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Which pads went first - front or rear?

Brake pads: Which ones go first - fron or rear

5K views 18 replies 11 participants last post by  FAR888 
#1 ·
There's a poll with this post. I recently took all tires off and inspected the brakes on my 500. At 28K, the fronts look like they have another 28K to go. The rears have about half that to go. On my Z with 230K, I'm still on my 2nd set of pads up front. The rears have probably been changed at least 6 times. Most experts say the fronts should go first, otherwise something's wrong with the system - thus my poll. My driving is predominantly highway, with minimal or nor BAS/ABS application (i.e., practically no snow, ice or anything that'll activate ABS/BAS) and that may have something to do with it. What's your experience.
 
#3 ·
Based on my experience, with all of my vehicles, front pads goes first. In some vehicle its almost 2 front pads vs 1 rear.

Have your brake systems thoroughly checked. Your brake pads wear indicates that rear brakes are gripping more than your front. As such, if you apply brakes while you make a sharp turn you might drift. This is the same as engaging your hand brake while turning. The result, if not expected, may not be good.

ED
 
#4 ·
The answer depends on the number of cylinders. For the six, the front goes first and the rears last about 3 or more front pads. For the eight, the rears can go first, a well known but irritating feature.

Of course driving conditions such as stop and go, many hills etc can change these handy dandy rules of thumb so apply them with a bit of reality.
 
#5 ·
pointman said:
damn. those are some insane numbers. definitely fronts first on ml. i have owned several ml's..all the same.
I know. I just pulled them out last week and was just as surprised. Like I said, I drive 95% highway and that accounts for the high mileage on the pads. But that also means that about 60% of the braking is done in city driving!!!
 
#6 ·
edcarls said:
Based on my experience, with all of my vehicles, front pads goes first. In some vehicle its almost 2 front pads vs 1 rear.

Have your brake systems thoroughly checked. Your brake pads wear indicates that rear brakes are gripping more than your front. As such, if you apply brakes while you make a sharp turn you might drift. This is the same as engaging your hand brake while turning. The result, if not expected, may not be good.

ED
I have had the Z checked several times, performed adjustments here and there, including parking brakes, I have ahd the 500 checked twice, been through one A and one B service, and not once has anyone reported disproportional braking. For the Z, I actually asked them to check this - no problem. And, I'm braking just as well as ever on both vehicles. I'm beginning to think that this front-brakes-wear-faster thing is a myth and depends on driving style, FWD/RWD and, maybe some other things that we don't quite understand.
 
#7 ·
mickey.1430 said:
The answer depends on the number of cylinders. For the six, the front goes first and the rears last about 3 or more front pads. For the eight, the rears can go first, a well known but irritating feature.

Of course driving conditions such as stop and go, many hills etc can change these handy dandy rules of thumb so apply them with a bit of reality.
I agree with this "theory" based on my experience. I wonder if MB brake specialists have any opinion on this!!!
 
#8 ·
I work on vehicles for a living. I am a Master Tech, and have more than 25 years of experience with brakes.
I would consider myself an "expert" on brakes and systems.

#1 most of the braking is done by the front brakes, however if the proportioning valve is not adjusted properly then the rear brakes may grab harder.
#2 the rear brake pads themselves may be made of a different material than the front pads causing them to wear out faster. They may look just like the the front pads but they may have a softer compound. Usually the rear pads are smaller than the front (but not always) and that is also a factor to consider.
#3 sticking calipers will cause brakes to wear out much faster than they should. That is something I would check if the rear pads were wearing faster than the front.
 
#9 ·
This is what I have found...

I believe that starting 2002 MB chose to crank up the front torsion bar, especially so on the ML500's and the Sport/Inspiration models of the ML320/350..

I noted the same break wear (rear more) on the 2004 ML350 Inspiration I bought, plus the suspension felt too "jiggly" as compared to my '99 ML320 (even though that car had AT's mounted for off-road) and as compared to the short 45 day stint I had a ML55.

Frist I had the MB delaer check the torsion bar for factory spec - and they used the tape measure height measurementt...(its bullshit using a tape measure, should be a fixed/marked standing bar) .. and they confirmed the front was in factory spec.

Then I drove 20 min to my tire/wheel boys, we marked the standing height using a pole, then put the ML up on the lift (torsion bar adjustment should be done with car weight off the front tires) and I had them crank the front torsion bars down 5 full turns (both sides of course).

The end result was the front end came down slightly less than 1/8", which convinced me before I got in the car the front torsion bars were over-cranked by the factory...

the true measure to me was MUCH improved driveability, which I subjectively measured on my "freeway" runs here which are relatively short 2hr-3hrs. With light traffic load here, I normally like to run at about 85mph, and at that speed on the highway NOTABLE improvement, and I actually now run a bit faster in the 90mph-95mph range.

