Tyres

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

gumpy

Fair Point about COG moving up... Never really thought about that too much...

Your grip is probably heaps up not only due to the lowering of the car but also the much larger footprint... does your car understeer more though? your rear increase in width is far greater than the fronts...

I get 10's also for daily driving, and I agree the biggest difference can be made by driving style... The thing is with a couple of 500km+ drives coming up for work larger RR would be awesome...

BGTV8

Handling is quite neutral, but on a track, my driving style is not to trail break deep into a corner which will cause mid-corner understeer, but to brake in a straight line, mthen turn in and nail it .... if anything, I am using all of the grip at the rear as I get oversteer until the rears come up to temp. At PI, T1 is a full drift (at 200kph - it is a real blast !!).

RB