Massive jumps, often several dozen metres long, are one of the highlights of the World Rally Championship. This year’s WRC 2 Pro champion Kalle Rovanperä from ŠKODA Motorsport explains the technique for a perfect jump.
Rally cars spend quite a lot of time mid-air and for their drivers, it’s a natural part of competition. For example, Eyvind Brynildsen flew his ŠKODA FABIA R5 a whole 39 metres on the legendary Colin’s Crest in Sweden. Still, the jumps don’t go perfectly every time. Ideally, the car should land on all four wheels at once – or at least onboth wheels on one axle. To achieve this, the driver must adjust his driving style to each jump’s profile.
Watch the video, in which this year’s WRC 2 Pro champion Kalle Rovanperä shares his recipe for the perfect jump:
“Considering the stress placed on the car, the worst case is landing on just one wheel. This situation is especially critical for half-shafts, differentials and other drivetrain components,”says Eric Mommey, chief engineer of ŠKODA Motorsport. This makes the right driving technique very important. For example, if the driver loses confidence before the jump and brakes too much, he may end up landing hard on the front axle.
Some rallies are especially well-known for their numerous long jumps – like Finland or Sweden. In these cases, the car is set-up specifically for jumping. Engineers try to assess the track’s profile as accurately as possible during the reconnaissance drives, and adjust the suspension settings accordingly.
“If there are several jumps on the track, the shock absorbers are set up stiffer, especially for fast compression, which is most important for landing after jumps. This allows the shocks to absorb more energy on impact. Besides that, the ground clearance can be changed. The higher ground clearance helps to increase the compression travel of the shock absorber during the shorter jumps, where it doesn’t have enough time to go all the way down”, explains Eric Mommey.
The engineers recognize two main types of jumps – short ones, where the car is airborne for less than a second, and the long ones. The short ones are, paradoxically, trickier. If the car flies through the air for more than a second, the wheels have time to go all the way down, so the full travel of the shock absorber is available on impact. During the short jump, the wheels don’t go all the way down, the shock absorber’s full travel is not available and it’s hard for all the energy to be absorbed by just the suspension travel. That’s why a hydraulic bump stop is installed in the shock absorber– it absorbs part of the energy.
So, how to properly jump in a rally car? Brake before the jump and straighten the car, then quickly step on the gas to prevent moving too much weight to the front axle and lightening the rear - and then just enjoy the flight with your pedal to the metal!