A quick search on YouTube for the new Toyota GR Supra GT4’s appearance at the Goodwood Festival of Speed and you will see just how eagerly anticipated the arrival of this car designed and built by Toyota Gazoo Racing was. Launched as a concept car at the Geneva Motor Show last January, the GR Supra GT4 will be available for private and customer teams to purchase, with a number of SRO (Stéphane Ratel Organisation) GT4 championships announcing their interest bringing the 430bhp machine to their grids.
The cars will be supplied by bespoke tyres from Pirelli, designed specifically with the GR Supra GT4 in mind, and developed and tuned exactly for the car.
But just how do you manage to create bespoke tyres for a racing car, and how easy is it to extract the most out of both parties? Because if it were easy then everyone would do it. The process is a complex but a fast one. The design starts with virtual modelling and then moves on to laboratory testing before the on-track testing process begins.
From the Pirelli side, it is a logical game of problem solving from start to finish. Understanding the car in question is a given but working out exactly how the car behaves faced with the extreme stresses it will invariably undergo on the circuit is the key to making the right tyre for the right circumstances. Getting the tread right is obviously crucial, as the engineers find the delicate balance between wear versus ultimate performance, but it’s not just about the tread, as there are so many elements that make up a successful tyre.
In GT racing, there’s a mix of sprint and endurance driving, which inevitably makes designing a tyre perfect for both incredibly difficult. At the same time as designing the structure, Pirelli’s engineers focus on developing overall performance of the different compounds in the laboratory, testing durability first and foremost. This then creates a baseline in which to extract the speed over one lap.
Once this baseline is identified, stress levels on the sidewalls are tested to make sure that the projected roll and forces going through the car at racing speeds will not break the tyre. All these elements are then combined to make a prototype tyre, from which the eventual bespoke race tyre for each model of car is born.
Now that the baseline is created and engineers and drivers understand it, work then begins on tuning the car to the tyre and the tyre to the car. The front-engined nature of the GR Supra GT4 means that front tyres will require more endurance capabilities, especially in cornering while the oversteer kicking the rear of the car out on acceleration means that the rear tyres also have to cope with a different kind of load than the fronts. This is an example of how every aspect of vehicle behaviour has to be considered when it comes to formulating the tyre design, with the Toyota having some particular characteristics that needed to be considered.
Tyre degradation is an aspect that Pirelli and Toyota have worked together on closely, and analysis of how quickly the baseline set of tyres drop off in performance will always dictate just how many options Pirelli will design. By this process of trial and error, the right tyre is eventually formulated.
The good news for potential customers is that they never have that long to wait to experience the benefits of bespoke tyre development. Whereas tyres for road cars can take around three years from start to finish of development, race car tyres hit the track much sooner – like everything else in the fast-paced world of motorsport.
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