T4 SERIES AND TILLOTSON RACING T4 KARTS: 8 INTERESTING FACTS (REGULATIONS, TIRES, GEAR/PINION RATIO) ABOUT THE 4-STROKE SINGLE-MAKE CHAMPIONSHIPS HELD IN OVER 40 COUNTRIES

The Junior, Senior, and Senior 168 categories of the T4 Series use Maxxis tires developed specifically for Tillotson Racing T4 karts (specifically, the T-MAX-DRY3 for dry conditions and the T-MAX-WET1 for wet conditions). These tires are designed to work according to the stresses generated by these karts, which are lower than those of 2-stroke direct drive karts. The difference is linked to the characteristics of Tillotson 4-stroke karts, which have lower speeds and cornering distances than a 2-stroke racing kart: in this context, the tires warm up more slowly and have a harder time reaching the optimal pressure during laps. For this reason, the compound is designed both to quickly reach the optimal operating pressure window and to ensure a wider range of use, making the tire easier to manage. As a result, the tires generally start with higher cold pressure values ​​than those used on 2-stroke single-speed karts. It's important to consider, however, that tarmac and wether conditions significantly influence the behavior of the tire and can lead to even significant variations in the starting values. To provide a practical guideline, Tillotson indicates that the ideal working pressure for dry tires is between 0.8 and 1.0 bar (about 12-14 psi). To achieve this value, in standard grip conditions (i.e., not particularly high and with cool asphalt), it is recommended to start with cold pressures between 0.55 and 0.85 bar (about 8-12 psi). For comparison, a professional mechanic told us that the Maxxis MA01 Prime slick tires used in the 2025 FIA Karting OKJ World Championship, in standard grip conditions, require a cold pressure of about 0.35-0.40 bar (about 5-6 psi) to reach an ideal operating pressure of between 0.65 and 0.70 bar (about 9-10 psi). This comparison reveals two main differences: both the cold pressure values ​​and the ideal operating pressure are lower for 2-stroke karts; furthermore, the operating window is narrower than that of the tires used in the T4 Series.

Editor's note
Want to understand how to correctly choose the cold pressure for every track condition? Read How To | The infallible method by Vega to manage kart tyre pressures in all conditions