The M8 nuts are for the sprocket, and I don't think the bolt turns while undoing them. The M10 nuts hold the cushdrive sprocket carrier onto the hub carrier plate and their bolt will turn when undoing the nut. However using an impact wrench sith slight off centre pressure undoes them fine, but you don't need to touch these to replace the sprocket. I've just been through this replace the nuts because they are furry on my bike. Previous owner must have been on salty roads.Fucks sake, I'm back to being a tit, can't undo the front sprocket, and the sprocket carrier nuts on the rear just keep spinning..... fucking simple be I
New owner BTW, just picked my 15 SDR up. Realy enjoying it. Need to look at suspension and slight clutch slippage under load, but thats for another thread. Im based in East Midlands if there is anybody about my way.