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3 Easy Questions(7 posts)

3 Easy Questionslc21998
Jan 30, 2004 1:10 PM
1. How do I figure out what size/type of bottom bracket I need? (The bike is a Softride tt7.)

2. How do I measure whether I have a 1' or 1 1/8 steering tube?

3. Are Shimano 8 speed groups compatible with Shimano 9 speeds?

After having done nothing more than change a tube, I'm trying to get up the nerve to build up my own bike. Wish me luck.

Answers...Andy M-S
Jan 30, 2004 1:34 PM
1. It's almost certainly English threaded, but as for the spindle, the type and width will depend on the crank you're using.

2. If you have (or can borrow) a quill-type stem, measuring 22.2mm in diameter, it should fit snugly in the steerer (the extended portion of the fork). If it doesn't, you have a 1-1/8" steerer.

3. Some portions are compatible, some aren't. *Generally*, derailers and cranks (and brakes) are compatible, shifters and chain may not be. 8s shifters and chain will work on an otherwise 9s drivetrain to shift 8 cogs; but you will need 9s shifters (and chain) to run 9 cogs.

More questions? Ask away!
Ok, I will!lc21998
Jan 30, 2004 2:27 PM
1. So as long as the crank and bb are compatible, I don't have to worry about the width of the bb? Do I need to have the threads "chased" before I install the bb?

2. That's easy. Thanks

3. I read somewhere that if your cranks and rear derailer/cassette aren't compatible, you will end up with a misaligned chain. Does this make sense? I'm trying to build up this bike for not too much money. That means I'll be buying some used components and maybe taking some off a different bike. Would you advise a newbie mechanic to just stick with, for example, all Ultegra parts?

Thanks again for your help

Ok, I will!TimA
Jan 30, 2004 3:56 PM
For starters do some searching and you will find the answers to many of your questions. Park has a nice site:

This site has the Barnett's manual for you to read:

The width of the BB refers to the width of the bb shell on the frame. the spindle length should be set such that the middle of the crank lines up with the middle of the cassette.

I personally have never needed to chase a bb shell. If there is significant paint or if the bb won't go in easy it might need to be chased.

Compatibility is a bit confusing. If you use all Ultegra 9 speed triple or double (one or the other) you will be fine. You cannot use a 9 speed shifter with 8 speed cassette or vice versa.

The rear der is either triple or double and doesn't matter if it's 8 or 9. Beware rapid rise ders do not work with non rapid rise shifters.

Your crank is either triple or double (8 or 9 speed doesn't matter) and should match your rear der. If you use a road cassette use a road der, mtn cassette use a mtn der (not a hard and fast rule).

I think the rules for Dura-Ace change a bit, but I've never looked into it, since I can't afford any of it anyway.

Also as a general rule campy and shimano are not compatible.

Thanks - That's a great site. nmlc21998
Jan 31, 2004 10:23 PM
Ok, I will!Andy M-S
Jan 30, 2004 7:21 PM
Once you have the crank, that sort of dictates the BB width. For example, and 8-speed double 105sc crank needs a 107mm bottom bracket; an 8-speed Ultegra will want 113 (115 is fine). Campy Centaur wants 111 (or 115 if you have an oversized downtube). There are some other rules--many newer Shimano cranks use a splined BB; Campy (and some Stronglight) cranks use a square-taper BB with a slightly different taper from Shimano square-taper BBs.

Lots of details, but don't let them put you off. Ask specific questions here, and generally, you'll get good answers.

And don't be afraid to mix things up a little. Things should work out can even (with a bit of work) get Campy 10s shifters to work with Shimano 9s drivetrains...but that's another story.
Thanks for your help.lc21998
Jan 31, 2004 11:02 PM
I think I'll stick with a matched bb and crank to avoid problems.