Well, the potenza RE92 stock tires which are 195/70R14s weigh 20 lbs each, the Pilot SX-GT 225/50R16s I have are 22.2 lbs each. You're right, the tire weight isn't usually as great of a differnece as the weights of the rims. The RX-7 rims I have weigh 13.8 lbs each, the stock alloys are approxomately that same weight (I don't know for sure), so the 225/50s on RX-7 rims weigh only about 2 lbs more each for rim and tire.

But you have to remember WHERE that weight is! With a 225 tire more of that weight is in the steel belts since it's wider, and that's at the very outer edge of the tire. That's why the weight may not be very different, but it's rotational inertia will still be much greater. So it is the LOCATION, or DISTRIBUTION of that mass which made the difference, not the actual mass itself.

You're right Mike, a 14 inch rim will be better than an 18 inch rim if the outer tire diameter is the same, but the MAJOR effect on the rotational inertia will be the tire, not the rim, because that weight at the very outer diameter of the tire will have the greatest effect on the rotational inertia.

Also, just because our cars are 2wd doesn't mean the the rear tires can be wide on heavy rims. You see all the honda guys at the drag strip put their stock tires on the front but keep the heavy rims/wide tires on the back. I love racing those guys :) they are typical rice boys who don't know what they are doing. Those heavy wheels may not have power going to them, but you STILL have to turn them! If they are on the front or the back, it should still have the same effect on the car, it would slow it down, which is EXACTLY why the top fuel dragsters have bicycle tires on the front, because it DOES make a difference.

And besides just turning them, the mass has to be accelerated in a straight line as well (as if you're adding 20 lbs worth of weights in your car's trunk), so it makes no sense to keep them there.

Todd Scungio
98 RS
15.803 @ 86.48 MPH