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Rear wing and effect on understeer

Suspension Tuning & Optimization

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Hello,

Next raceweekend we are driving on a high speed track (Spa). Our car is a FWD Seat Cupra (350hp). We are planning on experimenting with adding downforce to the car by adjusting the rear wing. The rear wing is 80cm behind the rear axle, so adding downforce will reduce the pressure on the front tires? The front splitter is not adjustable. Will this cause understeer? If so, can you counter this by changing the dampers (rear compression harder, front rebound softer?) Are there other options or thoughts?

Thanks in advance!

It will possibly reduce the front downforce, but in a much smaller proportion to the downforce you will add at the rear. So adjust the rear wing to find balance in high-speed corners.

With a fixed splitter at the front, typically lowering the front will increase downforce. You may not need to do this as the increased speed will have the tendency to reduce the ride height due to the downforce, and this increases the downforce (without something like a third spring), this can eventually lead to uncontrolled porpoising (see F1 in early 2022!)

Prepare to replace skid blocks on the front, and if you get severe bouncing at high speed, stop and raise the ride height before you destroy the front splitter (unless you have resources to fit a new one each session).

Change the wing in small steps and see what happens.

if I were to change damper settings, it would be stiffen rebound at the front so the nose stays low to the ground (increasing downforce) as much as possible.

Ther rear wing is a cantilever structure, as you say, increasing the downforce will lift the front, pivoting around the rear axle, in inverse ratio with the distances from the rear axle. You can't change that aspect of it, but you can make changes that may minimise the negative affects and/or balance them with the wing, such as rake angle of the vehicle.

Don't know too much about the car you're using, but may be worth checking out the videos on the ETC/WTC(?) races there and seeing what you can pick up on the setups they used.

There are some much smarter folks here, but it may be worth thinking about the front splitter ride height, usually it's helpful to run it as close as possible to the track surface but the compression through eau Rouge (and the reported bump this year) may cause the splitter to contact the track surface and/or bottom out the suspension (not forgetting the tyre compression).

Spa is mostly a high speed track, have you experience there that shows under, or over, steer to actually be a problem? I haven't been there, but I understand the main concerns, especially with the potential for snap oversteer, would be the dip at eau Rouge and the crest leading onto the Kemmel Straight - the latter being the bigger concern because the rear may get very light?

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