In an ideal world, racing drivers also make good test drivers so they can help engineers improve a car’s design. How much time does a racing driver spend test driving compared with training for the track?

I’d estimate the ratio to be 30 per cent testing and 70 per cent racing. Although most drivers aren’t exactly keen on test driving, we all know it’s necessary if you want to improve the car. A test driver has to take the car to its limits in every respect: that’s his job. It’s the only way to get any meaningful data.

Does a racing driver need to understand every last technical detail of their vehicle?

No. It’s useful, of course, to have a general understanding but keeping step with all of the complex technological progress is virtually impossible. That’s why I find it most important to work on precisely those issues with the engineers that can actually help me improve – and learn new things in that regard. But drivers don’t need to be technical experts, just like engineers don’t need to be ace drivers.

When you’re testing a racing car, do you follow a predefined, detailed plan laid out by the engineers or is it more intuitive?

Most test drives follow a specified, carefully worked-out development plan. Lots of things get tested in advance, off-site. But once you’re on the circuit, you don’t muck around with bits and pieces. On the test track, you give it all the stick you’ve got. Of course, you still come across interesting issues during test drives and then follow it up in more detail. I’d say it’s 80 per cent as planned and 20 per cent freestyle.

Do engineers prefer to rely on their measurement data or on the racing driver?

The data is incredibly powerful, there’s no denying it, and it’s getting more and more significant. By now, the technicians can trace every little twitch your fingers make in the vehicle. But it still happens that the data doesn’t match what my guts are telling me and, in those cases, it’s really important to trust your instincts.

What general skills does every test driver need?

They need to maintain a highly consistent driving style as there are loads of other parameters that keep shifting – tyre conditions, grip and so on.
So each person’s driving style needs to be absolutely stable. And test drivers need to have a healthy relationship with the engineers – there’s no space for personal friction there. It needs to be like a good marriage. That’s why you need to concede that the stopwatch makes the final call and not take criticism personally. Even if the engineering team were headed by my mother, if necessary I’d tell her: “mum, it ain’t good enough yet”.

What findings from testing racing cars can you transfer to the development of series vehicles?

Material developments and tyre technologies primarily. But technological advances like anti-lock braking and turbocharging came from motor sports back in the day, too.

How does testing differ for racing cars and standard-production cars?

Racing cars need to survive in a competitive environment. So their tests are far more extreme. Standard-production cars focus more on safety.