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  1. #1
    mtbr member
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    Sep 2009
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    SRAM External BB Spacer Question

    Breaking my bike down for the spring overhaul, have had some chainsuck issues when the drivetrain gets dirty/dry.

    Pulled the BB, it is a SRAM/Truvativ bottom bracket, says "BSA GXP" on it, have no idea which model it is exactly but looks like Truvatic GXP team (http://www.sram.com/en/truvativ/bott...bb.php)...this bike is a bit of a bastard build and I am pretty sure it was built by a completely inexperienced mechanic. The manual for the BB says that for a 68mm bb shell and 9spd drivetrain it should have one spacer on each side.

    It had one spacer on each side the way it was built...is this the way it is supposed to be set up for the mojo? Should I be putting another spacer on either side to reduce chainsuck or move one to the other side?

    On a related note, with a X9 setup, I have never been able to get the front derailleur setup well so that it doesn't rub on the outside gears...yes, I understand cross gearing, but I think I should be able to use all 9 gears in my middle chainring, I have never been able to get this to work (yes, I know how to adjust derailleurs, but this is my first 3x9 setup...

    Thanks!

  2. #2
    www.derbyrims.com
    Reputation: derby's Avatar
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    Jan 2004
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    Maybe email Ibis on the SRAM BB spacer question. My FSA BB uses 2 spacers on the right, 1 on the left. This may be related to the der rub issue. I found XTR front derailleur harder to align to not rub in any gear combination, the Sram der was easier.

    Chain suck is more prevalent with the Mojo's low chain stay location than others with higher stays. Be sure your chain isn't any shorter than wrapping big-big sprockets plus 1 inch (or 2 links pinched together) with suspension compressed to bottom travel. If you can remove any links and still have that minimum it will tighten chain tension. Also you can tighten the b-tension screw on the rear derailleur. Going to 2x9 allows removing 4 links, and then tension is much tighter with the same derailleur, and allows a medium length cage when it's time to replace for even more increase in tension. Otherwise keep your chain clean. I've found Squirt (dry) chain lube used as directed prevented suck better than any other dry or wet lube, even in muddy conditions, and chain wear is significantly reduced too.

  3. #3
    Church of the Wheel
    Reputation: mtb143's Avatar
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    Aug 2007
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    Neither I nor a couple of pro mechanics were able to get an XTR FD to be rub free for all nine cogs from the middle ring. I switched to an X9 and it's GTG now. The key was to get it down as low as possible with minimum clearance of the big ring. Dropping it about 1mm made the difference for me. Better shifting this way too.
    "I thought you'd never love me without my Mojo." -Austin Powers

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