Ajax Lesser

I always get off of this exit going back home everyday. Requires slowing down from 70 mph to 30 mph for the curved exit.

In the last two months, I started noticing a slight vibration in the steering wheel when I start to slow down from 70 mph down to 55 mph. It's pretty consistent. The vibrations can only be felt through the steering wheel; the rest of the car does not shake.

Tonight, I took the car on a different route and noticed the same pattern on any regular stretch of highway.

The steering wheel does not vibrate on gas or cruising speeds. Nor does it vibrate when braking at low speeds.

Did a bit of research and the common target for this type of issue is warped rotors. However, given the car is only 3 years old with <25k miles, could it be something else?

Taking it in on Friday to get it checked out.

ss3964spd

It could be something else, but not likely. The symptom you describe is classic warped rotor, only very minor at this point.

I recently purchased a '11 E550 with just less than 24K miles. The rotors were warped, bad. I replaced the rotors and pads and all trace of vibration while braking is gone.

KEY08

It doesn't take longer than 3 years or 25K miles for a rotor to become warped. A warped rotor is more than likely the cause of your vibration under braking at those speeds.

Ajax Lesser

Hmmm. A couple of additional questions:

1. Is it usually one of the four rotors that get warped? A few? Or all four?

2. How do rotors usually get warped?

3. I'm still under CPO warranty. I assume this will not be covered?

4. How much will this cost?

5. How urgent is it to get things replaced?

Thanks for your help!

ps. Again, the vibrations only can be felt in the steering wheel when braking at high speeds. I cannot feel anything in the brake pedal, anywhere else.

ss3964spd

Ajax,
1) It's almost exclusively the two front rotors.
2) Excessive heat generally, but uneven wheel lug torque, in conjunction with heat, contributes.
3) Not likely.
4) More than you want know. I've seen reports here of 600 to 700 for the fronts only.
5) It isn't. The car will still stop just fine. The vibration is likely to get worse though.

Dan

Ajax Lesser

Thanks for the fast reply Dan!

Two more questions:

6. I've done a bit of research and noticed a lot of the warped rotor complaints yield vibrations in mainly the brake pedal ... not the steering wheel. Do you know if there's a difference between feeling vibrations on braking in one but not the other? (I feel nothing coming from the brake pedal when braking at these speeds.)

7. If I leave the situation as is and not get it fixed, will it cause damage to other parts of my car (or increase wear and tear to other parts of my car)? I'm debating getting things replaced now versus in a year, for example. Especially if the rotors can get warped again in another 20k miles.

Many thanks!

KEY08

You could feel vibrations or pulses in the brake pedal if you are moving slower perhaps and have a badly warped rotor. In my experience when you feel them at high speed it is usually through the steering wheel and indicates that you will begin to feel them in the pedal soon enough. MB may help you with the replacement as their rotors have been known to be crap at times. Push the service advisor and see if they will help with the cost. Personally, even though you can put it off I would replace them. It drives me nuts to have that shaking steering wheel on a luxury car like this.

ss3964spd

I think it comes down to how severely warped the rotors are, Ajax.

Understand how it all works. The rotors (disc's) are mechanically attached to the front suspension, as are the calipers, and the steering components (tie rods, steering rack/box, steering column, steering wheel). The brake pads sit directly/physically against the pistons within the calipers. If the rotor is warped, and you view it from directly above, it actually moves in and out in relation to it's centerline. When you engage the brakes the pistons in the rigidly mounted caliper squeezes the pads against the rotor and, because the rotor is no longer flat, it tries to move the caliper from side to side - imparting that motion to the connected suspension components, to which the steering components are also mechanically attached.

However, the brake pedal isn't mechanically fastened to the front suspension, it is somewhat isolated by the flexible hydraulic lines, which connect to the caliper at one end and the steel, body mounted hydraulic brake line at it's other end. So unless the rotor is warped bad enough to actually force the caliper pistons back into their bores against the hydraulic pressure being exerted on them one probably won't feel much in the pedal.

Live Oak

I question that assumption --- although I am certainly not an expert.

