Subject: Re: Bottom brackets Posted by: Al on November 14, 2005 at 04:35:00: In Reply to: Re: Bottom bracket posted by Rob on November 13, 2005 at 20:11:35:

Message: >>Hi does anyone know if bottom brackets are a standard size or if there are different size and if theres is different sizes how do u find out the size of it. >>Thanks >They come in all different sizes for all different cranks. There are also a few that even have italian threads. I think first you should measure your bottom bracket shell; second, check the model of your crank to see what bottom bracket it uses; third, you could measure your old bottom bracket (there's often clue from the bottom bracket markings. >Cheers MOST frames from Italian frame makers use Italian threaded bottom brackets (70mm wide BB shell -- right hand thread on BOTH cups). Some of the less expensive Bianchis are made in Asia, so they may have English threaded bottom bracket shells. Masi is another "Italian" marque (made in the US for the past couple of decades) which may be using English bottom brackets; so, the name is NOT an indicator. Almost all other ROAD frames which you will encounter will have bottom brackets which use English threaded bottom brackets (68mm wide BB shell -- right hand thread on non-drive side & left hand thread on the drive side). Some French frames switched over to using SWISS threading (left hand thread on the drive side ... same thread pitch as French threaded bottom brackets) in the 80s -- close enough to English that English threaded bottom brackets can be used. Earlier French frames had French threaded bottom brackets (68mm wide shell -- right hand thread for both sides). Most mountain bike frames use English threaded bottom brackets. Generally dictated by the frame material or vintage, the width of the BB shell is either 68mm or 73mm. Early/(all?) Colnago mountain bike frames use the same 70mm wide Italian threaded BB shell as on their road bikes. Old/new "balloon" tire bikes generally use an American threaded BB (larger diameter) -- there are adapters to allow an English BB to be adapted. Some frame builders have recently adopted a larger diameter (the actual size is unknown to me) -- again, an adapter is available to allow a "normal" bottom bracket installation.