IS2000

I just upgraded my stock 16s on the GS430 to 18s. By doing so, I gained 5lbs per wheel. My current setup is 245/40-18 front and 275/35-18. I read somewhere on this board that an increase of 1lb on the wheels equals a x3 weight increase on curb weight since rotational mass is increased by the spinning wheels.

By my computation, 5 (wheel) x 4 = 20lbs x 3 rotational mass = 60lbs weight increase. So, I ditched my spare, trunk matting, jack which is good for roughly 55lbs (45 spare, 5 matting, 5 jack)

Gtech stock
0 to 60, same road, 1/2 fuel, normal launch (foot off the brakes and WOT), no A/C
2 runs yielded -- 6.32secs exactly!

Gtech with 18s
0 to 60, same road, 1/2 fuel, normal launch, no A/C, no spare, no matting and no jack
2 runs yielded -- 6.52 and 6.53

My question is, do wider tires, while retaining overall stock curb weight, affect acceleration?

pcmw

OHHHHH Physics questions!!!!!!

Arguments are either direction and can affect several ways.

First... Traction.... Some say wider would be MORE grip while the physicisist says that more weight per inch of traction would be BETTER. All of this depends on the grip of the individual tire. Yoko A008 racing tires or slicks would be different than 100000000 mile radials.

Second, more tire and less rim could be faster as most of the weight would be centered versus more rim less tire spreading the weight to the outer. hmmmm

Third, mental. You have expensive tires, rich boy rims, and a lighter foot as you scan the roadway for bubble-gum wrappers that could potentially bend a rim. Most people drive SLOWER and more cautiously with nice rims.

HAHAAH just my .02

RON430

Nothing wrong with physics questions. Doesn't seem to be much doubt that beyond a certain size, increasing rim size slows the car down. Increasing contact patch with larger tires would lower acceleration times if the stock setup lacked adhesion. Haven't fooled around too much but my stock 2k1 GS4 will not light up the stock 16 Michelins which are probably not the stickiest in the world, so a bigger contact patch wouldn't help in the traction department because I am not traction limited now. There is weight and then there is weight. Weight in tire/wheel combos is not just static weight as IS200 pointed out but I don't think you can relate it to how much static weight you have to remove. As you increase the rotating mass you have more to get turning (and more to stop turning in case you wondered about improving your brakes). You pay the price every time you need to accelerate because first you have to get a greater mass turning faster. As for mental, most people don't have a problem with full throttle 0-60 runs, heck that is freeway on ramp range. If you are afraid of nailing it for 0-60 because of new rims, you definitely did not add them for increased speed. On the good side you might have better handling because the larger contact patch is giving you greater ability to add side loading without breaking traction. But why worry, chances are you added the 18s for looks and you got it. They just also slowed the car up a tick.