Consistency in my driving usually comes down to managing variables, and the most volatile of those for me is tire pressure. Since I’m running a limited camber setup (-2°) on my M235i, a track day log is what keeps me from destroying my shoulders in a single afternoon.

Early in my journey I went throguh a lot of tires before dialing this into a repeatable science.

Here is the functional baseline I’ve settled on for my car for my 200TW Yokohama Advan AD09s, followed by the raw data from a few sessions at Sonoma and Laguna Seca on my old tires.

My Baseline: Yokohama AD09s

Autocross (Protecting the Sidewall)

I start extra high to keep the tire from rolling over on Run 1 before I have any real heat. Adjustments aren’t often really needed for any decently sized event–subsequent runs don’t really build up meaningful pressure.

  • Cold Start: 35 PSI Front / 34 PSI Rear
  • Hot Target: 37-39 PSI Front / 35-36 PSI Rear
  • Abort Zone: 40 PSI

Track Day (Managing Sustained Heat)

I can start lower than autocross to account for building pressures over a longer session, but if I overdrive on cold tires the sidewalls will pay a real price.

  • Cold Start: 33 PSI Front / 32 PSI Rear
  • Hot Target: 36-37 PSI Front / 34-35 PSI Rear
  • Abort Zone: 40 PSI

My Ground Rules

To keep the logistics predictable, I follow three specific rules of thumb that correlate the physics of air with the reality of my lap times.

  1. The 1-for-10 Rule: Air pressure is a function of temperature. I assume a delta of 1 PSI for every 10°F change in ambient or tire temperature. If a California morning is 50°F and midday is 80°F, my tires just gained 3 PSI sitting in the paddock.
  2. The Chalk Test: I mark the sidewall triangle. If the scrub passes it, I add pressure or back off overdriving. On my -2° camber M235i, I’m already at a disadvantage; if I roll onto the sidewall, I’m not just losing grip, I’m damaging the tire’s structure.
  3. The 170°F Thermal Ceiling: AD09s are high-performance 200TW tires, but they have a distinct operational window. While they start working at 120°F, they begin to grease over and lose structural integrity above 170°F. If I hit that ceiling, I do not bleed air. Bleeding air on an overheated tire reduces the carcass stiffness exactly when it needs it most. I pit and cool down instead.
  4. Pressure vs. Understeer: If I’m understeering at 40 PSI, I’ve reached the limit of what air pressure can fix. At that point, it’s a driving line issue or a mechanical grip limitation that air can’t solve.

Sample Track Logs

Sonoma Raceway (09/20/25)

Firehawk Indy 500s

Ambient was rising throughout the day. Chasing the delta meant aggressive bleeding in the afternoon.

  • Session 1 (60°): Start 28/30 Cold -> 32/34 Hot (+4/+4).
  • Session 2 (65°): Reset to 32/34. Ended at target. 0 adjustment.
  • Session 3 (70°): Reset to 32/34 -> Hit 37/37 Hot. Bleed -2/-2.
  • Session 4 (78°): Reset to 32/34. Ended 36/36. 0 adjustment.
  • Session 5: No further adjustment needed.

Laguna Seca (12/01/24)

Firehawk Indy 500s

This was the day I realized the RHS runs 2° hotter and that 170°F is the limit of the AD09 thermal window.

  • Session 1 (51°): 32.6 after highway -> 39/37 after three laps (+7). Bleed -4/-3.
  • Session 2 (61°): 31.5 Cold -> 37-38 after 5 laps (+6). Bleed -2L/-3R.
  • Session 3 (68°): Reset -> 36L, 38.4R / 36L, 38.4R after 7 laps (+5). Bleed -1L/-2R.
  • Session 4 (66°): Started 27/28 (Reset TPMS). 34-36 after full session. Result: Finally hit the pressure window, but tires were 170°F. Too hot.
  • Session 5: No adjustment. Perfect on pressure, but had to manage heat with cool-down laps.

Why?

Tires are expensive. Track days are expensive. The more you get of both the more fun it is.