Mastering tire pressure for track performance

Unraveling the complexities and impact on traction, wear, and overall driving experience

Porsche Gt4 Track

Monitoring tire pressure is crucial at all times, yet it becomes more important during track driving, as even a minor discrepancy can lead to significant tire degradation. Driving on regular roads doesn’t generate enough heat in the tires to necessitate constant monitoring. However, when a car is driven aggressively on a track, maintaining optimal pressure becomes crucial.

Why is tire temperature important?

  • Grip: Proper temperature provides optimal grip for traction and handling.
  • Wear: Extreme temperatures can speed up tire wear and affect durability.
  • Performance: Different tire compounds have temperature ranges for best performance.
  • Braking/Corners: Correct temperature is crucial for effective braking and cornering.
  • Consistency: Maintaining temperature leads to consistent lap times.
  • Safety: Incorrect temperature can compromise grip and lead to accidents.

The optimum pressure

Typically, the choice hinges on individual inclinations, yet a common guideline suggests commencing your drive with the manufacturer’s recommended pressure. As you complete a few relatively effortless laps, tire pressure will rise. At this point, return to the pit and restore the pressure to the factory recommended values. The aim is to maintain these values regardless of the tire temperature. Some drivers lean towards marginally reduced pressures; however, this remains a subjective matter, entwined with the specific tire model and individual driving style. At the end of a track day the pressure will be elevated by 0.5 to 0.7 bar compared to the default values. This provides a tangible insight into the extent of temperature increase while racing.

Usage case

The Cayman’s recommended tire pressure stands at 2.0/2.3 for cold tires (front/rear for Michelin Cup2). That is my starting point. Following a few brisk laps, the pressure tends to rise, prompting me to release some air. This may be repeated on hotter days to maintain recommended pressure. Longer breaks can lead to pressure dropping below 2.0 bar, requiring slight reinflation to prevent damage. By the end of the track day, warm tire pressure reaches 2.5/2.8 bar. Before heading home, it’s important to deflate to the recommended values.

Tire pressure is crucial as it directly affects the tire’s contact patch with the road, influencing traction, grip, wear, and overall performance

Rule of thumb: 0,1 bar = 10°C

The majority of vehicles allow drivers to check either tire pressure and/or heat levels. There is a connection between tire pressure and heat generation and it’s influenced by various factors including tire construction, speed, load, road conditions, and more. Though a general link between tire pressure and temperature exists, we can simplify it as a rule of thumb as suggested in the Porsche 997 GT3 manul: raising pressure by 0.1 bar equates to 10 degrees Celsius more heat. For enhanced precision, a temperature shift of 10°C results in a 0.06 bar increase at a starting pressure of 2.0 bar, and a 0.09 bar increase at a starting pressure of 3.0 bar, equating to roughly 3% difference. A change in temperature by 40°C leads to a pressure rise from 2.0 bar to 2.3 bar. At 3.0 bar, the pressure escalates to 3.4 bar. Working in reverse, a pressure shift from 2.0 to 2.5 corresponded to a temperature alteration of 75°C. This implies that the tire at its highest point had a temperature of 105°C.

 

Start temperature Start pressure: 2 bar Start pressure: 3 bar
30°C / 303,15 K 2,000 bar / 29,007 PSI 3,000 bar / 43,511 PSI
40°C / 313,15 K 2,066 bar / 29,964 PSI 3,099 bar / 44,946 PSI
50°C / 323,15 K 2,132 bar / 30,921 PSI 3,198 bar / 46,382 PSI
60°C / 333,15 K 2,198 bar / 31,878 PSI 3,297 bar / 47,817 PSI
70°C / 343,15 K 2,264 bar / 32,835 PSI 3,396 bar / 49,253 PSI
80°C / 353,15 K 2,330 bar / 33,792 PSI 3,495 bar / 50,688 PSI
90°C / 363,15 K 2,396 bar / 34,749 PSI 3,594 bar / 52,123 PSI
100°C / 373,15 K 2,462 bar / 35,706 PSI 3,693 bar / 53,559 PSI

Note: Please be aware that these values have been calculated assuming optimal conditions and circumstances.

Measuring gear

Several approaches exist for managing tire pressure, and among the more widely embraced options are the Makita inflators, including models like DMP180Z and DMP181Z. These inflators offer convenience and affordability, particularly if you already possess other Makita devices that share the same battery. They provide satisfactory accuracy and serve as an excellent starting point for those new to the racing scene.

You can take your expertise to the next level by upgrading to more advanced gear, such as RaceSense. Apart from enhanced precision, RaceSense offers the convenience of syncing with smartphones and the ability to record tire pressure and temperatures. This innovation allows a single individual to swiftly inspect and fine-tune pressures without the need to recall specific tire locations.

Precaution tips

  • Due to the rapid heating of the pressure tubes, it’s recommended to wear gloves, as the air inside can become quite hot.
  • To prevent the risk of losing tire valve caps, you may consider leaving them at home or in a secure place (avoid using the door storage space, as they may dislodge during hard braking)