Tech Tips

DISC BRAKE SERVICE
  • From selecting pads that match each driver’s lifestyle to performing a proper break-in after installation, these 10 steps will serve as a guide to completing your next brake job the right way, the first time.

  1. Choose the right brake pads - Make sure to choose the right brake pads based on the vehicle owner’s driving style. Ask a few key lifestyle and preference questions to determine which brake pads are right for the driver: What's the vehicle used for? Does the driver carry heavy loads? What's more important - low noise or clean wheels?

  1. Push the piston back from the caliper - After removing the caliper from the anchor bracket, use a brake caliper piston retraction tool to push back the caliper piston. Apply slight pressure before opening the bleeder screw. Make sure to take the time to inspect and lubricate the rubber piston boot before pushing back the piston – it should be free of any rust or debris. Now, determine if rotors need to be replaced. Skipping this step could result in tears to the piston boot, which can ultimately lead to the caliper needing to be rebuilt or replaced.

  1. Determine if rotors need to be replaced – It’s time to replace the rotors if (1) they are below the minimum thickness specification as noted by the manufacturer, (2) there is any damage to the surface, or (3) if run-out is above the vehicle manufacturer’s specification. Thickness should be measured in a few different places around the rotor using a micrometer to check for any variations. Surface damage to the rotor – such as cracking, corrosion, hot spots, edge lip or grooving can be noted by a visual inspection. And, finally, pedal pulsation can indicate excessive run-out, however smaller amounts of run-out should be verified by using a dial indicator.

  1. Wash and dry the rotors – If rotors don’t need to be replaced, machine them to desired thickness using a lathe and then apply a non-directional finish with a ball hone. Once done, wash each resurfaced rotor thoroughly in a shallow pan of fresh, warm soapy water using a fine wire brush. Then rinse with clean water and dry with a paper towel. If you’re installing a new rotor, look at it closely when taking it out of the packaging to see if there are any metal particles or adhesive residue on the rotors surface. Then, wash and dry the new rotor the same way as you would a resurfaced rotor before placing it onto the hub. Secure it with holding screws or a lug nut to hold the rotor in place when installing the caliper.

  1. Clean and lubricate caliper sliding surfaces - To prevent future run-out, clean and lube all caliper sliding surfaces and rubber components. Replace any corroded slide pins - cleaning both the caliper and bracket pin bores – and, then apply a thin coating of high-temperature brake lubricant. To prevent future corrosion, make sure that the rubber slide bolt boots are properly “seated” in the caliper anchor bracket, then spread a small amount of brake lubricant onto the end of the rubber boot and slide it into place on the caliper anchor bracket. This allows the boot to slip easily into the groove and help to prevent future rust.

  1. Clean the hub and ABS components - Clean both hubs with a mild abrasive pad, then inspect and clean the wheel speed sensors and tone ring to prevent false or premature ABS operation. The key to eliminating any potential run-out – make sure there is no debris or rust on the rotor or hub.

  1. Replace brake hardware - Remove all old hardware - including the abutment anchor clips and wire wear sensors - and clean any debris/rust off of the anchor brackets with a wire brush before installing the new pad. Fit anchor clips into the top and bottom of the caliper anchor bracket slots before installing them on the hub assembly. (Listen for them to “snap” into place to ensure correct fit.)

  1. Check brake fluid levels and color - It’s critical that the brake fluid is at the correct level in the reservoir before test driving. Check the color of the brake fluid to determine if it’s time to replace it. If the fluid is dark or black, it may be time to replace the fluid rather than just topping it off. Always follow the manufacturer’s recommendations when selecting the proper brake fluid for the vehicle.

  1. Tighten lug nuts - Tighten lug nuts in a star pattern using a torque wrench. Improper torquing can cause rotor lateral run-out. Read the manufacturer’s torque specifications for the caliper mounting bolts, caliper anchor bracket and wheel lug nuts.

  1. Perform a proper break-in - To break-in the pads, drive the vehicle at 30 miles per hour, performing 30 gentle stops, with a 30-second cool down between each stop. Improper break-in can result in a build-up of an uneven layer of pad material, causing your vehicle to develop a pulsation or vibration noticeable anytime the brakes are applied. This 30-30-30 method transfers a film of friction material onto the rotor surface, preventing pad glazing and ensuring quieter brakes and longer pad and rotor life.
DRUM BRAKE SERVICE
  • Before you begin any brake service, be aware of any existing mechanical or braking problems on the vehicle. If you’re a “do-it-yourselfer”, don’t ignore or minimize problems with the parking brake, or vacuum system – as they can have an effect on your brake job. If you’re a professional mechanic, talk to your customer about their vehicle’s condition and symptoms they’re experiencing.

