Brake Job Walk-through (pad & rotor)

A pad and rotor job is one of the most common repairs in the shop, and the driver feels every shortcut through the pedal. This walk-through follows a front brake job on a typical passenger car, in the order you do it. Rear brakes follow the same steps, with the piston differences noted below. It assumes you have already found the pads and rotors need replacing.

What You Will Be Able to Do

• Prepare for the job with the right specs and parts.
• Retract a caliper piston the correct way for the design.
• Service slide pins, hardware and the hub face.
• Install pads and rotors, and torque each fastener to spec.
• Bed in the new parts and prove the job with a road test.

Before You Start

Raise the vehicle on the correct lift points and rest it on the locks. Wear safety glasses and nitrile gloves. Treat all brake dust as if it might contain asbestos: use a low-pressure wet method or a HEPA vacuum, and never blow it off with compressed air.

Look Up the Specs

Find these numbers in the service information for the exact vehicle, and write them on the repair order.

Those are typical ranges, not your spec. Some bracket bolts are torque-to-yield, meaning they stretch on purpose when tightened and must be replaced. If the service information says replace, replace.

Check the Parts

Open every box before the wheels come off.

• Pads: correct set, with any wear sensors included.
• Rotors: the part number matches, and the vent style and hat height look right.
• Hardware kit: abutment clips, springs and boots if supplied.
• Brake grease: a silicone-based or synthetic caliper grease.
• Brake fluid: the correct type, from a sealed container.

Finding a wrong part now takes five minutes. Finding it halfway through can leave a car stuck on your lift.

Step 1: Remove the Wheel and Measure

1. Loosen the lug nuts on the ground if your shop works that way, then raise the vehicle.
2. Remove the wheel and keep the lug nuts in a tray.
3. Record the pad and rotor measurements on the repair order. You need the old readings if the customer asks, and they catch any part that does not match the original estimate.
4. Check the hose, piston boot and slide pin boots. A torn piston boot usually means replacing the caliper.

Step 2: Retract the Piston

Check the fluid level in the reservoir first. Pushing the piston back raises the level, and brake fluid damages paint. Remove some fluid with a clean syringe if the reservoir is full.

The old pads are still in place, so the outer caliper body gives you something to push against. Open the bleeder and run a clear hose into a catch bottle while you compress the piston. This pushes the old, contaminated fluid out, rather than back through the ABS unit, where debris can damage its valves. Close the bleeder as soon as the piston is back.

The right method depends on the caliper:

Warning: Forcing a screw-in rear piston straight back destroys its internal mechanism. Forcing an electric caliper can damage the actuator. Check the service information first, and confirm the direction of rotation.

Then remove the slide pin bolts and lift the caliper off.

Step 3: Support the Caliper

Hang the caliper from the suspension with a wire hook or a caliper hanger. Never let it hang by the brake hose. The weight can damage the inside of the hose, and that damage may not show until later.

Step 4: Service the Slide Pins

1. Pull each pin out of its boot.
2. Clean the pin and its bore. Replace pins that are pitted or badly corroded.
3. Check the boots and replace any that are torn.
4. Apply a thin film of silicone-based caliper grease. Do not use petroleum or chassis grease, because it swells the rubber boots.
5. Refit the pins. They should slide smoothly by hand, without any bind or click.

Step 5: Remove the Bracket and Rotor

1. Remove the caliper bracket bolts, and set the bracket on the bench.
2. Remove any rotor retaining screw. Use an impact driver bit if it is stuck, and note any screw that has to be drilled out.
3. Pull the rotor off the hub.

A rusted rotor can stick to the hub. Many rotors have threaded holes in the hat, so that a bolt can push the rotor off. A dead-blow hammer on the hat, between the studs, also works. Do not strike the friction surface or the studs.

Step 6: Clean the Hub Face

This step decides how the pedal will feel. Any rust or scale between the rotor and the hub tilts the rotor, which creates lateral runout. Even a small amount can lead to a pedal pulsation within a few thousand miles.

Use a hub cleaning disc, a wire wheel or a file until the mounting face is clean, bright metal, right out to the edge. Wipe it clean. Inspect the studs for damaged threads while you are there.

