A message on the cluster is not a measurement, and no Mercedes has any idea how much friction material is actually left. On the models built with an electric parking brake there is a second obstacle, because the rear caliper will not let go of its piston for anybody until it has been put into the right state first. So the wheels come off, the readings get written down, and you see photographs before a quote exists.
A message, a noise, or a job that stopped halfway. They put you at three different places, and each one changes what the first visit needs to look like. Tell us which is yours.
The wording shifts between model years and screens, but the meaning holds steady. A wear sensor circuit has been broken open by the disc grinding into it. Nothing is being counted down and nothing is being weighed up. It flipped once, it named an axle rather than a wheel, and it is a reason to get the car up rather than an answer on its own.
Send us the exact wording → 02A scrape under light braking, a squeal that clears after the first few stops of the morning, or a grinding you can feel coming up through the pedal. None of that needs a warning to go with it, because the sensor sits at one wheel on each axle and has nothing to say about the other two corners. Silence up front proves very little.
Describe the noise to us → 03The front axle behaved itself, then the rear piston refused to move and the car came back with a line about the conditions for replacing the brake pads not being fulfilled. Nothing is broken. The parking brake motor still has hold of that piston and it will not let go until the caliper has been walked into its fitting state properly. Bring the car exactly as it sits.
Tell us where it stopped →There is nothing clever inside a Mercedes wear sensor. It is a loop of fine wire moulded into a plastic carrier, and the carrier clips into one pad so that it sits a set distance away from the disc face. As friction material disappears, that gap closes with it, until the disc finally arrives at the plastic and takes the wire with it. An open circuit is the only thing your car ever detects. One shot, by design, which is why it is a part you buy again with the pads instead of something to unclip and reuse.
Then there is coverage. Two of them is the usual count on these cars, one looking after the front axle and one the rear, each clipped to a single wheel whose position shifts between models and years. Three corners out of four report nothing whatsoever. Where a guide pin has stuck and a pad is being eaten alive on one side, the odds are three in four that your car has no way of noticing it happening.
So a message tells you that one axle has hit a limit. It has nothing to say about how many millimetres are left up front, whether the disc underneath has already spent its allowance, or whether the opposite corner is worse than the one that triggered. None of that lives anywhere in the car. It comes into existence when a gauge touches metal, and not a moment before.
Which is why a quote here follows the wheels coming off instead of leading it. Every pad gets a thickness taken, inner and outer face kept apart, and every disc is checked against the wear limit stamped on its own edge rather than a number somebody half remembers. Written without a badge attached to it, the same method sits on our brakes and suspension page, and the Mercedes-Benz page covers the rest of what these cars ask for.
Fronts are much of a muchness on these. It is the back end that shifts with the model and the year, and it decides what has to happen before a rear pad can even be lifted clear of the carrier. Find your row, then message us with it.
Not on this table? Send us the model and the year before you drive down and we will place you on it, because the row you sit in changes what the visit looks like rather than only what it costs. If one line on that table repays a second look, it is the second. A rear pad change that was an afternoon in a car park on the older cars now carries an electronic step at both ends of it.
This part of a Mercedes brake job has almost nothing to do with spanners. Where an electric parking brake is fitted, the rear piston answers to a motor rather than to a thread, and that motor has to be taken out of the way in the right order and put back in the right order.
On the older cable cars none of the above applies, which is why two owners can describe the same rear pad change and mean two completely different afternoons. Those cars want the parking brake shoes inside the disc hat checked and the adjuster set instead, and that is its own small job worth doing while the corner is open.
A gauge settles this and nothing else gets a vote in it. Here is what each answer looks like once the wheel is out of the way, and why the heavier cars in the range land in the second column more readily than the light ones.
Weight has to go somewhere every time a car slows down, and plenty of it ends up in the disc as heat. The bigger saloons, the larger SUVs and the long-wheelbase people carriers therefore tend to use a disc up in step with one or two sets of friction material rather than carrying three. Lighter models hang on to theirs more often. Neither of those is a rule anyone should be quoting from without a gauge in their hand, which is why the figures arrive before the word replacement does. Where the thickness allows for it, skimming instead of renewing is a conversation worth having, although it is ruled out on the two-piece designs and on anything already near its limit, since a disc with nothing spare runs hotter, distorts sooner and brings you straight back.
The exact brake message, the mileage that day and whatever you have felt coming up through the pedal, all recorded before the car ever leaves the floor. Our own figures then have something to be tested against.
A thickness taken at all four wheels, inner face and outer face kept apart. Where the two halves of one caliper disagree with each other, that points at a guide pin or a piston rather than at your mileage, and it gets chased down.
Every disc read and set against the wear limit stamped on that particular part rather than a figure from memory, with the outer lip, the score marks and any bluing photographed in place instead of described to you.
Parts itemised, labour separate, the wear sensor written on the sheet by name instead of folded into a bundle. You are looking at your own brakes before you agree to anything, and no part is ordered until you have.
Guide pins cleaned and regreased, springs and shims renewed where they have had enough of life, a fresh wear sensor rather than the cut one going back in, and the parking brake shoes inside the rear disc looked over on the cars that carry them.
The electric parking brake run back out and shown the new pad thickness where your car has one, the cable adjuster wound up where it does not, then a drive to bed the friction material in before the keys come back to you.
