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  1. #1
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    What cranks for 2002 trek 4500?

    Hey all,

    I have a 2002 trek 4500 with a bent crank, and I was curious what crank I can replace it with. I see some relatively inexpensive (50-75) truvativ and raceface cranks on ebay, but I am not sure what bottom bracket size I have, and whatnot. If someone knows what is the proper size that would be great, as I road bike now, but kind of want to get into mountain biking once again, which requires a working bike ha.

  2. #2
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    can any one help, or is this just a lost cause?

  3. #3
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    You mean that you have a stock 2002 Trek 4500:

    http://www.bikepedia.com/QuickBike/B...4500&Type=bike

    Unfortunately, the Bontrager cranksets were available with several different interfaces (ie bottom brackets: Square taper, ISIS drive, Truvativ GXP) which is why people are reluctant to respond to your post.

    First, identify what crankset you have as the instructions for the removal of and the installation of the new ones will be tailored to them.

    Also, mention which crank (ie arm) is bent as you may only have to replace one instead of the whole lot. Check the inside of the cranks for numbers and letters stamped into the metal as these will tell you the exact model and length of the crank.

    To check the bottom bracket interface:

    1. If the bearing cups are outboard, then the interface is the Truvativ GXP system.
    2. To check for the other systems: remove the non-drive side bolt, if you can see a square hole then it is Square taper, if it is looks like a circular cog then it is most likely to be ISIS drive (but count the number of splines - there should be 10).

    Trek Mountain frames usually have a 73mm bottom bracket shell, with a British 24tpi thread.

    The correct bottom bracket spindle lengths to fit triple 44/32/22T cranksets for frames with disc mounts (Hayes 22mm, Trek Disco mount or IS mount) are more than likely to be these:

    Square taper: 113mm
    ISIS drive: 113mm

    Some of the earlier models required longer spindle lengths for the crankset (in particular the chainrings) to clear the chainstay.

  4. #4
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    thanks for the advice. I took off the non-drive side bolt, and it looks like it is square taper. Should I everything apart so I can measure the spindle, or is that not necessary?

  5. #5
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    also, if i know that it is 113mm wide, and a square taper, can I just buy any square taper crank off of ebay for example without a bottom bracket and the correct gearing, or are there other variables I need to watch for?

  6. #6
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    Most crank manufacturers (especially Shimano) recommend a certain spindle length to maintain a particular chainline for the derailleurs (especially the front) to work properly.

    If the spindle is too short, then you might get problems dropping down into the smallest chainring on a triple chainset. The chain will also catch on the shift ramps of the biggest chainring when the chain is on the middle chainring, smallest sprocket combination.

    If the spindle is too long, then the front derailleur cage may not be able to reach the biggest chainring. On the big-big combination, the chain will rub on the rear derailleur cage; and the chain will drop down onto the middle chainring when you back pedal.

    On a Trek with a 73mm BB shell width, the 113mm spindle length is correct for a square taper crankset with (44 or 42)/32/22T tooth numbers.

    So, yes, any 8/9 speed JIS square taper crankset will work. If the BB is in good condition (spins freely by hand), then just replace the crankset.

    When you come to install the crankset, do it like this:

    1) Lightly grease the spindle tapers and crank bolt threads.
    2) Bolt on the drive side crank first until it is handtight, but not all the way inwards towards the frame.
    3) Place the chain onto the smallest sprocket and middle chainring and from above check the path of the chain against the biggest chainring (remember what I said above about the chain hitting the shift ramps?). Now, tighten the crank bolt a bit more, but stop when the gap between chain and biggest chainring approaches about 2mm - this is the maximum amount you can bolt the crank inwards. The 2mm is like a buffer and accomodates for frame/crank flex when pedalling.
    4) Adjust the front derailleur as required for smooth shifts.
    5) Fit the left crank.

    If you've ever built bikes with flexy frames (eg 1980's Vitus road bikes), then you will come to appreciate how important the above steps are.

  7. #7
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    Just get some shimano LX or Deore Hollowtech II's, for under $100. Major upgrade and replaces the BB too.

  8. #8
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    i think i am just going to sell the bike and look for something a bit higher end. I bought a crank that i think should fit and i am going to attempt to put everything back together right now. It looks like it will all fit together, but thanks for the advice everyone.

  9. #9
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    Looks like i cannot get this crank on without it being too close to the bottom bracket, and still be able to use the inner chainring. It was a nashbar crank that said was for replacing riveted cranks that were square taper. I might just try to sell the whole bike, and make someone else find a crank that works.

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