Q: “My question is: Which is more important, tire pressures or tire temps? Or more importantly, how they influence each other respectively.”
A: I was initially going to answer, “Yes,” but I thought that was too snarky! 🙂 The quick answer is, tire pressures. I asked the race engineer on the team I’m working with (coaching a driver) and his answer was immediately “pressures.” Both the engineer and I say pressures because the temps will be impacted by the pressures. As a thought experiment, imagine running 10psi in your tires. They would overheat. So you need to start with the right pressures.
As with most car setup issues and tuning, there is a bit of a chicken and egg thing going on here, too. So once you dial your pressures in close to where they seem to generate the best grip, the tire temps may start running in a different range. For example, you might see higher temps because you’re now using the tires harder, since they’re giving you confidence to drive faster due to the extra grip. Therefore, what you once thought were the ideal temps may need to be re-thought. Or, if you’re running in extremely hot or cold track conditions, you’ll likely need to adjust your starting pressures so you end up in the ideal range, both with temps and pressures.
For more advice on how to tune your car’s handling – and tire pressures/temps – download my free How to Tune Your Car’s Handling eBook here.
I can reinforce the interaction between tire temps and pressures. We spent an entire test day just recently working on getting both right. We would set pressure first, as you advise, then go run a few laps and check both pressure and profile temp across the tire width. We would adjust pressure and go run a few more laps, then change camber and repeat. Eventually we got pretty even temps across the tire and the pressure where we wanted it. The racing tires we use like a relatively narrow range of pressure and the cold setting depends on ambient and track temps, so keep good notes!
To add more engineering perspective, pressure directly effects the tire’s slip angle. More pressure reduces its maximum slip, and visa versa. The sweet spot of PSi will depend on tire load midcorner. And for temperature… well let’s just say there’s other low hanging fruit out there. The only thing you need to make sure of is that youre temperature gradients are either even, or favoring colder outer shoulders, depending on suspension geometry. If you have the ability to use IR sensors, taking derivatives of tire temperatures is the golden ticket for tuning camber.