  1. Remove the drums and clean brake assembly – Using an OSHA-approved method, remove the drums and clean the brake assembly. Never use compressed air to clean brakes and wear an appropriate respirator when cleaning disc and drum brakes.

  1. Clean the backing plate - After removing old shoes and hardware, using a clean rag wipe off the backing plate in all areas where the shoe web contacts the backing plate. For those not familiar with the drum system being serviced, service only one side at a time. This will allow you to use the other side as a reference for assembly.

  1. Loosen seized bleeder screws – Once you loosen the seized bleeder screws, clean away all debris with a clean rag.

  1. Replace leaking or damaged wheel cylinders – They recommend replacing all leaking or damaged wheel cylinders. If you choose not to replace them, you must open the bleeder screw when installing new shoes and springs to prevent dirty brake fluid from contaminating the RABS valve (on vehicles with rear wheel only ABS / RWAL systems).

  1. Replace all hardware and return springs - Springs and hardware weaken over time. Replacing them restores the original performance of the system and helps prevent grabbing and wheel lockup.

  1. Install new shoes - Lubricate the backing plate shoe contact points, parking brake arm pivot point, self-adjuster screw, upper or lower anchor pin.

  1. Refinish the brake drum – Once the brake drum is fixtured in the brake lathe fast cut as needed, followed by a slow cut. Wash with soap and hot water. Dry with paper towels only.

  1. Measure drum diameter and pre-adjust shoes – Prior to installing drums, it’s important to measure the drum diameter. Then perform the final adjustment on the brake shoes.

  • Install wheels and tighten lug nuts - Tighten lug nuts in a star pattern using a torque wrench. Improper torquing can cause rotor lateral run-out. Read the manufacturer’s torque specifications for the caliper mounting bolts, caliper anchor bracket and wheel lug nuts.
GENERAL BRAKE SERVICE
  • At least once every year drivers should have their brakes inspected. Many times, pads won’t need to be replaced but a general brake service may be completed. They’ll take you through the six key steps to performing a thorough brake service, including replacing brake fluid, bleeding the hydraulic system, checking leaks and fluid levels, and performing a proper break-in.

  1. Replace brake fluid - Fill master cylinder with fresh clean brake fluid as specified by the vehicle manufacturer.

  1. Bleed hydraulic system - Using the manufacturer’s recommended bleeding sequence, bleed the hydraulic system. If there is any contamination in the master cylinder reservoir, remove the old fluid and replace with recommended fluid before bleeding or flushing. This prevents contaminants from entering ABS components. To properly maintain the hydraulic system and ABS valves, flush the system until clean fluid comes out of all bleeder screws.

  1. Re-check system for leaks – Visually inspect the system for drips and seepage.

  1. Perform final brake adjustment - Re-adjust rear brakes, check and adjust parking brake.

  1. Re-check master cylinder level – Be careful to not “top off” the master cylinder. Fill to OE mark.

  • Gently road test the car - If all is okay, perform break-in by driving the vehicle at 30 miles per hour, performing 30 gentle stops, with a 30-second cool down between each stop. Improper break-in can result in a build-up of an uneven layer of pad material, causing the vehicle to develop a pulsation or vibration noticeable anytime the brakes are applied. This 30-30-30 method transfers a film of friction material onto the rotor surface, preventing pad glazing and ensuring quieter brakes and longer pad and rotor life.
CLEANING BRAKE PARTS
  • Today’s brake systems are very sensitive to rust and corrosion and must be cleaned thoroughly before installing new pads, fresh lube, and hardware. Rust and debris in critical areas can cause brake problems almost immediately.

  1. Calipers. Remove each caliper completely and clean all areas that are subject to movement, including retainer hardware, anti-rattle clips and the inside of slide pin bores with warm soapy water and a round wire brush to remove any old lubricant and corrosion. Even if you won’t be replacing the rear brakes, take the time to clean and lubricate the rear calipers, drums and parking brake systems before the vehicle hits the road.

  1. Rotors. It’s critical to wash rotors (new or resurfaced) with warm soapy water and a stiff brush to remove any metal particles or adhesives. Any metallic residue on the rotor’s surface prevents proper “filming”, reducing the life expectancy of the pads.

  1. Pad abutments. Whether they’re part of the caliper bracket or steering knuckle, pad abutments must also be clean and smooth. If there are any notches or grooves caused by pad movement, replace them. Re-using worn abutments with grooves can cause excessive pad movement, leading to noise and vibration.

  1. Hub assemblies. Clean all rust and debris off the hub face, using a die grinder to remove any heavy deposits. Then use an over the stud hub cleaning tool to get in next to the studs on the entire hub and wheel mounting pads. Leaving corrosion in these areas is one of the leading causes of runout that can result in brake pedal pulsation after 3,000 miles.

