Crank and BB for '96 GT Budget Build?

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lucky53s

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Joined Dec 23, 2006

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78 Posts

Discussion starter · #1 · Aug 25, 2014

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I'm going to have to call in some experts here. I have tried researching and I'm just missing one of the pieces somewhere.

I can get my hands on an old GT frame for next to nothing and was doing a bit of researching to see if i wanted to build it up just for fun. I'm a little hung up on the BB/crankset. The original was a Shimano BB-CT91, 122.5 mm spindle (according to Bikepedia). From what I've read if I want to replace it I should pick out my crank first, then determine what BB to use. So, if I want to use this crank (SRAM S150 10-Speed Road Crankset 50/34T 172.5mm Black - Cranksets - Road) what BB should I get? I know it needs to be Octalink, sq taper, etc according to which crank I pick. But how do I get the right spindle length? Truvativ has a bunch in 73mm anywhere from 110 to 122 mm. Just don't know which to order.

 

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hatake

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Joined Jul 16, 2004

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1,194 Posts

#2 · Aug 26, 2014

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GT back then is typically 73 mm BB shell (just measure it) if I recall. And your cranks use Powerspline, which is neither Octalink nor square taper. You must use Powerspline BB, which is Truvative and 68 mm specific (road). I don't see Truvativ 73 mm BB... I read only Hope makes Powerspline bb for 73 mm but not sure. You maybe able to shim it but I wouldn't do that if I were you. So...I'm not sure if your decision can be easily implementable.

Why not getting some old LX or XT square taper cranks and put 40t on them? Or go with full modern and install a set of external BB and cranksets of your choice? I had 95 Zaskar with Shimano m960 for several years. I know it's not a period correct choice, but I don't subscribe to VRC craps on bikes that are being ridden

 

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lucky53s

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Joined Dec 23, 2006

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Discussion starter · #3 · Aug 26, 2014

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The question is kind of pointless now because I went to look at the frame and it was junk. But the task will still need to be tackled when I find another frame.

You are right, it was 73mm, I left that out when talking about the original BB. I could not care less about keeping the bike with correct period parts. It would have been to ride, not some type of rebuild with original parts. I found Powerspline BBs but they were varying lengths from 103 to 125mm. My question was how do you know which to order when you are getting everything online?