determining if a bb is good for 68mm or 73mm

rocketboy2000 · Jul 16, 2013

is there a simple way to determine if a bb will work for a 68mm or 73mm.

i'm wondering if this will fit my 68mm bottom on my brodie expresso:

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 1243227019

should i just avoid 68/73mm bb's for my bike?

thanks in advance.

Elysarian · Jul 16, 2013

A 73mm will go in a 68mm shell but it'll hang over on the non-drive side quite a bit (by an extra 5mm), not a massive problem just looks naff and can cause issues with sensitive knees.

rocketboy2000 · Jul 16, 2013

thanks elysarian, that's what I needed to know.

a quick measurement and addition of the 5mm to the non-drive side on my bike puts it damn close to the crank arm. i'll stick with looking for a 68mm.

FluffyChicken · Jul 16, 2013

That would have worked fine in 68 or 73.
68 just means you need to centre it properly. Thought they had lockrings on them as well.
With other 73's on 68 like shimano you just put a 2.5mm spacer on the drive side between the stop-lip and frame

cyclotoine · Jul 16, 2013

All syncros BBs were the same and could fit 73 or 68. The one in the ebay ad in the OP is missing the lockrings, there should be one on each side. This was actually a great feature which means you could adjust your chainline slightly in 68mm shells.

rocketboy2000 · Jul 17, 2013

ah, ok... i'm learning much here. that makes total sense to me that bb's without lips on the cups can be used either way. and that they need lockrings. bb's with lips on the cups need spacers if they are going in something smaller.

thanks again.

cyclotoine · Jul 17, 2013

rocketboy2000":31r1jn87 said:
ah, ok... i'm learning much here. that makes total sense to me that bb's without lips on the cups can be used either way. and that they need lockrings. bb's with lips on the cups need spacers if they are going in something smaller.

thanks again.

There were later versions that may not have had lock rings, but I think the one in the auction is a lock ring model.

determining if a bb is good for 68mm or 73mm

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