Bigger/heavier wheels absolutely do affect track times/mph. Any time you have more rotating mass, and/or move more rotating mass away from the center of the wheel, it will affect your times. Bigger wheels will affect dyno numbers as well.

 

My car went from a monster to suck when i put the same wheels you did on. I put some 3.73s and she came alive again. Dont let anyone tell you bigger wheels dont effect anything. They have more rotational intertia, therefore it takes more to turn them. Its a simple dynamics problem. If you put the stockers back on your times should drop with all conditions and launch the same. -foz

 

I ran a 13.8@101 bone stock down to the filter with my 6speed with 100k on it. Freak i guess.

 

those wheels would maybe make him run .1 slower, on the worst possible day when he left 10 lbs of weights on them...a simple inch will not bump him down .5 seconds and 5mph.

 

Change fuel fiter, air filter. Clean the tb, maf. Get a 160 thermostat. A stickier tire would also help and a cutout is only 30 dollars and 25-50 to have installed. After that go back to the track, things should be much better. good luck

 

It's because it's purple

 

^^^^^^^^

 

Rim size is not the only factor. Its the overall diameter. If the tires plus rims adds up to a 2 inch difference that is significant. An inch increase would even be significant. I=mr^2. Plug it in and see the difference. Say it was a 12 inch radius originally and a 13 inch radius afterwards. that is 144 vs. 169 for your r^2 term, equals significant. This is more complex than just that equation, but it gives a basis for my explanation. -foz

 

^^^^^^^^^^^^^

Thats why the sidewalls get smaller.. 275/40/17 vs. 245/50/16

The overall diameter should be pretty damn close.. Way less than an inch difference..

 

That is quite possibly true, but if he put 17x11 on his car, i guarantee if would suck even more. You also have to consider mass in that equation as someone noted before. a rim weighs more than a tire. its a partial explanation to the problem, most stock z28s run around 14.0-14.4 from what ive seen. You ought to try putting the stockers back on and running it to see if it affects it at all. -foz

 

I agree with you to a point, but a good 17x9.5 rim/tire combo will weigh just as much if not less than a stock "Salad Shooter"

It all comes down to the rim that he has.. If he has some badass Fiskes or Centerlines, then they are going to be light as all hell.. I mean look at CCW wheels, they are super light, but are in a 17x11 + size and they weigh as much if not less than salad shooters.. The tires may be heavier however, but overall with a good 17x9.5 wheel/tire, it shouldnt be that huge of a difference.. I would say .1 at the MOST.

 

It isn't just how much the wheel weighs, it's also where that weight is on the wheel. If you take two 17" wheels, one with more weight near the center and one with more weight near the outer edge of the wheel, the wheel with more weight near the outer edge will be harder to turn and rob more power to the wheels.

 

I also agree with 97bowtie is saying. It matters where the weight it centered. It matters all of the weight (significant amount) is in the center of gravity or not again for the rotational intertia. I think it could mean more than just .1 in my opinion, my guess is .3-.4, but thats just me and i dont feel like calculating the differences between rotational interia and torque transmittance.

 

so what you are saying is that switching from 16s to 17s cause u to lose almost half a second in a 1/4mile...ROFLMFAO...if thats the case why dont we all throw some slicks on 12s....yall are retarded...im sorry but a simple upgrade of wheels is not going to do that.

 

well the auto is killing you alot but i think you need to stall it up as much as possible. Mine is a six speed but on stock everything but the filter, no cat, and 4.10 gears i traped 13.42 @ 105 so i think you can do better with a little pratice