During our first ever track day, tire pressure ignorance may or may not have caused the cording of our Michelin summer tires… We continue to allow for the possibility that it was tire defect.
Nah, we're just bs-ing you. It was our tire pressure ignorance. We can't tell you exactly what pressures our rear tires achieved as we gleefully slithered around trying to find the racing line, but safe to say they were well outside of manufacturer spec. Actually, it's probably a minor miracle that they didn't explode.
No one told us about the absolute necessity of adjusting pressures before, during, and after a track day. So rather than continue the cycle of discourtesy and unnecessary tire destruction, we'll tell you the need to know.
First things first, you'll need a quality tire pressure gauge. Preferably something better than the pop up deals they hand out for free at tire shops.
Assuming you're starting at prescribed vehicle pressure specifications, you'll want to decrease the pressures by about 5-7 psi. Generally speaking, and while this can vary according to vehicle and tire types, the goal is to reestablish your car's tire pressure specification once the tires are hot out on track. So adjusting pressures downward prior to the session allows for the pressures to increase back up to the target psi as the tires heat up.
Head out for your first session, and come back in after 3-4 laps. Check pressures and adjust as necessary to reach the target psi. Rejoin the session.
At the conclusion of your first session, do the same.
Some track enthusiasts stop there, but we continue to adjust pressures as needed at the conclusion of each session throughout the day. Ambient temperatures, track grip levels, how hard/fast you're running and many other factors all influence pressure. And so the setting that was optimal after your first session of the day may not still be three or four sessions later. You've got plenty of downtime between sessions -- fill the time with some tire pressure monitoring.
The more experienced you become, the more you'll come to appreciate the tire pressure optimization process. Especially with track tires, variations of even a couple of psi tangibly influence tire grip, performance and handling characteristics.
Assuming you're driving home on the same set of tires, you'll need to wait after your final session of the day for tire pressures to once again reach (near) resting psi. Then inflate back to vehicle specification.
Some tracks have air pumps, others do not. Always bring your own portable tire pump to avoid driving home on potentially hazardously underinflated tires. Learn about other track day must-haves and supplies here.
Here's additional track day tire pressure guidance from Pirelli (see pg 18) as found in their Pirelli P Zero Trofeo R technical advice section. For all you Muricans out there, 0.4 bar equals approximately 6 psi.