New Crank, Old Road bike...- Mtbr.com
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  1. #1
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    New Crank, Old Road bike...

    Hey all I know its MTBR and all that but a quick road bike Q for those who know.

    Backstory: I've got an old Peugeot road bike that I use primarily as a commuter. Just took off the crappy 53-42 double crankset that was on it when I bought, replaced with FSA Vero compact double ( http://www.fullspeedahead.com/products/37/Vero-Compact ). FD shifts it okay (don't shift the front all that often anyhow) but gets funky when crosschained (especially on the big-big combo). I know the easy answer is to avoid crosschaining as you generally should anyway (cough cough andy schleck). I do and it certainly will be functional, I'm just scheming ways to fix the non problem anyways. After some pretty good measuring (using Sheldon's method detailed here: http://www.sheldonbrown.com/bbsize.html#chainline ) I've determined that the centerline of my front drivetrain is a good 1/2 inch farther from the frame centerline than my rear drivetrain.

    Cut to the chase: How do I remedy this 1/2 inch difference in chainline? New BB with shorter spindle length? I'm not sure what's on there but its probably old and shitty, and possibly odd sized since the bike is pushing 30 years old.

    Also It's got 27 inchers with a 6 speed freewheel on it that I plan on replacing with a 700c 8 speed or so. Will switching from 6 spd freewheel to 8 spd cassette help any or would I still need a new BB?

  2. #2
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    Reputation: mitzikatzi's Avatar
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    Yes a new BB with a shorter spindle length will move your chain line inwards.
    Just be careful that the chainrings will still clear the chain stays.
    Duct tape iz like teh Force. It has a Lite side and a Dark side and it holdz the Universe together.

  3. #3
    Never trust a fart
    Reputation: frdfandc's Avatar
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    The older bikes used a narrower hub spacing, 126mm vs. the modern 130mm. To do the rear wheel, you will need to respace the drop outs if the bike is steel. You can cold set them by gently, but firmly pulling the dropouts apart the 4-5 mm required to install an 8sp capable wheel.

    Then you can install an 8 speed cassette. It can help with the chain line a little bit, but if you didn't replace the BB with the crank install, you will need to match the BB to the crank.

  4. #4
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    Reputation: bbense's Avatar
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    It's likely your old BB has the wrong taper for that crank set and more than likely it has the wrong offset as well.

    However, Old Peugot means you might have a French Threaded BB which is retro bike hell.

    http://www.sheldonbrown.com/velos.html

    The JIS taper axle with the existing cups would be the cheapest solution.

    - Booker C. Bense

  5. #5
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    Thanks for the quick replies everyone. Wasn't aware that there were different tapers available. FWIW it seems to be seated just fine, the spindle is just too damn long. I'll pull the bottom bracket and replace it I suppose since that should be fairly cheap. It's not a super old Peugeot (I believe it's an '83) so hopefully the sizing isn't too funky. I already had to deal with replacing a funky 21.1 mm stem (actually had to machine one down from 22.2) though so who knows...

  6. #6
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    Quote Originally Posted by birdman829
    Thanks for the quick replies everyone. Wasn't aware that there were different tapers available. FWIW it seems to be seated just fine, the spindle is just too damn long. I'll pull the bottom bracket and replace it I suppose since that should be fairly cheap. It's not a super old Peugeot (I believe it's an '83) so hopefully the sizing isn't too funky. I already had to deal with replacing a funky 21.1 mm stem (actually had to machine one down from 22.2) though so who knows...
    Everything I know about this stuff is on Sheldon's Site somewhere, keep digging.

    - Booker C. Bense

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