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  1. #1
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    Another question on bottom bracket for '04 Epic with XT crank

    I posted yesterday about what the correct bottom bracket would be for my Epic. Turns out that the one that was on there (replaced by LBS a few seasons ago) may have been the wrong size. So after doing some more research, here's what I found out:

    The OEM bottom bracket on the '04 Epic was a Shimano ES-30, 68 mm shell, 121 mm spindle, with a 50 mm chain line. (That's from Specialized's website.)

    I have an XT crank (FC-M752) on my Epic. This is different than the crank that came on the bike new. Shimano states that the M752 crank requires an ES71 bottom bracket. However, the ES71 bottom bracket only comes in a 68 or 73 mm shell width, and a 113 or 118 mm spindle length.

    What do I do here? I called Specialized and they told me I needed to use a 121 mm spindle (the guy was reading this from something he looked up) so I can't use the XT crank.

    I find this hard to believe -- I can't be the first one to put an XT M752 crankset on an Epic. Should I use the 68 x 118mm bb? Will it be close enough? Add a spacer to the drive side? Is spindle length dependant on the frame, or the crankset?

    (FWIW, the bottom bracket that my LBS put on there was a 73 x 113 -- and eventually they added a spacer after I came back several times complaining of mis-shifts and chain skips. I could do this setup again, since I know it works -- but is it right??)

  2. #2
    mtbr member
    Reputation: bwalton's Avatar
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    I ran into the same problem with my 99 SJ and my 04 SJ until I bought a Shimano two piece crank set with separate outboard bearings that can be shimmed with 2.5mm spacers. For example, installing the two-pieced crank set on my 04 SJ has a 68mm BB (note; the bike came with an OEM Deore crank set with a Deore 68 x 121 BB) required two spacers on the drive side and one spacer on the opposite side. If it had a 73mm BB shell than one spacer would be required on the drive side only. I would suggest either downgrading to a Deore BB, which should still be available in 68 x 121 with a splined shaft or purchase a new LX or last years XT two piece crank set. If you use a 68 x 113 BB with spacers on the drive side than your other crank arm will be positioned very close to the chain stay and your foot may bump the frame when you pedal.

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