'Bent' carbon frame

Back by popular demand, the general all-things Road forum!

Moderator: robbosmans

Post Reply
TuplaO
Posts: 93
Joined: Fri Apr 08, 2011 7:00 pm

by TuplaO

I thought I'd present you with a bit of a conundrum.

Turns out my 2011 Cervelo R3 Red (with the 'SL' R5 fork) frame has somehow weirdly bent (I know, I use this expression for the lack of a better word). There are no apparent cracks and to the naked eye the frame seems OK. However, out of the saddle, NDS, the tyre touches the chainstay and seatstay. I'm running Arenbergs (25mm) on the older model FFWD F4Rs. Turns out the wheel sits more or less straight, but too close to the NDS. We went through these at the LBS: the wheel is true/the dish is OK and it sits perfectly normal on a new frame, the dropouts are out of alignment and the frame as well. Not by much, but apparently by enough to cause a problem.

What's going on? How does a carbon frame 'bend' like that? I haven't crashed it or hit huge potholes and the bike has been well maintained. I'm not very light at 90 kgs, but I would think that if it was my weight, the failure would have been/become more extreme/noticable. I did notice a couple of weeks ago the rear end being a bit skittish/'soft' all of a sudden, but I didn't think much of it until now. Last week, during the last 30-40 kms of my 100K ride, the bike started 'creaking' while out of the saddle. I thought it was the BB and took it in for maintenance. Turns out it was the rear tyre rubbing the frame, which sound-wise resembled a creak.

Seems like the frame is a write-off, I'm just thinking what to make of it all.

Thanks.

Marin
Posts: 4035
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

It's always the NDS because the chain pulls the right side of the hub forward in the dropout.

0.2mm of play at the dropouts = 2mm offset at the tire...

Put tape on the axles or build up the dropouts with epoxy?

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



TuplaO
Posts: 93
Joined: Fri Apr 08, 2011 7:00 pm

by TuplaO

Thanks for your input, Marin! NDS being the problem makes sense now that you spell it out. The dropouts seemed to be off by more than 0.2 mm, providing I got the right idea from what the alignment tool was showing (it was all new to me).

I'm wary of attempting any repairs/jerry rigs, as the frame being off-kilter is something that has happened all of a sudden and without a clear reason. I wouldn't be surprised if there was a frame-compromising hidden crack in there somewhere. We tried 'yanking' the rear fork a bit, but it felt and looked OK. Oh well...

racingcondor
Posts: 194
Joined: Fri Aug 27, 2010 4:22 pm

by racingcondor

Does the frame have asymetric chain stays?

You've covered my first thought (wheel dish) but I wouldn't be surprised if with 25mm clinchers and wide rims (not sure if the F4R's fit this description) it's just that there's not enough clearance and with asymetric stays one side is rubbing while the other is clear.

TuplaO
Posts: 93
Joined: Fri Apr 08, 2011 7:00 pm

by TuplaO

I not aware of the chainstays being explicitly asymmetric. The tyres and wheels are tubular.

I'd like to emphasise that I've been running 25mm tyres for a while now and without problems. The width of the rim or tyres isn't the problem here. The phenomena I'm describing are a fairly recent occurrence and it seems that something's happened with the frame.

Marin
Posts: 4035
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

Realign the wheel and run the QR a bit tighter, that might be enough.

joec
Posts: 100
Joined: Wed Mar 05, 2014 9:20 pm

by joec

did the shop check the dish, is it really ok? flip the wheel round and check if its the same.

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



Post Reply