what size for ultimate handerling?

[judgie]

jsut about all group N,A wrc and the super 1600, s200 run 17 or 18 on tarmac

[Simon]

Originally Posted by judgie

jsut about all group N,A wrc and the super 1600, s200 run 17 or 18 on tarmac

Thats all because of the braking/brakes. Their cars are heavier than ours so they need bigger/more powerful brakes.

On tarmac they have a lot more grip than on gravel (offcourse).
So on tarmac they basically use the biggest brakes possible (AFAIK up to 380mm diameter!), which needs at least 18" (or 17" for somewhat smaller discs), whilst on gravel they use smaller discs (300-320mm) and matching 15" wheels.

Since (as Humble said) 18" slicks are quiet expensive (especially compared to 15" or 13") for someone like us running lightweight cars on a tight(er) budget it is probably smartest to use wheels and tires up to 15".

[evilC]

i agree with $aint on this one. The larger wheels are to allow the potential for super sized discs since they can't run carbon rotors and in general their weight restrictions optimise around the larger discs. With the lower classes there is a bit of blind following but don't forget that modern wheel sizes are tending towards the 17"+ diameters. I think that you shouldn't buck the trend as it will eventually restrict your options. I would go for 17" wheels if you are committed to the 650(ish) rolling diameter. You then have another option at a later date should you need to lower the gearing - fit 15" wheels with low profile tyres @ say 580 rolling radius.

BTW low profile tyres/large dia wheels are heavier than high profile tyres/smaller dia wheels for the same rolling radius so the low profile route will increase unsprung weight that on the front of a bug will have a significant effect. Mind you unsprung weight never slowed the Mk1 and Mk2 Escorts that 30 years on are still winning!