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Thread: upgrade crank

  1. #1
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    upgrade crank

    I want to put ultegra 6700 series cranks on my 2009 Trek 1.5, is this possible and if it is what would i need to do it. I know it is a little overkill but i like the bike.

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    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by dain View Post
    I want to put ultegra 6700 series cranks on my 2009 Trek 1.5, is this possible and if it is what would i need to do it. I know it is a little overkill but i like the bike.
    You'll need tools to take the old crank off. If it's a conventional BB you'll need a crank extractor, some Allen wrenches to remove the crank and something to remove the BB. If it's a external BB, you'll need the same tools as you do for installation...an Allen wrench and a BB tool. You could even use the same BB.
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    if i have the square BB can i change to the external BB or would it matter. By the way i will probably have a real bike mechanic do it even though i am a machinist and have a very good mechanical backround.

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    coprolite fietsbob's Avatar
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    strip down the frame entirely, since square taper and external BB have nothing in common,

    except they thread into the same frame threads.
    then you are looking at 2 sets of tools to buy, one to remove, the other to install,

    making the shop service labor rate a wash, unless you want to get the tools anyway..

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    maybe i will try it, i have the park tool website to help on tork setting, it cant be that bad.

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    Quote Originally Posted by dain View Post
    if i have the square BB can i change to the external BB or would it matter. By the way i will probably have a real bike mechanic do it even though i am a machinist and have a very good mechanical backround.
    I wouldn't have a "real" mechanic do it or expect him to get it right even though I'm a professional computer guy who traditionally wouldn't be trusted with a screw driver.

    There's _very_ little you need to know.

    1. Bottom bracket threads vary, although the vast majority are British / ISO at 1.370 or 1.375" x 24 threads per inch. You need to get the correct part. You also need to note the non-drive side cup thread direction which is left-handled (counter-clock-wise to tighten).

    2. External bearing bottom brackets depend on the shell end faces being square. Quality frames seem to come machined that way. If it's shiny metal and not paint it was faced. In the (unlikely?) event you still have paint there you might take it to a shop to get it faced because in a lifetime you're unlikely to save $300 in labor charges to offset the tool cost to do it yourself. Width may be important for bearing life. Use your calipers to measure and validate it's in spec. If you lack a pair ~$20 will get an idiot proof digital set from Harbor Freight.

    3. Use anti-seize so you can remove the bottom bracket after it's weathered for the decade you might get out of it.

    4. Follow whatever directions come with the bottom bracket and/or crankset regarding wave washers, crush washers, O-ring seals, and whatever else is required.

    5. Some click-type torque wrenches don't click when turned anti-clockwise. Tighten the non-drive side crank about like the right side if this is the case for you and you're using a normal bottom bracket.

    6. Use a torque wrench to install the crank bolts). Let me re-iterate: Use a torque wrench to install the crank bolt(s). Torque to the high end of the spec. Modern non-square bottom brackets often have the splines bottom against a shoulder and they may not get there at the low end. This is less critical now that we don't have splines on the drive side which carries the ring spider with non-square mounting affecting front derailleur operation although you don't want issues where things get loose and you destroy the left crank arm.

    I wouldn't expect a "real" mechanic to get this right. Too many are either ignorant (bad) or just don't care (worse). As a person who can read and follow directions you'll do as well when they're doing their job and much better when they're not.
    Last edited by Drew Eckhardt; 07-12-12 at 09:49 AM.

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    Quote Originally Posted by fietsbob View Post
    strip down the frame entirely, since square taper and external BB have nothing in common,

    except they thread into the same frame threads.
    then you are looking at 2 sets of tools to buy, one to remove, the other to install,

    making the shop service labor rate a wash, unless you want to get the tools anyway..
    For the first bike.

    Even as a one-universal-bike guy additional bikes with traditional bottom brackets seem un-avoidable. You get a comfort bike for your previously non-cycling wife, you herniate L4-L5 in a horrible sneezing accident and get one to match until you recover well enough to ride a regular bike with some forward lean....

    Bike-friendly cities also tend to have bike-cooperatives where you can use their tools.

    Sometimes there's a shop where you can rent a stall (the Sports Garage in Boulder used to work like that)

    The same workshop (Techshop) I pay monthly membership fees to access all sorts of big goodies (I couldn't buy a CNC router/mill/water jet/laser even if I had space for it) also has bike tools.
    Last edited by Drew Eckhardt; 07-12-12 at 09:46 AM.

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    Thanks to all for the info i will be sure to return to this forum in the future, you guys have been a big help.

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