Braking in modern cars is a very computerized process. Brakes are not just applied; in hard braking, they are pulsed to prevent locking and skid. During braking, the computer "watches" the wheels very carefully, and at the first sign of locking the brakes are moderated.

With seriously warped rotors (and what is "serious?") I can't help but believe that the interaction between the warp-caused pulsing and the computer would really screw things up, or at least make things less than optimum.

In my mind, that is not "just fine." I'm convinced that warped rotors is a serious safety issue that MB is just barely avoiding --- especially E550, and I've heard it's prevalent on the other heavy models.

BTW, I'm on my fourth set of front rotors in a 2011 E550 at 52,000 miles, 3-1/2 years --- the first rotors new build, and two sets of which were provided under warranty. And I'm a very conservative driver who NEVER abuses or rides brakes --- I think I've had one incident of "hard" braking in this car.

The dealership does not seem surprised at all to hear an E550 owner come in complaining of "pulsing."

Ajax Lesser

Hey Live Oak, did you also experience my symptoms? Steering wheel vibration on braking at high speeds?

How were you able to get MB to pay for the rotors? Does CPO cover rotors?

ss3964spd

Disregarding any automated collision avoidance systems the brakes are indeed "just" applied under normal to almost extreme circumstances (I consider extreme to be having to hit the brakes hard enough to induce lockup). The ABS computer and module only jump into the party when the a wheel speed sensor finds that a wheel has stopped turning but the others still are.

The wheel speed sensors know nothing of the warped rotor. They monitor only wheel speed. The only way a warped rotor could cause any heartburn with the ABS system is if it somehow caused pre-mature lock up of that wheel. In that case the ABS would modulate hydraulic pressure to that wheel, thereby increasing stopping distance to some degree during an all out panic stop.

The only other consideration is this: with the brakes released the pads just barely, barely touch the rotors. So, when you apply the brakes the pads only have to move towards the rotor a minute amount before enough friction is created to start slowing the rotor. So theoretically, IF the rotor is warped a lot it will actually push the one of the pads farther away from the rotor than it normally would rest. It would take a fraction of a second for the system to take up that extra space resulting in increased stopping distance. But since were only talking about hundreds of an inch the difference probably is hardly measureable.

The biggest safety issue I see with warped rotors is a mental one. Meaning, if the vibrations and/or shaking bother the driver so much that he/she drives in such a manner as to avoid using the brakes, that's a problem. Such as it was for me.

ss3964spd

Ajax, the rotors on my '05 E500 were slightly warped and produced the same symptoms you described. The rotors on my '11 E550 were badly warped - to the point that even at 10 MPH when slowing for a stop I could actually feel a drag/release/drag/release of the brakes.

From what I've read here CPO technically won't cover them but some people have had success with some dealers.

Dan

Arrie

Any amount of warp will try to move the pistons of the calipers. There is no gap between rotors and pads so the slightest rotor sideways move will try to move the pistons.

Live Oak

New car.

My first warped rotors were at 9,000 miles. Replaced under warranty. Dealer said, if I passed 10,000 he wouldn't have warranted. (Then changed that to 12,000)

Replaced at 43,000. I paid for that, theoretically got 34,000 miles on those rotors, or 43,000, depending on how you want to measure it.

Recent, at 52,000, replaced under warranty. 9,000 since last replacement.

It was at the last incident that the dealer seemed much less surprised to get a rotor job after 9,000.

And, I'll disagree a bit with 3964. I can't believe that "pulsing" from warped rotors doesn't have negative impact on braking, especially emergency braking. But then, I've been driving for only 60 years.

Arrie

Man, have you ever driven on snow or ice? Your comment, "The only way a warped rotor could cause any heartburn with the ABS system is if it somehow caused pre-mature lock up of that wheel." is right on.


Warped rotors can render ABS equipped car basically brakeless in slippery conditions.


Warped rotor exactly causes the wheel to lock-up prematurely when the friction against the road would still keep it turning. ABS takes pressure off of the pads allowing the wheel to turn again and now when the warped spot on the rotor goes thru the pads you suddenly have a gap between pads and rotor so no brake force at all for a "microsecond". Then ABS tries to rush in with force again but when it does it another or the same warped rotor spot comes in again. And this goes on and on and the ABS system gets totally messed up.


