We know, there’s no such thing as a stupid question. But there are definitely some questions too embarrassing to ask your local shop or riding buddies. This is the first in a weekly installment where we get to the bottom of your questions – serious or otherwise.
Char asks – What the hell does BSA stand for?
In terms of the BSA we often see associated with bicycles, specifically bottom brackets, it originates from the Birmingham Small Arms company. Back in the day when manufacturing was fairly limited to a few large entities, the Birmingham Small Arms Company Limited started out with the manufacture of guns in 1861 and ended up branching out to bicycles in 1880. Bicycle parts soon followed in 1893. While we struggle today with standards for the type of bottom bracket used, back then there weren’t even standards for thread pitch and sizing. Eventually the threading that B.S.A. settled on for their bikes was accepted as B.S.C. or British Standard Cycle, which essentially was absorbed by ISO (International Organization for Standardization) sizing.
The short answer to your question is that when you see BSA in terms of a bottom bracket, it refers to a 68 or 73mm shell with 1.370/1.375″ x 24 TPI threads and a left hand thread on the drive side cup. These days, BSA, ISO, and English are used interchangeably to refer to what is now considered to be a standard threaded bottom bracket shell or bottom bracket.
Qwerty wonders – How do I convert an English Ultegra 6800 crank to fit a BB30 Frame?
In this case, you don’t do anything with the crank so much as change the bottom bracket or use an adapter. There are a number of options from threaded sleeves that are pressed into BB30 frames that English BB cups then thread into like this one from SRAM, to complete bottom bracket assemblies like the Praxis Works Conversion BB or BBInfinite that install into a BB30 bearing bore (without BB30 bearings) and are stepped down to fit the 24mm spindles used on Hollowtech II cranks like the Ultegra 6800. The third option is a simple bearing adapter like those from Wheels Manufacturing that sit inside the bearing of your BB30 bottom bracket and reduce the inner diameter and increase the width to fit the needs of the crank.
In my opinion the complete bottom bracket assemblies are the best option in terms of durability and creak-free operation, though the bearing adapters are probably the easiest to use from a home mechanic’s point of view.
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