Put my 15s back on my valver this weekend as it was sunny and i was bored!
I can confirm that 15s make it so much quicker on acceleration. It seems to rev up so much quicker from low revs.
As for the handling, it makes it so much more responsive and direct! But it doesnt grip aswell at speed i must say.
Im seriously looking into selling my 17s now and gettin some 15s or 16s with low pros!
Feels like my car has an extra 10bhp!