Originally Posted by BGTV8

These tyres are 15mm taller than the OEM tyre so your CoG is going to be 7-8mm higher and the front and rear roll-centres are also a similar amount higher. This WILL REDUCE your primary mechanical grip. Whether the greater footprint of the tyre gives the grip back again or not I cannot say, BUT I would not do this ... if anything, I would go smaller overall diameter, or up one size in width and down one in section size to retain (close to) the existing rolling diameter.

I have 235/40R18 and 275/35R18 on my car which has dropped the car by ~16mm and the overall grip is subtantially improved.

Another alternative is 245/40R18 and 275/35R18 which will drop the car by 12mm at the front and 13mm at the rear which gives a greater footprint and lower CoG/roll-centres to improve mechanical grip.

If you are concerned at fuel economy, even with my little tyres, I average 10.3 litres per 100kms commuting from Kangaroo Ground into the CBD each day - moderating your right foot on the throttle is the simplest way to improve economy - raising your car with increased overall tyre diameter is not the right way, IMHO.

RB