2020-2024 Mercedes-Benz GLE350 Front vs Rear Brakes: What Wears First and What to Replace

By Core Brake Parts Tech Team — Circleville, OH warehouse

On a 2020-2024 Mercedes-Benz GLE350, the front brakes usually wear out first, because they do most of the work when a heavy SUV stops. But this is a modern Mercedes with electronic brake force distribution and stability control, so the rear pads work harder than they did on older cars and can come due sooner than many owners expect. The right answer is to measure both axles every time, and replace pads and rotors as a set on whichever axle is worn.

How the GLE350 Brake System Is Laid Out

The GLE350 is a big vehicle for a four-cylinder. The published spec sheet for the 2020 model lists a 2.0-liter turbocharged inline four making 255 horsepower, a 9-speed automatic, and a curb weight of 4,696 pounds for the GLE350 4MATIC (a rear-wheel-drive GLE350 is also sold). Stopping that much weight is the job of a four-wheel disc system with four-wheel ABS, with disc brakes listed on both the front and rear axle.

Layered on top of the hydraulics are the electronic systems described in the owner's manual: ABS, BAS (Brake Assist System), EBD (electronic brake force distribution), ESP (Electronic Stability Program), Active Brake Assist, Hill Start Assist and the HOLD function. The GLE350 also uses an electric parking brake rather than a hand lever or foot pedal. Every one of those systems works through the same pads and rotors, which is why the wear pattern on this SUV is not as simple as "fronts first, rears maybe never."

Front vs Rear: Which Wears First and Why

When you brake, weight shifts forward onto the front tires, so the front axle can put more stopping force to the ground. That is why the front brakes have traditionally done most of the work and worn out two to three times faster than the rears on older vehicles.

Electronic brake force distribution changes that balance. Instead of a mechanical proportioning valve that limits rear pressure, EBD sends full pressure to the rear brakes as long as the rear wheels are slowing at the same rate as the fronts, and only cuts rear pressure when the ABS system sees a rear wheel starting to lock. The result is that the rear brakes carry a much bigger share of everyday stopping than they used to, and on vehicles with electronic proportioning the rear brakes may actually wear out faster than the fronts. Stability control adds to this, because ESP brakes individual wheels to keep the vehicle pointed where you are steering.

In practice on a GLE350, expect this:

• Front pads and rotors are still the most common first brake job, especially for drivers who do a lot of highway-speed stops or drive in hilly country.
• Rear pads can wear close to the same rate as the fronts, and sometimes faster, in stop-and-go city driving where EBD and the HOLD function are active constantly.
• Never assume. A shop that replaces fronts without measuring the rears is guessing. Pull the wheels or look through the spokes and measure pad thickness on all four corners.

Symptoms and How to Tell Which Axle Needs Work

The most direct warning is the instrument cluster message. The owner's manual describes a "Check Brake Pads See Operator's Manual" display message, which means the brake pads have reached their wear limit, and warns that braking power may be restricted. Mercedes' instruction is to drive carefully and have the brake system checked immediately.

That message comes from a wear sensor clipped into a pad. Bosch, which makes these sensors, explains that the sensor sits in contact with the rotor surface and wears along with the pad until its internal circuit is broken; on multi-stage designs, the vehicle uses the first break plus inputs such as mileage, wheel speed and brake temperature to estimate remaining pad life. Because the sensor wears out with the pad, it is replaced along with the pads. The important limitation: a sensor only reports on the pad it is installed in. The pad on the opposite side of the car, or the inner pad on the same caliper, can be thinner. The warning tells you it is time to inspect, not which pads are the thinnest.

Other signs to check for, and what they usually point to:

• Steering wheel shake under braking points to the front rotors.
• Pulsation felt in the seat or pedal with a steady steering wheel often points to the rear rotors.
• Grinding from one corner means the friction material is gone and the backing plate is cutting the rotor. Stop driving on it and inspect right away.
• Braking pulling to one side, or longer stops in winter can come from salt build-up. The manual notes that salt on the discs and pads can increase stopping distance considerably or cause braking on only one side, and recommends braking occasionally in traffic and gently applying the brakes at the end and start of a trip to clear it.
• A deep lip on the rotor edge or visible scoring means the rotor should be replaced with the pads.

The Fix: Which Parts to Replace

Replace brakes by axle, never one wheel. Both sides of an axle get new pads at the same time, and on a vehicle this heavy the rotors are normally replaced with them, since a worn or thin rotor sheds heat poorly and a new pad beds unevenly on an old, grooved surface.

