Q: “I have a question on trail braking when driving an active aero vehicle. I have a 2008 ADAC Dallara F4 with front and rear wings. Obviously, going into a corner with some speed, the front wing helps keep grip on the tires. I can add more with trail braking, but the question is: how much less braking input is required due to the wing? Ignoring all the technical details, generally, with a ground-effect, winged vehicle, what is the difference in trail braking vs a GT car, such as a Corvette? More? Less?”

A: I should begin my answer with the standard go-to… “It depends”! 🙂

Generally, whether a car has more aero or not, it won’t make a difference in the amount of trail braking. I say “generally” because the car’s aero balance could impact the amount of trail braking required; if the car has more rear downforce than front, then more trail braking would help, and vice versa.

A car’s weight distribution will impact the amount of trail braking required to go fast, though. Let’s pick a previous gen Vette, rather than a C8, for example. With most of the weight up front, more trail braking might help to get it to change direction (think of all that weight up front wanting to go straight and not change direction – you need to do something to help it turn). That’s the same with almost any heavy front-engine car.

Plus, there’s something called “polar moment of inertia.” Imagine a dumbbell with weights at the far ends of the bar; you hold it in one hand and twist it from one direction to the other. As you go to change direction from one to the other, it’s hard to do, right? Now imagine moving the weights closer into the middle of the dumbbell, until they’re touching either side of your hand, and twist it back and forth again. Much easier to change direction, right? That’s why a car with the weight concentrated in the middle – like mid-engine cars – are easier to get to change direction. And typically, but not always, they don’t need as much trail braking to get the car to turn while entering the corner.

Something else to consider: If the setup on your car – whether it’s a F4, C8, go-kart, Indy car, NASCAR Cup car, whatever – is such that it tends to make your car understeer, you’re going to want to use a bit more trail braking to help overcome that. If the setup induces oversteer entering the corner, then you’re going to want to use less trail braking.

I hope the take-away from my answer is that the amount of trail braking you use is less about what the car is, and more about what the car NEEDS. You could take two Dallara F4 cars with different setups, and they will require a different amount of trail braking. Same with two C8 Vettes; different setups result in different handling characteristics, and that means different amounts of trail braking.