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Dropout alignment on carbon road bike

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Dropout alignment on carbon road bike

Old 07-18-13, 03:23 PM
  #1  
mechantbruce
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Dropout alignment on carbon road bike

Hi,

I have a carbon Cervelo RS, and the dropout alignment looks like this;




how big a problem is this?
Can it be fixed (given it a carbon fiber frame)?
any words of wisdom?

Full disclosure..... I deployed my shoulder brake at ~40kmph. Got a broken collar bone as a prize. The bike only seemed to suffer some scratches on the hoods and (ominously) the rear quick release. I took it into the local bike store for a full checkover and full service. The said it was fine.

Also, since the drop (and before looking at the alignment), I went for a 8 day bike tour in the french alps with 699km and 16,575 vertical meters, with not (bike related) problems at all.

Thanks,
Bruce.
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Last edited by mechantbruce; 07-18-13 at 03:29 PM. Reason: more info added
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Old 07-18-13, 03:34 PM
  #2  
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It looks to me like just moving the right dropout would be sufficient, as it's not terribly off. But my advice would be to consult with a frame bulder familiar with carbon bikes or the manufacturer.
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Old 07-18-13, 03:46 PM
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How was the alignment prior to your crash? Carbon frames cannot be aligned and if it was a off from the shop-floor, there is little that can be done.
Dont try to realign as in a steel bike, you will crack the frame or at least cause some microfractures
Ask cervelo what their alignment specs are.
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Old 07-18-13, 03:46 PM
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Well, since the bike performed well on a major ride after the accident I have to assume the problem isn't a problem. I expect installing the rear wheel realigns the dropouts adequately to cover the misalignment you show. Short answer: if it isn't a problem, it isn't a problem.
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Old 07-18-13, 03:58 PM
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I had a misalignment problem in the front dropout that was able to be fixed by filing with a round file. In your case the dropout faces do not appear to be parallel but heigths at the dropout may be nearly the same. If they are the same, the wheel may sit perfectly plumb and be aligned with the front so that steering is still stable. You may be able to check this out at home with careful measurement and depending on what tools you have available. However, the misaligned dropout faces will cause an eccentric, twisting force that would be bad for the dropout, especially if aluminum. For myself, I would have it checked by the manufacturer.
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Old 07-18-13, 04:22 PM
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Thanks for the help so far, here are a few more thoughts;

Its a carbon frame I know its a bad idea to try to bend carbon into alignment.

I did not check the alignment before the fall (lesson learned).

When I look at the Alignment Guides from above they are aligned (the views in the photos are from behind)

Although I did a lot of riding on the bike after the fall, I am not a terribly experienced rider, and its quite possible that I would miss subtle (or event not so subtle) signs that something was wrong.

I live in rural France, so talking to Cervelo is going to be difficult.

... and I am now paying much more attention to proper cornering technique than I used to. This is the best cornering advice I have been able to find (I am more interested in cornering well than in doing it fast); http://www.flammerouge.je/factsheets/descend.htm

Last edited by mechantbruce; 07-18-13 at 04:23 PM. Reason: clarify text
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Old 07-18-13, 05:43 PM
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I looked again, and given the very small size of the dropouts I would advise against attempting to align them - not really possible to do so without stressing the bond between dropout and stay. This from Park Tool site - "....dropouts that are bonded into the frame, such as on carbon fiber frames, may not be repairable," and "If there is not a narrow section between the frame and dropout, it may not be repairable. Without this "neck", you are attempting to bend the frame tube."
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Please respect others by taking the time to post clearly so we can answer quickly. All lowercase and multiple typos makes for a hard read. Thanks!
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Old 07-18-13, 05:57 PM
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Hi,

Carbon doesn't bend *, it breaks. There are no bent carbon frames.
The frame is the same as it ever was. I doubt any bike would
line up with that sort of rear test, because it hardly matters.

rgds, sreten.

* Of course it bends elastically, but not plastically.

If you've checked it before in the same way and it lined up,
I'm missing something, e.g. the dropouts are not carbon.

Last edited by sreten; 07-18-13 at 06:08 PM.
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Old 07-18-13, 07:17 PM
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The standards used in steel frames do not apply to carbon frames. Andy.
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Old 07-18-13, 07:53 PM
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It looks like the right side crash pushed the hanger in and it took the drop out with it.

I can't see from the photo where the carbon ends and the aluminum dropout begins, but I would pull it back to line unless I saw a compelling reason not to.

BTW- it's not like you have much choice, since it is bad enough to stress and maybe break axles, and/or bind rear bearings.
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