Can you trust repaired carbon bike frames?

A cycle accident can leave a bike with busted bits, but that need not be the end. The broken pieces may not need to be discarded, as they may be fixable in the hands of expert carbonologists.

“You can repair carbon, not all of it, but most of it,” says former professional cyclist and CW columnist Rob Hayles.

Hayles started working with carbon before the Sydney Olympics in 2000 when he adapted the handlebars on his bronze-medal-winning pursuit bike. “It’s furthering my childhood obsession of building with Lego. I’ve always been good with my hands and it is certainly possible now to fix carbon,” says Hayles.

“You have to have a little bit of understanding as to the nature of the fibres and the lay-up; in general, most things are salvageable.”

With a frame, there’s a lot of surface area to work with, but there are limitations. Carbon, with all its qualities, also has its shortfalls. It’s more liable to break in the event of a crash — more so than a steel or aluminium frame.

Lightness versus strength

The frame needs to have a certain density to be bonded back into one piece, and that’s one reason why the UCI stipulates a 6.8kg minimum weight limit. As frames have got lighter, the tubing has got thinner, creating problems.

“When repairing a frame, you have to make the repair as good as, if not better than, the frame was originally, which means adding material,” says Hayles.

Modern oversized tubing offers more surface area, but at certain zones of the frame — such as the bottom bracket — it is difficult to add more material.

Wheels are another component that may undergo surgery to prolong their life. Again, wheels are expensive, so people want to repair them rather than put them out with the recycling. Safety can be a concern after repairs, and special care and expertise is needed with wheels.

“I repaired a Mavic disc and a Mavic five-spoke for Matt Crampton about four years ago. He’s on the track racing on them at the moment,” says Hayles.

“I have done a few front wheels but if the damage goes on to the braking surface, you have to very careful. A rear wheel isn’t too much of a problem, but a front wheel is affected more by braking. A tubular is easier to fix than a clincher. With clinchers, there are greater stresses on the rim from braking,” he adds.

>>> Is it the end for the 34t chainring?

“It’s even possible to mend parts of broken forks, depending where the damage is. I’ve done dropouts and a cracked steerer, but if it’s the fork blades, I’d recommend replacing them, as it’s not worth the risk. It’s the same as stems and handlebars.”

Our take

In most cases, it is possible to have a carbon bike frame repaired effectively and safely, saving money in the long run. But sometimes it is not possible. If the bike is insured, then it’s hard to see why you’d take the risk. Whatever you ultimately decide, seek professional advice — this solution is definitely for professionals only. Do not try to repair carbon at home.

Yes: Richard Matthews, carbon composite specialist, Cervélo

“Repairing a carbon composite frame is definitely possible but it’s a complicated process — one best performed by people with experience, knowledge and the correct tools. Original manufacturers and specialist composite bicycle repair companies are best suited to repair composite frames.”

No: Claire Beaumont, marketing manager, Condor Cycles

“We offer crash replacement at Condor. Most people who come to us with a broken frame have been involved in a serious collision with a car and the insurance company is paying for the damage. In which case, most choose a new frame — it’s always nice to get new things.”