When to replace brake pads
Brake pads are not replaced at a fixed point: how quickly they wear depends on the vehicle, the axle, the pads and above all on how and where the vehicle is driven. Their thickness decides. Look in the vehicle manufacturer's information for how the wear of the pads of your vehicle is assessed and at which point they have to be replaced; replace them before they reach that point, and at once when a wear warning appears.
Have the brakes inspected without delay when you notice one of these:
- The brake pad wear warning comes on, or the vehicle shows a message about the brake pads
- A continuous squeal or a scraping, grinding noise when braking, which on pads with an acoustic wear warning is the warning itself
- The friction material of a pad, seen through the wheel or the caliper, is thin, or thinner on one pad than on the others
- The vehicle pulls to one side when braking, or the brake pedal or the steering wheel pulsates
- The brake pedal travels further than before or feels soft, or the braking distance has become longer
- The level in the brake fluid reservoir has fallen, or the brake warning comes on
The wear warning does not watch every pad: depending on the vehicle and the axle, only some pads carry a wear indicator, and some vehicles have none. A pad without an indicator can therefore be worn out before any warning appears, so look at every pad of the axle. Pads that have worn unevenly, one much more than its counterpart or one end more than the other, point to a caliper that does not slide or a piston that does not return freely; new pads do not cure these faults. A falling fluid level, a soft pedal and a brake warning can also mean a leak or another fault in the hydraulic system, which this guide does not cover: have the vehicle checked by a workshop before you drive it.
Do not drive with brake pads that are worn to the point at which they have to be replaced, whose friction material has come away from the backing plate, or that grind metal on metal. The braking effect can fall away sharply, and the brake disc can be damaged beyond use. Have the vehicle recovered if need be.
Before you start
The brakes are what stops the vehicle: a pad fitted the wrong way round, a fixing left loose, a twisted brake hose or grease on a friction surface can cause the brakes to fail. Do this job only if you have the vehicle manufacturer's procedure for your vehicle and axle, its tightening specifications and the tools they call for, and are certain of every step. Otherwise leave it to a workshop, or have your work checked by one before you drive on the road.
- Obtain the vehicle manufacturer's procedure before you start: the design of the brake on the axle concerned, how the pads are removed and fitted, which fixings must be replaced with new ones, the tightening specifications for the caliper's fixings and the wheel fixings, where and with what the brake is lubricated, how the pistons are pushed back, the smallest permitted thickness of the brake disc, and what the parking brake needs before and after the job.
- Find out which design of caliper your axle has. On a floating caliper the caliper or its housing slides on guide pins and is unbolted or swung up to change the pads. On a fixed caliper the pads are as a rule drawn out through an opening after retaining pins and a spring have been removed. The steps below name both; other designs are worked on only by the vehicle manufacturer's procedure.
- Find out how the parking brake acts on the axle you are working on. Where it acts on the rear calipers, their pistons are as a rule not simply pushed back but turned back with a tool made for that. Where the vehicle has an electric parking brake, it has to be put into the service position the vehicle manufacturer provides before the caliper is opened, with a diagnostic tool or through the vehicle's own menu, and taken out of it afterwards. Do not work on such a brake without that, and never try to force its piston back.
- Replace the pads of both wheels of an axle together, with pads from one set. Never replace the pads of one wheel alone, and never mix pads of different makes or types on an axle.
- Brake dust is harmful when breathed in. Do not blow a brake clean with compressed air and do not brush it dry in a way that raises dust: use brake cleaner and catch what runs off, and wear a dust mask, eye protection and gloves.
- Brake fluid attacks paint and irritates skin and eyes. Pushing the pistons back raises the level in the reservoir, which can overflow if fluid was topped up while the pads wore. Have cloths, clean water and the means to draw off fluid ready, and rinse any spilled fluid off paint with plenty of water at once.
