front sprocket

[AMCQ46]

I think the rubber is there for the chain plates to touch on as they come onto the sprocket to cushion the initial contact, but in the end the rollers are in full metal / metal contact with the teeth. ...... its not like a cushdrive as the torque is not being transfered through the rubber, the sprocket is still steel underneath, I think these are just rubber cheeks stuck on the side

So only noise reduction, there wont be much improvement on driveability or chain life