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bottom brackets(3 posts)

bottom bracketsPeterRider
May 15, 2002 3:37 PM

what is the difference between english and italian bottom brackets ? Are those the only 2 kinds or is there others ?

Also, what size of BB should I use on an old Trek5200 frame, year 1997, in case of a double setup and in case of a triple setup for Ultegra ?


re: bottom bracketsSpoke Wrench
May 15, 2002 4:19 PM
There's pretty much just the two in common use in the US today, but there used to be several others.

Bottom brackets are defined by the thread system (English or Italian) bottom bracket shell width, spindle length and the type of connection between the spindle and the crankarms.

A Trek 5200 is going to be English thread and have a 68mm bottom bracket shell. If you have one of the newer, splined Ultegra cranks, you have to use a Shimano road splined bottom bracket. A double needs a 109.5mm spindle, a triple takes a 118.5mm spindle.
Bottom brackets "standards"Calvin
May 16, 2002 4:28 AM
The common bottom bracket threading today is the ISO threading. It is also called English or BSC. The thread size is nominally 1.37-inch x 24 threads per inch. The drive side thread is a left-hand threading. The non-drive side is a right-hand threading. Your Trek is certainly this common threading.

Italian threading is 36mm x 24 tpi, and is right-hand threading on both sides.

There were other threading out there, see these at

The the issue of spindle length is more compliated. If you are using a modern Ultegra in the Octalink this is pretty much decided for you.