Warped rotors are very dangerous with ABS equipped cars in slippery conditions what the ABS system was designed to improve to start with and it really amazes me that MB is getting by with this problem without a recall on the rotors.


What we talk about here as warped rotors can also be an issues with uneven wear of the rotors, i.e. rotor wear surface thickness is not even around the rotor. This would produce same kind of feel as warped rotor but could actually be even worse for the ABS to handle.

Ajax Lesser

Was it only the front two every time?

How much did you pay?

Live Oak

Yes, front two rotors. Pads replaced as a matter of completeness.

$708

ss3964spd

I have indeed, Arrie. although we don't get hit too much here in the DC area we do get ice and snow, occasionally quite a bit. I had been driving my '05 non 4M E500 for years in those conditions, with slightly warped rotors, and never once had any issue with the ABS getting "totally messed up".

I do understand your logic, that if the ABS is activated it rapidly releases pressure and applies pressure. You're saying that during that fraction of a second when pressure is released the pads are forced away from the rotor and when pressure is re-applied by the module that extra space has to be closed before braking at that rotor resumes. Remember, though, that the pressure that is re-applied is relative only to how hard the brake pedal is being pressed. In any instance the ABS is only re-applying the same hydraulic pressure that was present just before ABS was activated.

I'm sure I'm missing something but an interesting discussion non the less.

Dan

Arrie

The whole idea of the ABS system is that the driver can apply the maximum pedal force for the maximum stopping power and the ABS system then takes care of not allowing the wheels to lock. This minimizes the stopping distance on slippery surfaces AND very importantly allows the car to be maneuvered as the wheels not locking you can still steer the car. (On dry pavement ABS does not necessarily give the minimum stopping distance but that is a whole other topic.)


With warped rotors the system cannot use the maximum braking power simply because the rotors want to stop too easily when the warped spot goes thru the pads and then it depends on how fast the system is how much braking force can be applied between the warped spots on the rotors.


This same kind of a loss of brakes can happen (happens with my old Dodge truck) if the shocks on the car are bad or under sized for the weight of the wheels. When I drive my truck over a sharp bump on the road applying the brakes at the same time there almost is no brakes after the bump until the wheels stop bouncing. This is because the wheel is jumping so badly up from the road (still maintaining contact) that the friction against road is greatly lowered. This means the wheel wants to lock up and ABS takes brake force down not allowing that. Then the wheel comes down on the road but the system is not fast enough to apply force on the pads before the wheel "jumps" up again.


This is very scary when it happens and changing shocks did not help much.


If you had slightly warped rotors and it did not cause problems in DC area winter then fine but when the rotors are more than just slightly warped the things can get bad quickly on snow and ice.


I would not allow any defect on my brakes, MB should not either.

ss3964spd

ABS was designed and touted to allow the driver to maintain steering control of the vehicle by preventing the wheels from locking. Completely agree, it isn't there to minimize stopping distances - though it can be reasonably argued that for some, perhaps most, drivers it does exactly that.

I can relate to your truck analogy. I've got a '04 Silverado 1500 - which are known for having an issue with the wheel speed sensors causing very slow speed ABS activation. When slowly rolling to a stop, somewhere between 10 MPH and 0, and regardless of pedal pressure ABS would activate, thereby greatly increasing stopping distance. Talk about pucker factor when there's a vehicle already stopped in front of you. I had to remove the ABS fuse until I could replace the offending parts.

I don't disagree with your main point; that generally speaking warped rotors can increase stopping distance and therefore present a safety issue. Key word is "can" - if they are warped bad enough. I was addressing the OP's concern in his situation and I maintain that there is little concern. But I also cannot disagree that fi these cars have a documented history of this problem MB should be stepping up. Problem for MB is that there are external forces in play; like where the lugs properly torqued after the last tire rotation.

From my own experience with my '05 with slightly warped rotors I never once had a problem hauling that car down from any speed in any condition, and the slightly warped rotors never presented any symptoms below about 50 MPH. Ditto for my wife's BMW 330CiC.

My recently acquired '11, however, was horrible; thee worst I've ever experienced.

Great convo.....

Dan