Quote:
Originally Posted by Huehuecoyotl
Ok so i am back here, still looking to upgrade the brakes, now that I got my car back last week.
Well yesterday I squared up with Essex on the OE pad setup they sold me(and even shipped it without billing me by mistake), now its a race to wear out these pads asap
Why? cause next on my list is the Endurance upgrade, tho I am finding myself trying to talk myself out of it back towards the sprint. I was really hoping to find an objective review of someone who has driven both the sprint and endurance on similarly setup cars
... not that Jeff isnt objectove in his posts, but I just wanted to get a better idea of how they feel or perform different at the track, and , at the limits.
Does the endurance out break the sprint to the point of loosening the rear?
Does one lend itself to be more delicately modulated at the limits?
Is pedal feedback different between the two?
Feed me details, anyone who owns these, and sure, I'd love to hear more on these questions from Jeff
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Okay...here's my non-objective opinion.
Stopping Distance
The difference between the Sprint and Endurance kits is not a matter of one out-braking the other. If the systems are designed properly, and they both are, they should show nearly identical performance in terms of stopping distance (until they are both heat soaked). In other words, if we measured the stopping distance on a car with the same tires using both systems, they should stop in roughly the same distance. This is exactly what we did in our testing. Tires are what stop the car. Brakes are about managing heat!
Heat Capacity/Energy Conversion
Ultimately, the Endurance system has greater heat capacity. That is literally the only thing you gain with the Endurance system. It has larger discs, which can absorb more heat. It also has the built-in provision to attach a brake duct hose, which allows for cooling air and temperature reductions. The discs are floating in the Endurance system, meaning that when they do get hot, they can expand with less strain on the disc at the point where it attaches to the hat. Again, those are all related to heat. So, in a certain range of temperatures...from ice cold to fairly hot, performance between the Sprint and Endurance kits will be identical.
Only when a massive amount of heat is introduced to the system will any differences between the two kits become evident.
So what happens when a massive amount of heat is introduced, and how would the two kits react differently? At some point,
any brake system will run out of heat capacity. Brakes convert kinetic energy (a spinning disc) into thermal energy (the brake pads rub against the disc and generates friction). Energy is converted, not created. Depending on the disc size, pad volume, caliper design, cooling, etc., the conversion of energy happens at a certain rate, and the brake system has limitations on the rate at which it can convert energy. Here are the primary things that would push a brake system towards its limits of being able to adequately convert motion into heat.
- An increase in speed- Kinetic energy = mass x velocity (squared). As the car travels faster, the disc spins faster, and there is more energy that needs to be converted to heat. Since speed is squared in that equation, an increase in speed has the most dramatic impact on the amount of kinetic energy generated. In other words, if you add 200hp horsepower to your car, it will be have a far greater impact on your brake requirements than if you add a 200lb. passenger...and it will push your system towards its maximum heat capacity much more quickly.
- An increase in mass- Things in motion are harder to stop as their mass increases. The amount of leverage, torque, etc. to slow a heavy object is greater than what is required for light one. A freight train requires a very different brake system vs. a Lotus Elise.
- An increase in friction- The friction between the object in motion vs. what it is moving against makes a big difference as well. If you slide a book across a table, it slides easily. If you slide a book across a rubber mat, it won't go anywhere. The friction between the two objects is much greater. If you mash your brakes on race slicks, you have greater friction with the road vs. mashing the brakes on stock tires, which are far less sticky. With the race slicks and higher grip, you have a much greater capacity/ability to turn your motion into heat quickly.
So what does that all mean? It means that every car can find the limits of a certain brake system if it is made faster or heavier, or it is given more grip. Let's look at an example:
Little Timmy got his FR-S for Christmas. His paper route isn't earning him much chedda, so he has to leave his car stock. He goes to the track. It turns out Timmy is the next Kimi. He is super talented and fast. He is hitting high top speeds into the brake zones, and changing a lot of kinetic energy into heat. Since his stock pads aren't really designed for that, they melt (they're made to be quiet and work well cold). As they are melting, they smear all over his discs, giving him vibration and judder every time he hits the brakes. His discs are in the same boat...they don't move much air through them, and they are overwhelmed by the heat. They are cycling between extremely hot and cool, and they develop huge cracks. Since the pads and discs are not efficient at handling heat (they weren't made for that specifically), they are heat soaked. All of that heat has to go somewhere.
- It radiates into the air around the brakes, sits in the wheels, etc.
- It conducts- it transmit through the actual hard parts and metal. The wheel bearings get hotter, etc.
- It soaks into the brake fluid through the caliper via convection
All of that pad and disc heat wears on the other parts around the brakes, and it soaks into the brake fluid making it boil. When it boils, air bubbles are produced. Since air bubbles can compress...the brake pedal is no longer rock hard as it should be.
