If you replace the standard 17's for lightweight wheels you can reduce unsprung mass. So for example, reduce the front wheels weight by 3KG and rears by 5KG that's 8KG, i read 1KG of unsprung is equivalent to 10KG of sprung mass so 80KGS! sprung mass!.

That's easily enough to make a difference of 0.1 in a 1/4mile of a mile.

I read however on tests they made little difference to acceleration but helping breaking and the suspension working.

What do folk think?

Initially you believe they will help acceleration but it appears not the more you look into it.

 

Yes, all little things combine to make a huge difference in a na setup

 

I will say this... going to 24lb 18" wheels from 20lb 17" wheels made a VERY noticeable difference in feel and acceleration. I would imagine that going the opposite direction with lighter wheels would have the same effect in feel.

 

Didn't you lose a few pounds off each lesser volume tire, and at the very outer portion making for more net gain in accerelation and braking? I mean, I know all about unsprung weight/rotational mass and I support the lighter is obviously better (inspite of a few decent counter points) math but was a 4lb difference in RIM and hopefully a slightly lighter tire really that noticable?

It's like this, if you have a 20lb 17" rim with a 3lb tire vs a 24lb 18" rim with 2lb tire, there is a 3lb difference per corner. That 3lbs multiplies itself under various formulas for unsprung issues in numerous vertical movement situations to be decidely noticable. However, on a rotation movement, even with a +3lbs overall, you have moved the weight towards the center of the wheel where it is easier to move and stop. Essentially, the wheel may be harder to keep on the road while bouncing, but rotation can be controlled with less effort. I guess that's one more reason not to buy cheap tires, they are heavy.

 

I feel it in steering as opposed to acceleration, but I'm sure there's an acceleration difference as well.

I have OEM AP1s, Prodrive 17s, and Volk 17s that all weigh different, and all feel different.

-Mike