  • Wheel mounting pads. Steel and alloy wheels can develop corrosion in the mounting pad area (where the wheel contacts the rotor). If you leave the corrosion in place and then torque the lug nuts, it can distort the rotor and cause brake pedal pulsation. Use a wire brush to remove all corrosion.
MATCH PADS TO DRIVING STYLE
  • When it comes to choosing brake pads, there’s no “one-size-fits-all” solution. Different drivers need different brake pads. Their requirements are affected by cost, driving style and the vehicle design.

  • Today, there are three main pad types sold in the aftermarket: ceramic, semi-metallic, and low-metallic. Each friction material has its own unique set of characteristics.

  • Ceramics offer the quietest, cleanest operation. And they’re easier on rotors than the other two formulations, making them a great choice for everyday driving. That’s why they’re so popular with vehicle manufacturers. In fact, 8 out of 10 new cars come from the factory with ceramic pads these days. However, if your customer is operating his or her vehicle with heavy loads or needs better stopping power, ceramic pads may not be the best choice.

  • Semi-mets are the most fade resistant, are very durable, and provide great performance in higher heat conditions and heavy stop-and-go driving. However, they can have slightly higher noise levels than ceramics and can wear rotors. This is usually more likely if semi-metallic pads are used on a smaller vehicle designed for ceramic formulas.

  • Low-mets have excellent pedal feel and great stopping power. But they tend to be noisier and dustier than other formulations, and they can be hard on rotors. These pads are used by many German vehicle manufacturers – and most often seen on high-end European vehicles that are equipped with upgraded or performance brake packages.

  • Once you know the driver’s habits and preferences, you can fit the right brake friction material to their needs. Here are the important considerations:
BRAKE PULL
  • Anyone that works on brakes is sure to run across “brake pull” complaints sooner or later. It’s just part of the business. Here’s a short list of the most common causes: (1) sticking caliper, (2) restricted pistons or delayed piston retraction, (3) friction material contamination, (4) unequaled side-to-side brake fluid pressure.

  • Although tire-related and suspension issues are less common causes of brake pull, don’t discount them. If you’ve already checked the most likely causes of brake pull noted above, swap the two front tires. If the vehicle then pulls in the opposite direction, that’s a sign of a tire-related issue. Take a look at uneven tire pressure, alignment, worn suspension parts, uneven tread wear (caused by out-of-spec camber), tire-size mismatches or belt separations.

  1. Sticking caliper. Most vehicles use a floating caliper design that pulls the outboard pad in contact with the rotor during brake application. The caliper “floats” on slides. However, if the slides become corroded or the wrong lubricant is used, the caliper can’t release the hydraulic pressure and the outboard pad remains in contact with the rotor, causing a brake pull. Start your diagnosis with the slide mechanisms. Caliper pins must be corrosion-free, smooth, and lubricated with a high-temperature synthetic brake grease. The bores they ride in must also be in good condition, and the protective rubber boots must be intact and flexible. Be sure to clean any corrosion or old lubricant deposits from the pin bores.

  1. Restricted pistons or delayed piston retraction. This is fairly common on higher mileage vehicles and those with brakes that have severely overheated. The square-cut piston seal rolls slightly forward during brake application and back in place when released. If the piston seals are old and hardened, they may delay caliper release or not release at all. So the caliper clamping force keeps the pads in contact with the rotor, causing a pull. Rebuild calipers with new seals to eliminate the problem.

  1. Friction material contamination. Brake fluid, engine coolant, chassis or CV grease, and engine oil can contaminate the pads on one side of the vehicle, altering their friction characteristics – making them grip either more or less than the opposite side. Most often the contamination is permanent and replacing the pads is the only real fix (after you’ve eliminated the source of the leak and cleaned off all the contaminants). When replacing the pads, be sure that both sides are using the same friction material. Differences in formulations can create pull issues.

  1. Unequal side-to-side brake fluid pressure. Tube blockage, hose damage, master cylinder wear, malfunctioning proportioning/combination valve, and stuck ABS valves can cause these kinds of unequal pressure problems. The easiest way to find and isolate the problem is to measure rotor/hub temperatures with a non-contact infrared thermometer. The problem wheel will be much hotter than its axle companion and the thermometer will also show the brake that’s not functioning.
REAL WORLD TESTING
  • As a major supplier to both domestic and overseas car and truck makers, Honeywell Friction Materials ensures that all of the pads and shoes meet strict government and car makers’ standards. One way to test the products is to subject them to grueling dynamometer (dyno) testing. But company don’t stop with these tests. Bendix installs their brake pads and shoes on vehicles and take them out onto the open road for real world testing too. First, here’s what brands products must endure before they hit the road.

It starts in the lab.


