I held my old sprocket in one hand and new aluminum sprocket in the other and the weight difference was obvious. The new chain was also noticeably lighter. 1-2 lbs total difference I'm guessing. I regret not actually weighing each piece before the install. Significant might be the wrong term, "noticeable" would be more appropriate. The main idea is to lighten the rotating mass your motor has to spin before the power gets to the wheel...i'll deal with the lowered sprocket life when that time comes.

 

it helps a bit, however... More than likely the new lighter weight tires were why it is working better. They also will have a lot less rolling resistance.

 

i'll agree my new aluminum sprocket was MUCH lighter than my old one.

I stayed with the 525 chain though.