As you prepare to head to your next HPDE weekend, you are probably thinking about one thing: speed. That is perfectly normal. Speed is a drug that most NASA members are completely addicted to. And since you are addicted to speed, you might be considering upgrading a part of your car to help you get around the track quicker. But, before you start buying some speedy bits online, allow me to suggest a really smart upgrade you should do to your car before heading to any race track: replace the brake fluid.
The brake fluid the manufacturer put in your car is perfectly sufficient for getting you to the grocery store to pick up some bacon wrapped jalapeno poppers. However, at the racetrack during about lap three as you head into Turn 1 after a flying down a long straight, you will need to slow down 3,500 pounds worth of quickly moving mass. As all of this steel, glass, and rubber (with your body inside) heads into Turn 1 at ludicrous speed, you will probably feel your brake pedal get soft and go closer and closer to the floor. Will your car slow down for the curve? Not knowing is scary. You have created an enormous amount of heat in your braking system as you drove around the track and now a portion of your brake fluid is boiling, creating gas, and gas compresses, hence why your foot is going dangerously closer to the floor pan. It will be difficult to have this vehicle get you to work on Monday if it is upside down.
Braking during track days create lots and lots of heat. OEM brake fluid doesn’t have a high enough boiling point for the fluid to withstand racetrack temperatures. DOT 3 brake fluid is designed to have a boiling point of 401 degrees Fahrenheit, which is an easily attainable temperature during an HPDE weekend — in fact, it is attainable within three laps. The good news is there are plenty of manufactures who sell brake fluid with a higher boiling point. ProSpeed RS683 Xtreme Performance Brake Fluid has a boiling temperature of 683 degrees Fahrenheit. That is a 41 percent increase in temperature before it boils. This higher temp fluid can be easily poured into your brake master cylinder reservoir under your hood. You do not need to replace any other brake components to allow your braking system to work as designed during moderate higher temperatures.
Once you have the upgraded high performance brake fluid of your choice — do not use silicone-based fluids — it is time to bleed the brakes. You will want to replace every drop of your O.E.M. fluid with the new fluid, which means while adding new brake fluid you will have to push the old fluid from the master cylinder (under the hood) to each brake caliper (at each wheel) by pressing the brake pedal and opening and closing the bleeder screw at the brake calipers. Since you can’t be in two places at once, you will want a shop buddy for this project. Whomever you choose to help you does not need to be a mechanic, they simply need to possess the ability to press the brake pedal over and over and over again. Any one-legged idiot will work.
The number one thing you don’t want to do is add air to the braking system during this process. Air compresses and makes your brake pedal super soft. The whole point of this project is to keep the brake pedal stiff. Getting air into the system while bleeding can happen one of two ways. The first way is to not have enough brake fluid in the master cylinder and pump the master cylinder dry. We avoid this by having a third buddy just stand over the master cylinder and continually add fluid. If you don’t have a third friend to help out, my suggestion is to continually check the master cylinder fluid level after every five bleed cycles — a bleed cycle will be explained below.
The second way air can enter the system is if a bleeder screw is left open on the caliper and the brake pedal is allowed to come up sucking air into the system. We ensure this doesn’t happen by using a work flow for opening and closing the bleeder screw in sequence with the person in the driver seat pressing and releasing the brake pedal. This will all make sense in a few paragraphs.
Once you have your car up on jack stands, all four wheels off, the hood up, a friend chilling in the driver seat, and the master cylinder topped off with your new racing brake fluid it is time to get start with the brake caliper that is the farthest away from your master cylinder. For left-hand-drive cars shipped to the United States, that is usually the right rear brake caliper. Here you will need the perfectly sized boxed end wrench for the bleeder screw on your brake caliper. When your brake pedal buddy presses on the brakes and you slightly crack this bleeder screw corrosive brake fluid is going to come squirting out. To keep your garage from being completely covered in brake fluid, we suggest using a brake fluid collection bottle with a see through tube that fits perfectly on the bleeder screw nipple. This will keep things nice and clean and also let you see if any air bubbles are coming out of your braking system.
Now that you have your brake bleed bottle in place, your end wrench ready to go and your friend sitting in the driver seat, it is time to go over the order of operations for a bleed cycle.
BLEED CYCLE
1. With the bleeder screw tight yell out, “Pedal!”
2. The one-legged idiot in the driver seat pushes down on the pedal and yells out, “Pressure!”
3. You slightly loosen the brake bleeder screw and watch the fluid pour through the tube and look for any bubbles as the fluid enters the bottle.
