Thread by @llluis555

Do you know why #Rally1 cars have such high wheel arches? And why Toyota and Hyundai's rear arches are the only exceptions to this trend? Aerodynamics is behind it, read on this thread to find out why.... 📸by @MSportLtd #WRClive #WRCliveES #WRCjp #YpresRally

Removing air from the wheel well (and therefore the underbody of the car) is a clever way to reduce the pressure under the car. As the pressure on the car remains constant, the force pushing the car towards the road increases (more downforce = more grip).

In the 2017-2021 #WRC car generation, the air was extracted from the wheel well through the rear fender vents... How can we forget the CD holder on the Toyota Yaris WRC/ Ford Fiesta WRC, or the vertical air vents on the Hyundai?

The regulations for 2022 banned fender vents, forcing teams to search for alternative air extraction, so they increased the space between the wheel arch and the tyre, eliminating the side protection 📸by @HMSGOfficial

With this design, the air has a larger area to escape from the wheel well, reducing the pressure under the car. So why isn't the Toyota's rear arc as high? Because there the air has another alternative to escape📸by @TGR_WRC

Inside the rear wheel arch of the Toyota is an internal duct that carries air to the rear bumper, on either side of the hybrid cooling system fans. The air coming out of this duct is drawn in by the air expelled by the cooling fans and sent to the rear of the car.

Ultimately, the cooling system's fans indirectly help to draw air out from under the car, thus generating some downforce, and making the use of high rear wheel arches unnecessary.

In the case of the Hyundai i20 N #Rally1, the rear arch shows a mixed design, but still with a large open space at the front to allow air to escape.

This is especially important in tarmac events such as the @ypresrally, where car ride height is minimal, and any contribution to reducing the pressure under the car will translate into better grip, i.e. higher speed, especially in the corners. 📸by Nacho Mateo / @Motor_Esport