Why Manual Brakes are used in the Fastest Track Cars
8 minute read
By Bryan Leonard, Pro Race Car Driver and Chase Bays Builds Manager
When searching for speed on track, the most misunderstood and hardest to accomplish properly...and best place to find a lap time...is in the braking zone. How you apply brake pressure, when to apply it, how much is needed, and when do you release. Those are crucial to getting the speed out of your car. I have driven everything from bone stock miatas to big horsepower time attack cars to 992 GT3 cup cars, and everything in between. I have driven these cars from a general track day to a professional wheel to wheel race series, and again, everything in between.
The one thing all properly built and sorted race cars have in common? Manual brakes. There are multiple reasons for this but the biggest one is, consistency. The brake pedal feels the same way everytime. When you can rely on that, you can produce a much better lap time. Is the pedal harder? Absolutely, and that’s a good thing. Its not hard enough to generate fatigue. If it's that hard and the car doesn’t stop properly then the bore size or pedal ratio is incorrect (assuming the right pads are used and/or heated properly if a race pad is used). I have completed 4 hour stints with manual brake setups and haven’t remotely felt any leg fatigue.
The analogy I always use with newcomers to manual brakes is as follows. If you press your finger against a wall, and I ask you for a little pressure you can feel that in your finger. Now I ask for medium pressure, you press harder the wall doesn’t move, you feel that in your finger. Now I ask for a lot of pressure, you can see where this is going. Just because the wall didn’t move didn’t mean there was no pressure. The same holds true with manual brakes. There is some movement in the pedal since you are displacing fluids.
In our analogy, you can see that your finger feels the pressure. The wall is consistent therefore you can easily apply different pressures without having to worry about an inconsistency in the wall. This is true with a manual brake as well. Under braking you will be able to feel in your body the exact pressure you want. Every lap of every turn you will be able to build a game plan. Also not all braking zones are the same, some require high pressures some require just enough to scrub a couple MPH off. With a manual brake you can feel that pressure much easier.
Have a look at this brake trace, for those of you who haven’t seen brake traces through data acquisition such as VBOX or Motec, a brake pressure graph shows you how much pressure and at what point in time you used it. Initial brake pressure should be your highest, generally, and you should trail off as you add wheel angle. As you can see in the first photo, my brake pressures are almost vertical each zone. This is good. The car is a Porsche 992 GT3 Cup car with no ABS. You can see in the second photo how much more pressure I was able to use with ABS in a different car, in this case a Cayman GT4 MR.
So imagine those lines, now, with a brake booster those lines end up building what I call “mounds”.
The onset of your brake pressure is more rounded with the peak being in the middle of your brake trace. What happens is you will continue to brake for too long, then snap off your brake pressure. So you end up with a “mound” then a snap off. The reason why is, you realize you have been braking to long and its time to turn, thus snapping off brake pressure. This will unsettle the car and cause a fight between you and the car at mid corner. I do not have an example of a power brake with data since we do not use that type of system in race cars. I drew a theoretical one compared to an above trace. Hopefully this helps with the question, why are manual brakes better. There is certainly more detail available but this is a good generalization.
Now that we are convinced and believe in the manual brake, we should discuss cost effectiveness. The two cars I showed have incredibly expensive systems. If you were going to create your own, you would start with a pedal mount system which is roughly 900 dollars before you purchase master cylinders. Now you have the option, floor mount or overhung? Both have extreme challenges from a fab standpoint. If you aren’t doing this yourself be prepared. We built a system for a Gen V camaro that was just over $9,000 dollars from modifying the floor board to accept the pedal assembly, to the parts (brackets, master cylinders, throttle pedal, throttle pedal attachment, false floor, lines, fittings, etc) the labor to cut and weld and build something beefy enough to not rip the pedals from the floor during heavy braking. There are a few setups that are firewall mounted that protrude into the engine bay that run roughly $4,000 dollars for a few select cars.
These are all dual master setups with balance bars. They are great, but it’s not exactly in most of the grassroots/amateur motorsports worlds budget. Enter the Chase Bays Dual Piston Brake Booster Delete with Bolt-On 6:1 Pedal Ratio. This system allows you to receive many benefits from the manual brakes, without the fab/cost of an expensive system. Having now driven with this system, and won our first race with one, I can confidently say this is your ticket to faster laps. We took someone with zero experience with a manual brake, installed this system on his car, he immediately went faster. The only piece of advice I would give is to pump your brakes before the braking zones. Not a large amount of pressure, maybe 10%...just enough to reset the pads. Unless you have anti-knock back springs you need to do this. The power brakes give off the false sense of not needing to do this. I can assure you, you need to. When you strike curbs or load a side, the pads will push back a little. Thus the pedal will travel further making it seem like you have a long pedal. This happens on manual or power brakes. The power brakes just mask this a little bit more. By giving the brakes a small tap with your left foot pre-turn, you will have knocked the pads back into place.
Anyone that I have introduced to manual brakes have questioned why they didn’t do this sooner. I would list this Chase Bays mod as a must for any track day/ grassroots/Am racer where the series allows it. Its compact, its attractive, the engineering is already finished.
As I said before braking is the most crucial thing you can do on track. People should stop worrying about horsepower and start wondering how to get their mid corner speed up. The way to do this is to properly execute braking zones. Ditch the factory components, get a Chase Bays Dual Piston Brake Booster Delete. You will easily go faster immediately and become a better driver. Things to remember:
Set the pads in the straights right before a braking zone
Initial brake force is the highest, trail off, as you wheel angle increases, steering angle should decrease.
Release gradually, do not snap off.