Avar928

You can put wider tires on the rear on stock manholes? What's the best set up for 16s? I'm planning on getting new tires for my '86 real soon. Ever since I installed the S3000 chips the wheel spin is getting too much on my crappy tires. Lost traction and fishtailed a little going in a straight line when she shifted to 2nd gear on a hard acceleration. I can't gun bunny her anymore or they'll light up.

pcar928fan

I certainly prefer the way my 928's handle when the front and rear tire widths are closer to the same vs rear wider than front. 245 and 255 on my PanAm rims on my '95 GTS feels SO GOOD!!!! That car does not have a grip problem in acceleration though as it is stock (for the most part...some exhaust might make it a touch faster than stock)... The '93 with the S/C on it is HIGHLY grip limited even with 275's... So that car carries 275 and 235... feels pretty good and needs the rear grip, but the '95 is far more neutral handling which I prefer!

Captain_Slow

Doesn't matter...rotational inertia doesn't care if it's down a hill or off the line. Rotational inertia would matter more in a drag race than aerodynamics. Not saying it's a major factor, but rotational inertia has a surprising impact on lots of common experiences. Hold a 2x4 vertically with hands grabbing at same position. Twist the board on it's axis (back and forth..clockwise then counterclockwise). This is easy to do as fast as your hands can twist back and forth. Now hold the same board like a tight rope walker and try to twist back and forth...it becomes a big challenge. The only thing that's changed is the distribution of the mass relative to the axis of rotation. There are obviously deliberate intentions for the larger wheels with open centers, e.g. lower unsprung mass, and better brake ventilation. But the rotational inertia is increased because the combination of larger open wheels with very low profile tires concentrating mass as far away from the axis of rotation makes this increase unavoidable. So it's a bunch of trade offs. Seems that since dragsters don't need to ventilate brakes, nor handle curves, the wheels can be designed to reduce moment of rotational inertia as much as possible. 100ths of seconds matter.

But I'll stick with my Panamera wheels...cuz they look cool.

rnixon

We seem to be agreeing on most of this, but the downhill race is won by the assembly that you don't want. There, the more massive object accelerates more quickly, as it has a lower rotational inertia to mass ratio. However, it has a higher rotational inertia, so it will accelerate more slowly for a given force, e.g. on a car on the level.