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  1. #1
    mtbr member
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    Sinz ISIS cranks -- what BB axle length?

    After reading a few threads here, I bought a 135mm Sinz ISIS crank from eBay for my son's 20" bike. It currently has ~156mm cranks on it which are way too long, and I'm hoping the 135mm's are short enough.

    The current cranks have a ~47mm chainline. I need to buy a BB, but can't find anything on the net that indicates what length I need (searching mtbr, only three posts appear for "sinz isis", and only one of those has the BB they used).

    It looks like 68x113mm is the most popularly available size, but I have seen 68x108mm as well as 115mm+.

    I'd like to have a BB ready to go when the cranks arrive. Anyone suggest the right length? It has a 7spd'ish freewheel on it now, but I'll be replacing everything with the cast off parts from my bikes (XT/x.9'ish) so would like something that'll shift cleanly.

  2. #2
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    I have built up a few bike with the same cranks. I used the 68x113. Anything shorter and the arms might hit the frame. I have also used a 68x118 with a chain guide on my full suspension frames.
    Hope that helps.

  3. #3
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    Thanks.

    Cranks arrived today, quicker than I expected. I haven't had any luck finding any shop within a reasonable, and even unreasonable, distance with a BB in stock, so I'll be waiting on mailorder.

  4. #4
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    68x113 seems like the way to go.
    You'll find some excellent info in this thread:
    "Some work to do on my son's Hot Rock 20"

    (Sorry I can't post the link as I have less than 10 posts.)

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