Bicycle Mechanics - Help- Diameter of bottombracket?

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Frankie15
08-02-03, 03:59 PM
I recently purchased a used Colnago mountain frame. When I removed the bottom bracket I found it to be Italilan threads. I attempted to insert a new bottom bracket (English threads)which doesn't work (obviously). The diameter of the bottombracket (hole the bottom bracket goes into), is larger than the english model. Is this how it is supposed to be? Not ony different threading, but different diameter? So if I order the correct size Italian bb it will fit my frame? Meaning the Italian bb is slightly larger in diameter? How about if I wanted to use a splined bb? Do they come in different diameters (Italian threaded)?
Thanks for any info. Please e-mail me directly.
FSpence687@aol.com

John E
08-02-03, 06:15 PM
Italian standard = 36mm x 24 TPI, RH thread on both sides.
English/ISO = 1.375" = 35mm x 24 TPI, LH thread on the fixed cup.
Both are readily available.
Don't ask my how the Italians ended up with a metric diameter and British threaed pitch!
Rev.Chuck
08-02-03, 10:04 PM
Shimano offers the splined BB in Italian spec