- Park the vehicle on firm, level ground and switch off the ignition. Chock the wheels that stay on the ground on both sides. Where you work on the axle the parking brake acts on, the parking brake has to be released for the job as the vehicle manufacturer describes, so the chocks alone hold the vehicle: select a gear or the park position as well where that holds the vehicle, and make sure that it cannot roll before you raise it.
- Raise the vehicle only at the points the vehicle manufacturer gives and support it on axle stands made for its weight. Never work on a vehicle that is held up by a jack alone, and keep it securely supported for as long as you work on or inspect the brake. Loosen the wheel fixings slightly while the wheel still stands on the ground, and remove them only once the vehicle rests securely on the stands.
- Let the brakes cool before you touch them: discs and calipers stay hot long after a drive.
- Work on one wheel at a time and leave the other side assembled, so that you can see how the parts belong. Do not press the brake pedal or operate the parking brake while a caliper is off its disc or pads are out: the piston would be pushed out.
Choose the right brake pad set
Brake pads differ in their shape and dimensions, their thickness, their friction material, their wear indicator and the parts fitted to them or supplied with them. The same model is often built with several brake systems, depending on the engine, the equipment and the production period, and the front and the rear axle can take different pads. A pad that can be pushed into the caliper is not therefore the right one. Fit only a brake pad set that is listed for your vehicle and axle and matches the brake system fitted to it.
Select your vehicle with the selector on this page to find the part numbers suppliers list for its engine. On the vehicle's part page, each part number is shown with the specifications its supplier states, such as the brake system the set is for, the width, the height and the thickness of the pads, whether they have a wear warning contact, the WVA number, a test mark such as ECE-R90, and what is supplied with the set. Under the part's name the page shows a fitting position, such as the front or the rear axle, where the supplier states one.
- Brake system: suppliers name the maker of the brake system a set is for. The maker's name is as a rule cast or stamped on the caliper. Where sets for several brake systems are listed for your vehicle, identify the system on the axle concerned before you buy, and compare the pads' dimensions with the pads fitted.
- Wear indicator: suppliers state, for example, that a set has an integrated wear sensor or wear warning contact, that it is prepared for a wear indicator, that it has an acoustic wear warning or that it has none. Take the version your vehicle's brake has. A separate wear sensor that is not part of the set is as a rule replaced with the pads once it has triggered, and whenever it is damaged; obtain it beforehand.
- What is supplied: for some part numbers the supplier states that the set comes with or without an anti-squeak plate or shims, bolts or screws, springs, counterweights, slide rails, or a piston clip fitted to the pad. Check what is in the box against what the vehicle manufacturer's procedure requires to be replaced, and obtain separately any fixing, spring or retaining pin that has to be new and is not included.
- The WVA number identifies the shape of a pad and can help to compare sets from different suppliers. It does not by itself say that a set is approved for your vehicle.
- Where more than one set is listed for an axle, they can be equivalent parts from different suppliers or parts intended for different versions of the vehicle. Where a supplier states conditions for a part number, such as a production period, a chassis number range or an equipment code, the vehicle's part page shows them with that part number: check them against your vehicle. If what is stated does not settle whether the set fits, ask the supplier or the vehicle manufacturer before you buy.
Compare the new pads with the old ones before you fit them, but do not take the old ones as the specification: pads that were fitted earlier may themselves have been the wrong ones. What decides is the part number listed for your engine whose stated conditions match your vehicle, its axle and its brake system, and a difference in shape, in the wear indicator or in the fitted parts needs the supplier's or the vehicle manufacturer's confirmation.
Remove the old pads
- Secure, raise and support the vehicle as described under Before you start, and check that it stands securely on the stands before you take a wheel off. Where the vehicle has an electric parking brake on the axle concerned, put it into its service position as the vehicle manufacturer describes before you raise the vehicle or open a caliper, as the procedure requires.
- Remove the wheel fixings and the wheel. Put the wheel down flat where it is not in the way.
