Originally Posted by WhyFi

It's the same ol' thing - math showing that increasing rotating mass doesn't affect average speed very much... and I actually agree with that. Where I disagree is that, IMO, this always overlooks what makes lighter wheels feel so different - angular momentum/the gyroscope effect.

Anyone that had ridden light wheels can immediately feel the difference - it's not in your head. But it's more side-to-side than straight ahead - lighter wheels change direction/orientation much more readily than heavier wheels and make the bike feel much, much more snappy and responsive whether you're cornering or thrashing out of the saddle - you don't feel like you're fighting the bike as much.

If anyone needs to demonstrate this to themselves, it's easy: the next time your changing a tire/tube, hold the wheel in front of you, by the ends of the QR/TA. Give the wheel a good spin and then try tilting the wheel side-to-side. It'll resist very noticeably. Next, take out the tube (or tire, if you're tubeless), give it another spin and try tilting side-to-side again. Very big difference and that difference is magnified with speed.