Q: “I love watching footwork and how great drivers use their feet and work with their hands. I notice that some drivers tap the brake pedal on most straights. Is this just testing to make sure the brakes are still working? This is interesting to me. I race SPB with PCA and it is a similar in horsepower to the MX5. I love watching the MX5 Cup races because of the similarities to the spec racing I do. Should I be checking the brakes with this frequency? I honestly never do it because I am afraid tapping the brakes will slow me down. “
A: In some cars, “pad knockback” is an issue. What happens is the small amount of flex in the hub, or play in the wheel bearings cause the brake rotor (and entire wheel) to move side to side, slightly. And this pushes the brake pads back away from the rotor. So when the driver first goes to apply the brakes, some amount of travel is needed just to get the pads back up against the rotor before they can start applying pressure against the rotor. If a car has a loose wheel bearing, this will show up bad. Often, driving over exit curbs causes this to happen more because it loads the hubs and bearings more, and ultimately pushing back the pads from the rotors.
So drivers will often give the brake pedal a little tap just before the brake zones to get the pads up against the rotor, and that makes the pedal feel solid with the initial application of the brakes going into the brake zone. If your brake pedal feels solid, and doesn’t “pump up” with the first application of the brake (in other words, the pedal doesn’t feel “long,” traveling too far when you first apply the brakes), then you don’t need to do this because your car doesn’t have pad knockback. But if you often feel that the pedal is a little long when you first apply the brakes (and it gets more solid after one application of the pedal), then try giving the pedal a gentle tap before the brake zones.
Notice that sometimes your car will only have the longer pedal in one or two brake zones, but it feels solid everywhere else. That could be because you used more exit curb – or the curb was rougher – in the previous corner, and it’s not like that in other corners. If you feel that the brake pedal is a bit inconsistent this way, it’s probably because you’re only getting pad knockback in some parts of the track, and not others. Again, that’s often because of the amount and roughness of the exit curbs, or even because it’s a right-hand corner, for example, while all the other corners that lead to a brake zone are left-hand corners – and it’s because of a loose wheel bearing on one side of the car.
Does that little tap of the brakes cause the car to slow – or not accelerate as much as it could? Good question. If done right – with a fairly light touch of the pedal – probably not. But if done improperly, then for sure it can cause a problem and hurt straightaway speed. Of course, in spec classes like MX5, every tiny bit makes a difference, so if I was coaching you, I would ask you to try tapping the pedal to see if it made a difference. It might just be a confidence thing, so you know for sure that your brakes will be there when you need them. If the car didn’t really need this tapping of the brakes, then I’d say not to do it. But I know drivers who do this out of habit, just because it makes them feel more confident.