- Look at the brake before you take anything apart and record how it is assembled, for example with a photograph: which pad is on the piston's side, where each spring, clip and shim sits, and how the wear sensor's lead and the brake hose are routed.
- Open the bonnet, make sure that its stay or struts hold it securely, and look at the level in the brake fluid reservoir. If it stands near the upper mark, draw off some fluid with a clean syringe that is used only for brake fluid, so that the reservoir cannot overflow when the pistons are pushed back. Put the drawn-off fluid into a sealable container for disposal; it is not reused. Lay a cloth around the reservoir and close its cap again.
- If the brake has a wear sensor, unplug its connector after releasing any lock, free the lead from its holders as the vehicle manufacturer describes, and draw the sensor out of the pad where it is a separate part. Do not pull at the lead.
- Take off any retaining spring or clip on the outside of the caliper as the vehicle manufacturer describes. Such a spring is under tension: hold it while you release it, and wear eye protection.
- On a floating caliper: remove the caps of the guide pins if they have any, and undo the guide pins or the caliper's fixing bolts as the vehicle manufacturer describes, holding the guide pin with a second spanner where its design requires that. Depending on the design, both are removed and the caliper is lifted off, or one is removed and the caliper is swung up on the other. Do not undo the bolts that hold the caliper's carrier to the hub carrier unless the procedure calls for it.
- On a floating caliper: lift or swing the caliper away from the pads without straining the brake hose, and hang a caliper that has been taken off from the suspension with a hook or wire so that its weight is not on the hose. Never let a caliper hang by its hose, and do not twist or kink the hose.
- On a floating caliper: take the pads out of the carrier or off the caliper. Note which pad was where: inner and outer pads often differ, and their wear pattern shows how the brake has been working. Take out the pads' guide plates or anti-rattle clips from the carrier if the vehicle manufacturer's procedure or the new set provides for replacing them.
- On a fixed caliper: remove any retaining clip of the retaining pins, then drive the pins out in the direction and with the tool the vehicle manufacturer describes, holding the spring down so that it cannot fly off. Take off the spring, and draw the pads out through the caliper's opening, if need be after pushing each a little away from the disc. The caliper itself stays bolted on. Note which pad was where, as on a floating caliper.
From here until the new pads are in and the caliper is assembled, nobody may press the brake pedal or operate the parking brake. A piston that is pushed out too far loses its seal, and the brake then has to be repaired and bled before the vehicle can be used.
Check the disc and the caliper
- Look at the old pads. Uneven wear between the inner and the outer pad, between the two sides of the axle or along one pad, friction material that has come away, cracked or glazed, and pads soaked with fluid or grease all have a cause that has to be found and put right before new pads are fitted.
- Check the brake disc. Measure its thickness with the measuring instrument at several points of the braked surface and compare it with the smallest thickness the vehicle manufacturer permits; the value is as a rule also marked on the disc, and where a brake disc's supplier states it, this site shows it beside that part number. A disc that is at or below that thickness, that would reach it before the new pads are worn, or that is cracked, deeply scored, blued by heat, badly corroded on its braked surfaces or worn with a pronounced ridge at its edge has to be replaced. Discs are replaced as the vehicle manufacturer's procedure describes, as a rule as a pair on the axle and together with new pads; that is a separate job.
- Clean the carrier and the caliper where the pads rest and slide: remove corrosion and old deposits from the guide surfaces with the wire brush and brake cleaner, catching what runs off, without raising dust. Keep the wire brush and the brake cleaner's jet away from the rubber boots of the piston and the guide pins as far as the cleaner's instructions require, and do not damage the surfaces.
- Check the caliper. The boot around each piston must be undamaged and seated, and no brake fluid may be escaping at a piston, at the hose connection or at the bleed screw. On a floating caliper the guide pins must slide smoothly and without play in their bores, and their boots must be sound; clean and lubricate them only as the vehicle manufacturer describes and only with the lubricant it specifies.
- Check the brake hose over its whole length while you turn the steering or move the caliper as far as the job requires: it may not be cracked, swollen, chafed, damp or twisted.
