Road and Track's new issue features a tire comparison (this time on a Scion FR-S) of stock tires on stock wheels, high performance tires on stock wheels, and high performance tires on a +1 wheel combo (using the same high performance tires).

Results were pretty conclusive, going from stock tires to summer high performance ones in the same size was worth 2.3s in lap time shaved, +0.05g in cornering power, and 2.4mph in the slalom test. In other words, performance was improved in every way with a tire swap in stock size.

When they went to a +1 wheel and tire combo (215 to 235 width, 17" to 18"), they added another 0.02g in cornering power, and 1.0mph to the slalom speed. Somehow the lap speed suffered by 0.6s due to increasing the gearing and slowing the car down on the straights. Tires in 18" were 0.8" taller than in 17".

As this is a high strung small motor that needs high revs and a manual trans to make move decent, this makes sense. For a big TQ car like any V8 3rd gen, the engine would have enough power to overcome the gearing (and equal or better lap times).

Here's the link:

http://www.roadandtrack.com/special-...transformation