Chainline & bottom bracket spindle length- Mtbr.com
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  1. #1
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    Chainline & bottom bracket spindle length

    I put a new Endless Bike Kick-A**-Cog on my MC 29er a little while ago and decided to measure the chainline since the new Cog is 1/4" thick and has the teeth centered in the width.

    The front chainline measurement is 47.5mm, and the rear is 51.5mm. I'd like to just stick a new $20 bottom bracket in there--a UN53 or something. The current bottom bracket is 68x110 (not the 68x116 on the Redline spec sheet), I pulled it out to make sure. So I'd like a spindle that is 3-4mm longer on the drive side.

    My question (finally) does Shimano center the spindle lengthwise with their square-taper cartridge bottom brackets or are they offset to one side or the other? Or both? Would a 68x113 be 3mm longer than a 68x110 on the drive side? Or only 1.5mm longer on the drive side?

    If it's centered I guess I need a 68x118, otherwise I could get my with something shorter.

    I know I could put a ring on the outside of the spider instead of the middle, but I have two good middle rings that I really don't want to have to reverse to mount on the outside (to get the recessed bolt holes to line up).

    Thanks for the help!

  2. #2
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    Bump!

    I'd also like to know the answer to this question that was posted a couple months back...

    Even though the particulars are a bit different in my case, I basically have the same question about which side(s) the extra spindle length shows up in.

    Thanks!

  3. #3
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    I called around and talked to a couple of bike mechanics and they both basically said that there is no standard method for splitting the extra spindle length between the drive and non-drive sides when you go to a longer spindle, other than it is *not* split evenly between the two sides. And the manufacturers don't supply that information on their spec sheets.

    I finally ended up at the LBS with a vernier calipers measuring the drive side of several bottom brackets. I got the spindle length I wanted but they only had it in one of those crappy Shimano half-plastic things. But I had to buy it there because they were great sports about letting me check the things out.

  4. #4
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    Might help, for future reference anyway. I went through a similar situation before finding the right BB for a square taper crank I was using.

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

    Brian

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