A tire change per race is mandatory for every DTM driver. In the extremely close competition of the racing series, the change of the four wheels is a very decisive moment. Every step, every grip must fit perfectly. And that’s why there is practice every day.
Motorsport is a team sport. Following this basic idea, at least one pit stop per driver is mandatory in every DTM race. During this pit stop all four wheels of his car have to be changed.
In addition to the driver and the engineer responsible for his car (race engineer), nine other team members are decisive. These are in detail: a “jack man”, one “tyre gunner” and one “tire carrier” each for the left and right side of the vehicle as well as one “wheel-off man” each per wheel, as these mechanics are called in technical jargon. Apart from these nine persons, nobody else is allowed to work on the car during the prescribed wheel change.
And this is how the stop works: With the maximum speed of 50 km/h allowed in the pit lane, the driver rolls towards his own pit on the fast lane. During the current lap, his team has given him the order to come in via the pit board. Just before his garage, the driver turns into the work area directly in front of it and stops in the transition zone marked on the asphalt. “He must not stop more than twenty centimeters too far in front or too far behind, otherwise he will miss his crew. The crew then has to reposition itself and valuable time is lost,” explains Erich Baumgärtner from Audi Sport Team Rosberg. Baumgärtner is Jamie Green’s race engineer in the 2019 DTM winning team.
The next steps: The car is stationary. With the air lance the “jack man” activates the air jacks built into the car floor. They drive out and lift the car. This happens on the left and right side of the car in parallel: The “tire gunner” loosens the central nut of the rear wheel with the impact wrench, which is also driven by high air pressure. He takes one hand from the impact wrench and rips the loosened wheel off the hub. The “wheel-off man” catches it so that it cannot roll away and does not get stuck in the way. Meanwhile the “tire carrier” has put the new wheel together with the fresh tire on the hub. The “tire gunner” puts the wheel nut remaining in the socket of the impact wrench back on and tightens it.
After that, “tire gunner” and “tire carrier” on both sides of the car change to the front wheel, where a new “wheel-off man” is added each time. The exchange process is repeated. When the last two new wheels are fixed, the “lancer” lets the air jacks drive in. Since stopping, no more than seven seconds should have passed on the stopwatch by then. Otherwise the service was too long and one or even several position losses are imminent. “When the car goes down again, that’s usually the sign for me to start,” says defending champion René Rast. Exception: His race engineer sparks “Wait!” in his ear because the Fast Lane is not yet free for threading. Anyone who drives off anyway and obstructs a competitor in the process will be punished for “unsafe release”.
By the way, the order in which the wheels are changed is optional in the DTM. “We start at the rear axle with the drive wheels, mainly because it’s safer. This way, we avoid the risk of a mechanic being injured if the driver releases the brakes too early,” says Erich Baumgärtner explaining the philosophy of Audi Sport Team Rosberg. At Audi Sport Team Abt Sportsline and Audi Sport Team Phoenix, the crews change like this: on the side of the car facing the pit wall first at the front and then at the back, on the side of the car facing the pit first at the back and then at the front. “In this way our mechanics on the impact wrench can work on the wheel nut first, whose hub they can see better from their standing position when the car is pulled over, and therefore can aim better,” says Thomas Biermaier, CEO of ABT Sportsline.
The sources of error during pit stops: The driver misses the transition zone. The “tire gunner” misses the wheel nut at the first target attempt with the impact wrench. The “wheel-off man” stumbles with the removed old wheel. The “tire carrier” jams the new wheel and has to maneuver it onto the hub again. “With the app. 30 kilograms that a tire and rim weigh, this happens quickly despite all the practice,” says Erich Baumgärtner. And particularly time-consuming: The car is lowered before all the new wheels are on it. After all, the race engineer can make a mistake: If he lets his driver drive off despite traffic on Fast Lane.
Plenty of power, precise coordination and strong nerves are the most important requirements for a job in a pit stop crew. “In winter we do more strength training, coordination and concentration exercises,” says Baumgärtner. In the workshop of Audi Sport Team Rosberg there is also a drivable dummy of a DTM car on which wheel changes are practiced twice per working day during the season in a race-like manner. “The key to permanently successful pit stops, I think, is mental strength,” says Ernst Moser. The director of Audi Sport Team Phoenix should know: Since 2011, his pit stop crew has been the best in a DTM season four times – most recently three times in a row. “You can’t train the mental strength required for this, it grows over time due to the long collaboration of the same team,” says Moser.
For faster pit stops, Audi Sport Team Abt Sportsline will have its change crew trained by a former professional soccer player from the German Bundesliga and the German U21 national team from the 2020 season onwards: Frank Wilblishauser. The former defensive player of 1. FC Nuremberg, today an alternative practitioner, was hired as a fitness coach. “In the unbelievably close competition of the DTM, the pit stops are so crucial that we have to practice them as professionally as possible and complete them as flawlessly as possible,” Thomas Biermaier says.