Oversteer and Understeer Explained - Simpit Driving School

Shaun Cole On March 2, 2015
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This is our fourth episode in the Simpit Driving School.  In this lesson we cover Oversteer and Understeer which are both conditions that can not only effect, but actually control the car.

In this still a beginner level lesson we explain, the difference between the two and what a driver can do to overcome this handling characteristic.  

Each episode of the Simpit Driving School is a step in building our understanding of vehicle dynamics.  In our last episode we talked about weight transfer and it is a big part of cornering.  It is also a big part of over or understeer.  

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Andreas Wagner On 2015-03-03 09:13:25
Andreas Wagner

Very nice video. It might be worth mentioning that the under/oversteer behaviour also depends very much on the brake balance and the characteristics of the tire. In my experience the Formula Mazda doesn't like (is slower) combined lateral and longitudinal conditions when you try to brake into the corner untill just before the apex. It's faster to release the brakes and put all the tires capacity into lateral acceleration.

Concerning understeer, oversteer and weight transfer a little excursion is important to understand why you can fix under- and oversteer with the setup (when transfering weight on one tire this loaded tire has more grip than the unloaded tire -> because of tire degression rate the loaded tire doesn't gain as much grip as the unloaded tire looses -> weight transfer is a bad thing in general so racecars have a low COG and wide track widths to minimize weight transfer -> you can shift the weight transfer in the car by adjusting the rollstiffness of front and rear axle -> common misconception: softer springs don't add grip but only shift grip "capacity" to this axle => the overall grip stays the same unless you change the aero downforce).

In particular I'm interested when to use ARBs and when to use spring stiffness to adjust the steady-state-cornering.


Tim Chitwood On 2015-03-02 19:25:50
Tim Chitwood

I do have a serious question about the under and over steer on iRacing comparing using the "render each seperately" versus "rendering all." I ask this because I have triple screens rated at 120hz but pc set at 60hz because of cabling, with a GTX780 3Gb video card and 16Gb of RAM. But I can really feel a difference in grip between triple rendering or not. It is looser but quicker to recover in not rendered sepeprate. Of course the fps jumps from around 120- 150fps variable in triple rendered up to 180- 220fps in not triple rendered. Plus my pc runs cooler. So it is "loose is fast" or "triple is tighter." There is a small drop off in picture quality, steadiness and color, but I wonder if I am the only one that notices the grip? Sorry it is a bit off subject, but I don't know many people with triples. 


Tim Chitwood On 2015-03-02 17:32:27
Tim Chitwood

That is an excellent video on how the driver can compensate for the conditions of over and understeer. Now if only my reflexes were fast again... LOL


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