Hi, I've been reading some threads on the effects that different wheel/tyre profiles have on the gearing of the car. I wanted to know if anyone running 18's has actually noticed any difference in performance? And will I notice on a 300bhp coupe when I finally finish her!

I ask as I've swapped my standard wheels for a set of dynamics 1.2, pretty good deal I thought! They all have 40 profile tyres on so they're quite tight! The front 2 are stretched 215's which I might replace with 225's, I'm not really diggin the stretched look.

I run 225 35 18s
They are virtually the same height at the stock wheels and tyres

Not noticed any performance difference

But ride quality is the issue - had my 16`s on last year for Stanford hall - Auto italia - felt lovely

But 18s do look cool

They will affect performance as the effective rolling radius (distance from the ground to the wheel centre) will change.

With a 215/35 my speedo reads bang on.

I wonder if there really is a massive difference betweeen 17's and 18's? My ride is pretty good with 17's, and I'm thinking about trying out some 18's.

Bear in mind that 18's are usually heavier as well, which will impact on ride quality and handling.

So as regards a performance increase, unless the weight is the same as a standard wheel or less, your unlikely to benefit from any other changes.

Ross

Rolling radius wise with a low profile tyre you shouldn't notice a great deal of difference performance wise! Only thing you will find is they're heavier and the ride will be firmer due to the lack of tyre lol!

The 225/35-18 tire has the exact std Fiat radius so no change at all there. Better grip/reactions and worse comfort is the actual result.

Does anyone know if you can run 7.5J 18" rims without any problems?

Actual or effective rolling radius? The two are very different.

I believe if you run 35 profiles you'll have no probs, not sure about 40's though.

Biggenz, I think mine are 8.5 j, 18"

Cheers, but I'm more after the max width of the rim you can run.

I've got 17x7 on at the moment, and the rims I want only come in 18x7.5 or wider.

What's the widest rim you can put on the coupe, does anyone know?

Look above mate, lol. Mine are 8.5.

mine are 8.5j with a 215 tyre on , lowered 30mm and i get no rubbing but i wouldn't go any wider .

Oops!

How do you fit a 215 tyre on an 8.5J rim?? Surely the tyre is way too narrow?

it has the drift look but the rolling radius is the same as the 20vt standard wheel , when i need to change the tyres i will be going for a 225/40 or 35 .

I think 225/40 might just rub here and there. I have 225/35, no problem!

Nismo you have PM.

225/40 will rub on full lock. I have 215/40/18 on mine and I had to remove the first 5mm of the vents in the front wheel arch to stop the rubbing.

35's it is then and i'v replyed to you pm roly .

I had 18's on my old coupe and had no rubbing.

I ran 215/35/18's with 20mm spacers. Bk racing wheels.

Ross

225/40/18 will rub Ross, it's a wider tyre and has a higher side wall so the combination will cause rubbing. Spacers don't solve rubbing issues, they just give the correct offset or clearance from the caliper.

Yeah edit note was to explain noticed 225/40. Only mentioned spacers to show setup when fitted.

Makes sense now.

Ross

I think 40s are to tall My wheels with 35s are just slighty taller than stock wheels (205 50 16)

215/40 is a correct rolling radius EDz. The 40 just gives you that extra side wall to make the ride slightly more bearable.

I was talking about 225 so should be 35s and there still very slightly taller than stock

But what ever work for everyone -

215/35/18 is a correct rolling radius for the standard wheel on a coupe with 205/50/16 or 225/45/16

check for yourself - http://www.rtecshop.com/?p=calculator

with 215/40/18 your Speedo will be 3.3% too slow and When your speedo reads 60 mph, your actual speed will be 62.0 mph

with 225/35/18 your Speedo will be 0.8% too slow and When your speedo reads 60 mph, your actual speed will be 60.5 mph

Looks like your wrong

I can live with 225 35s

More PM for you nismo.

Actually with a Fiat speedo might be spot on