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Raybestos Police-Specific Brake Parts
Affinia Under Vehicle Group produces Raybestos® brand brake pads, rotors and calipers specifically for police vehicles. With many aftermarket companies, the brake pads for a retail Dodge Charger R/T and a police package Charger are the same part number—the same exact part. Not with Raybestos. Its Police Patrol/Pursuit pads use unique friction materials for police applications. See the March-April 2009 issue of Police Fleet Manager or the May 2009 issue of LAW and ORDER for the Ingham County, MI Sheriff’s Department’s testing of these brake pads.
Several Raybestos Police Patrol/Pursuit brake pads are OE-equivalent based on independent dynamometer testing by Greening Testing Labs in Detroit. Specifically, these pads are in compliance with the same Federal Motor Vehicle Safety Standards (FMVSS) that the Original Equipment (OE) manufacturer is required to meet. The Police Patrol/Pursuit pads are also in compliance with the High Speed sections of FMVSS 135 that simulate police pursuit conditions.
A written copy of this formal documentation is available for police departments that are willing to consider adding “OE-equivalent” to their bid specs, which currently call for OE-only. There is a difference between a replacement part and an OE-equivalent part. An aftermarket brake pad manufacturer should be able to prove its OE-equivalent claim. Raybestos does.
The Patrol/Pursuit friction compounds are unique to the Raybestos Police pads and are not a heavy-duty truck formulation, nor a sports car formulation. And as successful as Raybestos is in racing, the Police pads are not a racing friction. This is a chemistry specific to police use and proven with departments like the North Carolina Highway Patrol.
The Complex Compromise
Brake pad material is expected to: 1) have high performance stopping power under all driving conditions, 2) be quiet and dust-free and 3) last for tens of thousands of miles. The problem is that you cannot have all three—period. You can almost get two out of three, but never all three. For fleet managers, that means if you pick a brake pad that gives longer wear, you will give up stopping performance. If you pick a quieter, cleaner brake pad, you will also give up stopping performance.
You cannot fix noise, dust and wear issues by going to a ceramic pad and then expect the ceramic to perform well in police applications. There is a good reason police package vehicles come from the factory with semi-metallic brake pads—not ceramic, not carbon fiber. The Raybestos strategy with the Patrol/Pursuit pads is to produce a friction material that has equal or better stopping performance than OE and aftermarket competitors. Then it minimizes noise and dust and maximizes wear.
Like most aftermarket brake pad manufacturers, Affinia tests the performance, wear and noise of its Police brakes compared to the competition and the OE pads. Some brake pad manufacturers have their own competitive data based on in-house testing. Here are the in-house results from Affinia on its Raybestos Police Patrol/Pursuit pads.
For performance testing, Affinia measures pad effectiveness based on pedal effort and fade at operating temperatures from 350 F to 800 F. During police pursuit testing, the brakes really do hit 800 F. According to Affinia data, the Raybestos Patrol/Pursuit pad and the Ford OE pad had even pedal effort (no spikes in effort) pre-burnish, post-burnish and post-fade operation between 350 F and 800 F. (The Ford OE pad and the Motorcraft aftermarket pad are different. The OE pad is from TMD Friction, while the Motorcraft pad is from Federal-Mogul.)
In comparison, the Wagner Severe Duty and the Motorcraft Federal-Mogul pads had increased pedal effort on first fade at 800 F. The Bendix Fleet MetLok pad had a pre-burnish pedal effort spike at 800 F, and the Wagner Severe Duty had a first fade pedal effort spike at 800 F. Both of these spikes were into the power brake booster runout, i.e., no more power assist was available.
For brake pad noise, the test records both the frequency (kHz) and the number of occurrences of noise during a test procedure that includes the application of the brakes over 1,400 times. In this test, more than 70 dB is annoying, while more than 80 dB is objectionable enough to create a brake noise complaint. According to Affinia data, the Raybestos Patrol/Pursuit pad, the Ford OE pad and the Bendix Fleet MetLok pad were equally quiet, i.e., all had less than 10 noise occurrences over 80 dB. On the other hand, the Wagner Severe Duty pad and the Motorcraft pad from Federal-Mogul were especially noisy, i.e., both had more than 75 noise occurrences over 80 dB.
The low noise from the Raybestos pads comes from “quiet” pad material specifically for police vehicle applications and from rubber-coated abutment clips, shim materials, compound chamfer angles and slot configurations.
Better Wear by 20%
Wear testing was conducted using an Affinia internal dyno procedure for all of these pads. Again, according to Affinia data, the Raybestos pad had less than 0.010 inches of wear at pursuit temps of 800 F. The Wagner Severe Duty, Motorcraft Federal-Mogul, Bendix Fleet MetLok and Ford OE-TMD pads all had the same high-temp performance. At the patrol-like braking temps of 350 F and 600 F, the Raybestos pad had less than 0.005 inches of wear. All the other pads had between 0.040 inches and 0.100 inches of combined wear.
Based on these in-house Affinia tests, the Raybestos claims of being OE-equivalent appear totally legitimate. The Raybestos Police Patrol/Pursuit pad equaled the Ford OE (TMD) pad in terms of noise and performance across all temperature extremes. However, the Raybestos pad seemed to have better wear characteristics at patrol-oriented brake pad temperatures and the same wear under pursuit conditions.
All this leads to what is essentially “The Raybestos Challenge.” Affinia indicates that its Police Patrol/Pursuit pads will last 20 percent longer than whatever is on the police car, whether OE or aftermarket. That would be about 10K miles between front pad changes instead of 8K miles. About 7,500 miles instead of 6,000 miles. About 18K miles instead of 15K miles. For more information on this Challenge, contact Dwight Motley, Fleet Sales Manager, Affinia Global Brake and Chassis.
