Bicycle Mechanics - Crank / BB Tools
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06-10-09, 10:13 AM
I'm looking at replacing my crank soon and may swap out the BB as well. From what I've read here, torque isn't that big a deal for the crank arms, but what about the BB? I could go with a spanner (http://www.amazon.com/Park-Tool-BBT-9-Hollowtech-brackets/dp/B000C12BMW/ref=sr_1_5?ie=UTF8&s=sporting-goods&qid=1244649798&sr=8-5), but how can I verify the torque? The other option is to use a wrench attachment (http://www.amazon.com/Park-Tool-removing-16-notch-external/dp/B000VX5FJ2/ref=pd_sbs_sg_1) and verify the torque that way. The BB I currently have is a FSA MegaExo and I'll probably be going to a Hollowtech II. What is the better solution?
06-10-09, 10:38 AM
Torque on a BB is not hugely specific, IIRC - you can judge it pretty easily with a wrench. (BBs are highly unlikely to come unthreaded regardless thanks to backwards threading on the left side.) Approximately 30 pound-feet should do it. Remember to use lots and lots and lots of grease.
The things you want to look for in a BB are as follows:
-Width. Some BBs are wider than others for various reasons. Most road bikes are (AFAIK) 68mm.
-Threading. The two main varieties are Italian (right hand threading on both sides) and English (left hand threading on left side).
- Splines. There's four main types today - Campagnolo square, standard square, ISIS, and Octalink 2 (Octalink 1 is outdated and best avoided.) The latter 3 BBs look very similar, but are NOT compatible. If you want a Shimano crank, you need a Shimano BB , and vice versa.
From what I've read here, torque isn't that big a deal for the crank arms,
You read that here? :eek: Well don't believe it. Failure to torque the arms sufficiently is (or was) a major killer of cranksets. The problem is a lot worse with tapered BBs, but affects splined BBs too. Proper torquing of the crank arm bolts/nuts is arguably the most critical application on the typical bike. Right after it is the BB, but again, that depends on the type of BB.
For a HollowTech II, most of these issues go away.
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