Oversteer overanalyzed: tuning

In part 1, we discussed that oversteer is caused by having more grip on the front than the rear. That can be accomplished by simply having a lot of weight in the front of the car (FWD), transferring weight to the front of the car by decelerating, locking the rear tires (hand brake or clutch), or smoking the rear tires. A car can also be tuned to oversteer. In the following video, look at how easily the car spins.

You might wonder how the builders achieved that. In a FWD car, it’s not too difficult because the weight is already forward. But does your street car spin every time you turn with the throttle off? No, because the designers tuned understeer into the car with the alignment. Setting the toe is a very effective way to tune handling. There’s a great article on a great website that does a much better job of explaining it than I could. Check this out: http://winhpde.com/track-alignment

Let’s watch another spin that is caused by tuning.

A car isn’t supposed to spin when decelerating in a straight line! Does the driver downshift? No. Does the driver grab the hand brake? No. The rear tires are locking up though, and that causes the spin. Why would this happen? There are several possibilities. Perhaps the rear tires are a different compound from the front and very slippery. A drifter might choose to do that, but not a racer. Another possibility is that the front brake pads are completely worn and the backing plates on rotors provide little stopping power compared to the rear. I think the most likely explanation is that the car’s brake balance was tuned incorrectly either with the use of a brake prop valve or by mixing pad compounds. A prop valve lets you dial in how much pressure goes to the front vs. the rear. It’s easy to use and makes a huge difference. But if set incorrectly, you can spin when braking in a straight line. You can also tune your brake balance depending on what brake pad compound you use. If you find that your front race pads are worn out and all you have to replace them with is OEM equivalents, you may find that your rear brakes are now overpowering your fronts and you’re entering spin city.



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