Two-piece crank
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Thread: Two-piece crank

  1. #1
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    Two-piece crank

    Gentlefolk;

    One of the upgrades I got when I got my bike was a "2 piece crank" which the LBS mgr. sd. was way-cool in this pricerange bike. We got onto other topics, and I never got around to asking why a two-piece crank is better than a one-piece...or, I presume inferior to a three-piece....

    I generally subscribe to the possibly apocraphal Boeing engineer who said that two-engine planes were safer across the Atlantic than four-engine planes because there were fewer parts to malfunction.

    As a crank just goes round and round, Im mystified why one needs this done in one piece, two pieces or three pieces...

    Thx!

    Don

  2. #2
    Cycling induced anoesis
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    http://www.sheldonbrown.com/gloss_tp-z.html

    Scroll down to two piece cranks and follow the links from there. BTW, that site is an excellent resource for these types of questions.

    The following link relates more to how the last generation of cranksets/ BB's compare to current, but (IMO) it's a pretty good answer to the question "which is better":

    http://answers.yahoo.com/question/in...3182338AAfFzkh

  3. #3
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    Ahh...thanks, PJ...clearly this is covering issues beyond my level at this point, but your resources are great!

    Now, if I could figure out this "pie" thing....

    I thought I knew how to ride a bike....

    Now, next step is to see if the LBS offers bike maintenance courses. I figure that, for some reason, my motorcycle chain lube won't be appropriate for a bicycle. I am basing that on the experience that I can't possibly have one item in my life that could satisfactorally fill two requriements.

  4. #4
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    Quote Originally Posted by Cadent
    Ahh...thanks, PJ...clearly this is covering issues beyond my level at this point, but your resources are great!

    Now, if I could figure out this "pie" thing....

    I thought I knew how to ride a bike....

    Now, next step is to see if the LBS offers bike maintenance courses. I figure that, for some reason, my motorcycle chain lube won't be appropriate for a bicycle. I am basing that on the experience that I can't possibly have one item in my life that could satisfactorally fill two requriements.
    How does your wife feel about that?
    Other countries need to stop hatin' or we'll unfriend them. - Christine

    Apparently I left my reading comprehension glasses in my ass. - DrRoebuck

    Still, it felt great and I felt like I was sitting on some kind of vibrator -Touch0Gray

  5. #5
    old school drop out
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    Hmmm... I'm not sure that the "answers" site is terribly accurate.

    "The 2-pc cranks developed as a complement to newer bottom brackets that were aiming to be more durable..."

    The 2-pc crank has been around since about 1980, and the first (modern) external bearings since the mid-90s. External bearings are possible because of 2-pc cranks, but were certainly not "developed as a complement" to them.

    So far, the newer bottom brackets (called "external bearing") seem to last longer, so it appears to be a good thing...

    I'm not sure that this is true. From what I've seen, experienced, and heard, external bearings may last as long as cartridge bearings but not longer. Older style cup and cone bottom brackets will outlast either.

    One thing that I like about the newer external bottom brackets/2-pc crank systems is that there is less waste when you need to replace the bottom bracket.

    This is partially true. Compared to cartridge bottom brackets this is true. Compared to cup and cone this is completely false.


    The "supposed" benefits are weight savings and increased stiffness. The actual benefit is that they are a little easier to install, and they limits the number of components that manufactures, shops and consumers need to deal with (no more, "what size BB do I need?". Their introduction has more to do with marketing than anything - Shimano introduced their 2-pc crankset almost immediately after the US Patent on the 2-pc crank expired.

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