Viewing 7 posts - 1 through 7 (of 7 total)
  • Crank installation – Noob question (there’s a theme here…)
  • thinksta
    Full Member

    I’m progressing my hardtail build slowly, and have a further couple of questions I wonder if people can help with. For reference, the frame is a Ragley Big Al (with 73mm BB shell), it’s a Shimano MT800 BB (with a single spacer on the drive side), Shimano SLX 7120 cranks and Shimano SLX M7100/M7130 chainring.

    1) How important is the tightness of the chainring lockring? Does it matter if it isn’t the 35Nm specified? I’m waiting for a tool to arrive (from China as it’s a fraction of the price of the Parktool equivalent) so I can only do it hand tight for now.

    2) On installing the cranks, there is a gap between the crank and BB – per the image below. I wasn’t expecting to need spacers, but a couple came with the cranks. I believe the non-drive-side crank is installed correctly onto the shaft/splines as the little plastic sticky-outy-thing presses in ok.

    …if I do need spacers, how do I know which side to put them on?

    Thank you!

    Cranks

    rockthreegozy
    Free Member

    Dealer manual (from a Google search) states a 3mm spacer either side with “the rubber surface side facing inward”

    You will need the tool for the lockring if you want to avoid stripping the threads, hand-tight is not sufficient..

    Instructions are here pdf linky

    mrchrispy
    Full Member

    spanner in open toes will end in tears….mark my words 🙂

    Fresh Goods Friday 696: The Middling Edition

    Fresh Goods Friday 696: The Middlin...
    Latest Singletrack Videos
    thinksta
    Full Member

    Thank you wonderful people – just what was needed!

    …plus I’ve learned a new word as a result of reading the manual: “Hexalobular”

    Excellent.

    martinhutch
    Full Member

    Get the lockring tool, you need to tighten it properly or it will loosen off a bit, your shifting will go to shite and you’ll get a clicking sound.

    Is this not cheap enough? It doesn’t have to be the Park Tool one.

    https://www.evocycles.co.uk/shimano-tl-fc41-bb-chainring-tool/mpn:TLFC41/

    Make sure you follow the assembly instructions for fitting the NDS crankarm carefully, torque the bolts up properly – 15nm – and don’t overtighten the plastic preload cap.

    EDIT: Re spacers – it seems like you need a 3mm spacer between the BB and crank both on the drive side and non-drive side.

    andrewh
    Free Member

    You definitely need spacers.
    As to which side, try both and see which gives you the best chainline. There might be a ‘proper’ way to do it but that works for me. Just remember how many were on each side when you take it apart to clean or you have to experiment all over again

    mrdestructo
    Full Member

    And….if when you tighten the cranks onto the axle it binds up, you have too many spacers fitted to the BB.

    Done that a couple of times recently when putting new cranksets and BBs on blind. Frustrating putting everything on and taking it off multiple times until you get it right, and the chainline.

    So, yes, buy the correct tool for the BB. I’m in China and these things are cheap here so I got a closed one instead of an open generic one and I only slightly take the paint off the BB now, instead of mutilating it!

Viewing 7 posts - 1 through 7 (of 7 total)

You must be logged in to reply to this topic.