2011-2019 BMW M5 Brake Caliper Problems and Replacement

By Core Brake Parts Tech Team — Circleville, OH warehouse

Most brake caliper trouble on a 2011-2019 BMW M5 comes down to three things. Torn piston dust boots on the big six-piston front calipers let grit and salt in until a piston sticks. The rear floating calipers can drag when their slides or pistons bind. And the electric parking brake motor on each rear caliper has to be put into service mode before any rear pad or caliper work. The usual fix is a front caliper rebuild or a replacement caliper, done together with fresh pads, a rotor check and a full fluid flush.

This year range covers two different cars. The F10 M5 ran through 2016, and the F90 M5 arrived for 2018 with all-wheel drive. Both use the same basic layout: a six-piston fixed caliper up front and a single-piston floating caliper at the rear. The problems and the repair logic below apply to both. Always confirm your generation and brake package before ordering parts.

How the M5 Caliper System Works

BMW fitted both generations with what it calls M compound brakes. Up front, a six-piston fixed caliper is bolted to the knuckle and does not move. Pistons on both sides of the rotor push the pads in from each side. At the rear, a single-piston floating caliper slides on guide pins, so one piston pushes the inner pad while the caliper body pulls the outer pad in. On the F90, BMW paints the standard M compound calipers blue.

The rotors are compound (two-piece) discs: a cast iron friction ring on a separate hub, cross-drilled and internally vented. The optional M carbon ceramic system uses gold-painted calipers and completely different rotors and pads. BMW says the F90 carbon ceramic package takes 23 kg off the car, and the F10 ceramic option was reported at 19.4 kg lighter than the standard brakes. Carbon ceramic parts do not interchange with the iron-rotor parts, so identify your system by caliper color and rotor type before buying anything.

Common M5 Caliper Problems and Symptoms

Torn dust boots and sticking front pistons

The F10 iron-brake front calipers use aluminum pistons in three sizes: 36 mm, 34 mm and 30 mm. The rubber boots around those pistons are the weak point. Once a boot tears, road dirt and winter salt reach the piston. The piston then corrodes or scores and stops retracting cleanly. Hard street or track use makes it worse, because heat hardens the seals and boots. Watch for these signs:

• The car pulls to one side under braking.
• One front wheel runs much hotter, or collects more brake dust, than the other after a drive.
• A pad wears unevenly across its face, or the inner and outer pads wear at very different rates.
• A burning smell, or drag you can feel when coasting.
• A torn or missing section of boot when you look at the caliper with the wheel off.

Rear caliper drag

The rear floating caliper depends on clean, lubricated guide pins. When the pins or their boots corrode, the caliper cannot float. The inner pad then wears out well before the outer one and the rear rotor runs hot. A seized rear piston does the same thing.

Electric parking brake faults

Each rear caliper carries a geared electric motor that applies the parking brake. These faults point to the motor, its connector or the caliper mechanism rather than the hydraulics:

• A parking brake warning on the dash.
• A motor that whirs but does not release.
• A rear wheel that stays locked after release.

How to Diagnose Before You Buy Parts

1. Drive a short loop with light braking, then compare the temperature of each wheel with an infrared thermometer, or carefully by hand near the hub. A corner much hotter than its partner is dragging.
2. Lift the car and spin each wheel by hand in neutral. A front wheel that is much harder to turn than the other side points to a sticking piston.
3. With the wheels off, inspect every piston boot and measure pad thickness at both ends of each pad. Tapered or lopsided wear tells you which piston or slide is binding.
4. Check the brake fluid condition. Old fluid absorbs moisture, which corrodes pistons from the inside and shortens caliper life.
5. For a parking brake warning, scan the chassis modules for stored faults before you replace any caliper.

Rebuild or Replace the Caliper

On the front six-piston calipers, a rebuild is a real option. Rebuild kits for the F10 M5 iron-brake calipers include new aluminum pistons and a full set of high-temperature seals, which fixes the damage a torn boot causes. A rebuild makes sense when the caliper body and bores are clean. Replace the caliper instead if a bore is pitted, the caliper has been overheated, or you need the car back on the road quickly. Fixed calipers are side-specific, so order the correct left or right unit.