• Front job: front pads, front rotors, a new front wear sensor if your pad set does not include one, and fresh hardware. Shop brake pads and replacement brake rotors by vehicle.
• Rear job: rear pads, rear rotors and a new rear wear sensor. We carry Bosch ceramic rear brake pads for the 2020-2024 GLE350, a low-dust ceramic compound that suits a daily-driven luxury SUV. Browse the full ceramic brake pads and Bosch brake parts ranges as well.
• Hardware: anti-rattle clips and guide-pin boots are cheap and prevent noise and uneven wear. See brake hardware kits.

Before ordering, confirm the exact fitment for your vehicle, including drivetrain and trim. Mercedes builds GLE models with different brake packages, and rotor size must match your caliper.

What to Replace or Service at the Same Time

• Wear sensor. Once its circuit is broken it cannot report again, so a new one goes in with new pads on that axle.
• Brake fluid. The manual warns that brake fluid constantly absorbs moisture from the air, which lowers its boiling point and can cause vapor pockets and reduced braking under hard use. Have it renewed at the specified interval and use only fluid approved to MB-Freigabe or MB-Approval 331.0. A brake job is a good time to check when it was last changed.
• Caliper slides and pistons. Clean and lubricate the guide pins, and check that the pistons retract smoothly and the boots are not torn. A sticking caliper will eat a new set of pads quickly. Replacement units are in brake calipers.
• Tires. The manual notes that new pads, rotors and tires all need several hundred kilometers of driving before they reach optimum braking effect and grip. Plan for that break-in period and press the pedal a bit harder until then.

How Hard Is the Job?

Front brakes are a reasonable job for an experienced home mechanic with a torque wrench, jack stands and the right sockets. The key points are cleaning the hub face so the new rotor sits flat, installing the wear sensor correctly and routing its wire away from the rotor, and torquing caliper bolts and wheel bolts to the values in the factory service manual.

Rear brakes are harder because of the electric parking brake. The parking brake must be released and the system put into its service mode before the rear pads are changed, and it has to be reset afterward, which often requires a scan tool. Forcing the rear pistons back without following the service procedure can damage the parking brake mechanism. If you do not have the tool and the procedure, this is the axle to hand to a shop.

After any brake job, test the brakes at low speed in a safe place before driving in traffic, and expect the pedal to feel a little less sharp until the new parts are bedded in.

Frequently Asked Questions

Do the front or rear brakes wear first on a GLE350?

Usually the fronts, because they carry more of the stopping load. However, electronic brake force distribution and stability control make the rears work harder than on older cars, so the rears can wear at a similar rate or even faster in city driving. Measure all four corners.

Does the Check Brake Pads warning tell me which axle is worn?

Not reliably. It means a sensor-equipped pad has reached its wear limit. Other pads, including the one on the opposite side, may be thinner. Inspect both axles when the warning appears.

Do I have to replace the wear sensor with new pads?

Yes, on the axle where the sensor has been triggered. The sensor wears along with the pad and cannot report again once its circuit is broken.

Should I replace the rotors every time I replace the pads?

On a heavy SUV like the GLE350, replacing rotors with pads is the normal practice. Always replace rotors if they are below minimum thickness, scored, or causing vibration.

What brake fluid does the GLE350 use?

Mercedes specifies brake fluid approved to MB-Freigabe or MB-Approval 331.0. Check the container for that approval before adding or flushing.

Can I do the rear brakes without a scan tool?

The rear brakes work with the electric parking brake, which normally has to be put into a service mode before the pads are replaced. Follow the factory procedure; if you cannot, have a shop with the proper tool do the rear axle.

Sources

1. Mercedes-Benz 2020 GLE SUV Operator's Manual - Check Brake Pads message, electric parking brake, brake fluid MB-Approval 331.0, break-in of new pads and discs, salt build-up, onboard brake systems
2. CarSpecs: 2020 Mercedes-Benz GLE 350 4MATIC specifications - 4-wheel disc and ABS, engine, transmission, 4,696 lb curb weight
3. AA1Car: Brake Balance and Electronic Brake Proportioning - front vs rear wear rates and how EBD shifts work to the rear brakes
4. Bosch Mobility: Brake pad wear sensor - how pad wear sensors work and why they are replaced with the pads