4. When the brake pedal hits the floor the idiot in the driver seat yells out, “Floor!”
5. You tighten the brake bleeder screw and then yell out, “Release!”
6. The idiot in the driver seat takes his foot off the brake.
You will complete this six-step bleed cycle process over and over again. After every five sequences, stop — when the system is closed — and top off the master cylinder brake fluid reservoir. You will continue this process until you see the dirty brown O.E.M. fluid coming through the tube suddenly change color. This is the brand new fluid coming through the brake caliper.
By now your friend in the driver seat will be getting impatient and start to complain that his leg is sore. Too bad! We still have three more calipers to bleed. The good news is the first caliper takes the longest since the entire reservoir had to be flushed. The last three calipers will go pretty quickly because it is just the brake line from the proportioning valve to the individual brake calipers that still needs to be bled. Here is the order you should bleed the calipers.
1. Right Rear (just completed)
2. Left Rear
3. Right Front
4. Left Front
The order of calipers to be bled is based on their distance from the master cylinder. We try to go furthest to closest to get all of the old fluid out.
Brake fluid has a tendency to absorb water. Water is a fluid that will not compress, however it will quickly turn into a gas at 212 degrees Fahrenheit, and gas does compress. It is important your racing brake fluid does not have any water in it. It is recommended on cars that see a lot of track duty that the brake fluid is flushed once every 12 months. Brake fluid does not circulate through the brake system. The fluid that is in the caliper, remains in the caliper constantly. The brake caliper is where most of the heat is concentrated in a brake system. Many racers will bleed just a few inches of brake line to ensure the fluid that is in the caliper is fresh. The process for this is exactly the same as explained above except instead of pushing all new fluid through the system, you will just do two brake pedal depressions per caliper or until you see clean fluid come through the tube. Top off the brake master cylinder and you are good to go. To battle keeping water out of our brake fluid we label any bottle we open with the date the seal was cracked on it. We toss out any bottle that has been opened for a year.
Besides brake fluid, which we have proven is a simple upgrade, you can also upgrade your brake pads to sustain high temperatures during track days. Similar to the OEM brake fluid, OEM brake pads are manufactured for day-to-day passenger car travel. They are designed to not squeal, not leave a lot of dust and not cost very much. A racing brake pad is designed to withstand high racing temperatures, fit inside your stock brake calipers and endure hard repeated use. There is a tradeoff though, most racing pads will leave your wheels black from dust after a day on the track and squeal like a school bus. Some people choose to swap in and out their racing pads for track days. Other folks just rock the racing pads on the street. Choose your own adventure.
HPDE events are extremely fun, and NASA wants them to always be a fun and safe experience for you. By upgrading your brake fluid, you can help ensure you won’t run into a scary situation on track where your brake pedal goes to the floor. This simple upgrade project can be done for $60 in brake fluid and a half an hour’s worth of work – which is an extremely inexpensive investment for safety. So, before you register for your next track day, be smart and upgrade your brake fluid.
hi temp dot4 is expensive, instead of tossing bottles with unknown moisture content, use a $15 tester, less waste that way
A $15 brake fluid tester is not going to be very reliable. Plus perspective is important … fresh high temp brake fluid will seem really cheap in hindsight if you used old fluid that seemed OK, then boiled the brakes and hit a wall. Start with a fresh bottle every time.
Not all brake bleed sequence is in the order mentioned, so be certain to check for each specific make and model; e.g., mine is RR, LF, LR, RF. Also, dual reservoir calipers need to be bled in order, usually inside, then outside for best results.
Great information and a must read for an new DE driver.
Thanks for the well written, informative, and entertaining write-up!
If you don’t have a friend willing to sit in the seat and pump the pedal, you can use a “pressure bleeder” system, such as the one sold by Motive. I don’t put the fluid in the pressure bottle. I just open the system and add more fluid to the master cylinder reservoir when it starts to get low, then pump it up again.
Be careful not to press the pedal all the way down, especially if the master cylinder is more than a handful of years old. If you stroke it past its usual range of travel, you can damage the seals inside it.
realize this is a bit late to the party but if you don’t have someone to help, and the idea of a pressure bleeder system sounds like more trouble than it’s worth, just get some speed bleeders (a quick google search will locate some that fit your car). They replace the normal bleeder valves. Remove the stock ones, replace with the Speed Bleeders and bleed the system yourself. These have a check valve in them which prevents reverse flow and sucking air back into the lines. Put your hose/bottle line on the bleeder, crack it open, pump away, everything else remains the same, add fluid as needed to prevent sucking air in from the master cylinder. It’s still easier with a friend because you can watch the fluid coming out of the system. If your fluid is dark, when the color changes back to clear/tan you know your getting the new fluid all the way through.
Flooring the brake pedal while doing this procedure is a good way to cause damage the brake system. If a master cylinder has any corrosion at the end of travel of his piston flooring the pedal will cause the Piston to scrape on that corrosion.