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Downforce calculation

Professional Motorsport Data Analysis

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Hello everyone! I would just like to ask as I was curious as Tim had mentioned it in one of the webinars about using damper potentiometer data to calculate the downforce being produced by the vehicle. My question is how does one go about doing so? Does it also involve taking into account the width of the rear wing for example and it's relative angle in conjunction with the logged data for the damper potentiometers?

Hi Jon,

Using the displacement of the suspension combined with the spring rates can give you a rough estimate of the downforce generated but these do not take into account any tyre squish that is also happening from the increase in the load applied. They will give a good idea of the trend of the downforce generation, and what the balance is. For example, if the front is rising at speed and the rear lowering, then it is showing that there is more load applied to the rear of the vehicle (or positive lift is applied to the front).

Hello Stephen,

Thank you for the reply! I really appreciate it and it did improve my understanding on the topic.

Hi Jon,

Stephen is on the right track. Essentially if you know the spring rates, motion ratios of your suspensions and how much the dampers are moving (from the damper pots) then you can estimate the amount of downforce on each axle. With this method, you don't need to know anything about the aerodynamic configuration of the car.

It helps to run the softest springs you can get away with practically speaking to magnify the amount of compression you will get - this helps to minimise some of the measurement error. You do have to be careful you understand if and when the bump stops are engaging. If they are, you need to take this into account in your deflection/stiffness calculations too.

The best way to do this is with a roll down test on a straight section of race track. Zero the dampers on the setup patch, then get the car up to as high speed as practical and let it roll down in neutral. This is to try to minimise any suspension deflection from load transfer that comes from braking or accelerating.

When using supension travel to calculate changes in downforce, "trye squish" is irrelevant - however, if using a ride height sensor, such as a LASER directed to the ground, it will be.

As Tim said, while it isn't a perfect method, coasting to remove any chassis 'tilt' will give the best overall affect - and can be used to give some indication of what affect the changes will have on drag.

That said, if one has the time, getting data on loadings under acc'n and braking can also be helpful, as can data from different chassis ride heights, as the relationship of the chassis/body to the ground can have a significant affect on how the air passes under and around the vehicle and affects the aero'.

Thank you so much Tim and Gord! I really appreciate it.

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