likely be overbuilt and a lot more durable.

AL is a great option here though!

For MTb I picked up a pair of Reserves. Got 20% off and basically now have a rim for life or until they go it of business. Whatever comes first.

Can you tell me what advantages of carbon rims for mountain bikes are?

For reference, I do own carbon wheels for my road bike and the aforementioned aluminum wheels on my mountain bike. On a road bike the difference in ride quality is clear. However, on mountain bikes, aero is not a factor, and quality aluminum wheels seem plenty stiff and robust. Ride quality is dominated by tire pressure and suspension settings.

It seems the advantages on the mountain biking side are smaller — not zero, but smaller. What am I missing? (Besides approval from my wife … :wink:)

A good specialist carbonfibre repair centre might be able to help you out but even then for a load bearing wheel I would still feel uneasy :open_mouth:

Yeah, on a MTB, there’s not much difference between AL and Carbon. The AL rims are probably better for ride quality.
As implemented, the carbon rims are a lot more durable at the rim lip than the AL ones. They both tend to weigh about the same (highend AL vs low end carbon), but you carbon rims are next to unbreakable while the AL ones dent or break at the joint. They’re also easier on the tire; again because of the wider bead area. Price wise, a welded joint highend AL rim is about $115-150(street) for a Stans/RaceFace/DT Swiss.
For example, I hit a concrete pot hold (shape edge and deep) with a DT Swiss gravel rim (which is basically a stiffer/deeper XC rim). It flexed so much that it flatted the tire. A cheap carbon rim is usually way overbuilt, it wouldn’t flex anywhere near as much an move as an entire unit. I’ve hit some stuff with a carbon rim and you can’t even tell. You can just under-inflate your tire and beat on a carbon rim.

Looking at a XR 391 25mm (int) XC rim vs Lightbicyle i24 rim
440gr @ $140 vs 395gr @ $170 (shipped with sales tax based on a pair)
(There’s, of course, cheaper options at $50-75 for AL and $150 (Amazon Hulk/Superteam wheelset you’d disassemble)

If you’re hitting rocks, don’t need the cheapest rim in the world, and can get a wheel built up, a cheap carbon is the only way to fly here.

1 Like

Thanks for the detailed response. I will consider a carbon rim for my next mountain bike, I thought the price differential was larger than that.

(I have XTR M9000 hubs on my wheels, so I cannot use 12-speed cassettes except for the cheaper, heavier 11-50 cassettes. First world problems. :grin:)