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There is forward & backward play on my Schlumpf Mountain Drive chainring. Is this a problem? If so, how do I fix it?

When I hold the crank steady, there is back-and-forth play on the chainring in the pedaling direction of my Schlumpf Mountain Drive installed on my 2015 Brompton M6R. See the following video:

video shows the chainring is moving forward & backward, even with the crank arm held in a fixed position

Is this play a problem? If so, how should I fix it?

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I only have a sample size of one Schlumpf bike I've done an install and some maintenance for, but it appears normal. See page C-1 of the user manual you link to.

enter image description here

The "some play between the cranks and chainring in the direction of rotation is normal" clause is what's relevant here. Basically it's fine, they all do it.

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  • Can you clarify what they mean by "Only adjust the gearing play, if the chainring has play along the axis of the spindle" and "Preload on the gearing system may damage the bearings". Please ELI5, not like I'm a bicycle mechanic. Apr 8 at 18:36
  • “Play along the axis of the spindle” means side to side across the bike. Grab the chainring and attempt to wobble. If there is play (not just flex) that’s a problem and you need to tighten in small increments to eliminate that. “Preload on the gearing system may damage the bearings” means just like cup & cone bearings if you over tighten the LH nut the bearings will not run freely, will cut into their races and damage themselves. You want a Goldilocks amount of pressure in the system, enough to minimise play but not enough to bind the bearings. Apr 10 at 10:46

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