High Performance Vented Brakes
By Larry Saavedra
Volkswagen enthusiasts live in a world of "bolt-on" horsepower. High performance components like dual carburetor kits, turbo systems and maximum-flow headers provide the basis for pure, bold speed. Zero to 60 no longer relates to VW's great gas mileage. Instead it refers t timed miles per hour! As in zero to 60 in seven seconds.
But ironically, the fundamentals of braking as opposed to wide range boosts of horsepower available - still remains a mystery to many. Brake fade is just something that shouldn't be a "learned behavior" at 100 mph! Stock air cooled Volkswagens offer an adequate braking system. There's nothing thrilling about it. - small drums and pads - that's it. They'll do their job under a minimum of stress and speed. Because of high engine horsepower, the stock late model water pumper like the Scirocco, sport a more sophisticated system: disc brakes in the front and drums in the rear.
But beef up and VW engine with a cam change, turbo kit or header package and braking becomes a new issue.
Obviously, high performance engines take more stopping power than stock power plants do. The brake drums or discs become hotter much quicker, which shorten the longevity of the pads, binders and related components. When the brakes get too hot, the heat causes a gassy-vapor to build up, either between the drum and the shoe or the rotor and the pad. Like putting two magnets together, gassy-vapor develops brake fade, and it takes an act of Congress to stop the high performance Volkswagen.
One solution that puts the freeze on hot brakes is called "brake venting." You've probably seen vented brakes on high performance, road racing motorcycles like the Ninja by Kawasaki. The venting or drilling of small holes in the drums and rotors allows the air in the shoes/pads and drums/rotors to escape. This helps to eliminate a vapor gas build up in the system and the components stay much cooler than stock. However, this is a procedure that shouldn't be done by the do-it-yourselfer. Improper venting of drums and rotors can cause imbalance, or breakage of these components.
One of the leading innovators of brake venting is Vince Bunting of C.H. Topping & Co., a specialist in the field of Volkswagen brake systems. "One of the great things about venting brakes is that you can get more than 50 percent longer brake life" Bunting said.
A lot of off road drivers prefer vented rotors and drums because the holes actually will throw out sand and water by centrifugal force. Vented rotors and drums also help release break dust build up" he added.
C.H. Topping & Co. are the veterans of this procedure. For more than ten years, C.H. Topping has been perfecting the process and to say the least hesitant to divulge much information about it. But, it's safe to say the venting process begins with either the drums or the rotors. The patterns of these holes (venting) varies, but the entire diameter of the drums and rotors are covered. Imagine a chalk line drawn along the inside of a drum and circles on the face of the rotor. The drilling would touch every line at specific points. Moreover, left and right drums and rotors have different patterns of ventilation.
The diameter of the hole itself also varies from vehicle to vehicle. These are techniques that Vince knows best. Off road and street performance Volkswagens will take entirely different drilling diameters. By randomly drilling holes in the rotors and drums, you personally run the risk of weakening or destroying your components.
Since the test Scriocco had been modified with high performance engine and handling components , the improved braking could only be a feather in it's cap. Sciroccos are not light. They weigh approximately 2900 pounds (GVWR), and combined with improved in engine horsepower, the stock braking system takes a lot of punishment. Especially since the car is a front wheel drive.
As the Scirocco is lifted on the hoist and the wheels are removed. Vince and Tom Kor of C.H. Topping get to work removing the front rotors and rear drums. Upon inspection, Tom discovered that the Scriocco was in need of new wheel cylinders and pointed out that it's a common problem that cause brake fluid leakage on the rear pads. Tom suggested that the brake lines be periodically checked for leakage, too. Once the drums and rotors are inspected for defects and wear , they are cleaned using a solution that doesn't leave a film deposit like most cleaners.
Next, the rotors and drums are drilled. These particular rotors come stock with cooling fins which Vince avoids with the precision of a jeweler. Approximately, 30 minutes pass, and Vince begins the process on the other rotor. Finished the rotors are taken to another work bench where the holes are "countersunk" so that the face surface remains smooth. Now Vince begins on the drums. Using a custom-tooled device, the drums are clamped together and drilled. They are then taken to be "turned" on a lathe and are ready to be re-installed on the VW.
First new brake pads are installed on the front and rear "We use Repco brake pads . They make three different brands", Vince said. "We use the Repco BMX-B metallic pads on these frontwheel drive VWs. These pads give better heat dissipation than inexpensive non-metallic pads," he added.
While Tom put the finishing touch on the braking system, Vince went over the benefits on a "open style" wheel like the American Racing Type 219 on the Scriocco. "An open wheel will allow more air to pass across the rotor and drum, which increases the cooling of the brakes. A closed wheel like a Centerline has a tendency to trap the air around the rotor or drum", he pointed out.
The Type 219 offered by American Racing proved to not only enhanced the looks of the Scirocco, but its performance as well.
The Scirocco was ready to roll. It was like the difference between day and night as we headed home on the Los Angeles freeway system. It was rush hour and the traffic was stop and go. Gone was any indication of brake fade during panic stops. Gone too, was the need to apply an enormous amount of pressure to get the brakes to work. Once the foot touched the brake pedal , the Scirocco's new venting braking system immediately began to slow the car down to a complete stop. But another test was yet to come, however. Mountain road driving!
The car was running on a set of General VR-XP2000 low profile tires. These "high performance" street tires from General are considered one of the finest tread patterns for fast cornering ability. These tores allowed the car to gain maximum speed under optimum handling conditions.
The mountain roads in California can be misleading. Many of the mountain resorts are located at an altitude of 5000 to 10,000 feet (above sea level) and the roads to get there are narrow and of curving course. Going up isn't too bad, it's the fast ride down that cab be risky.
The first thing that was evident with the new vented brakes was the response. There was no hesitation. It was like was like having power assisted brakes, in a VW not already factory-equipped with the unit. Another plus for vented brakes was apparent when the VW splashed across a pool of rain water on the road. That's an easy way to lose braking power. Do to the loss of friction between the pads and rotors. The new braking system seemed to handle it fine, though. The vented rotors are designed to release the water by centrifugal force, as Vince explained prior to this "seat of the pants" test.
In conclusion, the drive went perfect. The brakes worked flawlessly and there was no overheating of the brakes that could be noticed upon inspection. But, you'll be hearing more about the new vented braking system in a future issue, as the Scirocco prepares to challenge its competition at the slalom races (solo II SCCA racing) in the spring.
As an interesting note to the article, the folks at CH Topping will handle out-of-state requests for vented drums and rotors. UPS is available, they explained. The cost ranges from $25 to $30 per rotor or drum, plus shipping and handling charges. It would be wise to call ahead before shipping any components.