I wouldn't say 'not much use' but I think the main benefit is as you say (all IMHO)

Reduction in rotational mass will also have a positive effect.

Like I say, you wouldn't catch many race teams fitting heavy wheels.

 

I've read a bit more and see where folk are coming from as far as tyre weight and offsetting weight inwards/outwards from the hub.

From the more reading i have done, it seems the greatest benefit is handling as far as suspension reaction/speed and making the car more nimble so to speak. Acceleration increases are not as much as it made out to be.

 

Tyres weigh ****** loads. Always amazes me.

 

Interesting MB - that was the effect of tyres on the NA-series MX-5. Mine was fitted with lightweight alloys (of course!) and there was a special lightweight tyre (Dunlop) for it - and the original MR-2.

Incorrectly fit it with the normal weight Dunlop (Civic tyre) and it started crashing & thumping like German rubbish/Alfa Brera/etc. Which of course numpty dealers did...

And as LJKS was wont to assert, what is good for the ride is usually good for the handling too.

 

I can't say I noticed any change in performance when I went from the BBS 16s to 17" OEM wheels, but I certainly did notice the much better and much more direct feel of the lower profile tyres on 17s.

In theory ride and handling come down to the ratio between sprung mass and unsprung mass, so all those who fit lighter exhausts, or seats, or "strip out" their cars are making them handle worse.

 

I was having a look at the springs installed on my car http://www.swiftsprings.com/products-sport_springs.html, i bought them off a fella who had installed them to his standard coilovers that had only done 4k and were best suited to the standard coilovers, he didnt want them as they were not low enough - interestingly in that link swift mention if you want lower springs then look elsewhere as they focus on other elements. My car doesnt really sit that low probably around 20-22mm lower IIRC.

Is the weight a spring still classed as 'unsprung weight' (i think it is)? as all 4 springs weigh ~3.5KG's lighter than stock ones - not a massive difference but still.

There are only 2 owners on here who have driven my car, Pete (peteron) and Adrian (Mug3n) but both commented on the ride was a little harder than standard but handling was definitely a 'bit' better than standard, Adrian pushed it quite a bit

 

The bottom of your springs is unsprung mass; the top is sprung mass. So probably 50/50 overall. Same with the dampers, and sort of the wishbones. Brakes are unsprung mass of course; those calipers and disks are pretty heavy.

 

Oh, FFS - an Arcturian mega-dump following a Vindaloo would have as much effect on performance!

Suspension may be oscillating at a good few Hz, which is why unsprung is so significant.

Dembo's semi-right, in that SIGNIFICANT loss of sprung mass may make the vehicle over-sprung & over-damped. It is however part of a virtuous circle, that results in mass reduction of every component in turn.

 

Believe me you will not notice any difference in performance on the "butt" dyno Try to race from 2nd gear rolling with a friends S2000 having the 17 inch wheels and then change to 16 BBS ones and repeat the race. You will see the difference on higher gear and speeds. After 100mph with the BBS wheels the car will accelerating faster than before.

 

Also depends how the wheels are lighter, not much use if the reduction is close to the axle centre
But if you can get a wheel and tyre combo that reduces the weight from the outer edge it makes a difference
Think of them as 4 flywheels, they need power to make them spin faster and more braking power to slow them down, the more you reduce the spinning mass the less you need to make them stop and go