Does Decreasing Tire Pressure Decrease Performance? - Fact Or Fiction

Arguably the most effective example of "state the obvious" marketing in the automotive industry came in the early '90s, when a certain tire manufacturer reminded everyone that their product is the only part of a car that actually contacts the road. Without saying so, that one line underscored the importance of a car's most overlooked part. In braking, handling and acceleration, tires are the difference between success and failure--especially in the performance driving realm, where increasing traction seems to go hand-in-hand with increasing performance. But, can one of the most basic methods of increasing traction actually decrease performance?

Decreasing tire pressure increases traction... but can it decrease performance?Harkening back to our test-n-tune drag racing days, one of the most commonly employed methods of increasing grip at the line was to decrease the drive tires' pressure, causing them to `flatten out'--which increases their contact patch, increases traction, and decreases wheel spin. But what's not often said, is that doing this also increases rolling resistance, which robs power. Would the benefits of increased traction from decreasing tire pressure outweigh the drawbacks of increased rolling resistance?

To find out, we first needed to determine how much power, if any, was lost by deflating tires. For this, we strapped our project DC2 down to the Dynojet rollers of MD Automotive in Westminster, CA, and made three pulls with its Nitto NT01s inflated to the recommended 35 psi, then three more with pressure reduced to 20 psi.

Fact
The Verdict:
Our DC2 ran quicker elapsed times with the lower tire pressure, but the margins by which it did decreased the farther and faster it traveled. Traction was increased, and with regard to our 1/8-mile ETs, the benefits of lowering tire pressure outweighed the drawbacks. But such wouldn't be the case in an entire 1/4-mile run, where the benefits of higher pressure/lower rolling resistance would begin to outweigh those of lower pressure/increased traction. The bottom line: trial and error--use it to find the perfect tire pressure that will bridge increased traction with decreased rolling resistance, for the quickest and fastest runs.