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  #1  
Old 09-21-2010, 09:26 PM
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My recent brake story

After my pad wear indicator light started glowing I immediately ordered new pads, sensors, rotors, and MB grease from Phil and put them on the front of the wagon here about 4 - 6 weeks ago. The braking had a little 'warpage' pulse before I replaced them - couldn't really tell from which end it was, but thought I'd go ahead and replace the rotors as I figured they were possibly original equipment.

After reading many posts from this great site, I decided that I would use the Zimmerman brand rotors as there wasn't much 'bad' stuff about them. After doing the job I was careful to break-in the new parts as prescribed from the many posts I read. IF my 56 year old brain cell is firing on all 4 cylinders, I recall that I was to make a couple "firm" stops from ~40 mph to "seat" or "set" (ahh, there it goes, can't remember!) the pads and rotors. This I did and from then on for the next couple hundred miles used caution when hitting the brakes so as not to 'jam' on the brakes.

Over the past couple weeks the car has been getting progressively worse with regard to the pulsating rotors - almost vibrating when brakes are applied - can not feel anything in the steering wheel so that seems to indicate that it is coming from the rear rotors.

An unrelated issue that has needed attention is wheel/tire balancing. One of my pet-peeves is unbalanced wheels/tires BUT I don't think about it until I am on a 'road trip'! Well I remembered it this week and called a local European Indy shop (I actually met this tech several years ago before I ever owned a Mercedes through selling him a dump truck I used to have and we have just kept in touch over time!) that I thought I'd take it to and have them balance the tires and do a quick look-see under the front end, etc. After a little while I received a call from him and he stated that I had several issues going on:
  • Right front tire has a broken belt (Continentals)
  • Warped rotors
  • Sway bar bushings could stand to be replaced
  • Shock/strut mount bushings have settled and could be replaced (not essential but will "definitely improve ride")
When he told me about the rotors I asked him which rotors? He stated "all of them, especially the rears". When I told him that I had just replaced the front brakes he went on to explain that MB's and BMW's don't do well by replacing only front or rear brakes, they should be done at all four corners. Why, I asked. His theory is that when fronts are new (pads and rotors) that there is the break-in period and during that time the braking force is not what it should/will be when completely seated, thus it puts more strain on the rears to get the car stopped causing them (rear) to heat up more than normal and causing them to warp. It seems to make sense - any thoughts?

My close second pet-peeve is pulsating brakes. I don't like 'em! He suggested that the fronts may be "ok" after replacing the rears but that I will need to use extreme caution during break-in since the fronts would then be the primary stopping force while the new rear hardware is seating in. The fronts apparently are only warped "slightly". Oh yeah, another theory of his that makes a lot of sense is when one comes down off the interstate from highway speeds and the brakes are hot, one shouldn't sit with their foot firm on the brake pedal at a traffic signal but rather let the car 'creep' forward slightly so the pads don't press against the rotors in one spot allowing heat to transfer to THAT one spot only - potentially causing the rotors to warp. Thoughts or comments?

Dale

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Dale
1995 E320 Wagon 185K [SOLD]
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  #2  
Old 09-21-2010, 11:27 PM
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I personally haven't had a pedal pulse problem on a benz- brake squeel yes.

I don't think zimmerman etc are particularly bad rotors. I went this last time with one of the prefered aftermarket brands. But honestly, all these brands are being off-shored and coming back with cheap metal- so problems crop up.

Replace the rears... what pads are you running? I make it a habit of checking the steering dampener and return lines every few years.

No way to warp them. On rotors I do like the factory ones- the special coating helps with brake squeels and pad seating quickly. At wholesale pricing with my MBCA card.. nearly the same price as the aftermarket. Difference is a drive instead of UPS delievery.

Michael
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  #3  
Old 09-22-2010, 07:51 AM
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Dale, first time I've heard the theory of replacing brake pads on front & rears at the same time. Makes no sense to me.

Once rotors are warped they are warped. They are not going to get better as time passes. Recommend buying new rotors from a MB dealer rather than buying them online. Aftermarket rotors can be warped right out of the box ... good idea to perform a runout check on them during installation. Best to use a torque wrench to tighten lug bolts, if not you may get rotor warping.
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Old 09-22-2010, 10:23 AM
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What did you torque your wheels to?

Brakes designed for Mercedes are very sensitive to torque because they are relatively thin compared to other vehicles (of the same gross weight category). That's one reason why shops shy away from turning them, and MB never recommends you do.

I had the same exact symptons as you mentioned, I went back retorqued everything exactly to spec and also after a 100 miles of driving and the vibration went away, not completely gone but definitely MUCH better. What little vibration is left I chalk up to permanent warpage that I caused for over-torquing and can't be felt unless I'm breaking relatively hard at >75MPH.

I have a 1994 Wagon, same generation as yours.

Edit: My wheel torque was lowered from 100ft/lbs to 81ft/lbs
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  #5  
Old 09-22-2010, 04:50 PM
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My experience with mechanics who have lots of stories about what does and doesn't cause rotors to warp while trying to sell you stuff is that they are exactly that: stories.

I've bought lots of rotors on line. No problem with that, unless of course you're buying unknown junk off ebay, etc. Zimmerman from a known seller is fine.

Bedding in is very important when you replace rotors. One thing you did *not* mention is whether you let them cool down during the process. The repeated faster stops heat the pads and deposit pad material into the face of the rotor (that's the point of bedding in). If you then stop and sit with your brake on the pedal, that will screw up all you just did.

Once properly bedded in, in normal driving you don't have to worry about sitting at the light with your foot on the brake. Now if you've been playing boy racer in the canyon for the last twenty miles and the rotors are nearly glowing, drive in light traffic for fifteen or twenty minutes and let them cool down.

On newer MB (since like late 80s?) the rear rotors seem more prone to warping than the front. Perhaps it's because they are relatively thin and not vented, who knows. They're cheap enough, just change them out.

My guess is your guy was shotgunning his guesstimate and tried to explain himself out of it once you told him you just replaced the fronts. That tells you he didn't really inspect things properly, just wanted to work up an estimate. Whether you want to trust him as a mechanic may be an entirely different issue; I tend to try and avoid business relationships with those who exhibit dishonesty. No one's perfect, to be sure, but this is a bit more weasel-like than I'm comfortable with.

Good luck.
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Old 09-22-2010, 08:16 PM
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Thanks guys for all the replies and input, I take it all with a grain of salt!

Just picked up the car this afternoon and turned the wifey loose with it as I needed to head in another direction. After getting home a little bit ago I took the car for a spin to see if there is any difference in the way it drives and I discovered that it is quite a bit better than it was! I'm very pleased.

The sway bar bushings made a tremendous difference with the *feeling* in the front end. Feels *tighter*, no thunking noises.

As far as the warped rotors, they are still there of course, however, they don't seem as bad after the rotating and balancing.

FWIW to anyone interested in looking, HERE is a link to the shop I went to.

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Dale
1995 E320 Wagon 185K [SOLD]
1988 260e Sedan 165K
2007 F-150 XLT 188K [SOLD]
2003 Harley Davidson FLTRI Anniversary 26K
-----------------------------
2006 BMW 330Ci 110K - [SOLD]
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