Two things I can guarantee will occur during a NASA High Performance Driving Event. First, I know you are going to have a great time on track, and second, your brakes are going to get super hot! Especially for folks who are using a daily driven street car, I assure you that your brakes are going to withstand temperatures they have never seen before. I don’t care how many spirited trips you make during the weekend to Ace Hardware to buy toilet parts. Trust me, your brakes will be much hotter after one session on track. This is simply a function of a relatively heavy car slowing down from high speeds over and over again as you drive around the track. All of that kinetic energy is transformed into thermal energy as your brakes slow you down. This is a good thing. It ensures you don’t fly off the track in a turn. But too much heat in a brake system and you may find your brakes can’t slow you down enough, and then you might fly off the track in a turn. Nobody wants that. Don’t worry, we have a solution.
We previously covered How To Ensure A Safe HPDE Experience With Upgraded Brake Fluid in an earlier story here at Speed News. A simple bottle of high performance brake fluid will do wonders to ensure your brakes don’t fade — or worse, fail — during an HPDE session. But the fluid is just part of the story. For those who want to go harder and deeper into the corners, you may find that even with really good racing brake fluid in your brake lines, you still may begin to find some brake fade — the pedal becoming soft, or the car not slowing as it normally should. If this happens you may want to consider finding a way to cool your brake components.
The good news is cooling brakes isn’t difficult. As a car moves down a race track air is swirling all around the car. The trick is to try to divert some of that air directly into the inside of the wheel where the brake components are located. In most cases, this is only needed for the front brakes. Average commercially sold front-engine vehicles have a front weight bias and thus have larger front brakes than rear brakes because the front brakes do most of the work. If you use a pyrometer to check your brake rotor temperatures after an HPDE session you will see the front rotors are considerably hotter than the rears. If you can divert some air at the front of the car toward the front rotors, you will effectively solve the issue of too much heat in your brake system.
You have probably seen professional racecars with some sort of a ducting system and silicone hoses to lower their brake temperatures. If you watch pit stops during the 24 Hours of Le Mans, you will spy systems designed to divert to cool air toward hot components of a car. You don’t have to possess a dedicated track car or be a professional race team to harness this technology. To cool brakes, all it takes is a duct and some hoses to make this rudimentary system work. For our team’s 2019 Ford Fiesta ST, which we prepared for the NASA sanctioned One Lap of America event, we sourced some ducts and heat-resistant silicone hoses from I/O Port Racing Supplies and built our own system. We used square ducts that feed round hose, but NACA ducts also can be used.
If you are wondering what a NACA duct is, don’t feel dumb. I had no idea what the acronym for NACA stood for either, and it was created way before I was born. NACA stands for the U.S. National Advisory Committee for Aeronautics, which in 1945 was the precursor to what we know now as NASA. No, this time I don’t mean the National Auto Sport Association, but the “Let’s go to the Moon” NASA, the National Aeronautics and Space Administration. The National Advisory Committee for Aeronautics designed the NACA duct as a low-drag air inlet design for aerospace. Now we use it on racecars. Congratulations, you learned something today.
For our brake cooling system, we simply cut two rectangular holes into the front air dam of the Fiesta. We cut the holes just a bit smaller than the overall size of the duct inlets. We drilled four holes through each duct as we held the ducts up to the air dam (simultaneously drilling holes into the air dam) and then used aluminum rivets to hold the ducts into place. Then we took the silicone hose and used a basic radiator clamp to hold the hose on the duct. The trick to setting up one of these systems is ensuring all of your diameters are the same. NACA, round and rectangular ducts and silicone hoses come in different diameters. For our Honda Challenge racecar, we use a smaller, 2.5-inch-diameter hose, but for the Fiesta, we used a larger, 3-inch-diameter hose because the car was heavier and the brakes were smaller, thus they would require more air for effective cooling.
A word from the wise here: Do not go to Home Depot and buy household dryer vent line to attempt to cool your vehicle’s brakes. Even though it is for a “dryer” which you would assume is hot, those temperatures are nowhere near the temps your car’s brakes will attain. Secondarily, even though the household dryer vent tubing is designed for air to move through it, it is not designed for high speed air, like 120 miles per hour air. Yes, the dryer vent tubing looks very similar to the silicone hose used for venting brakes however, if you put household vent tubing on your car it will melt during the first session and what isn’t melted will be blown to smithereens by rushing air. Don’t do it. Only use heat-resistant silicone hose designed for brake cooling. Okay, parental warning over.
To make a brake-cooling system effective, it really comes down to where you aim the exit of the cooling tubing. The closer you can get it to your target, which should be the front brake caliper and disc, the more success you will see in this system actually cooling the brakes. I have fabricated more complicated versions of this by having a piece of metal tubing attached to the brake caliper, which the silicone tubing was attached to with a radiator clamp. And I have simply zip-tied the tubing to suspension components and then aimed the tubing at the brake rotor. Both work. Sometimes the simpler method works best.
Heat often can be the enemy when it comes to a braking system, and a single HPDE session on track can find that amount of heat. With just a few simple components totaling less than $100, and a project that took us less than three hours, we were able ensure our front brakes were cooled down, allowing us the ability to brake later, harder and deeper. The goal here is simple: stay cool. Get your car up on some jack stands, look around and see if there is space and an opportunity to build your own brake-cooling system. Good luck and remember that more passes are made under the brake pedal than under the gas pedal. Happy fabricating!
Great technical info. as always.
Lets not forget about higher temp track pads as well. Perhaps that should come before the cooling ducts.
That last statement may not be appropriate for group 1-3 drivers LOL
The NACA inlet you refer to, is not the one you used. The low drag NACA duct is shaped like a Concord wing plan form. Sits flush on a panel parallel to the air flow.
This article would have been a great time to mention that silicone brake hose is more expensive than regular black spiral hose. The air passing thorough the hose if cool from outside so the silicone expense is overkill.
I would question the wisdom of drilling holes in a highly stressed part like the lower control arms especially with stiff springs.
A simple air coop is not a NACA duct. NACA ducts are used on flat surfaces parallel to the air flow.
The car of the article thinks well, but the design is very poor quality, I would say dangerous. Having it fastened with plastic straps so close to thermally stressed components is very silly. The hose ends in front of the brake cover plate, so the effect will be minimal – it is necessary to drill a hole in this plate, fit the seat and direct the air flow directly at the disc and the brake caliper. In addition, it will soon fall out of the car. The idea is good, but next time to fine-tune and install better.
In addition, I have now noticed that holes have been drilled in the lower arm of the front axle to secure the hose! In that case, you can only say that the idiot did it. The arm is a very stressed part of the profiled material, sooner or later there will be a rupture and fatal accident of the whole vehicle in the place of the hole. The incredible idiocy of the one who did it ..