18inch alloys

the move from 17 to 18 is not worth it in terms of economy against extra grip and looks.

i think 17 is the much better option

economy, doesnt effect the 2.4's so why any of th others, me personally beleive the pro's outweigh the cons, but each to their own, think the economy is more to do with the right foot rather than going an inch bigger on the wheels tbh

The only way the 18 will provide extra grip is with a larger footprint. That in turn will have quite an affect on economy (and even more pronounced on smaller engines). Then there's the harsh ride and tyre roar which are likely to be worse than on a 17.

I must say - it'd be an easy choice for me

smaller side walls on 18's offer a much bigger reistance to cornering forces, i.e the tyre doesnt wobble so much left to right while unde cornering as much as one with large side walls, every little bit helps on track but not everyone goes on a track so point taken.

but the schui is no more less economical than a normal abarth, so why no difference there

To be perfectly honest Red, I never realized the Schui came with 18's

If that's the case then I'll shut up now

I'll just be pedantic and mention it was only the GP with the 18" Super Ts as standard (something Red clarified on the Performance Stilo site). The normal Schui had 17" Claws

not changing my driving style or anything, i saw an immediate drop of around 4-5mpg once the 18's went on. in a world of constanly rising diesel prices it does add up, plus your car doesnt drop as much when its lowered on 18 than it does on 17

it may just be me, not feeling too happy with the 18" Jordan-R's at the moment, despite all the compliments i get on them

err, it gives the same drop if you keep the rolling diameter the same, might not give the impression its dropped but its the same.

and the gp was tuned for grip by prodrive so the 18's must have some benefit, like the smaller sidewalls, but as i said not everyone does tracks so no benefit to the everyday driver

I think this is a good point. Your 18's are matched to the suspension

On so many cars with after market alloys (meaning lower profile tyres) the suspension can struggle to keep the tyre in contact with the tarmac because it has never been matched correctly in the first place.

I've come across cars with which are 'overtyred' in shall we say competitive circumstances and watched the rear tramp severely on bends whilst I drifted (at the limit with a standard setup) under far better control and could maintain unrelenting pressure on the driver in front.

It's a mistake to think 'bigger' always give you an advantage

Yep good point,when i was at donny.on the last chicane kept on the brakes while turnin in the back end very slowly come round ever so slightly to stop it understeer,was very suttle and very controlable. Iv driven a standard one,and prodrive did a bloody good job, but you will very rarely notice the difference on a normal road.it needs to be really pushed to see the real difference.

Why do you think F3 cars have 13" rims, and massive sidewalls!?

As I've already said, it's the bigger footprint that provides the grip but there are a whole stack of other parameters to consider too and you're never going to find those better matched than in F3.