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  1. #1
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    Broke Crank/Bottom Bracket need help

    I dont know much about Cranks and Bottom brackets so i ned your opinions to help me out. I ruined my old crankset and bottom bracket on my Trek 4300 (it had Shimano Alivo) and I need to replace it. My lbs recommended that with the beating i put on the old one, even though i do hard xc riding (hopefully racing soon) and am light weight (5'9 125 lbs) They recommended Deore LX everything which would cost me $160, or Deore which would be much less. Ive been researching these two cranks while im waiting for the trek guy to come to see if its under warrenty, and the main difference i see ( correct me if im wrong) is the LX is splinned. So which one would be the best for me and my riding style for the $ and wouldnt break like my old ones. Please help me out here i dont want to waste money, thanks.

  2. #2
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    Deore and LX are both splined. Both use Shimano Octalink, but the LX has a catch: it must be used with ES51 bottom brackets with unusual 121 or 126mm spindle lengths. (Deore, XT and OLD LX Octalink cranks use bottom brackets with conventional 113mm or 118mm lengths).

    $160 sounds a little bit high, but I assume that includes installation. You can pick up an LX crank and ES51 bottom bracket online for under $100 online. For this price, LX is definitely best bang for the buck and gives XT and most of the ISIS stuff stiff competition for high stiffness, weight, and dependability.

  3. #3
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    Yea i thought $160 was alittle high to since I found it online for $104, but I assume it includes installation to which I would like to do but I dont have the tools or the knowledge of how to do it so I guess I will just let them. What do the different spindle lenghts do? Would one not fit my bike? explain that alittle more.

  4. #4
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    Both ISIS and Octalink standards decided that 113mm spindles would give you a 47.5-48mm chainline. This was a touch longer than the "normal" 110mm spindle length for tapered cranksets, although there was some variability there between manufacturers where anywhere from 108 to 113, and even more in some cases, was necessary for this "normal" chainline.

    Splined did away much of the variability hence you see so many bottom brackets in 113 and 118 spindle lengths only, to cover 47.5 and 50mm chainlines.

    But as it turned out, when paired up with an ES70 bottom bracket, LX was too good a value. 1% less stiff than XT cranks and just a few grams heavier, it seems Shimano realized that they had to do something so LX wouldn't erode XT sales.

    They dealt with it by recessing the splined interface a few millimeters deeper on each crank arm, necessitating a 121mm or 126mm spindle to provide the same chainline on an LX, as 113 and 118mm spindles were providing previously. They then only manufactured these longer length spindles in their "LX Level" ES51 and "Deore Level" ES30 series bottom brackets, but not in the lighter weight, better sealed, higher quality ES71 series bottom bracket. If you try to mate a current LX up to a 113 or 118 spindle, the chainline will sit in too far and the crank will probably bottom out on the frame before it's completely tightened.

    So the 572 LX crank arms are equivalent in stiffness to 752 XT (last generation), and within a few grams of weight, and come with a more durable steel granny, but with the ES51 bottom bracket you've got to settle for a 50g weight penalty and a slightly lower bearing quality.

    Nevertheless, not a bad deal, just not as good as it was originally.

  5. #5
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    alright, thanks for the help.

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