I have a 99 528/Prem/Sport with 17' BBS wheels...what is the benefit of increasing the rear tire size to 255/40's?

I like the larger look, and there is more tire on the ground. I have the Conti's and they have lasted one year! I purchased the car 7/99.

Henry

Minimal with 528 due to "modest" power. With 540 it was determined that due to power (and weight distribution) more rubber=better power to pavement as well as theoretical understeer/oversteer dynamics. It is a long-time "trick" of the industry-esp tuner segment--to put larger tires (ususally by 20mm, but on Porsches even more, due to extreme rear weight bias)...starting with 6 Series BMWs in late 70s early 80s. Esp productive on car with much power but light rear end (Porsche 911s notwithstanding). 528s are more balanced weight-wise as well as less power, so you would be doing MOSTLY for cosmetics. Like E39 528 Sports, E34 M5s ran same all around (235s) so you can see even with BMW "M" staggering is not always the solution/don't know, but most E34 M5s I've seen saty with the 235s all around....BUT part of that may have been rear clearance restrictions to begin with. NOTE: you can add 255s to your rear now with E39's Style 5 (528 Sport wheels) in 9 inch now--over the counter BMW or @ bmwwheels.com so you can at least keep fronts. Neat. Also, ALWAYS increase rim width when going to a wider tire in back (when staggering). Good luck.