Speed News vol. 1 Issue 4-May : Page 54
SPLITTING COMPOUNDS IT’S NOT NUCLEAR SCIENCE Using Different Friction Characteristics Front to Rear Can Balance Your Braking — Story By Richard S. James W 54 hat difference can a hundred degrees or so make? To a pot of water, it’s the variation between warm and boiling. To a human it can be the difference between life and death. To the brakes on a racecar, it can translate to maximum velocity reduction effi ciency and brake pad life or, conversely, watching your competitor outbrake you at the end of the straight on your fi nal lap. In other words, the difference between winning and losing. Brake temperatures are a critical component of choosing brake pad compounds. Each compound is designed to operate within a specifi c temperature, and the characteristics of the pad material helps determine at what range the brakes will operate. But braking force, whether you can adjust your bias or not, is seldom the same front to rear, and neither are temperatures. That’s why using the same compound at every corner isn’t always the right solution. Sometimes, for maximum braking effi ciency and pad life, using a different compound front to rear – or, in the parlance of the brake industry, split friction – is the best way to ensure maximum effi ciency.
Splitting Compounds It’s Not Nuclear Science
Richard S. James
What difference can a hundred degrees or so make? <br /> To a pot of water, it’s the variation between warm and boiling. To a human it can be the difference between life and death. To the brakes on a racecar, it can translate to maximum velocity reduction efficiency and brake pad life or, conversely, watching your competitor outbrake you at the end of the straight on your final lap. In other words, the difference between winning and losing.<br /> <br /> Brake temperatures are a critical component of choosing brake pad compounds. Each compound is designed to operate within a specific temperature, and the characteristics of the pad material helps determine at what range the brakes will operate. But braking force, whether you can adjust your bias or not, is seldom the same front to rear, and neither are temperatures. <br /> <br /> That’s why using the same compound at every corner isn’t always the right solution. Sometimes, for maximum braking efficiency and pad life, using a different compound front to rear – or, in the parlance of the brake industry, split friction – is the best way to ensure maximum efficiency. <br /> <br /> “One of the good reasons [to use split friction] would be to help balance out your brake system to give you maximum brake front and rear based on a system that you could be restricted to under the rules,” says Mathew Roskey, motorsports sales manager at Hawk Performance Products. He and fellow motorsports sales manager Edwin Mangune travel to tracks around the country all racing season long to see how their products are being used and offer advice to racers on how to get the most out of them. As a result they’ve figured out how to maximize braking power and life.<br /> <br /> The first step is to determine the brake operating temperatures (see sidebar). That information can go a long way toward solving braking problems, or even exposing inefficiencies a driver may not have even known existed.<br /> <br /> “Once you have the temperature readings and where they run, you’re able to match up the material that is going to perform in that temperature range the way the driver wants it,” says Roskey. “How much torque you’re going to get from the pads, how it modulates, what kind of feel the driver wants from the pedals. Once you have the temperature range, a drive can choose pads for the feel he or she wants.”<br /> Often those pads will be different from front to rear to achieve the desired outcome. Mangune outlines a couple of different scenarios where he has used split friction to come up with a good solution.<br /> <br /> “Typically, in a Mustang or Camaro, a car with a live rear axle, often the rear brake will want to lock up,” Mangune explains. “Let’s say it’s a Mustang, and I have him on DTC-70s front and DTC-30 rear, and he likes the way the brakes perform, but at certain tracks the rear wheels are locking up. I can adjust that by changing the rear compound to an HT-10. Our HT-10 is so silky smooth and so linear that that pad can help prevent rear lockup.”<br /> <br /> In another case, a driver was happy with the way his braking was working, but the temperatures told a different story – the driver was satisfied, but the brakes weren’t. <br /> <br /> “Let’s say a guy drives a Porsche, and he’s on DTC-60s front and rear. I’ll shoot his rotors to see if we could optimize a combination. He likes the way the brakes work, but I say look at the rotor temperatures – the fronts are at 900 degrees, which I feel is a little on the high side, and the rear rotors are cool, let’s say 500 degrees. I stepped up the rear brakes to a torqueier pad, so now the bias is different. He has a torqueier brake pad in the rear and one step lower in the front. That lowered the temperatures on the front brake pads, increased he temperatures on the rear, but he had more brake torque.<br /> <br /> “The driver liked that feel better,” Mangune continues. “The brake system liked it better because we cooled the temperatures up front and made the rears work a little more. From that, cars with rear engines, typically I’ll start them off with an even brake pad torque combination front and rear; but at the end it’s all about driver feel. I may like one combination and someone else may like another one. But in this case, there was room for improvement, and we found it.”<br /> <br /> Split friction isn’t only a tool for drivers who can’t or choose not to use a brake bias controller. Using pads with different characteristics allows the brake bias controller to fine tune the system to the driver’s preferences, or make adjustments for changing conditions, without having to use it to mask a greater problem. <br /> <br /> “As the session goes on, you can start with the setup the way you like it, but as you start losing weight at one end from fuel burn, you can tweak it to keep the same balance throughout the run. If you’re in the sweet spot, you can use the bias valve to adapt to conditions,” says Roskey. <br /> <br /> Adjusting the friction characteristics front to rear not only can make braking more predictable and give the driver what he wants, it can save money in the long run. In the case of the Porsche above, with its 900-degree front brakes, the driver was probably using up front pads at a much greater rate than necessary.<br /> <br /> “Heat will wear down the pads quicker, wear down the rotors quicker and reduce the brake pad’s performance,” says Mangune. “By properly balancing the car you get longer life out of both front and rear pads.”<br /> <br /> It all comes down, they say, to heat management, driver preference, comfort and durability. Tuning the friction front to rear can help a driver achieve his or her goals in all those areas. SN
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