No figure appears on this page, and that is not coyness. One axle on a small saloon and four corners on an AMG estate get typed into Google as the same three words, so any range broad enough to cover both would be worthless to you. The useful thing is the list below, because those six items are what the number is built from.
Front discs and pads are the bigger components and do most of the slowing down, so the parts side always reads higher at that end. The rear on a modern Mercedes carries a parking brake motor and the sequence that comes with it, which lands on the labour side instead. Which axles are genuinely due shifts the total further than anything else below.
A cable rear axle is a conventional pad change with the parking brake shoes checked while the disc is off. An electric one adds a release before and a calibration afterwards, and both have to be done properly rather than briskly. That difference lands in the labour line and not in the parts line.
One per axle on most of these cars, so doing both ends means buying two. Some pad sets arrive with one in the box and some do not. It is the cheapest thing on the list and the first item a keen quote leaves out, and putting a cut one back in is exactly why a message returns days later.
A disc with something to spare keeps this a pad-only job. One that has reached its limit brings a second parts line along with it, and a two-piece design is a bigger step again. None of that is visible with the wheels on, so the gauge goes onto the metal first and the figure follows it.
AMG parts are priced in their own bracket, and on some of those cars the disc is built in two pieces rather than cast in one. Reading the specification off the chassis number is the only reliable way to avoid a wasted order and a car sitting in the bay an extra day waiting on the right box.
Guide pins, springs, shims, and on the cable cars the parking brake shoes and adjuster hiding inside the rear disc hat. Most of that cleans up and costs you nothing. A seized pin, a split boot or a set of shoes worn thin is a genuine part, and the photograph reaches you before the line reaches your quote.
An itemised quote, parts and labour kept apart, sensors listed by name, and pictures of your own brakes sitting beside the figures they produced. Should anything look worse in the flesh than it did on the gauge, work halts and the phone rings, rather than a surprise line turning up at the bottom of the final bill. Everything that came off the car leaves with it, cut sensor included.
Because the rear caliper is still busy doing its other job. On a Mercedes with an electric parking brake, a motor on each rear caliper drives the piston out to hold the car when parked, and until those motors have been driven back into their fitting state the piston will not retract far enough for a new pad. That message is the car refusing rather than the car breaking. The same applies at the far end of the job, where the brake has to be run back out and taught the thickness of the new pad before it will leave that state. If a pad change has stalled here, the car is fine to bring in exactly as it stands.
Most carry one per axle, so two on the car, and each is clipped to a single wheel on its axle. Which wheel that turns out to be moves around between models and years, so it is worth having somebody look rather than assuming. The three corners without one are not monitored in any way, which is how a pad chewed down by a sticking caliper on the wrong side gets a long way with nothing showing on your cluster. That is the reason all four corners get measured here.
No. It is a wire loop inside a small plastic carrier clipped to one pad, and the disc cuts through that loop once the friction material has worn far enough. Broken circuit, message on. There is no gradual stage to any of it and nothing anywhere in the car counts millimetres down, so the message marks a limit arriving rather than a measurement being taken. The only real number comes off a gauge, with the wheel out of the way.
The mechanical half is ordinary enough. The obstacle is the electric parking brake, because the rear caliper motors have to be put into their fitting state before the old pads can be lifted clear, then brought back out and calibrated once the new ones are in. Without that first step the piston will not move at all, and driving it back by force is how the motor and the caliper get ruined together. On the older cars with a pedal and cables there is no electronic step anywhere in it, which is why two owners can describe the same job and mean very different things by it.
Not as a rule, though it lands that way often enough to be worth expecting, particularly on the heavier models where discs give up their allowance alongside the pads instead of outlasting several sets. What decides it is the reading against the minimum figure marked on the disc, together with whether a lip has formed at the outer rim, because a new pad cannot lie flat against a ridge. Both figures, the one taken off your disc and the one stamped on it, go in front of you before a decision is asked for.
Nearly always the sensor. A severed loop stays severed, and the car goes on reading an open circuit regardless of how much friction material is now sitting in the caliper, so putting the old one back leaves the message exactly where it was. A damaged or unplugged sensor lead does the same job. Where a message comes and goes rather than staying put, the lead is usually the suspect rather than the pad. None of those take long to fix and all of them are worth fixing, because an alert you have taught yourself to scroll past has stopped being an alert.
Yes. An AMG car runs a bigger disc and a friction material blended for higher heat than the standard model gets, and some are built with a two-piece disc on an alloy centre where fitted, which is not something anyone skims. AMG Line specifications vary with the model and the year, so the badge on the boot settles less than owners expect it to. Send us the chassis number and the correct set gets identified before anything is bought, rather than after the wrong parts have turned up and the car is waiting.
No. The Competition and Consumer Commission of Singapore has required authorised dealers to remove warranty terms that tie servicing to their own workshops, so you can service or repair at any qualified workshop without losing the manufacturer warranty, as long as compatible parts are used and the manufacturer’s procedures are followed. We do both, and the written report is your record of it. There is more in our piece on your right to service where you want.
Suspension that rides on air, gearbox trouble on the automatics, oil escaping from a seal that has gone hard, and every model of Mercedes we are set up to work on.
See the brand page →The measuring routine at each corner, calipers and fluid included, plus the written report that travels home with the car at the end of it.
Open the brakes page →What each letter carries underneath it, why brake fluid so often lands in a B, and how the counter on your cluster works the date out for itself.
See what each letter covers →