So Timmy has some problems. His pads are melted, he has judder since they smeared all over his discs, his discs are cracking, and his brake pedal is soft because his fluid boiled. Timmy needs some help. He needs some brake components designed to handle high temperatures.
Timmy buys a Sprint Kit and a pyrometer to take disc temperatures, because he wants to learn more about vehicle dynamics, and he wants to get faster. He leaves everything else on the car stock, and goes out to Willow Springs raceway (a relatively easy braking track). The day goes great and he has a blast as he starts to realize that track driving is addictive. His discs were hitting 950F consistently, but he had no brake problems. The pads didn't fade, and his pedal remained firm all day. Timmy wants to go faster though, because all of the Corvettes were passing him all day. He goes out and buys some race slicks before his next event at Buttonwillow.
Timmy heads out to Buttonwillow. The race slicks allow him to get through the corners much more quickly, exit turns faster, and hit a higher speed at the end of the straights. He now has to go from a higher speed down to reach his corner entry speed, which transfers a lot more energy into heat. His driving skill is also steadily improving as he gets more experience. He's getting through the turns faster, and getting closer to his tires' ideal slip angle. He still can't catch the Z06 vettes, but he passed a couple of M3's and 911's. His brakes worked great all day, but when he was checking temps, he noticed that he was hitting 1200F consistently on his discs. He also saw a few spider cracks develop on the discs. By the last session of the day on Sunday, a lot of people had already gone home. He was out there with very little traffic in his run group, and he actually did 40 minutes straight instead of the usual 20 mins. At the very end of that last session, he started to feel a little softness in his brake pedal. When he went home and bled his brakes he noticed that a couple of air bubbles came out.
At this point, Timmy goes a little apesh*t. He decides that he is going to make the Z06's feel silly when they're passed by a lowly FT86. He installs a turbo kit that adds 150 whp. He goes back to Big Willow for his next event. Something similar to the last event happens, and they get the chance to run for an hour straight at the end of the day. He runs the car a full hour flat out, but doesn't have any brake troubles at all...no soft pedal, nothing. He doesn't see any air bubbles when he bleeds the brakes. He sets the fastest time of the day, passing a Gallardo down the front straight.
Back to Buttonwillow next time. Because he is so fast, Timmy runs in the fastest group. He goes out and tears it up in the first session. By the end of 20 mins. though, he's having some brake issues. At first he notices that even though his pedal is hard when he brakes, the car isn't slowing down like it's supposed to (brake pad fade). Uh oh. A few laps later, his pedal starts to get lower and lower going into brake zones...double uh oh. Timmy pulls into the hot pits and his friend zaps the front disc with the pyrometer. 1350F...ouch! Timmy wisely decides to go back out for a couple of cool down laps before the session ends, to get some air flowing through the brakes.
So what happened during Timmy's journey? He found the limits of his stock system quickly, as they were simply not designed for what he intended to do to them. Then he increased his car's ability to generate brake heat by adding better tires. He also improved his driving ability, allowing him to increase his speeds at the end of straights and pour even more heat into the system as he slowed from higher speeds. To offset those things, he installed a brake system specifically designed to handle the heat of heavy track use.
Ultimately though, he threw a bunch of HP at the car with his turbo, and radically changed the amount of energy being transferred from motion to heat. When he did so, he found the limits of the upgraded brakes.
Timmy sold his Sprint kit to his friend who didn't have any plans for forced induction. He ordered and installed an Endurance kit. Now he had larger heat sinks in the form of bigger discs. They could absorb more heat before transmitting it to other components. He also hooked up some brake ducting to the caliper brackets, allowing for more cooling air to get into the center of the disc, and pump air through them. Since the discs could now swallow and dissipate more heat, and his cooling ducts were bringing in a nice stream of cool air, his pads never got as hot...nor did his calipers...nor did his brake fluid. He went out to Buttonwillow and didn't have any problems at all.
A couple of points to note:
- Every driver and track are different. What works well one place, may not be enough somewhere else, or with someone different driving.
- Any brake system can find its limit with enough speed. It's just a matter of finding where that point is.
Choosing between the Sprint and Endurance kits is simply a matter of determining where you lie on Timmy's journey. At the time I write this, I have yet to hear of a single report of anyone running into any pad or fluid fade, premature disc cracking, etc. with the Sprint kit. That includes several forced induction cars, and loads of very fast drivers on tracks that are tough on brakes. Nobody has yet run into Timmy's problem with the Sprint Kit. It has been enough. That said, eventually, someone is going to take it too far due to too much power, too much speed, too much skill, too tough a braking track...you get the picture.
This is all leading up to my next post on brake feel.