Taming Tarmac

“The main changes we make to the car set-up for an asphalt rally are the tyres and to the lower ride height. We lower the ride height because we don’t need as much ground clearance on the Tarmac. The reduced centre of gravity is a big step in terms of the cars’ performance especially lateral acceleration.

“If you look closely enough, you will also see that the brake disc diameter is a lot bigger. Tarmac disc diameter is 355mm compared to 300mm on gravel. With the Tarmac wheels we can package the bigger brakes that are needed to dissipate the heat energy from the extra deceleration a Tarmac car has compared to a gravel car.

“The gravel tyres are fitted on 15-inch rims and the Tarmac tyres are on 18-inch rims. The tyre/wheel combination weighs less for Tarmac than it does for gravel.

“A Tarmac car also has stiffer suspension (springs and anti-roll bars) with reduced suspension travel compared to a gravel car. Tarmac surfaces offer more grip than gravel so the Tarmac set-up tends to focus on stability in the chassis.

“As for the drivers, they need to adopt a smoother and cleaner driving approach. They must focus on staying on the Tarmac, rather than taking cuts at the side of the road like they may do on gravel rallies. The tyres have an optimum temperature range that they work best within so leaning on the tyre in the corner rather than sliding the car around the corner is better for the tyres performance and the stage times. Taking cuts will also sap the temperature in the tyre.

“Other subtle changes are in the front and rear differentials, gearbox, engine mapping and suspension geometry.”

Ford will run a brace of Fiesta RS WRC for factory drivers Jari-Matti Latvala and Petter Solberg in Germany. Both will be bidding to give the make its first win on a pure asphalt rally since 2004.