Picked up an e46 m3 w/ :
245/40/18 front - circumference is 80.8
255/40/18 rear (w/ spacers). Circum - 81.8

I was debating keeping this sizing as the car feels great.

or going with :
235/40/18 - circumference - 79.8
265/35/18 - remove spacers. - circum - 79.5

I know the speed will get affected if going away from the 81.6” circumference based on the stock sizing of 225/45/18; 255/40/18

Any thoughts ? Prob going with mps4s.