- Check the wear sensor and its lead, where the brake has one. A sensor that has triggered, whose tip is worn through or whose lead is damaged is replaced.
If a piston's boot is torn, a piston or a guide pin is seized, brake fluid is escaping anywhere, a hose is damaged or the disc has to be replaced, do not go on fitting the pads onto it. These faults are repaired first, and repairs that open the hydraulic system include bleeding the brakes, which this guide does not cover: have a workshop do them.
Push back the pistons and fit the new pads
- Push each piston back into the caliper in the way the vehicle manufacturer describes, with the piston tool made for it: slowly, squarely and without damaging the piston or its boot. Where the parking brake acts on the caliper, the piston is as a rule turned and pushed at the same time with the tool for that design, in the direction the procedure gives, and set to the position the procedure requires for the pad's locating feature. On a caliper with several pistons, keep the others from being pushed out while one is pushed back. Do not lever against the brake disc's braked surface with a tool that can damage it.
- Watch the level in the brake fluid reservoir while the pistons go back, and draw off fluid before it can overflow. Some vehicle manufacturers require the fluid displaced from the caliper to be released at the bleed screw instead of being pushed back into the system; that procedure includes bleeding, and if your vehicle requires it and you are not equipped and practised for it, have a workshop do this job.
- If a piston cannot be moved back with moderate, even force, stop. Check that an electric parking brake is in its service position and that the right tool and direction are being used; a piston that is seized means that the caliper has to be repaired or replaced.
- Check the new pads against the part number listed for the vehicle and compare them with the old ones, as described under Choose the right brake pad set. Find out from the set's instructions and the vehicle manufacturer's procedure which pad belongs on the piston's side and which on the outside, on which side of the vehicle a pad marked for a side or a direction of rotation belongs, and where a pad with a wear indicator is fitted. Do not touch the friction surfaces with greasy fingers, and do not fit a pad that has been dropped, is damaged or is soiled with oil, grease or brake fluid.
- Fit new guide plates, anti-rattle clips, shims or springs where the set supplies them or the vehicle manufacturer's procedure requires them, each in its seat and the right way round. Remove any protective film from an adhesive shim only if the set's instructions say so.
- Apply lubricant only where the vehicle manufacturer's procedure or the set's instructions provide for it, only the product they specify and only as thinly as they describe: as a rule at the points where the pads' backing plates rest and slide in the carrier. Never put lubricant on the friction material, on the disc or on a rubber part it is not approved for. Where the instructions provide for no lubricant, use none.
- Put the pads in their places. On a floating caliper, set each pad into the carrier or onto the caliper as its design provides, with a pad that has a piston clip pressed fully into the piston, and check that every pad lies with its friction material towards the disc and moves freely in its guides. On a fixed caliper, slide the pads in through the opening, fit the spring and drive the retaining pins fully home with their retaining clips, using new pins and a new spring where the procedure requires them.
- On a floating caliper, bring the caliper over the pads without trapping a boot, a clip or the hose, and check that the brake hose is not twisted. Fit the guide pins or fixing bolts, new ones where the vehicle manufacturer requires them to be replaced or the set supplies them, start each thread by hand, and tighten them according to the vehicle manufacturer's specification with a torque wrench, holding the guide pin where its design requires that. Refit the caps of the guide pins and any retaining spring on the outside of the caliper.
- Fit the wear sensor into the pad it belongs to, where it is a separate part, route its lead through every holder exactly as it was, clear of the wheel, the disc and the suspension, and plug in its connector until it locks.
- Compare the finished brake with the side that is still assembled or with your record, and check that no tool, cloth, hook or wire remains on the brake. Brake cleaner on a clean cloth removes fingermarks and grease from the disc's braked surfaces; let it evaporate fully.
