I bought a Raleigh gran sport frame and forks, which was originally fitted with a gran sport BB. When I got it it was fitted with a cheap FAG ISO BB, with an axle length of 119mm. To this I fitted a 7400 dura ace chainset, and the resulting chain line is about perfect. But I'd like to fit a better quality BB, preferably campy. But all of the ones I see on eBay and such seem to be 112mm axle. Is all of the difference between 120 and 112 seen on the drive side? Or is it split 50 50? There is about 10mm of clearance between stay and chain ring, but I don't want to mess up a chain line that works well. Did campy do any 120mm Square taper BBs?
tolerance on BB size
- Thread starter GazK
- Start date
GazK":2c3y4597 said:
Yes agreed Campag & Shimano have different tapers. Am surprised it did not work loose or creak like crazy, 10mm is a biggish gap (my bike with Campag double 39T is 5mm or so, what size ring are you running and where are looking to assess the chain-line?
I checked with Sheldon before I did it, and his advice is that its not generally a problem. I'll try and get a pic of the back side of the chainset to see if there is a gap to the end of the taper... watch this space. Chainrings are 42/52, chain line is eyeballed from the back of the bike when in middle rear sprocket.
OK here we go - I thought I had checked for this exact issue when I fitted the chainset, and sure enough there's taper to spare:
And here is the chainline, 4th sprocket of 6 onto inner front:
Returning to my original question, would a longer axle be spread 50/50 or all on the drive side?
And here is the chainline, 4th sprocket of 6 onto inner front:
Returning to my original question, would a longer axle be spread 50/50 or all on the drive side?
ScillySuffolk
Retro Guru
Dura-Ace 7400 requires a 112mm BB anyway, so no problem.
EDIT
To answer your original question: a modern BB will be 50/50.
EDIT
To answer your original question: a modern BB will be 50/50.
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