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Shimano BB spindle length(s) question(6 posts)

Shimano BB spindle length(s) questionDale Brigham
Apr 14, 2003 8:03 AM
Anybody have a Sutherland's manual or a couple of Shimano bottom brackets and a measuring caliper/micrometer handy? I'm looking to replace the Shimano UN-72 BB, 107 mm spindle length (68 mm BB shell) on my Steelman with one that is a bit wider, since my LH Ritchey Logic crank arm is very close to the LH chainstay, and on the RH (drive) side, the chainrings are similarly uncomfortably close to the RH chainstay.

I'm thinking of trying a 110 mm spindle UN-72, but am not sure if the extra 3 mm is mainly (or all) on the drive side (which, if so, would not help me).

Do any of you shop guys/gals have access to UN-72 BBs in 107 and 110 mm spindle lengths that you could measure on both sides (i.e., how far the spindle extends from the cartridge cups) to answer my question? Also, this info might be in Sutherlands or another shop manual. I have found nothing helpful at Shimano's website (not surprised), but maybe I missed something there (not unusual for me).

Any help or advice is greatly appreciated.

Thanks for listening!

correct chainline...C-40
Apr 14, 2003 9:58 AM
What you should strive for is the correct chainline. The standard is 43.5mm from the center of the BB shell to the midpoint between the chainrings.

The extra length on double BB spindles should be symmetrical.

Check your chainline first, then pick a spindle length, or cantact Ritchey and ask for the correct length. Why guess?
More basic concern than optimal chainline...Dale Brigham
Apr 14, 2003 11:04 AM

I appreciate your response, which is both concise and entirely accurate. Unfortunately, having an optimal chainline is currently playing second fiddle to my main concern, which is simply trying to keep the inner chainring and the LH crank arm from colliding with and/or chewing up the chain stays. Yes, they are both THAT close (approx. 1-2 mm).

I've had this same little problem (overly close chainstay clearances) with another Sugino crankset (the Ritchey Logic road cranks I have on the Steelman were made by Sugino) I have on my old Kona Jake the Snake. It seems to me that Sugino crank arms seat down just a tad farther on the spindle taper than do Shimano crank arms.

I went with the longer (110 mm) spindle on the Jake to give the inner chainring a bit of breathing room away from the chainstays. I might just try a 110 mm UN-72 on the Steelman to see how it shakes out. Your note that the extra 3 mm (=110-107) should be equally distributed ("symmetrical") on both sides (1.5 mm each) is good news to me. I need a bit more space on both sides, I think.

Again, many thanks for your reply, C-40.

something else seems wrong...C-40
Apr 14, 2003 12:15 PM
Never heard of a properly designed frame than would not accept any brand of crank with the spindle length that is standard for the crankset.

Any brand of crank that has the correct chainline will fit the same. There is something wrong with the frame if a standard crank and BB combo does not fit right.
Why guessRusty Coggs
Apr 14, 2003 1:41 PM
The recommended spindle length for the Ritchey double is 107. Depending on chainstay design,that may cause clearances to be too close for some peoples liking. The extra 3mm(1.5mm per side) won't totally hose the chainline,and chainlines are often manipulated either side of ideal to suiit specific pruposes.I also do similar things that are not 'by to the book'. The sun still comes up in the east every day.
As long as I don't make the heavens fall...Dale Brigham
Apr 14, 2003 5:28 PM
... I may go ahead and try a 110 mm spindle BB. If I find one on the web for $20 or so, even with shipping, it's only a $25 experiment.

I concur that the 107 is the recommended spindle length for the Ritchey, and that's the one Brent Steelman installed on the frame before he shipped it to me. I'm just getting a bit nervous looking at the small chainstay and chainring clearances. If something else catches my eye, maybe I'll just ignore it!

Thanks for the good advice, RC!