Bottom Bracket specs, I need help
 

Hi folks,
I emailed a seller on ebay about a bb that was included in his auction. He messaged me back the following "Bottom bracket is 68mm x BSA 1.37" x 24T." What does this mean? Will it fit a late 80's Cannondale?

The info he sent is that the bottom bracket fits a 68 mm wide bottom bracket shell and is English threaded (1.37" diameter cups with 24 threads per inch). This is standard on most road bikes and certainly on all Cannondale road bikes. He didn't include the spindle length but if it's the correct bottom bracket for the crank that accompanies it you should be ok.

BTW, be aware that English bottom brackets have LEFT-HAND threads on the drive side (the side with the chainrings and chain) so the cup threads in counter-clockwise. The non-drive side cup has standard right hand threads.

As always, Sheldon Brown's pages cover this subject comprehensively. However, all road BBs are 68mm and this BSA thread form is the norm, your frame isn't Italian or French which are the other threadforms sometimes found. You don't say what Cannondale you have but assuming it is a road frame then all should fit. Easiest thing for peace of mind is to measure the width of the BB between the two faces. Some MTBs have a 73mm BB.

My road bike has a 70mm BB, but yeah, all C'dale road bikes have a 68mm.

OP, the seller left off the spindle length which is what you need to know to find out if you're going to get a good chain line with whatever crank you're going to be using.

I don't think even MTB's had 73 mm bb shells in the '80's.

No spindle length = no idea whether it is the right size or not. BTW, spindle length is related to the crankset you are using, rather than the brand of bicycle. Digital calipers, available for about $10 at Harbor Freight, are a must if you are going to do much work on bicycles.

Some items, it can be best to pay a little premium and just get at your LBS. Buying parts on the internet is best where you know exactly what you want. The hassle of getting an item that is not the right size makes it not worth it.

Yup, just not French or Italian thread .. if you don't have a clue
about what spindle length you need
It is a fool's errand you are on.

the guy may be dumping old parts on you.

visit your Local Bike Shop.. service after the sale..

NB different crankarm designs need different spindle lengths ,
So, bring the crankset you want to use , with you.

...except Cannondales that use BB30 bottom brackets. (But those were introduced long after the OP's bike was built.)

Right but the OP didn't have a clue about what he was getting and confusing him with terminology and technology from way after his bike was built seemed to serve no purpose.

I'm not sure of this but the OP seemed to imply that the bb in question was part of a purchase that included the crank. If so, I trust the bb spindle length matches the accompanying crank so I didn't get into that either.

+1 to wrk101's comment that buying from the internet is only for those who know exactly what they need. It's an expensive and frustrating trap for the unknowing.

Thank everyone for the reply's. I love Sheldon but I prefer the combined expertise of the the BF group.

Education is not without some cost.

I don't remember the 80s, (some days I can't remember my name) but yes my old Cannondale M600 does have a 68mm BB. So when did 73mm start?

After the early '90's is all I know. I had a '92 or '93 (I bought it NOS so I'm not certain of the model year) Trek 7000 aluminum frame MTB and it also had a 68 mm bb shell.

Are you....serious? You'd sooner listen to US YAHOOs on the web than you would SHELDON BROWN? When he was still around (RIP), it would be easy to say that he forgot more than we all KNOW!


Let me illustrate:

--------> GOD;










-------->Sheldon
-------->Julien DeVreise, Rick Parker











--------->the rest of us that know what we're doing.

68mm & 73mm co-exist quiet happily together still for MTB's, I have a 1997 GT Bravado which is 73mm, and a 2011 Tomac Silver which is 68mm, what has changed, is now the spindle is part of the crank (external BB), not the BB, this is a fixed length, so spacers are used on the BB to make all MTB BB's 73mm regardless of if the physical shell is 68mm or 73mm. Road is 68mm, and BB30 and other standards are different still