Acceleration with lighter wheels

[RIC172]

Hi I'm thinking of changing my 182 wheels to lightweight 15" wheels (maybe TD Pro Race 1.2, OZ F1 from a Phase 1 or Speedline Turini). I'd go for a 195/50/15 tyre size too.

Is the difference in unsprung weight and acceleration noticeable?

I have a 172 cup but unfortunately the previous owner decided to put 182 wheels on it and they're not the lightest!

 

[DrR]

Acceleration, no IMO. But the car does drive differently

 

[RIC172]

Ok thanks that's interesting, I presume the car feels lighter on its feet does it? Only thing that puts me off is perhaps less grip on 15" compared to 16" wheels

 

[imprezaworks]

Be the best move you make.

And no the grip query is wrong

 

[Budgie]

Ok thanks that's interesting, I presume the car feels lighter on its feet does it? Only thing that puts me off is perhaps less grip on 15" compared to 16" wheels

There's no better change to make on a 1*2 going from 16's to 15's IMO. Changes them completely.

 

[RIC172]

There's no better change to make on a 1*2 going from 16's to 15's IMO. Changes them completely.

Thanks Budgie, what differences have you noticed from smaller/lighter wheels?

 

[imprezaworks]

Better feel. Cheaper tyres.

Winner.

 

[Budgie]

Better feel. Cheaper tyres.

Winner.

This.

 

[RIC172]

I’m already impressed with the steering feel and acceleration on Cliosports but if this gets better still with lighter wheels I’m up for getting some. Cheaper tyres appeals too although the range does look worse for 195/50/15 compared with 195/45/16

 

[Budgie]

I’m already impressed with the steering feel and acceleration on Cliosports but if this gets better still with lighter wheels I’m up for getting some. Cheaper tyres appeals too although the range does look worse for 195/50/15 compared with 195/45/16

If it's an all year round road car, look no further than Michelin PS3's. If it's a fast road car, AD08R's. If it's a track car, well, you choose there.

 

[Coops Mk1]

Basically everything above is all the advice you need!
15", lightest you can find (I run OZ superleggera, 4.9kg a wheel) and either the Michelin or Yokos Budgie recommends

 

[OssPoop]

http://www.formula1-dictionary.net/unsprung_weight.html
Brief explanation of why lighter wheels are better.

 

[Gc8]

Also the standard 182 wheels don't seem to let a lot of air through to the brakes. Not important if you never track the car but if you do it's another excuse to swap them out..

 

[BashRacing]

Reduction in unsprung weight makes the suspension keep the tyre on the road more of the time,

BUT!

Faster acceleration comes form the moment of inertia, which is

''a quantity expressing a body's tendency to resist angular acceleration, which is the sum of the products of the mass of each particle in the body with the square of its distance from the axis of rotation''

basically:
a 8kg 16'' wheel with an 7kg tyre (182 wheel with 205/45/16 Toyo T1R tyre = 15kg total) will have a lower moment of inertia (accelerate faster)
than

a 5kg 15'' wheel with a 9kg tyre (Superleggera with Toyo R888 205/50/15 tyre = 14kg total) which although is lighter it has a higher moment of inertia

it's all about how far the weight is from the axis of rotation when it comes to acceleration, rather than overall weight of the wheel & tyre.