The Affinia goal for Raybestos Police Patrol/Pursuit rotors was to meet or exceed OE rotors by every means of evaluating rotor performance, including wear, noise and pedal feel. This was a three-year product development project. Because the front brakes do 75 to 80 percent of the braking, Affinia developed the front Patrol/Pursuit rotors first.
For 2010, Affinia is developing Patrol/Pursuit rotors for the rear of a few police package vehicles. Police Fleet Manager expects to test these new rear rotors on a police Charger in the near future. These damped iron rotors on the front are an upgrade from the G3000 (OE) iron rotors on the rear.
In the rotor development, Raybestos started with its Advanced Technology® product line. The Police Patrol/Pursuit rotor began as the best rotor the company made, and then it added high carbon damped iron metallurgy and police-specific internal vanes. More carbon is not necessarily good unless the extra carbon is offset with additional alloying. As a result, the Police Patrol/Pursuit damped iron rotor meets the needs of the vehicle for automotive brake rotors while providing improved NVH characteristics.
Damped iron metallurgy with higher carbon content has a greater number and size of graphite flakes than G3000 metallurgy. This higher carbon content with a different micro-structure disrupts harmonic vibrations and suppresses noise from the rotor. The damped iron rotor isn’t necessarily any stronger than the standard rotors; it is just a lot quieter and dissipates the heat better.
Quiet Rotors, Cool Vanes
Affinia performed over 1,400 deceleration cycles on a dyno following the standard test protocol for brake noise. It compared the Raybestos Patrol/Pursuit rotor to the Ford CVPI OE rotor. According to Affinia data, one percent of the time the Raybestos rotor exceeded 70 dB and one-half percent of the time exceeded 80 dB. The OE rotor exceeded 70 dB about 40 percent of the time and exceeded 80 dB about 25 percent of the time.
Raybestos makes rotors with hundreds of internal vane designs. Raybestos aftermarket rotors typically follow the OE form, fit and function. In the case of the Patrol/Pursuit rotor, a unique vane design was developed to balance noise and cooling air flow. The internal vanes on the Patrol/Pursuit rotor are not directional. That means the rotor can be mounted on either side of the car.
The Raybestos rotor has the mounting flexibility of a non-directional rotor with cooling ability similar to that of a directional vane rotor. The vanes allow air to quickly exit, whether the rotor is mounted on the left side (rotate counter-clockwise) or on the right side (rotate clockwise). Cooler rotors also have a more solid pedal feel and, of course, have less of a chance for brake fade during aggressive driving.
The vented Police Patrol/Pursuit recovers from a heat rise (i.e., cools off faster) than Affinia’s own top-of-the-line Advanced Technology rotor. When the rotor dissipates heat, it takes heat out of the entire brake system. If the rotor cools faster, it takes heat out of the brake pad, and the friction material lasts longer. Of course, less heat also lowers stress on all other brake components.
High Tolerance Machining
For all its special police features, the Patrol/Pursuit rotor has a significant advantage over most replacement rotors. The Raybestos rotor starts out as a high tolerance machined part right out of the box. Many brand new aftermarket rotors have a lateral runout of 0.004 inches. Excessive runout can cause the brake pad to wear the rotor until pedal pulsation is felt in as little as 3,000 miles. The Raybestos rotor has a lateral runout of 0.002 inches or less.
The Patrol/Pursuit rotor also has a thickness variation of 0.0004 inches or less. Again, excessive thickness variation can cause pedal pulsation. In fact, it is thickness variation, either during initial machining or as a result of uneven and intermittent pad contact, that causes the pedal pulsation most people attribute to “warped rotors.”
Finally, the Patrol/Pursuit rotors are balanced by machining away the plate material near the vanes—not by hammering in weights. This mill balancing is to within 2 inch-ounces. Typical aftermarket rotors are hammer-weight balanced within just 3 inch-ounces. The Patrol/Pursuit rotor has a smooth surface finish between 15 and 60 Ra (Roughness Average), while many aftermarket rotors have a much rougher surface finish, i.e., between 100 and 160 Ra. A lower Ra results in less brake noise.
To complete the police-specific brake system, Raybestos has added high temperature calipers, which use silicone dust boots. This caliper assembly is an especially good idea for vehicles used in EVOC training. The dust boot is designed to move with the piston to keep the piston cylinder bore clean and under pressure. If the boot degrades from high temperature, the potential exists for the loss of brake system pressure. The OE boot is made of EDPM rubber, which can withstand up to 300 F; this is acceptable for all patrol duties and the majority of pursuits.
However, some police vehicles constantly operate with racing hot brakes, like EVOC and police academy vehicles. For these vehicles, where the brakes get hot enough to flash or melt EPDM rubber, the solution is calipers with high temperature silicone boots. Silicone can withstand up to 600 F for a sustained period of time. EPDM will harden and crack after extended exposure to higher temperatures. Silicone boots will remain flexible.
If you have to replace calipers, which certainly doesn’t happen as often as pads and rotors, think about these calipers. But for an EVOC or Academy car, you probably ought to put these calipers on during the very next brake service. A quick inspection of the dust boots on the EVOC car will almost certainly reveal them to be melted, burned, torn, cracked or flaked. You simply cannot let dust and debris get past this boot!
Raybestos brake pads, rotors and calipers are premium parts—a step above generic, aftermarket parts, but still reasonably competitive in price. As a premium brand, it may not be available at some of the common auto parts stores. Instead, go to www.raybestos.com and click Dealer Locator for your local Raybestos distributor. Or contact Dwight Motley, Fleet Sales Manager, Affinia Global Brake and Chassis, at 919-452-7180 or at Dwight.Motley@affiniagroup.com.
Published in Police Fleet Manager, Jan/Feb 2010
Rating : 5.5
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