At the rear, a sticking floating caliper is usually replaced as a unit, with the guide pins and boots serviced or replaced at the same time. Browse replacement brake calipers and brake hardware kits for pins, clips and boots.

What to Replace at the Same Time

• Pads: a sticking caliper overheats and glazes its pads. Replace pads in axle sets, never one side only. See our brake pads.
• Rotors: a dragging caliper overheats the rotor. Check thickness against the minimum marked on the rotor, and look for heat spots or cracks around the drilled holes. The M5 uses two-piece compound rotors, and upgrades such as the EBC Racing SG two-piece floating front rotors for the F10 M5 use the same construction. Some OEM rear rotors are sold as separate left and right parts, so check the side before ordering. More options are in brake rotors.
• Brake fluid: any caliper job opens the hydraulic system. Flush and bleed with the fluid specified on your reservoir cap or in the owner's manual.
• Wear sensors: once a BMW pad wear sensor has worn through and triggered, replace it along with the pads.
• Brake hoses: replace any cracked or swollen hose while the system is open. See brake hoses.

How Hard Is the Job?

Replacing a front caliper on an M5 is a moderate job if you have good tools. The caliper unbolts from the knuckle, the hose moves across to the new caliper, and the system is bled. Rebuilding a six-piston caliper is harder. It needs a clean bench and patience, because all six pistons must go back in straight with new seals. Torque every caliper bolt to the value in the factory service manual.

The rear is where people get caught out, because you cannot simply push the rear piston back with a spreader. A guide based on a 2016 F10 M5 lays out the process in three steps:

1. Use a scan tool to put the parking brake into workshop mode, which retracts the piston.
2. Swap the pads or the caliper.
3. Use the scan tool to run the startup routine, which resets the piston.

The same guide warns you to wait 30 seconds after the retract finishes before unplugging the caliper connector. Skipping these steps can damage the motor or leave the parking brake in a fault state.

Frequently Asked Questions

Why does my M5 pull to one side when braking?

The most common cause is a sticking piston in one of the front six-piston calipers, usually after a torn dust boot let dirt and moisture in. Check that corner for heat, uneven pad wear and a damaged boot.

Can I rebuild the M5 front calipers instead of replacing them?

Yes, as long as the bores are not pitted. Rebuild kits for the F10 M5 iron-brake calipers supply new pistons and high-temperature seals. Replace calipers that are badly corroded or have been overheated.

Do carbon ceramic M5 brakes use the same calipers?

No. The M carbon ceramic system has its own calipers (gold on the F90), rotors and pads. Parts for the standard M compound brakes will not fit a car with ceramic brakes.

Do I need a scan tool to replace the rear brakes on an M5?

Yes, or another tool that can control the electric parking brake. The rear pistons must be retracted electronically before new pads go in, then reset afterward.

Should I replace calipers in pairs?

It is not required, but it is common on high-mileage cars because the other caliper on that axle has seen the same age and heat. Pads should always be replaced in axle sets.

Sources

1. BMW Group PressClub - The new BMW M5 - F90 six-piston front and single-piston rear calipers, blue M compound calipers, gold carbon ceramic option and 23 kg saving
2. BMWBLOG - F10 M5 with M Carbon Ceramic Brakes - F10 six-piston fixed front and single-piston floating rear calipers, cross-drilled discs, 19.4 kg ceramic weight saving
3. BimmerWorld - F10 M5 Front Caliper Rebuild Kit - 36/34/30 mm aluminum pistons, torn dust boots causing sticking and seizing
4. BimmerWorld - OEM Rear Brake Disc for F10 M5 - two-piece floating rear disc sold as a side-specific right rear part
5. ECS Tuning - BMW Rear Brake Pad Replacement with Electronic Parking Brake - scan-tool retract and reset on a 2016 F10 M5, 30-second wait before unplugging