- The longest jump ever made in the World Rally Championship was 278 feet
- Most rally cars are made from tiny little compact cars that can barely handle potholes
- We explore how rally cars’ design and engineering makes them capable of such massive jumps.
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Following is a transcript of the video.
Narrator: This right here is the longest jump ever recorded in the World Rally Championship – 278 feet! That’s nearly the length of a football field! So what kind of car did driver Sebastien Loeb have for this incredible feat? A CitroÃ«n C4, a simple European compact car known for its safety and reliability. But how do you send an average economy car into orbit and safely back down again? You transform everything that makes it an average car. From adding a suspension that can handle the landing to an aerodynamic body kit that will prevent it from flying away, it’s all in how rally cars get completely re-engineered from the inside out.
The first important difference between rally cars and road cars is a more aerodynamic design that makes flying through the air a whole lot easier – and safer. Let’s compare a rally car like Hyundai’s i20 WRC model and the automaker’s i20 compact car that it’s based on. Besides both being built on the same steel shell, they look completely different. One screams “race car” while the other screams “new parents”. But those eye-catching additions aren’t just for show. Once the i20 takes flight, it’s aerodynamic additions make sure it comes back down as soon as possible and on its wheels
This requires creating downforce, one of the most important parts of racing in general. Downforce is the downward vertical force on a car that keeps it glued to the ground. In a sport like IndyCar racing that takes place on a smooth flat tarmac, creating downward force is important for simply giving racers more grip in tight corners. But in rallying where there’s constant elevation changes on loose gravel and snow, downforce keeps cars from flying off the track
To generate downforce, rally cars like Hyundai’s i20 WRC are fitted with sloped carbon fibre wings throughout the body. While most obvious is the six-foot long one in the back, there are also small wings positioned over the wheels. These are known as dive planes. Although they may be a different size and shape, their function is the same: As the car drives forward at high speed, it has to cut through air. High pressure air forced under the car creates an upward force on the vehicle known as lift. The wings counteract this lift with downforce. Incoming air forced over the car is slowed down and pushed upward by the wings. The equal and opposite reaction is slower-moving high pressure air now pushing the car downward.This is the downforce needed to keep the car properly balanced.
This downforce is especially useful for jumps. In a rally car that constantly finds itself in the air, having plenty of downforce to stay level and coming straight back down on all four wheels is especially important. Just ask driver Petter Solberg who lost his rear wing in the 2005 Rally Finland.
For the air going underneath the car is a piece known as the splitter added up front right under the bumper. Just as its name suggests, it “splits” the air travelling at the car, sending tighter low pressure air underneath and quickly out the back before it can enact too much lift on the car. Large amounts of slower-moving high pressure air are forced over the car, creating extra downforce. This again helps keep the car level as it takes flight. Without it, the car would be flipped backward right as it took off!
But even if you can send a car flying into the air level and straight down on all four wheels, it means nothing if that car doesn’t have a suspension that can handle the landing. That’s why the suspension that ends up on a WRC rally car looks nothing like what you’ll find on your typical road car, especially the dampers. Dampers or shock absorbers, are the key part of a rally car’s suspension that keeps it from crumpling to pieces when the car comes back down.
On a regular road car, every time your car bounces over a rough surface or hits a nasty bump, the intense energy and vibrations on your wheels are absorbed by a large coil spring. But while those springs are great at absorbing energy, they need something in the way to keep them from bouncing back uncontrollably like a trampoline. That’s where dampers come in. Positioned inside the spring, they’re made up of a long telescopic body with a piston and oil inside. As the spring compresses during a heavy bump or impact on your wheel, so does the damper, and that piston slides down through the oil. As the spring bounces back, the damper is what keeps it under control, as the oil slows down the piston’s return and converts that energy into heat. On a road car the goal of the suspension and dampers is to keep the ride as smooth and comfortable as possible, ideally so you barely notice those bumps at all.
But on a WRC rally car, comfort is the engineers’ last concern. There’s no question there are bumps and bangs coming. You’ve got 1.2 tons of metal crashing down from heights of over 3 feet. The goal is for the car to survive – and keep going as fast as possible. This calls for dampers twice as big and strong so they can handle more intense compression. They’re built thick, heavy and tuned with the intention of absorbing an enormous impact, not making sure the passengers are cosy.
A motorsport like rallying also requires an additional canister connected to the damper. In an especially active damper, oil temperatures are reaching up to 248 degrees Fahrenheit. This can cause your shock absorbers to overheat, which leads to them compressing irregularly and the driver losing control of the vehicle. An additional canister, or “remote reservoir”, allows you to carry more oil and have a place where it can cool down.
The most crucial feature rally car dampers have though is how adjustable they are. With knobs found on both the dampers and throughout the car, everything from ride height, to compression speed, to how fast they rebound can be adjusted. For rally courses that feature more jumps, drivers need a car that’s both higher off the ground with a suspension that they can count on bouncing back immediately and as smoothly as possible when they make a heavy landing.
Just as important to the rally car’s suspension though are the tires. Even if your shock absorbers can handle a jump, if your tires collapse on impact then you aren’t going anywhere. In a league like the WRC, teams have many different types of bespoke tires. For gravel courses where jumps are especially found, the most important thing to have is thick tires with stiff reinforced sidewalls for puncture resistance.
On a normal road tire, tiny steel belts inside the tread provide extra support to the tire’s contact patch. This is the part of the tire that touches the road. However, the tire’s sidewalls are thin and flexible, to make for a more comfortable ride. Gravel rally car tires are the exact opposite, with little support under the contact patch, but sidewalls that are practically bulletproof. This is to prevent hard cornering and hard impacts from causing the rally tire to fold over on itself, or remove itself from the wheel.
Rally tires are also softer than regular tires in terms of the rubber compound used. This allows them to absorb more bumps and shocks. It also gives them more grip when ripping down a gravel stage or landing a high impact jump. The softer compound provides this but won’t last as long as your street tire. Fortunately they aren’t needed to last nearly as long, just until the end of the race.
But even if your car has the aerodynamics to soar through the air smoothly, and a suspension that can handle the landing, it’s going to mean nothing if your car’s undercarriage isn’t protected properly. The undercarriage has many exposed components, like fuel lines that are easily penetrable by sharp rocks and race debris. Consumer cars use carpeting for the underside of the vehicle to reduce road noise and improve airflow, but this does nothing to prevent damage. So the i20 WRC is fitted with three quarter-inch thick steel plates bolted to the underside of the car. Known as skid plates, or sump guards, these tools can also be made from carbon fibre or aluminium. Their main objective is to protect the oil pan, transmission, gear box, and fuel tank from loose stones and debris.
Skid plates help drivers against a number of major car problems, the most dangerous being fuel and oil leaks. While these two issues usually just result in engine failure, they have also caused a number of major fires in the WRC. Esapekka Lappi’s unsolved car fire at March’s Rally Mexico is believed to have been caused by an oil leak. Skid plates drastically improve your chances of avoiding them.
Still the skid plate alone can’t protect you from everything. Just ask driver Elfyn Evans who landed on nothing but his sump guard at last year’s Rally Estonia, and suffered two compression fractures, cutting his season short. No matter how prepared you may be, some rally car disasters are just unavoidable.
So while cars only take to the air in NASCAR and Formula 1 after something has already gone wrong, in the World Rally Championship it’s a major part of the competition. Between being equipped with an aerodynamic body, heavy duty suspension, and a steel plated undercarriage, jumping nearly the length of a football field is something these incredible vehicles can handle day to day. While they may be based on compact cars that can barely handle a pothole, the right kind of engineering can transform them from family vehicles into high-flying tanks.
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