uneven BB spindle, offset cranks?- Mtbr.com
Results 1 to 9 of 9
  1. #1
    viva la v-brakes!
    Reputation: FishMan473's Avatar
    Join Date
    Jan 2003
    Posts
    2,135

    uneven BB spindle, offset cranks?

    I recently noticed that my non-drive side crank is farther away from my chainstays then my drive side crank. I took it apart and found that this was due to the bottom bracket spindle being longer on the non-drive side.

    What's up with that? Is that normal? My cranks (Kooka) are just some geared cranks that I have only one chain ring on. Are geared cranks usually offset like this? If so, why? Also, my ring is mounted in the outermost, 'big ring' position. This seems odd. Perhaps the BB spindle is too narrow overall? I like the low q-factor though.

    My BB is a 68x110 UN52 in a Salsa Ala Carte with the afore mentioned Kooka cranks. Is something wrong with my set up? This seems weird.
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
    I have a car. I made a choice. I ride my bike.

  2. #2
    viva la v-brakes!
    Reputation: FishMan473's Avatar
    Join Date
    Jan 2003
    Posts
    2,135
    Hmm, no replies here, is the drivetrain forum a better place for this?
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
    I have a car. I made a choice. I ride my bike.

  3. #3
    Fight the Kakistocracy!
    Reputation: veelz's Avatar
    Join Date
    Jan 2004
    Posts
    259

    Just put one in like this last night

    Quote Originally Posted by FishMan473
    Hmm, no replies here, is the drivetrain forum a better place for this?
    I was watching your thread for an answer.

    Anyone, Beuller, Beuller, Beuller?
    veelz

    Gravity, not just a good idea, it's a law.
    The only one consistently and constantly applied, no exceptions.

  4. #4
    Flyin Canine
    Reputation: shanedawg's Avatar
    Join Date
    Jan 2004
    Posts
    2,272
    seems like you just would need to get a 68x108 or something and it would fix it. I think I have seen this issue before but I can honestly say I don't understand why it happens. I mean if the bb is desgined for a 68 it should stick out the same on both sides right? I don't know if this helps but I wanted you to know at least people where scratching their collective heads pondering the problem.

  5. #5
    mtbr member
    Reputation: bidaci's Avatar
    Join Date
    Nov 2005
    Posts
    134
    Quote Originally Posted by FishMan473
    I recently noticed that my non-drive side crank is farther away from my chainstays then my drive side crank. I took it apart and found that this was due to the bottom bracket spindle being longer on the non-drive side.

    What's up with that? Is that normal? My cranks (Kooka) are just some geared cranks that I have only one chain ring on. Are geared cranks usually offset like this? If so, why? Also, my ring is mounted in the outermost, 'big ring' position. This seems odd. Perhaps the BB spindle is too narrow overall? I like the low q-factor though.

    My BB is a 68x110 UN52 in a Salsa Ala Carte with the afore mentioned Kooka cranks. Is something wrong with my set up? This seems weird.
    Wouldn't a 73mm with a spacer offset the BB by about 5mm. Also, is it possible if the crank took a big hit to shift the assembly in the bearings? Just some random thoughts!

  6. #6
    mtbr member
    Reputation: MudInMyEars's Avatar
    Join Date
    Apr 2005
    Posts
    246
    Quote Originally Posted by shanedawg
    seems like you just would need to get a 68x108 or something and it would fix it. I think I have seen this issue before but I can honestly say I don't understand why it happens. I mean if the bb is desgined for a 68 it should stick out the same on both sides right? I don't know if this helps but I wanted you to know at least people where scratching their collective heads pondering the problem.
    I don't know if this is of any use, but I recently replaced an old cup and ball bottom bracket with a Shimano sealed bearing unit. The original different offsets for the drive/non-drive side were different. I used a web page from Harris Cyclery (http://sheldonbrown.com/bbsize.html) which has a database of spindles and suggested equivalents to replace with non-offset spindles. It worked for me, although I did have to use some bottom brackets shims to get the chainline just right since I couldn't find the exact lenght recommended.

    I hope this helps.

  7. #7
    French for "Suck"
    Reputation: Aeroplane's Avatar
    Join Date
    Sep 2005
    Posts
    140
    symmetrical vs. Assymetrical BB's: I've heard of them before. Basically, it helps to know which one you have when calculating your chainline. I always thought that they generally stuck out more on the drive side though, to account for the bulk of a granny ring and all that.

    If it were a cup and cone BB, I would just say take the spindle out and flip it. Done deal. I did it on one of my road fixes to give me a better chainline. But this is a Shimano cartridge. A curious situation indeed.

    If you want to make each end stick out the same, measure the difference between how much each side of the spindle sticks out. Use a spacer on the fixed side that is half of that value. Or, just buy a new BB that has a symmetrical spindle.

  8. #8
    mtbr member
    Reputation: Mudflaps's Avatar
    Join Date
    Sep 2005
    Posts
    1,150
    After more than 25 years in the business, I have seen almost every possible configuration of offset on BBs. Bottom line, if the chainline works, DON'T SWEAT IT. Any offset can work as long as you get adequate clearance on the drive side and the chainline is straight.

    I will caution those with cup & cone BBs to avoid flipping the spindle due to the danger of ruining a functional chainline. I have had to install a spindle "backwards" before to achieve a good chainline since there are very few cup & cone spindles available any more.

    Notice that the recurring theme here is "chainline". Little else matters.
    Now, repeat afer me; " It's all about the chainline"

  9. #9
    bob
    bob is offline
    mtbr member
    Reputation: bob's Avatar
    Join Date
    Jan 2004
    Posts
    490

    I had the same problem

    I had the same problem with an Ellsworth frame and a Truvativ set up. I had used the same cranks and BB on another bike and never noticed anything. On the Ellsworth the crank on the drive side came much closer to the chainstay than the non-drive side. Scary close but it worked just fine.

Members who have read this thread: 2

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

THE SITE

ABOUT MTBR

VISIT US AT

© Copyright 2019 VerticalScope Inc. All rights reserved.