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Bottom bracket spacers

Posted: Sat Mar 16, 2013 1:01 pm
by AP81
Hi,

I recently bought a Deore BB51 bottom bracket and Deore crankset to replace an old square taper crankset. Bottom bracket shell is 68mm (measured with calipers). I've pulled this bike to pieces and am rebuilding it with some recycled and new parts. The existing crankset had the same ring set-up (44/32/22).

Anyway, for a 68mm shell the docs recommend 1 x 2.5mm spacer (non-drive side), and 1 x 2.5mm + 1 x 1.8mm + 1 x 0.7mm (drive side). After installing it all the big ring looks too far out. There is around 11mm chainstay clearance on both crank arms. I put the front derailleur back on and when stretched to full it doesn't seem like it can move that far over.

Is this just a case of removing some spacers on the drive side? In my opinion I could get away with no spacers on the non-drive side, and a single 2.5mm on the drive side, like the 73mm set-up.

Docs are here: http://techdocs.shimano.com/media/techdocs/content/cycle/SI/FC/SI-1L60A-001/SI-1L60A-003-ENG_v1_m56577569830674840.pdf

Re: Bottom bracket spacers

Posted: Sat Mar 16, 2013 1:58 pm
by takai
Spacer configuration for a 68mm BB is 2.5mm non drive, 5mm drive as you say. The crank will have lateral play if it is underspaced.

Have you tried backing off the limit screws on your derailleur? My SLX one came from Shimano with the limit screws quite heavily wound in, limiting travel.

Re: Bottom bracket spacers

Posted: Sat Mar 16, 2013 2:15 pm
by AP81
takai wrote:Spacer configuration for a 68mm BB is 2.5mm non drive, 5mm drive as you say. The crank will have lateral play if it is underspaced.

Have you tried backing off the limit screws on your derailleur? My SLX one came from Shimano with the limit screws quite heavily wound in, limiting travel.


I'll try and back them out completely. Failing this I'll just buy a Deore front derailleur. BB and crankset are Deore, so they'll match. Thanks.