Step 7: Prepare the Bracket and New Rotor

1. Wire brush the bracket's abutment seats, then fit the new clips from the hardware kit. They should snap in fully.
2. Clean the new rotor with brake cleaner and a clean rag. New rotors come with a protective oil on them, and it will contaminate new pads.
3. Fit the rotor on the hub, with its retaining screw if the vehicle uses one.
4. Fit the bracket and torque the bolts to spec. Replace them first if they are one-time bolts.
5. Check runout with a dial indicator if the vehicle has a history of pulsation. Temporarily fit lug nuts to hold the rotor flat against the hub for this check.

Step 8: Fit the Pads

1. Fit any shims or wear sensors as supplied. Wear indicators usually go on the inboard pad, as the service information shows.
2. Apply a thin film of grease to the pad ears and backing plate contact points, if the pad maker allows it. Some pads with bonded shims must be fitted dry, so read the box.
3. Keep grease and oily fingers off the friction surface and the rotor.
4. Seat the pads in the clips. They should move freely with light finger pressure.

Step 9: Refit the Caliper

1. Lower the caliper over the pads. If it does not fit, check that the piston is fully retracted.
2. Install the slide pin bolts and torque them to spec.
3. Check that the hose is not twisted, and that it clears the wheel when turned from lock to lock.
4. Repeat on the other side. Always replace pads as an axle set.

Step 10: Restore the Pedal

Warning: Do not move the vehicle until you have a firm pedal. After retraction, the pistons sit far from the pads, and the first pedal press will go to the floor with no braking at all.

1. Pump the pedal slowly until it is high and firm. This moves the pistons back out to the pads.
2. Check the reservoir and top it up to the MAX line with fresh fluid of the correct type.
3. If you opened a bleeder or a line, or the pedal is soft, bleed the system.
4. Check for leaks around the bleeder and caliper.

Step 11: Fit the Wheels

1. Clean the mating faces, and fit the wheel.
2. Start each lug nut by hand.
3. Lower the vehicle until the tire is on the floor.
4. Torque the nuts with a calibrated torque wrench, in a star pattern, in two passes. An impact gun can distort the rotor and bring pulsation right back.

Step 12: Bed In the Pads

Bedding, or burnishing, lays a thin, even film of pad material onto the rotor and gives the pad its full grip. Without it, pads can glaze or leave uneven deposits. Use the pad maker's procedure if it provides one. A common routine is:

1. Make 10 moderate stops from 30 mph, leaving about 30 seconds between stops.
2. Make 5 firm stops from 45 mph, leaving about 1 minute between stops.
3. Drive for about 5 minutes at highway speed, with as little braking as possible, to cool the rotors.

Do this only where it is safe and legal, with no traffic behind you. Avoid stopping hard and then sitting with your foot on the pedal, since hot pads held against a rotor can leave a deposit. Tell the customer to avoid hard stops for the first 200 miles or so.

Step 13: Road Test

Check for all of these:

• A firm, high pedal from the first press.
• No pulsation.
• No pull to either side.
• No grinding or squealing.
• A parking brake that holds.
• No warning lights.

Closing the Job

• Record parts, measurements and torque on the repair order.
• Reset any brake wear or service reminder.
• Put used fluid and rags in the shop's correct waste containers.
• Clean any brake dust from the wheels, and grease from the car.

Common Mistakes

Check Your Understanding

1. You start to press a rear piston with a C-clamp, and it will not move. There is a parking brake cable on the caliper. What now? Stop. It is probably a screw-in piston, so use a wind-back tool and confirm the direction.
2. A car comes back with pedal pulsation 2,000 miles after you fitted new rotors. Which things do you check first? Lateral runout, the hub face and the lug nut torque.
3. The new pads will not fit over the rotor. What did you probably miss? The piston is not fully retracted. Retract it, and check that the reservoir has room.
4. You finish the job and start to back the car off the lift. What must already have been done? You must have pumped the pedal until it was firm, and checked the fluid level, before moving the car.

Key Takeaways

• Look up torque specs and check parts before you start.
• Use the right piston method, and never force a rear piston with a parking brake.
• Service the slide pins, fit new hardware and support the caliper.
• A clean hub face and a torque wrench prevent most pulsation comebacks.
• Pump the pedal to a firm feel before the car moves.
• Bed in the pads and road test every job.