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Thread: MTB BB & Cranks

  1. #1
    Retrogrouch in Training bostontrevor's Avatar
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    ArgH! So I have literally spent the last *2 hours* breaking apart my bottom bracket.

    As you may recall, I have a Bridgestone MB-2 FG/SS which I love a great deal. If you've really been paying attention, you'll recall that I bought it with cranks whose extractor threads are stripped. If you've been stalking me, you'll know that the arms periodically loosen and I've been periodically tightening knowing that it's going to all end badly.

    Well tonight it ended badly. I popped the head off the drive side crank arm bolt. The good news is the drive side crank slipped right off. The non-drive side...well, that's a whole different matter. See the first sentence in this post.

    Anyhow, the net result is that I have a bottom bracket (UN71, thanks) that has the shaft of a bolt sunk in the drive side spindle and a 110 bcd crankset that I really don't want to put back on a new bottom bracket.

    So... I'm looking for some advice here. Anyone got a 110 bcd bottom bracket and crank combo that won't run me too much money but will end me up with a standard mountain bike 52mm chainline. Bueller? Bueller? Bueller?

  2. #2
    Retrogrouch in Training bostontrevor's Avatar
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    Oh, and by got, I'm not saying you personally. I'm looking for favorite recommendations. Basically, I did some quick shopping around and all the cranks I saw were stupid expensive and/or 4-arm pattern (dammit! what is this crap!?). I'd rather not have to buy a new chainring too.

    Just tell me where I should be shopping.

  3. #3
    Retrogrouch in Training bostontrevor's Avatar
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    Alright, so I went back to the scene of the crime to survey the damage in the clear light of day. A few things became obvious to me:

    1. The driveside and non-driveside cranks, while cosmetically similar, weren't matched. This has nothing to do with the story but it surprised me that it took me so long to notice. Oops.
    2. The end of the bolt shaft, while buried about 1/2 cm down in the spindle had a ragged enough end that I could wedge the end of a needle nose pliers against it and spin the BB to back it out. Sweet!
    3. Despite what I had thought, I cleaned out the driveside extractor threads and found that they weren't bad at all. I can't say for sure, but they seem quite serviceable.


    So forget all of the above! I just need to swing by the LBS and pick up a 170mm NDS mountain crank. That's gonna be like $5 from the used bin. Oh, and I guess I need a new bolt too. Meanwhile it gave me a nice excuse to drill a drain hole in the BB shell and clean out the shell threads. Whoever assembled it last didn't use grease in the threads, I think.

  4. #4
    Perineal Pressurized dobber's Avatar
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    Just for future reference the BulletProof cranks with a 113mm (thick chainring) or 118mm (thinner chainring) bottom bracket will get you around 52mm on the chainline.

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