going from a 18 to a 17 will make a difference. its not the 1lb, it sthe fact that its now a half an inch (everywhere) closer to center. weight off the outside of a rotating mass matters more than weight on the inside.

is it really worth 450 bucks for 2 piece rotors? you could take out the spare, tool kit and go on a diet and get the same results for free.

 

You must've missed where I explained that the heavier tire of the 17" wheel/tire combo equals out the heavier wheel of the 18" wheel/tire combo.

In other words...

The combo of a 255/40R17 tire on a 17x9" wheel weighs the same as the combo of a 255/35R18 on an 18x9" wheel. Since that 1lb difference is contained in the taller sidewall of the 17" tire (that extra 1/2" all the way around the tire) and in the extra spoke length of the 18" wheel... well, you get the idea. You're not shifting all that much more of the mass towards the outside of the wheel...

 

So if i were to go from a 20lb 18" wheel to a 15lb 17" wheel do you think there would be any difference to be noted?

What about from a 20lb 18" wheel to a 16lb 18" wheel, obviously there will be a difference, do you think it would be noticable (acceleration wise?)

 

yes you would notice. i did

 

Quite a bit noticeable, I would imagine. That's quite a bit of weight savings.

Again, you need to look at overall tire/wheel weight, not just wheel weight...

 

If you want to be totally pedantic, like me, you look at the wheel/tire moment of inertia, not the wheel/tire weight.