- Fit the wheel after cleaning the contact surfaces of the wheel and the hub as the vehicle manufacturer describes. Start every wheel fixing by hand and tighten them evenly in a diagonal sequence. Then do the same work on the other wheel of the axle.
A pad fitted with its backing plate towards the disc, a pad in the wrong position, a retaining pin or spring left out, and a guide pin or fixing bolt that is not tightened as specified can each make the brake fail. Check every one of these on both wheels before the wheels go on.
Finish and test the brakes
- With both wheels of the axle fitted and the vehicle still securely supported on the stands, press the brake pedal slowly and repeatedly until it is firm and its travel is normal. Where the vehicle has an electric parking brake, keep to the order the vehicle manufacturer's procedure gives for pressing the pedal and for taking the parking brake out of its service position, which the next step describes. On the first strokes the pedal can travel much further than usual, until the pistons have brought the pads into contact with the discs; the brake does not work properly before that. Do not press the pedal to the floor with force on the first strokes.
- Where the vehicle has an electric parking brake, take it out of its service position as the vehicle manufacturer describes and carry out any step the procedure requires afterwards. Where a mechanical parking brake acts on the calipers, operate it several times and check its adjustment as the vehicle manufacturer describes.
- With the vehicle still supported and the brake released, turn each wheel of the axle by hand: it has to turn, with at most light contact of the pads. Look at both calipers with the lamp: no fluid may be escaping. A wheel that is held fast or drags heavily has a cause that is found before the vehicle is lowered.
- Lower the vehicle onto its wheels and tighten the wheel fixings in a diagonal sequence according to the vehicle manufacturer's specification with a torque wrench. Where the vehicle manufacturer's instructions call for the wheel fixings to be checked again later, do that as they describe.
- Check the level in the brake fluid reservoir and bring it between the marks, with new brake fluid of the specification marked on the reservoir's cap or given in the handbook, from a sealed container. Do not fill above the upper mark. Close the cap and wipe away any fluid.
- Switch on the ignition and check the brake warning and the brake pad wear warning as the vehicle manufacturer's procedure describes: both have to go out, the wear warning after being reset where the procedure requires that. If the pedal stays soft, sinks under steady pressure or travels further than before, or if a brake warning stays on, do not drive: have the vehicle checked by a workshop.
- Before the vehicle moves at all, press the brake pedal once more and make sure that it is firm. Test the brakes at low speed in a safe place away from traffic before you drive on the road: the vehicle has to brake evenly, without pulling to one side and without unusual noise, and the parking brake has to hold it.
- New pads do not give their full braking effect at once. Bed them in as the pads' maker describes; unless those instructions say otherwise, brake gently and early over the first drives, avoid hard and prolonged braking as far as traffic allows, and leave more distance than usual. Look at the brakes and the fluid level again after the first drives.
- Hand in the old pads, the drawn-off brake fluid and used cleaning cloths at a collection point for hazardous waste or where you bought the parts. They do not belong in household waste or the drain.
Mistakes to avoid
- Working on a vehicle that is not securely supported on axle stands
- Replacing the pads of one wheel only, or mixing pads of different sets on an axle
- Pressing the brake pedal while a caliper is off or pads are out
- Letting a caliper hang by its brake hose, or fitting it with the hose twisted
- Forcing back the piston of a caliper with a parking brake mechanism, or working on an electric parking brake that is not in its service position
- Letting the brake fluid reservoir overflow, or topping it up with the wrong fluid
- Blowing brake dust out with compressed air
- Fitting a pad the wrong way round or in the wrong position, or leaving out a spring, clip, shim or retaining pin
- Putting lubricant on the friction material or the disc, or using a lubricant that is not specified for brakes
- Reusing fixings that the vehicle manufacturer requires to be replaced, or tightening them by feel
- Fitting new pads onto a disc that is below its smallest permitted thickness or damaged
- Fitting new pads to a caliper with a seized piston or guide pin
- Moving the vehicle before the brake pedal has been pressed until it is firm
- Braking hard on new pads that have not been bedded in