Chainring movement on steps with SRAM ring

[Trickz]

I haven’t got a picture of what I noticed today but I could see that the chainring had slipped round and you could nearly see the start of the hole in the chainring,the bolts were tight but I undid and reset it’s position,looking at the setup though shouldn’t the back nut be longer(because it’s wider diameter) to stop the chainring moving?or is this normal with the torque of an ebike.

 

[R120]

Are you saying the chainring has slipped on the spider, or that the spider has slipped on the motor axle?

 

[R120]

Cant say that I have heard of that happening unless there's been a screw top in the installation

 

[Trickz]

Are you saying the chainring has slipped on the spider, or that the spider has slipped on the motor axle?

Yes buddy the chainring had slipped round the spider only the amount of 1.5mm until it found the chainring bolt,I reckon the back nuts are too shallow ie if they were to stick out of the spider material into the chainring they would fill up the chainring hole diameter,even though I thought the bolts were there for a clamping friction fixing not a shear one?I wonder if it’s a compatibility issue with SRAM and shimano,I’ve ordered a better chainring nut spanner so I can get a bigger purchase,the key shank one I had is tricky to use even with removing the motor bash guard but even so I got at least 10NM with the torque wrench which should be enough,I’m going Cannock tomorrow so I’ll see how it goes?

 

[R120]

Yup sounds like a bolt issue

 

[Trickz]

Ive just looked and the standard back thread acts as spacers / drive face in the chain ring
so your bang on i would say in your conclusion
i thought all the rear threads on crankset outer rings came through and locked the chain rings at least all i have seen and had do otherwise as yours has theres nothing to stop it slipping till it hits the thread

thanks buddy?ive just been searching for longer back nuts but they all seem to be the same,even the Shimano steps ones look (No dimensions given)any way about the same length so I’ve ordered some steel raceface ones,thinking about it though(even though I’d like to know why mines different somehow?)the back nut if it was longer would only aid the position for you too tighten the bolts up,the bolts tension should hold it in place..maybe? I wonder if mine was just built like that and ive only just notice,hopefully tomorrow I’ll find out for sure?yesterday I was riding up an old unused moto x track and it was steep...as in I was on the 50 tooth with my belly rested on the stem,I couldn’t believe I got up it let alone my non ebike onlookers,so that probably didn’t help??

 

[Trickz]

Ordered some replacement single chainring bolts by raceface and even though they are still single length not double or bash guard versions they are nearly 2mm long so now hold the chainring central