lieu

What pads usually go first? the backs or the front? Rear wheel drive..

PaulR7

9 times out of 10 on every car it will be the front brakes.

superswiss

Historically, yes, most cars go through the front brakes first because they have a fixed brake bias. However, modern cars such as the W205 have electronic brakeforce distribution, so the brake force is continuously adjusted for each wheel, and many EBD systems initially distribute more braking pressure at the rear brakes to reduce the effects of weight transfer. It keeps the car from nose diving. Under light braking, especially with DISTRONIC it may even exclusively use the rear brakes to slow down, and combined with traction control using the rear brakes to slow down spinning wheels, it's not unusual for the rear brakes to be worn first nowadays.

https://en.wikipedia.org/wiki/Electr...e_distribution

MDMOORE99

Rear

PaulR7

Yes I realise that modern cars have plenty of different systems but it doesn't change the fact that in case of W205 in terms of standard driving (and braking) most of braking is done by the front brakes which is not only confirmed by my own experience but also by common sense when you look at the fact that front rotors and pads are like a good third bigger than the rears.

superswiss

You'd be surprised. Anecdotal evidence doesn't' indicate a larger pattern. It may be for you, but that doesn't mean it's for others as well. Case in point, my C63S coupe wears down the rear brakes first as do pretty much all C63, and the brakes are far beefier than on a C300, so common sense can be deceiving. And my driving is anything but normal. I regularly go tear up canyon roads with heavy braking, and I did European Delivery driving almost 6000 miles in Europe, mostly high speed driving with lots of high speed braking on the German Autobahn. The rear brakes were still the first to trip the brake sensor. Now granted a C63S has much more torque to manage on the rear wheels than a C300, but it's also aided by an electronic looking differential and a far superior 9-stage traction control which is integrated into the ECU and manages traction mostly by engine torque management, rather than the rear brakes. I also have the full driver assistance package and do frequent long highway journeys with DISTRONIC engaged, which as I said uses the rear brakes predominantly to reduce speed.

At the end of the day, you actually want the front and rear brakes to wear out at about the same time, so you can replace them together. While my rears went first, the fronts needed to be replaced less than a 1000 miles later.

chassis

@PaulR7 The old adages aren't applying well to recent MB vehicles. Physics of weight transfer says more braking effort should happen at the front. Limit braking at wheel lockup certainly results in larger braking forces at the front tire patch.

But reality says rear pads are consumed first on MBs. As stated by @superswiss assist systems utilize the rear brakes, and it's possible although unknown whether or not MB uses a faster wearing pad material on the rears. Also we don't know with certainty the fluid proportioning front-to-rear that the master cylinder delivers. Furthermore, vehicles with electric parking brakes use the rear caliper pads. While small, the parking brake contributes to rear pad wear.

The rear pads are thinner than the fronts when new, and have a smaller surface area. So the volume of rear pad material is for sure less than the front pad.

MDMOORE99

C300, rear goes first, EPB side.

lieu

conflicting answers, or should i just change all of them at the same time?

lieu

also i buy from rmeuorpean.com, if i dont go oem, what aftermarket ones are the go to

superswiss

Nobody can specifically say it for your car as it ultimately comes down to how you drive it. Dealerships will want to replace them all at once, pads and rotors, the whole caboodle. It's easier and more profitable for them, and they don't get into liability situations, if they only replace one set. Also, not all models have a wear sensor in the rear, so unless you regularly check your rear pads and rotors, you may run the risk of wearing them down to the metal. I don't know if the C300 has rear wear sensor.

Having said that, the general consensus is to replace brake pads once they are down to 3 mm. That's also typically when the wear sensor trips. During regular service they will measure your pads, so you get an idea of their wear level and can then decide. Rotors are a similar story. They have a minimum thickness that's typically about 2 mm less than new on the front and 1 mm less than new on the rear. The minimum thickness is typically stamped on the hat. A technician or you yourself can measure the thickness of the rotor and decide if you need to replace them. The rear rotors often last for two sets of pads, whereas the front rotors may need to be replaced with each new set of pads. In the past, rotors could also be turned to true them up and remove grooves etc, but today's rotors are as thin as possible to begin with to save weight. If the rotors are damaged like if they have grooves for example, then you need to replace them, too.

Dealerships don't want to deal with these nuances, though, so they will talk you in to replacing everything. If you want to be more specific have your brakes serviced by an indy. They can also assist you with possibly getting better aftermarket parts if you don't have anything specific in mind yourself.

MDMOORE99

Replace what needs to be replaced ?

lieu

I order some oem rears for now

mikec35

My rears went first, replaced them at 153,000 miles. My front's are at 166,000 miles and still have at least 1/3 pad left

lieu

just had an inspection due to squeaking, pads have plenty of meat, he is saying my front rotor is wearing and causing the noise.

mikec35

I’d get another opinion. The rotor itself does not squeak because it’s wearing. Either the pad is worn and causing a metal to metal sound or the squealer is touching or occasionally touching because the pad is real close to being worn enough for the squealer to do it’s job or the noise is coming from somewhere else.

lieu

thats what i was thinking, mercedes will tell me soon

miketc

Checked mine today and the rear brakes are about 30% remaining and 60% for the front. Rear wear down first for my 2015 C300 4matic.

Congo100

Question on rear brakes...

Bought front and rear Akebono pads and replaced the fronts today. Wear sensor came on a couple weeks ago. The front pads were Mercedes brand that I believe were the second set along with new rotors when the dealer did the CPO work before I purchased. Pads had maybe 2 mm left. The rotors were in excellent shape with just a slight lip at the outer edge so I put the new pads on. Work well and are quiet and smooth.

On to the question. I started the backs and realized I did not have a 7 mm hex socket to remove the caliper so I went and got one. In checking the rear rotors, I see the wear holes in the rotor are almost gone. What's the consensus on replacing the rotor at this time. They are expensive as aftermarket in Canada and I haven't checked with Mercedes for their pricing.

TwoC400s

The rears on my wife's went first (dealership said the fronts were over 75% material remaining), my car is only at 44k miles so still a bit of pad on both front and rear.

The rears on my previous 2005 Audi A8 were also always first to go, by about 15-20,000 miles.

I've used Akebono pads on all my previous Euro cars to with good results.