Intermediate Topic #2: brake pressure

This series of posts is aimed at you, the intermediate driver. Let’s identify and fix some common errors. If you’re not an intermediate driver, just know that you can become one if you try hard enough.

If there’s one defining flaw of the intermediate driver, it’s too much emphasis on the phrase in slow, out fast. This leads to several related problems, which I’ll be discussing in the next couple posts.

The problem with threshold braking

Remember those days when you were afraid to hit the brakes hard? Probably not. Your mind was so full of the track that you were barely aware of what your limbs were doing. There was no spare attention for self-assessment. I’m guessing that like a lot of novices, you coasted into your braking zones. We all did at one point. But not anymore! Your car brakes so well it feels like your eyes are going to pop out of their sockets. Once you get a little experience, you start to feel the fun in braking. There are more Gs in braking than there are in accelerating or cornering. While threshold braking is a skill that is important to master, it may also be holding you back. We all know that exit speed is the key to a corner. But what you might not appreciate is that the entry speed determines the exit speed. However, that comes with some risk.

Exiting a corner on the limit is like tightrope-walking; entering a corner on the limit is like jumping onto a tightrope while blindfolded –Mark Donohue

There is an ideal speed at the entry that maximizes the exit speed. Too slow and the corner is ruined. Too fast and you may end up off track. Most drivers recognize that too slow is a lot safer than too fast and therefore drive too slow. Now let’s imagine you have a blindfold on and there is a rope in front of you and you are forced to walk it. Are you going to jump blindly or inch forward to feel where it is? The more time you take to inch forward, the more likely it is you’ll find the rope and have some success walking it. And so it is with entry speeds. The more time you give yourself to feel the entry speed, the more you’ll be able to maximize it without going too far over. The problem with aggressive braking is that it robs you of the time you’re allowed to probe. To get more experience in optimizing your entry speed, you need to spend more time sensing it, thinking about it, and adjusting to it.

The exercise: triangular brake pressure

In the figure below, I’ve loaded up some demonstration laps from Assetto Corsa into Race Studio Analysis. The blue line is hard braking while the red line is soft braking. Note how much higher the blue traces are than the red. They are also much more rectangular in shape. That’s not only because the top is flat, but the sides are vertical. This is using the brake as an on/off switch. For the exercise, I want you to make your brake pressure triangular. Build it up and then trail it off. Yeah, this is exactly what some instructor told you not to do at one point. Go slowly enough that you can spare the attention to your braking foot.

Try to build up your entry speed by braking less and less. However, the goal isn’t to stop braking but to stop over-braking. Drag your brake through the corner entry and you will feel the steering wheel start self-centering. This is a kind of tactile speedometer that your hands will learn to read. My favorite reason to trail-brake isn’t rotation but speed-sensing. A relaxed grip will help you in this endeavor.

U-shaped speed trace

If you’re rolling more speed through the corner entry, your speed traces will have U-shaped bottoms (red) rather than V-shaped bottoms (blue). A V-shape indicates an abrupt change in speed. That typically happens if you mash one pedal and then the other. If you’re holding speed, the speed trace is much more gradual in descent.

But wait, there’s more

In the graph above, one thing you may notice is that the red laps are more consistent than the blue laps. It’s easier to drive when the car isn’t being yanked fore and aft. The red laps are also faster by about 1 second. If you counted up how many lines there are, you would also observe that there are 10 blue lines and 11 red ones. That’s because soft brakes increased fuel economy by 10%. Can it really be true that braking softer results in faster laps, less wear, increased economy, and more consistency? Yes, but don’t take my word for it, try it yourself.

So when do you go back to threshold braking? Is never okay? Yes, I think it is. By giving yourself more time to set the ideal entry speed, you’re on the path to advanced driving techniques (like zero steer). Mashing the brake pedal leads to flat-spotted tires, understeer, bad decisions, and remaining an intermediate driver forever.