Carbon frame chainstay breaks, common causes

[Ridgeway]

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

it was the bargain of the year Dogma F8 with Campy Super Record, standard rims but a lovely bike for the money. It’s now sitting in my utility room waiting fir some TLC and fine tuning. Full degrease and clean this weekend and then setting the gears up properly. Took her for a 60km spin this afternoon in a hoolie and all went went well. The repair has been well done and the company that did it offered a guarantee to the life of the frame which I assume means their confident the repair is as strong as the rest of the frame. Any way there was no creaks or groans from it with my lardy ar$e on this afternoon.

 

[Colin Grigson]

it was the bargain of the year Dogma F8 with Campy Super Record, standard rims but a lovely bike for the money. It’s now sitting in my utility room waiting fir some TLC and fine tuning. Full degrease and clean this weekend and then setting the gears up properly. Took her for a 60km spin this afternoon in a hoolie and all went went well. The repair has been well done and the company that did it offered a guarantee to the life of the frame which I assume means their confident the repair is as strong as the rest of the frame. Any way there was no creaks or groans from it with my lardy ar$e on this afternoon.

How did it feel compared to your K8 ? .... you’ve now got two very nice bikes to choose between

 

[Ridgeway]

How did it feel compared to your K8 ? .... you’ve now got two very nice bikes to choose between

Shorter, stiffer and slightly twitchy it was very wet out today and the F8 is on 25mm vs 28mm tyres on the K10. But i could feel it is more reactive, faster to accelerate and on the 1000m of climbing i did it felt light shame that just before i add 2kgs over Christmas

 

[BigWheels]

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

For what its worth, a few years ago I broke my rear chain stay on my Cervelo S2 road bike. It was a real mess, the chain went over the cassette, ripped off my rear mech and destroyed my 404 wheelset in the process- alot of damage.

I had it repaired and was anxious to ride it again. this is a bike I used to average 20mph on and would get to some big numbers downhill. When it was returned from the repairer I was assured that it was stronger than the original... i was hesitant but I still have the bike and its been through some rough times since with no issues.

If you are happy that the repair was carried out by a reputable company then buy it. I have known bikes to be rejected for repair because the repairer was unhappy that they could safely repair it.

 

[Ridgeway]

For what its worth, a few years ago I broke my rear chain stay on my Cervelo S2 road bike. It was a real mess, the chain went over the cassette, ripped off my rear mech and destroyed my 404 wheelset in the process- alot of damage.

I had it repaired and was anxious to ride it again. this is a bike I used to average 20mph on and would get to some big numbers downhill. When it was returned from the repairer I was assured that it was stronger than the original... i was hesitant but I still have the bike and its been through some rough times since with no issues.

If you are happy that the repair was carried out by a reputable company then buy it. I have known bikes to be rejected for repair because the repairer was unhappy that they could safely repair it.

Good feedback, yes the repair seems good and has been done a reputable carbon bike frame repairer. I picked the bike up last week and also had a friend take a look at it, he's quite expert on carbon manufacturing as he builds E-Foils with carbon boards although he's not an expert in bike frames. He thought it was well finished a decent weave and had been "well baked" (his words). One thing he mentioned that i thought was relevant is that the frame is probably stiffer in that area now after the repair, probably not ideal as i'm sure the frame is designed to flex to a certain degree, in the worse case this could put extra strain on another part of the frame, the opposite seat stay for example.

Anyway i'm happy with it and it rode well last week, need to get some more miles done on it once it's ready to rock and roll.

 

[SkipdiverJohn]

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.

The difference is metal frames are easy to recycle and they have some value as scrap, so they will actively be recycled if uneconomic to repair. CF bikes have a negative scrap value in that there is nothing of any salvage value in them, yet they still cost money to process. Recycling only ever works if there's money to be made from doing it. It's funny how people who claim to be concerned about sustainability will still buy CF bikes, despite them effectively being a large expensive piece of single use plastic!

 

[Ridgeway]

The difference is metal frames are easy to recycle and they have some value as scrap, so they will actively be recycled if uneconomic to repair. CF bikes have a negative scrap value in that there is nothing of any salvage value in them, yet they still cost money to process. Recycling only ever works if there's money to be made from doing it. It's funny how people who claim to be concerned about sustainability will still buy CF bikes, despite them effectively being a large expensive piece of single use plastic!

if I only used a carbon frame once then threw it away I’d agree that’s it SUP, I plan to use it more than that🤫

 

[SkipdiverJohn]

That's true, but you can't repurpose a CF frame into anything else once it has become redundant. Before christmas I needed a piece of sheet aluminium to finish a car repair. Rather than buy a new piece, I salvaged a cover panel from a bit of scrap electronic equipment at work, cut it to size, and used it. My motivation was purely to do it on the cheap, not saving the planet, but by re-using something i saved the energy cost of extracting and refining a new piece of metal.
When I've scrapped steel frames, I've salvaged the fork if it's rigid - either as a spare or for use as a wheel-truing jig. CF might last a good few years, but when it's done with, it's a total loss in terms of what went into producing it. You can't do anything useful with it.