Re: Older Tetra Pro and External BB question: Bikefanclub.com

Hi! I think Sobrien's response is very accurate. Chainring clearance is only dependent on when the frame was made and what clearance measurement tool we were using at the time. Our tool looks like a BB with a short crank arm on the drive side only. The arm is wrapped with carbon fiber, to which we add more material when the tolerance changes on new parts. Then we file down the fiber to exactly the clearance needed, and in the case of Campy UT, the tool must pass the chainstay without contact before the frame is shipped because, as Sobrien aptly pointed out, there is no room for spacers on that spindle. If you have a frame that was made before the UT stuff came out, we were using a different version of the clearance tool, so adding a zero-tolerance BB to your build will likely mean you have to send it in to us, and let us trim the stay for you, according to the updated measurement tool. It sometimes requires only 1mm of trim- or up to 4mm- especially if you are switching to a new English-threaded BB shell, which takes out 1-2mm right there... CalfeeJames, Repairs Guru.

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