Question on BB Spindle Length

[Sean B.]

I'm replacing the BB on my Homer. Went into a shop asked for a 68 x 110 BB (the box was labeled as such), but when I got home I noticed the actual part was labeled as 68 x 110.5. Can a .5 variance cause any issues with the chainline? 

[Victor Hanson]

no same width.   There are 1/2mm bottom bracket washers.

On Wed, Apr 30, 2025 at 2:39 PM Sean B. <seanc...@gmail.com> wrote:

I'm replacing the BB on my Homer. Went into a shop asked for a 68 x 110 BB (the box was labeled as such), but when I got home I noticed the actual part was labeled as 68 x 110.5. Can a .5 variance cause any issues with the chainline? 

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VIctor R. Hanson

Gen Mgr

Schmier Industrial Properties

o:  510-652-0800

c:  510-207-8593

[Sean Bowers]

Are you saying there’s a washer that can be removed?

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[Steve]

Sean, my  $0.02  -- If the spindle is indeed 110.5 mm in length it WILL shift your chainline outboard by 0.5 mm.  To my mind that's negligible and I would not anticipate a discernible effect of shifting performance. At the most, you might need to tweak the A/B screws (hi/low) on the derailleur. 

Steve in AVL

[Bill Lindsay]

The dimension that determines your chainline has to do with the spindle stick-out relative to the fixed cup.  Hold the new unit up to the old unit with the drive side ends facing each other.  Are they about the same length?  Then the chain line will be about the same.  If they are not the same length in the drive side stickout, then that tells you how much your chainline will likely change.  

Now, in the real world, the two spindle tapers may not be identical in geometry so the same crank may push on farther or not as far onto one versus the other, but let's just pretend that all JIS tape BB spindles are close enough to identical that we can ignore that part.  

So, maybe the extra 0.5mm is on the drive side.  Maybe it's on the non-drive-side.  Maybe it's 0.25mm on each end, or some other distribution.  At the end of the day, the impact will likely be small.  If you are the mechanic, you need to apply your mechanic's judgment.  

Bill Lindsay

El Cerrito, CA

[Steve]

Good points Bill - I didn't consider that the 110.5 spindle might be asymmetrical. 

Also, if it is symmetrical, it will only push the drive side out 0.25mm (duh).  Sean, if you decide to use the 110.5 let us know the results. It's always good to keep learning and this forum is a great place to do so.

Steve in AVL

[Ben Miller]

This is nothing to lose sleep over. As Bill already pointed out, the most this could be off by is .5 mm and more likely closer to .25 mm. That's 10 thou. Or 250 microns. Or a few human hairs. Or a couple of sheets of paper. Just ride my friend.