Looking for advice on my 1X11 set up on a bike I’m (trying to) build:
The chain slips off single front chainring, on the inside, when I move into biggest rear cogs (gear 1 or 2). When I align the chain straight by changing rear gear, it doesn’t sit on middle gear, so I assume the front cog is aligned too far out.

Pics below (with chain in 2nd gear) and Parts involved are:
73mm bottom bracket SM-BB52 - As per instructions I’ve used 2.5mm spacer on chainring side of BB
Crank is SLX FC-M7000-11-1
Shimano SLX: Cassette CS-M7000 and Derailleur RD-M7000-11-GS
SRAM 11 speed chain
Any help appreciated, thanks! rear view chain top view side view

  • 2
    Boost or non-boost? How much clearance do you have between chainring and frame?
    – MaplePanda
    Commented Oct 9, 2021 at 22:40

1 Answer 1


The M7000 cranks come in Boost and non-Boost versions. Everything about what's going on here suggests you're working with the Boost version, FC-M7000-11-B1 (as opposed to the non-Boost model, which doesn't have the -B1 at the end). You can find the model code on the inside of the right crank arm.

Somewhere on the list of things that can explain this problem when everything should be right is frame alignment problems.

  • Which BBs don’t need the spacer? Would love to be aware of them.
    – MaplePanda
    Commented Oct 10, 2021 at 16:58
  • 1
    @MaplePanda A co-worker told me a while ago they had encountered this, but I just looked through all the diagrams and couldn't find any like that, so I seem to be mistaken. Commented Oct 12, 2021 at 13:37

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