Spec Boxster Build

[thstone]

Tire Pressure Testing

Last Friday, I spent the morning at Willow Springs (prior to the race weekend) doing tire pressure testing.

Why? I've been running various tire pressures based on my own experiences and hearing recommendations from others. However, like a lot of drivers, I felt that I wasn't really maximizing or optimizing this important variable - it was all a bit of hit and miss for me.

What did I do? I ran the following test plan:

(1) 10 laps to warm up the car, the tires, and my driving. The goal was to run consistent 1:34 - 1:35 lap times to set a baseline. This isn't a super fast lap time for a Spec Boxster at this track (the record is 1:31) but it is fast enough to get the tires up to temp and to evaluate the handling and feel.

(2) Pit and quickly set the tires to 35 psi hot. Then immediately go back out and run 5-7 laps with as low of a lap time that I could muster while making note of the grip level, handling characteristics, and min lap time.

(3) Pit and quickly set the tires to 32.5 psi hot. Then immediately go back out and run 5-7 laps with as low of a lap time that I could muster while making note of the grip level, handling characteristics, and min lap time.

(4) Pit and quickly set the tires to 30 psi hot. Then immediately go back out and run 5-7 laps with as low of a lap time that I could muster while making note of the grip level, handling characteristics, and min lap time.

The total test time was about 50 mins and 28 laps. The goal was to keep the track and weather conditions as constant as possible. Of course, the biggest variable was the driver but I did my best to run consistent laps from group to group.

What did I learn? My fastest lap time came in the second, 32.5 psi group, however I felt that the car had more grip in the 30 psi session but I didn't take full advantage of it.

Based on these results and some other qualitative inputs like how I like the car to feel, I settled on a tire pressure setting for the upcoming weekend of racing that was highly successful in terms of providing strong grip and consistent handling characteristics throughout the three races.

The exact tire pressure that I selected is somewhat irrelevant since it is highly dependent on the setup of my car and my particular driving style - the key point to share is that if you haven't done any testing like this, you might want to consider it to help you dial in a more optimal tire pressure.

As usual, it was a weekend of very tight racing (so tight that I had a bit of incidental contact!). Race videos are coming soon!

[MaxD]

That was a great test session - good info

Did you take any tire temps before adjusting?

[thstone]

Originally Posted by MaxD

Did you take any tire temps before adjusting?

I didn't take any tire temps on this test date. They were taken at another test day and then I had the car aligned/set up taking the tire temps into account. This was done before I attempted to fine tune with tire pressure. And yes, as the tire pressure changes, I might need to make minor alignment changes to make them all work together. The same is true if I happen to find more speed and lower my lap times which means the tires might be working harder. It can seem like an endless loop but at some point I just set up the car to the best of my knowledge and drive it!