Carbon frame chainstay breaks, common causes

[Ridgeway]

Been offered a nice carbon road bike that has had a left/upper chain stay break, this has been repaired by a reputable carbon specialist (they've even given a guarantee on the repair) and the bike has been made good, sold by a shop and the current owner that bought it is now selling it on, seems a genuine sale and story and i sort of know the guy (friend of a friend so to speak). I'm going to see if the LBS know's the history of the bike and what caused the break but having done some searching i found that chainstay breaks seem to be about the most common carbon frame failures and it got me wondering how this likely might of happened, i can only assume at this stage in some sort of accident. What i want to rule out is any other potential risks in buying such a bike and without thermal scanning the entire frame i guess i'll never know for 100% sure..... but wondered if there's any other typical damages that can occur when a carbon frame ends up with a chainstay break ?

I suppose i'm just looking for reassurance for an unknown risk

 

[DCLane]

There's a number of reasons; an easy point to stress and crack, chain coming off and the rider not paying attention, bike fall, etc.

Lots of repairs done on them, and seatstays. I've a frame away for repair as it's had a big chip on the down-tube and I'd prefer to be sure with it: it's the Raleigh SP Race I built earlier this year and will probably replace my Wilier Montegrappa as a better commuter bike.

 

[Ian H]

'Upper chainstay'? Is that the seat-stay?

 

[Ridgeway]

'Upper chainstay'? Is that the seat-stay?

yes correct

 

[Big John]

Some years ago I was doing the Tour of Wessex with some club mates when the rear mech got caught in the spokes. It ripped the back wheel to shreds and broke the carbon chain stay. To say I wasn't happy is an understatement.....anyway.....long story short I gave the frame away to a chap who was hell bent on having a carbon bike. I told him he could have it and if he wanted to get it mended he could. There was no way I was going to ride it after that sort of damage. I just felt I could never totally trust it even if I'd had a professional job done. The guy I gave it to had it miraculously repaired - you couldn't even see where it had been repaired. He never told me how much it cost but he ended up with his carbon bike and rode it without any problems.

 

[Drago]

Best way to mitigate the risk is not to buy it. It's probably fine, but why take the chance when there are so many for sale that haven't had to be repaired?

 

[cougie uk]

Mate's S Works broke on the seat stay in transit. His had very slender seat stays to improve the comfort of the ride.

If this one has been repaired then great - better than new but you'd want it at bargain rates.

 

[Ridgeway]

Mate's S Works broke on the seat stay in transit. His had very slender seat stays to improve the comfort of the ride.

If this one has been repaired then great - better than new but you'd want it at bargain rates.

Yes in this case the price is good and in my opinion is correct for such a bike.

 

[Cycleops]

If it's been properly repaired and the price is compelling go for it.

 

[si_c]

A while back GCN did a video on carbon bike repair - as something that I was unfamiliar it certainly put my mind at ease about a professional repair - in the same way that sending a steel frame to a framebuilder would. Not sure the expense would be worth it mind, depends on the frame but given Mrs C and I are trying to reduce our waste it's probably something I'd do.

 

[Ridgeway]

A while back GCN did a video on carbon bike repair - as something that I was unfamiliar it certainly put my mind at ease about a professional repair - in the same way that sending a steel frame to a framebuilder would. Not sure the expense would be worth it mind, depends on the frame but given Mrs C and I are trying to reduce our waste it's probably something I'd do.

Yes saw the video they did of the company Carbon Bike Repair, very informative

 

[Cycleops]

Not sure the expense would be worth it mind, depends on the frame but given Mrs C and I are trying to reduce our waste it's probably something I'd do.

If you're trying to reduce waste should you be buying carbon in the first place?

 

[si_c]

If you're trying to reduce waste should you be buying carbon in the first place?

Good point!

When I say waste, I mean the stuff we throw away unnecessarily so repairing a carbon frame seems an ideal way to reduce waste - especially if it's not an old frame. I have two frames in the loft which are broken - snapped chainstay on a steel frame and seat-tube junction on an alloy bike. The latter I don't think is economically repairable as finding someone able to effect a repair seems difficult at best. The steel bike will eventually be repaired, cleaned up and built back up though.

 

[Ridgeway]

So managed to talk with the LBS and get the story on the frame break and repair. Seems the original owner was hit from behind at a set of traffic lights by a late braking car, it destroyed the rear wheel, cracked the left seat stay and sent the rider to the deck. As it was an insurance claim it was repaired by a known carbon frame repairer that the LBS informed me about and i know 2 guys that have had work done there and they seem to know what they are doing. The current owner is selling it as he's grown out of the frame as it's a 51.5cm frame (my size) and he's 18 yrs old now so must have been 16 when he got the bike so i can believe the story to be correct. Off to see it on Thursday and do some checks, have a test ride etc, all things being equal if it's as i'm told them it will hopefully be coming home with me

 

[Colin Grigson]

So managed to talk with the LBS and get the story on the frame break and repair. Seems the original owner was hit from behind at a set of traffic lights by a late braking car, it destroyed the rear wheel, cracked the left seat stay and sent the rider to the deck. As it was an insurance claim it was repaired by a known carbon frame repairer that the LBS informed me about and i know 2 guys that have had work done there and they seem to know what they are doing. The current owner is selling it as he's grown out of the frame as it's a 51.5cm frame (my size) and he's 18 yrs old now so must have been 16 when he got the bike so i can believe the story to be correct. Off to see it on Thursday and do some checks, have a test ride etc, all things being equal if it's as i'm told them it will hopefully be coming home with me

Exciting ... and 51.5 is my size too
What is the ‘mystery machine’ ... something decent I reckon