Nominal thickness of EQS SUV rear brake pad - 8mm
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Nominal thickness of EQS SUV rear brake pad - 8mm
I scheduled the annual PA State inspection for my EQS SUV at the selling MB dealer on 1-Oct-2024. I am expecting to have about 45K miles on the car at the end of September and I wanted to be prepared for the possibility that the SA will try to sell a brake job to pass the inspection. I purchased a spare set of rear brake pads in order to confirm the thickness of new pads. I used calipers to measure the thickness at the inner and outer edges of the pad and got readings between 7.6mm and 7.9mm. So I would consider the nominal thickness to be about 8mm. The rear pads measured about 6mm when I checked at 40K+ miles. I had a set of new 2006 SL55 rear pads in my garage and measured the pad thickness to be a nominal 10mm. The holes for the brake pad sensors are positioned for both the EQS 8mm pads and SL55 10mm pads to "trip" the brake wear warning message at a pad thickness of about 3.5mm. Assuming about 1mm of wear on the rear pads per 20K miles of driving (without LKA toggled on), I expect to get about 80K miles on the rear pads.
Edit: My understanding is that the brake pads need to be at least 50% of the thickness of new pad to pass the CPO inspection for an MB ICE vehicle. I wonder if there is a different thickness threshold for MB EVs, since a 50% thickness on rear pads would not be far from tripping the brake pad warning.
Edit: My understanding is that the brake pads need to be at least 50% of the thickness of new pad to pass the CPO inspection for an MB ICE vehicle. I wonder if there is a different thickness threshold for MB EVs, since a 50% thickness on rear pads would not be far from tripping the brake pad warning.
Last edited by LAZARU5; Sep 2, 2024 at 11:55 AM.
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Not sure I understand. Why do MB EVs trip brake wear sensors at 50% when braking is supposed to be primarily recuperative? And why would any state inspection station fail brakes if 50% of the pads remain?
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Old rule of thumb was to change them when the friction material thickness gets as thin as the steel backing plate.
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The EQS front pads start out thicker than the rear pads, but I am fairly certain that the sensor will be tripped at ~3.5mm just like the rear. So 50% thickness on the front pads would be well above the minimum state inspection threshold for the front pads.
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2025 E53 Hybrid
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2025 E53 Hybrid
Parked in front of Boyertown Auto Body Works factory which closed in 1990. Now the Boyertown Auto Museum in Boyertown, PA.
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The minimum brake pad thickness for the Pennsylvania annual safety inspection is 2/32" (~1.6mm). This thickness is well below the 3.5mm to 4.0mm thickness that will trip the sensor warning when the rear pads are at 50% thickness. I inspect the pads when I rotate the tires every 5000 miles. I am considering removing the sensors when the pads are at 4mm and getting another 20K miles out of the pads before changiing them out at 3mm thickness.
The EQS front pads start out thicker than the rear pads, but I am fairly certain that the sensor will be tripped at ~3.5mm just like the rear. So 50% thickness on the front pads would be well above the minimum state inspection threshold for the front pads.
The EQS front pads start out thicker than the rear pads, but I am fairly certain that the sensor will be tripped at ~3.5mm just like the rear. So 50% thickness on the front pads would be well above the minimum state inspection threshold for the front pads.
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I made a closer comparison between the EQS SUV rear brake pad and an SL55 rear brake pad. I was surprised to discover the following:
EQS SUV rear brake pad:
- Overall thickness (including anti-squeal shim) of just under 15mm.
- Thickness of friction material just under 8mm.
- Thickness of steel backing place just over 6mm.
2006 SL55 rear brake pad:
- Overall thickness (including anti-squeal shim) of just over 15mm.
- Thickness of friction material about 10mm.
- Thickness of steel backing place about 4.5mm.
I suspect that keeping the overall thickness of the brake pads close to the same dimension of 15mm allows the calipers to be used on both EV and ICE vehicles.
EQS SUV rear brake pad:
- Overall thickness (including anti-squeal shim) of just under 15mm.
- Thickness of friction material just under 8mm.
- Thickness of steel backing place just over 6mm.
2006 SL55 rear brake pad:
- Overall thickness (including anti-squeal shim) of just over 15mm.
- Thickness of friction material about 10mm.
- Thickness of steel backing place about 4.5mm.
I suspect that keeping the overall thickness of the brake pads close to the same dimension of 15mm allows the calipers to be used on both EV and ICE vehicles.
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Why wouldn't it? The big difference with an EV is that the mechanical brakes are used much less due to regeneration. So the pads will wear much more slowly as they are used much less. But in the end the mechanical brakes still work the same way they always have, so the wear limits should be the same.
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Why wouldn't it? The big difference with an EV is that the mechanical brakes are used much less due to regeneration. So the pads will wear much more slowly as they are used much less. But in the end the mechanical brakes still work the same way they always have, so the wear limits should be the same.
EQS SUV:
New rear pad: 6.15mm backing plate, 7.9mm friction material. Changing pads when friction material is 6mm thick would be very wasteful since warning light does not come on until about 4mm.
SL55:
New rear pad: 4.5mm backing plate, 10mm friction material. Changing pads when friction material is 4.5mm thick makes sense since brake sensor is just about 0.5mm from being tripped.
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The reason I don't think changing the pads when the thickness of the friction material equals the thickness of the backing plate on an EV makes sense is that the backing plates are noticeably thicker on the EQS than they are on a car like the SL55.
EQS SUV:
New rear pad: 6.15mm backing plate, 7.9mm friction material. Changing pads when friction material is 6mm thick would be very wasteful since warning light does not come on until about 4mm.
SL55:
New rear pad: 4.5mm backing plate, 10mm friction material. Changing pads when friction material is 4.5mm thick makes sense since brake sensor is just about 0.5mm from being tripped.
EQS SUV:
New rear pad: 6.15mm backing plate, 7.9mm friction material. Changing pads when friction material is 6mm thick would be very wasteful since warning light does not come on until about 4mm.
SL55:
New rear pad: 4.5mm backing plate, 10mm friction material. Changing pads when friction material is 4.5mm thick makes sense since brake sensor is just about 0.5mm from being tripped.
