https://www.facebook.com/groups/4080209228/permalink/10155459818999229/ OK, that makes a lot more sense. It still seems funny though. The limiting factor would be engine braking, I'm assuming that engine output is more torquefull (it's not power, it's torque that matters here   ) than engine braking. The friction between the driven plate and whatever it touches (shoulder on the axle? inner race of the ball bearing? I'd have to check. Probably doesn't matter, they're both supposed to be fixed to each other) has to be less than engine braking forces for this to be an issue. If the clamping force is high enough to keep engine braking from moving anything, the driven flange will move *once*, and stay there, and there won't be movement. But if the friction from the clamping force is lower than engine braking, it'll move back and forth. Or put another way: If the nut is too loose, it'll slide for sure, and if it's tight enough, it won't. Where "enough" isn't "what the book says", but rather "enough to overcome engine braking" A quickie web "clamping force calculator" (the math of which I don't understand) suggests 5,200 lbs of clamping force. I measured 5cm diameter thrust washer, and about 22cm sprocket, so a little less than 5:1 ratio. total reduction from the engine to the front sprocket in first gear is