  • Bendixs engineers constantly work on new friction formulations. Once they think they’ve got a contender, they send it to the lab for testing. There, lab technicians test the friction material for material strength, compression, heat and corrosion resistance, material degradation, and sheer strength. Then they mount the materials on a dynamometer to check friction characteristics under a wide range of conditions, noise behavior (both high and low frequencies), and the durability performance of both the pad and the rotor.

Then company take it to the streets.


  • Brands pads and shoes are installed on cars and trucks equipped with all necessary measuring equipment to help monitor vehicle braking performance. This typically includes pressure gauges, thermo-couples, and fully calibrated decelerometers/speedometers. Vehicles are loaded to their full rated capacities and perform baseline testing prior to test-drive startup. Then - following strict industry standard or SAE testing procedures - Bendixs engineers perform a battery of tests.

  • Between brands rigorous lab testing and hard driving-hard stopping road tests, Bendix and JURID friction materials perform up to customers expectations – as well as their customers’.
REAR DRUM BRAKE LOCK-UP
  • Bendix receive quite a few calls regarding rear brakes that lock-up during the first few stops in the morning. Here’s what’s going on - rust forms on the surface of the drums and shoes, causing the friction materials to grab. It can happen in the drum brakes of any car or truck, but occurs more often in vehicles where the rear brakes carry a relatively high percentage of the braking load.

Why so much rust?


  • The problem is most prevalent when economy drums and high metallic content friction materials have been installed on the vehicle. Simply put, economy drums are made from less expensive raw materials and are more prone to rusting. You can reduce the incidence of drum brake lockup by installing only premium drums and shoes - like Bendix® brake shoes that are specifically formulated to resist surface rusting.

What can be done to prevent surface rusting during the install?


  • Completing a proper break-in procedure after new pad installation is very important. This process embeds a layer of friction material into the surface of the drum, thereby reducing the incidence of rust. Also, make sure you install rubber hole-cover plugs in the knock-out adjustment holes. Leaving the holes open creates ventilation that can contribute to humidity build-up inside the drum.

What can the car owner do?


  • Car owners can reduce the likelihood of brake lock-up by lightly applying the brakes right away after a cold start in humid conditions in order to heat up the shoes and drums and drive out any condensation. Gentle brake application on cold brakes is especially important right after brake service. The lighter touch completes the break-in cycle.
RESURFACING ROTORS
  • Many people like to blame the pads when a brake job goes awry. But if you install a rotor with a rough surface, you’ll most likely encounter poor stopping performance and increased pedal effort, at least until the friction materials stabilize after a few hundred stops.

  • The rotor’s job is two-fold. First, is it has to provide a rubbing surface for the friction material. And, second, it has to dissipate the heat generated during braking. In order to do both jobs well, the rotor surface has to be smooth.

Properly Machining Rotors:


  1. Measure the rotor’s thickness to make sure that machining will not reduce it beyond the minimum thickness or machine-to spec required by the manufacturer. A lathe that can measure the groove depths will confirm if the rotor can be reused before it is machined.

  1. Thoroughly wash the inner and outer hat area with warm soapy water and a fine wire brush so that it’s free of rust and corrosion. A rotor cannot be mounted correctly in the lathe if there is rust/corrosion present.

  1. Choose the adapters and dampers that best fit the rotor. Perform a “scratch test” to be sure the rotor mount is repeatable. Run an insert in on one side of the rotor close to the outer edge to “scratch” the surface at one point. Then, loosen the arbor nut and rotate the adapters and cones 120° away from each other. Turn on the lathe and move the insert so it will make a scratch close to the previous one. They should “scratch” the rotor at the same point. If not, further cleaning or different adapters can be chosen to get a repeatable test. This insures the rotor is mounted correctly on the lathe and runout will not be machined into it.

  1. Complete one or two fast cuts once the rotor is mounted to clean up the surface and correct any run-out. The last cut should be made with the slowest possible tool feed speed and fastest arbor speed. This ensures that the resulting finish will be as smooth as possible. Save time by using a lathe that can measure the rotor directly will be able to refinish the rotor in one pass.

  1. Mount rotor in a drill or die grinder and use a brake rotor flex hone to achieve a non-directional finish by pressing lightly against the surface of the rotor while it’s turning. The flex hone smoothes out the peaks and valleys on the surface. Note: If the lathe can produce a finish of 20- 50 Ra, then a non-directional finish is not needed.

  1. Check for a smooth surface on the finished rotor using a hand held roughness gauge. Most new out-of-the-box OEM and quality aftermarket rotors have a finish somewhere between 30 and 60 micro-inches RA (roughness average). They recommend a finish of approximately 50 micro-inches for acceptable performance. The higher the number, the more likely noise and accelerated wear will occur.