When I had my V6 with my Heads and cam motor I made 225rwhp and 225rwtq. I wanted to put a 12 bolt in my car because I got sick of breaking the 10 bolts but aside from the cost of the 12 bolt I didnt want to loose power. There is a bigger drivetrain loss with the 12 bolt over the 10 bolt. On a LS1 car its not bad because the car makes 320 rwhp stock and loosing 5 hp isnt a big deal but on a car that makes 225 rwhp I felt I needed ever HP I can get.

I wanted to keep my car at stock weight. I did not want to start weight reduction because I drove my car to much. If you are worried about rotating mass and adding more weight then dont get new wheels! Of course there is another option for aftermarket rims. I had the Prostars skinny fats on my car. My front skinnies with 165 15 tires on them weighed about 22lbs and the rears with 265 50 15's weighed about 35 lbs. I had Futura tires from pepboys. My stock 16 inch chrome wheels with the 255 50 16 tires on them weighed around 48 lbs each. when it was all said and done my car lost about 80 lbs over stock with the new wheels and Aluminum D/S. If I had to do it over again I would have gotten the 16 inch Pro stars or the 15 inch Drag lights so I wouldnt have to grind the brakes down.

I did go from my stock 17 inch WS6 wheels on my 02 WS6 with Y2k 17/18 inch wheels. They are heavier and I did notice a little difference in acceleration with them.

you pretty much covered that one..... minus the mathematical formulas
Its a simple concept.

if you really want more.... you have to wait till my real work is done ;)

I enjoy learning about this stuff. Matt's post equating it to a flywheel and such jives with what I've learned too. The heavier flywheel stores more energy or 'keeps the revs up' between shifts. So depending on intended use and application (car wt, gearing, engine setup, etc.) a lighter flywheel could be a gain or a problem. But I digress, we are not talking flywheels.

Not directly but it is the same deal in terms of physics. Doesn't matter if the weight is all metal or metal and rubber.

Having a lighter than stock flywheel is good to rev fast but bad for launching. A heavier than stock flywheel is good for launching due to stored kinetic energy but it's slower to rev up.

Applying that same thinking doesn't work for wheels (obviously). I don't see a benefit in using anything but the lightest wheel possible that meets your criteria (price, strength, tire choice).

To the OP:

I noticed a difference going from a 255/70/15 on a 15x7 steel wheel to a 275/50/15 on a 15x8 lightweight aluminum wheel. Yes, part of that can be attributed to the big aspect ratio change, but the wheel weight difference was 12 lbs PER WHEEL so it had to make a difference. Counting the tires, it was around 16.5lbs saved per corner in total.

Regarding handling, I haven't driven the car with the old wheels vs. new wheels enough to really notice. But from all I know and have heard, less unsprung weight will allow the wheel to better follow uneven road surfaces, leading to better handling.

Wolfblitz just went from stockers on his base v-6 to y2k vette rims...ask him about how the car feels now.

I've had:

stock ABS 16's with 245's
17x9 OEM zr1's with 275's
17x8/18x9.5 OEM y2k's with 245's/275's
17x9 OEM ws6 wheels with 255/285's

and the only difference i've ever felt is the difference in sidewall stiffness of the tires. 16's have felt mushy with both sets of tires i've had. zr1's with toyo t1s's were better. y2k's with kumho mx's were awesome. ws6's with kumho spt's are decent. no noticeable difference i can attribute to weight. the car follows ruts a bit more with wider tires but that's it. i suppose i did pick those wheels since they were lighter than something like a torque thrust. i'll take a slightly less blingy wheel to save some rotating mass/unsprung weight. i like the clean subtle look better anyway.

I can definitely say the OEM ZR1 5 spoke wheels are lighter than the aftermarket ones. My old 96 SS had the 5 spoke wheels and I bought a pair of 17x11 AFS ZR1 wheels and I found out one of my stock 17x9 wheels was aftermarket, not OEM. I had the tires dismounted and you could definitely feel the weight difference. 275/40/17 tires will handle a lot better than 245/50/16 tires so it's up to the individual if you want better handling for the added weight. But go with OEM wheels over the aftermarket if possible. OEM 17x11's are the wrong offset so you don't have much of an option if you want to go that wide.