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Dropbolts on carbon fiber frame and fork.

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Dropbolts on carbon fiber frame and fork.

Old 10-13-12, 09:02 PM
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KaisoArt
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Dropbolts on carbon fiber frame and fork.

I'm doing an experiment, 650c wheels on a 700c carbon frame. (don't ask why) However, the brakes need an additional 25mm of reach. People do dropbolts on metal frames at the time. Shouldn't it be fine for carbon also. These frames take the same stresses as the metal ones when riding. I did look into long reach brakes, but none are long enough. And if drop bolts would not work because of stresses, wouldn't long reach calipers have the same effect?

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Old 10-13-12, 09:21 PM
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Drop bolts wouldn't be any different on a carbon fork or rear bridge than on a steel one, but I don't know if anybody makes one with 25mm of drop.

Now since you mentioned torque, let's consider it. No problem of the front, but it might be on a rear if the bridge is built only strong enough for the torque of a short brake. But you're right the total bridge to rim distance is what matters, so drop bolt or long brake is the same. I wouldn't worry except if the bridge appears to be underbuilt.
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Old 10-13-12, 09:34 PM
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Originally Posted by KaisoArt View Post
I'm doing an experiment, 650c wheels on a 700c carbon frame. (don't ask why) However, the brakes need an additional 25mm of reach. People do dropbolts on metal frames at the time. Shouldn't it be fine for carbon also. These frames take the same stresses as the metal ones when riding. I did look into long reach brakes, but none are long enough. And if drop bolts would not work because of stresses, wouldn't long reach calipers have the same effect?
How much more reach do you need? These go out to 78mm:
https://www.biketoolsetc.com/index.cg...em_id=TK-800AF
https://www.biketoolsetc.com/index.cg...em_id=TK-800AR
Kind of cheesy looking, but I ain't asking...
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Old 10-13-12, 11:01 PM
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Wouldn't it just be easier to swap the fork for one that is 650C compatible? Just thinking that risking your existing fork might not be wise.
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Old 10-13-12, 11:35 PM
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Originally Posted by cale View Post
Wouldn't it just be easier to swap the fork for one that is 650C compatible? Just thinking that risking your existing fork might not be wise.
Swapping in a shorter fork will steepen the head angle and lower the bottom bracket. This does funny things to a bike's handling. (I've done this- 30mph speed wobbles are not fun, nor is grounding your pedals around every darn corner.)

Besides, he's talking about a 650B conversion, not 650C. There's a lot of difference.
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Old 10-14-12, 10:16 PM
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Originally Posted by Jeff Wills View Post
Swapping in a shorter fork will steepen the head angle and lower the bottom bracket. This does funny things to a bike's handling. (I've done this- 30mph speed wobbles are not fun, nor is grounding your pedals around every darn corner.)

Besides, he's talking about a 650B conversion, not 650C. There's a lot of difference.
Thanks for the replies. Actually it is 650C, I've already got the wheels. Just FYI, the bike is carbon fiber race recumbent. But all the same problems apply. Except the bottom bracket. (In this case bringing down the BB would be a good thing as it is currently over 30") A 650c fork is available as the bike used to be sold with 650c wheels. However, I have been warned that the change in head angle will make it twitchy, and the bike is already quick steering. I feel I can make some sort of extended bridge/drop-plate if necessary. I just wondered because, in a metal bike I would not question the strength. Shouldn't CF be of equal strength? Attached are pics of the bike and the rear brake.

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CA2.0 rear2.jpg (98.8 KB, 6 views)
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