Hi, I figured if I was going to find an answer to this anywhere, it'd probably be here. With so many PhDs knocking around, someone has to be a physicist or engineer. I hope it's not on the wrong part of the forum, I couldn't really find one that it fits into properly. Right, here goes... We're always told that the wheels are the best place to lose weight on a bike, as it's rotating mass, which has a greater impact on the force required to accelerate. What I'm looking for is a way (purely out of interest) to quantify the difference between rotating and non-rotating mass. The rims on my bike right now are 525g per rim. I'll shortly be upgrading them to a set that weigh 400g per rim. If this was non-rotating mass, big deal. I weigh 80kg, the bike weighs about 23. Seeing as F=ma, 102.75kg isn't going to accelerate much faster than 103kg. Seeing as the 250g saving is rotating mass, is there any way to estimate roughly the amount of static mass you'd have to lose to have the same effect, or does it require knowledge of a whole bunch of other variables? The radius is approx. 330mm (13").