AND the factory spec height only came down a slight measurable just less than 1/8" on the marked pole.

After 3K on new and rotors (drilled/slotted/plated/cryo'd Benbo's) and Textar pads (yes, scored actual TexTar's both front and rear) the brake pad wear went back to slightly more on fronts than rears.

I hate what MB did to their torsion bar "spec" in 2002-2004... I "felt" it in my 2004 Inspiration - and I like the ML to begin with, or I wouldn't have bitten into another one... I choose this 2004 Inspiration for the pre-paid maintainence out to 50K and the textured/softer leather seats, which I prefer over the old style ML flat/hard leather seat material..

The only other beed I have is my transmission which has not adapted over to my more neighborly but agressive driving style - I tronic a lot more down to 4th/3rd in my driving. MY dealer and I may address this this next month after they get a new control unit is that we plan to plug in and try..
 
#10 · (Edited)
The MLs don't have a fixed proportioning valve between front and rear brake pressures, but use electronic brake pressure distribution which adjusts the pressure dynamically. Here's a plot of rear versus front brake pressure which I simplified from a plot supplied by Bosch:



Curve 1 is the ideal brake pressure distribution which allows maximum brake pressure applied to both front and rear wheels without them locking up.

Curve 3 is the brake force distribution as installed as determined by the area of the brake pads, the area of the brake pistons, the diameter of the brake lines etc etc.

The electronic brake force distribution works such that the rear wheels dont lock first. For example when in a curve with little weight on the inside rear wheel it senses that the rear tires are getting close to locking up and it will reduce the pressure to the rear brakes, so the fronts brake more than the rear in this case. But when always braking in a straight line on a highway, then EBV would not need to reduce the rear brake pressure as often as when braking in curves, so the rear pads might show relatively more wear in this case.

Regarding lifting of the vehicle. Continental put out a press release around 1999 (sorry I didn't save it :)) on their website showing why it is advantageous to have EBV in a lifted vehicle. Since it automatically adjusts to the higher center of gravity. In vehicles without EBV folks often tend to forget to adjust the fixed proportioning valve when lifting it, so that the rears might lock up first (unstable).

Here is more if interested :) :
http://www.whnet.com/4x4/abs.html#EBP
 
#11 · (Edited)
But when always braking in a straight line on a highway, then EBV would not need to reduce the rear brake pressure as often as when braking in curves, so the rear pads might show relatively more wear in this case.
Darkmann, I know this is a relatively old post but I am interested in finding out whether you solved your problem of your rear brake pads wearing out faster than your fronts and whether, according to Wolgang's technical explanation, (re highway driving) it means that nothing was actually wrong with your brakes in the first place?
 
#13 ·
Hey FAR888, I hope you're enjoying the 55 and no fuel issues. Yes, I believe I did resolve this question. I talked to a master tech after my rear brake replacement and he explained to me the at highway speeds, the rear brakes get activated before the fronts to avoid the truck diving - front dipping down during braking - and that at city speeds, the fronts do most of the braking. It makes sense in my case because I do 90% of ML driving on interstate highways, usually at speeds of 70-90 mph. I will conduct a poll between highway and city drivers to see how driving styles affect brake wear. I just pulled my tires a couple of days ago and I still have about 50% pad left on the fronts!!!!!!!
 
#14 · (Edited)
Hey FAR888, I hope you're enjoying the 55 and no fuel issues.
Ha ha - The 55 is still on the ship over here - It should arrive in a week's time - cant wait!

I talked to a master tech after my rear brake replacement and he explained to me the at highway speeds, the rear brakes get activated before the fronts to avoid the truck diving - front dipping down during braking - and that at city speeds, the fronts do most of the braking. It makes sense in my case because I do 90% of ML driving on interstate highways, usually at speeds of 70-90 mph.
That's what I thought and just wanted to confirm that with you.

I just pulled my tires a couple of days ago and I still have about 50% pad left on the fronts!!!!!!!
Wow that's a lot!

Considering that the rear brake pads cost less than the front brake pads, I guess that's a good thing in your case sir! (Laugh)

ps. Will post pictures of the ML55 in the container before before being loaded on ship to West Africa soon.
 
#15 · (Edited)
My 98 ML320 wore out the Front brakes almost 2:1 to the rear brakes. In my 05 ML500 the Rear brakes wore out long before the front. I think this is due to what Wolfgang and Darkman stated in their posts. According to the manual the 05 ML's apply more brake pressure to the rear brakes in straight line braking to increase braking efficiency and disables this feature in turns so I guess it depends on individual driving styles.
Mike
 
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