UKH

Hi there,

I have a carbon bike (BH RC1) that I have ridden for about 18 months. It fell over in the back of a friend's van recently, and soon after started creaking when pedalling sitting down. So I let a friend have a look at it, who took the seatpost out, cleaned the clamp and post, and then put it back. When he was tightening one of the clamp bolts back up, with a 5Nm torque key (clamp has printed on it 5Nm, max 6Nm) there was a really loud bang, and the thread was stripped out of the clamp. Whilst I guess the noise was probably just the alloy clamp failing (the thread stripping), especially as the torque limit hadn't been reached, I am really worried about any damage to the frame or post. The seatpost has a very straight, visible vertical line up it, that can be felt with a fingernail. However this isn't visible from the inside, and doesn't appear to go around the bottom edge of the post at all (the line does go right to the end of the post). The 'coin test' also doesn't make any unexpected noises. I guess this line could just be a scratch from inserting the post with dried up carbon paste in the seat tube etc, and I haven't had chance to check the frame itself (the bike is still at the friends house). A new seatpost, besides being expensive, is likely to be really tricky to get hold of as it is a proprietary shape, and BH stuff isn't very available in the UK, and even then, there's the issue of possible damage to the frame itself.

So the question is... how worried should I be?

Thanks in advance

Also, this is the clamp I'm describing: http://www.bhbikes.com/en/equipment/components/bh-seatclamp-g5-2-bolts-3845...

In reply to Strachan:
I'd probably not be too worried if it just fell over - I'd be more worried about chipped paint

Maybe get someone to follow you riding and see if they can see any flex? Is it the saddle or the frame that's creaking?

I recently snapped the seatpost clamp bolt on my Trek OCLV with similar loud bang and also at way below the torque limit - where they are means they'll get sprayed in any road muck, especially salt if you've been riding through the winter, so can corrode easily. I managed to get the remains of the old bolt out and replace it - seems fine so far.

In reply to Strachan:

The line running up and down your seatpost sounds like an imprint of the join line from the mould in which case it would be nothing to worry about.
jk

In reply to Strachan:

Carbon frames are much stronger than you think and falling over in a van isn't going to do any damage unless a sharp object punctured a tube wall. The creaking was probably just the post moving in the frame as the clamp bolt had probably stretched.

In reply to Strachan:

doubt there is a problem with the frame, but if you are worried go get an Xray

In reply to Strachan:

I wouldn't worry. If carbon is going to fail, it's not going to be in a nice orderly straight line - it's just not made that way. There will be pinged fibres and deformed resin and stuff all over the place. If you're really worried, try and polish it out with a bit of car polish and see what happens.

Creaks can develop for any number of reasons - correlation is not causation, so I wouldn't worry about it falling over in a van either. If it fell over with a body on it when it was doing 50 mph downhill - well have a good look at it then, but even so damage will be visible.

However, it is possible to damage carbon frames in relatively beign ways - a fairly typical one is a bike falling over with a full bottle in a cage, and the fixing bolts for the cage rip out. That's a fairly easy repair for a specialist who knows what they're doing. Additionally, a repeated abrasion that wears away paint will then start to wear away the carbon structure beneath as this is no more resitant to abrasion than the paint. It's also easy to shove a sharp object through the thin side wall of an aero tube. THe latter two may not be repairable.

In reply to IMA:

This is a popular myth that is often trotted out on bike fora.

Firstly, where would you suggest taking the bike for an X ray? The local A&E department? There is nobody who X rays bikes....

because....

An X-ray wouldn't show anything anyway. The best test is to stress the frame in different ways and listen for cracking or creaking noises. Damage to the resin that carries the fibres will soon become evident. A damaged tube will be crushable and the hard resin will be visibly cracked.

In reply to Rigid Raider:

Thanks very much for all the answers on this... when the manufacturer eventually (!) gets me a new clamp sorted I'll just have to ride it and just listen/ feel out for signs of damage I suppose! Cheers