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'08 ML320 CDI
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Discussion Starter · #1 ·
I just came back from a trip and the brake wear message popped up. Without looking at them, I ordered a replacement set but it looks like I have 50% orso left?!? That sensor seems way conservative if you ask me?!

Anyone know how much is typically left once the message appears?
 

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13 GLK350, 02 325, 94 sonoma, 12 RAM, 01 WS6
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the sensor will usually trip the light with 2-3mm of pad remaining.

BUT the sensor is only located on 1 pad. you have 4 per axle. IT is common for pads to wear uneven.

you have 1 sensor for the front and 1 on the rear. both on right side (passenger) of vehicle.
 

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'08 ML320 CDI
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Discussion Starter · #3 ·
the sensor will usually trip the light with 2-3mm of pad remaining.

BUT the sensor is only located on 1 pad. you have 4 per axle. IT is common for pads to wear uneven.

you have 1 sensor for the front and 1 on the rear. both on right side (passenger) of vehicle.
Oh! That totally makes sense then! I did not know there was a sensor in the rear; most vehicles only have them in the front. I know the rears are low so I will only replace those for now. The fronts should still last a while.
 

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2008 ML320 CDI
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Rear wears out faster.

Also 2-3m is correct, but it will wear out much faster now since heat is easier to get to the outside of the pad due to the smaller surface distance.

I would get them changed in a week or so. I had about 1.5 mm left on mine, this was about 1.5 weeks after the sensor came on. ML is a heavy car so it wears quickly.
 

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'08 ML320 CDI
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Discussion Starter · #5 ·
Rear wears out faster.

Also 2-3m is correct, but it will wear out much faster now since heat is easier to get to the outside of the pad due to the smaller surface distance.

I would get them changed in a week or so. I had about 1.5 mm left on mine, this was about 1.5 weeks after the sensor came on. ML is a heavy car so it wears quickly.
That is bizarre. Any particular reason the rear wears faster? On all cars I've owned, the front usually wears about 1.5-2x as fast as the rear.
 

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2008 ML 320CDI
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That is bizarre. Any particular reason the rear wears faster? On all cars I've owned, the front usually wears about 1.5-2x as fast as the rear.
These brakes are biased to the rear to limit front end dive on braking. If you do a lot of hard braking, you will see the rears go much sooner than fronts. Light braking and they will be much closer in wear.
 

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'08 ML320 CDI
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Discussion Starter · #7 ·
These brakes are biased to the rear to limit front end dive on braking. If you do a lot of hard braking, you will see the rears go much sooner than fronts. Light braking and they will be much closer in wear.
Very interesting. I guess that explains why they put wear sensors in the rear as well. I'm usually pretty good at getting a lot of use out of brakes, so the replacements should last a while :)
 

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2002 C230 Sport Coup and 2006 ML350
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If you can, go with new rotors and Akebono ceramic pads.
Likely the last rear pads you'll ever need.
I'm running them on both my mercedes.

The ones on my C (but with AMG brakes added) have
well over 100K miles on them and lots of pad left.

I say go with new rotors because the pads last so long, you really want to start fresh.
Oh and they grab great, have almost no dust, and don't squeal!
And they are made in the USA (Kentucky) despite the asian sounding name.
And no, I don't work for them or sell their products.
 

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2008 ML320 CDI
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Yup, Car is rear brake biased. It will brake hard first at the rear then fronts. It's common in alot of cars actually. If you squeeze the front first the car can cause steering wheel to warp back and forth.

Like others said. replace both the rotor and pads at the same time. Both surfaces wear/tear. Peace of mind for even pad wear.

Just use the brake very lightly for stop and go traffic. The car decelerates fairly quickly without pressing the gas pedal. It should last awhile.
 

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My rotors lasted 109K miles; 1 set of pads were replaced around 60K.
As the pads wear more, the brake message will show up more often (or you'll hear a sound) and eventually up to every time you pressed on the brake.
 

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2011 ML550
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Rotated my tires last week and noticed that the rear outer passenger side pad was down to almost nothing (~1.5mm). The rotor was also gouged up pretty well so I decided to order Zimmerman coated rotors and Akebono ceramic pads. I'm at 58k miles so I figured it was about time to need pads, but I'm wondering what the deal is with my wear sensor. It has not gone off yet and had I not rotated the tires I may not have known how bad they were. The front brakes still look very good so I think they had been replaced at one point before I became the owner. The point I'm trying to make though is don't always rely on those sensors.
 

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'08 ML320 CDI
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Discussion Starter · #14 ·
The sensor may be missing altogether or perhaps the wire is damaged?

I always do a visual check as well since a lot of cars don't even have rear pad sensors! When it went off on mine, I assumed it was the front and was surprised because there was 40-ish % left. When I realized the w164 has rear sensors, it made sense since I knew those were getting low.
I just replaced my rear pads with Akebono Ceramic; I was planning on rotors as well but my mechanic said they still looked in great shape so I left them alone for now; the pads wore evenly as well. 52kmi on mine.

It is always amazing to me how people rely on all the electronics to tell you if something’s wrong. Some basic checks go a long way: brakes, tires, oil and coolant level should be on the list to check regularly.


Rotated my tires last week and noticed that the rear outer passenger side pad was down to almost nothing (~1.5mm). The rotor was also gouged up pretty well so I decided to order Zimmerman coated rotors and Akebono ceramic pads. I'm at 58k miles so I figured it was about time to need pads, but I'm wondering what the deal is with my wear sensor. It has not gone off yet and had I not rotated the tires I may not have known how bad they were. The front brakes still look very good so I think they had been replaced at one point before I became the owner. The point I'm trying to make though is don't always rely on those sensors.
 

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'08 ML320 CDI
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Discussion Starter · #16 ·
Why would it be too late?! There's always a few mm left, so unless you're driving like a mad man, it should be just fine. I'd say it's too late when the brake pad is GONE :eek

I've always done it this way without issues.

My take is that if the light came on, it is too late already. Do it ASAP..... This is coming from someone who's been through few brake jobs with 2 ML's and few hundred thousand miles between them....


Good luck!
 

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2009 ML320 Bluetec, 2013 Tesla Model S 85
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Rotated my tires last week and noticed that the rear outer passenger side pad was down to almost nothing (~1.5mm). The rotor was also gouged up pretty well so I decided to order Zimmerman coated rotors and Akebono ceramic pads. I'm at 58k miles so I figured it was about time to need pads, but I'm wondering what the deal is with my wear sensor. It has not gone off yet and had I not rotated the tires I may not have known how bad they were. The front brakes still look very good so I think they had been replaced at one point before I became the owner. The point I'm trying to make though is don't always rely on those sensors.
The sensor for most MLs is only on one rear wheel and one front wheel. None have a sensor on every pad. I think what you are describing is a binding caliper, one that is not floating correctly on its pins. You need to pay special attention and try to find out why it is binding when taking it off. And fix whatever when assembling.

The piston applies to the inside pad. The caliper has to float for inside and outside pads to grip the rotor. If the caliper binds the outside pad continues to rub with force against the rotor. There is a lot of force to grip the rotor but when that is relaxed everything has to freely move to float to neutral. For some models M-B has a technology for retracting the piston a fraction to lift pads off the rotor. Not sure how, perhaps they suck a bit of brake fluid back?
 
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