GWSHARK

My 2017 C43 Sedan has approx 7000kms on it and was just in to dealer for a droning vibration at highway speeds, anywhere between 100 to 140 km/h the car has a vibration that drones through the car , not the steering wheel. The dealer rebalanced my run flats and changed a bearing on the propeller shaft. I’ve had it back for a couple of days and the vibration is still there. The strange thing is the vibration is doesn’t increase in speed or intensity even if I increase road speed. I wanted to see if anyone on the forum has experienced anything like this and how it was recitified before I go back to the dealer and go through the same process. Thanks

FirstMBAMG

This may be off base, but I know that tire tread and road surface can impact the noises inside he car. If you listen carefully, different surfaces can often create different sonic frequencies that resonate inside the car. Again, that could be way off but I have heard of a similarity in the past.

Other possibilities:
- very slight wheel deformation (perhaps most likely and at times tough to diagnose)
- rusting on wheels
- emergency brake slightly catching

not certain, but often times this comes from the whee area.

Big Goober

I've noticed a louder "droning" with my run flats as the mileage increased as the tread wears away. I'm only at 10k miles so more than what you are showing but I would place my bets on this being the issue.

I'm currently replacing the tires with Michelins so I'll know more in an hour.

5ilver-5urfer

Just wanted to clarify - by "Harmonic vibration", you do mean a vibration that you feel in a pattern correct?

I've noticed the same thing if that's what you meant. When I am traveling at highway speeds, the car has an extremely subtle harmonic vibration that happens for half a second, disappears for half a second, happens for half a second, etc. You really have to pay attention to notice it, but it's always there. It, like your observation, doesn't increase or decrease in frequency as you adjust your highway speed.

My car has been doing this for as long as I can remember - pretty sure it has been doing it since day 1 out of the dealer delivery area. The car was manufactured in Germany.

I've just grown to live with it - I had / have an incredible problem when it comes to being overly observant and not letting myself enjoy the bliss known as ignorance

GWSHARK

5ilver 5urfer, that is exactly it, as you described. I noticed from day one with car but attributed it to runflats, car sitting on lot for some time etc etc. I had the head tech at local dealership ride with me and he felt it immediately as well. It’s to the point where my wife who infrequently rides in the car noticed it. Based on you noticing it as well, I’m concerned that this may be inherent in the car thus not likely to be easily resolved of at all, which will undoubtedly bother me for the duration of the time with the car. I too find myself listening for noises and things as opposed to enjoying the car, which is a terrible thing. Going to give it one more try at the dealership and see what they think may be a solution( tire replacement ?..). Will advise here once I get an answer / resultion.

ajmerc

I've got a similar vibration in my 2017 C43 AMG (of/on every 1/2 sec) but I can feel it in the steering wheel & always b/w 100km/h-120km/h. Wheels were re-balanced at dealership but its still there. Funny thing is that its not there all the time. Often it goes away after 10-15 mins on the highway. I have another service appointment this Thursday and will have them check it out again.

GWSHARK

Thanks for sharing, mine is set to go in a week this Monday, would be appreciative if you could shar whatever feedback or fixes they may suggest or come up with. Good luck with getting it resolved.

ajmerc

Ok, will do. Look forward to comparing notes.

SteveE400

Any chance this could be some form of wind turbulence? If one of the underbody covers ("belly pan") is being vibrated by airflow, it could feel like that.

ErikM

First off RUN FLATS SUCK... I really wish manufactures would stop installing them or at least offer as optional normal tires and a spare.

So that said first off is balance. Make sure the dealer has a Road Force Balancer.. It will typically be a Hunter Engineering https://www.hunter.com/wheel-balancers and that they know how to use it..that may sound odd but different Technicians are better than others.. Did I mention RUN FLATS SUCK!
There is also a procedure called Match Mounting see if you can find the balance mark on your wheels, and tires. Google: Match Mounting

Does the car vibrate at all speeds or above certain speeds? That's a balance issue or it can be an out of round tire.. Out of round is also called Runout.. and it can be measured.. If you can, when the tire is being balanced look and see if it's moving up and down, hopping.. That's out of round.. Or laterally, wheel moves left and right.. when tires are correct you should see virtually no movement up down or side to side.

Flat Spotting this is when a tire gets a Flat Spot from sitting. Some tires do it more than others. This will usually smooth out in 5-15 miles as the tire warms up. But it feels like the wheels are out of balance. You notice that new car dealers will keep the tires pressures way high like 50psi to help prevent permanent flat spots. Audi even has dealers move the cars once a month and check tires pressures to avoid this. Not sure about MB or BMW.

If you feel vibration in the hands only it's usually front tires. if you feel it in the seat of the pants or in the pedals that's usually rears. Did I mention Runflats Suck.. Because of their extremely stiff sidewalls they generally ride like crap, and exasperate any of the normal issues, along with wearing very quickly, being noisy, and other issues.

Also 19" wheels are even worse than 18" with the even lower sidewall ( profile) the tires are even stiffer..

ajmerc

ErikM: Thx for your pointers. Here's some answers:

Yes, the first time I took the car in to Merc dealer for this issue they re-balanced all wheels (Road Force). So (apparently) they are in balance.

But the vibration (off&on "harmonic" in steering wheel, not in seat) is still there but only b/w 100km/h-120km/h. BUT it's not always there: after driving for awhile, it seems to go away. I sometimes think its when the car is cold - but maybe its as you say: the tires have flat spot after sitting overnight or at my office all day and then "smoothes out" after about 10km (or 5-15 miles) as you said. I will ask service tech about that possibility when I take it in this Thursday.

And I have the 19in run-flats....

ErikM

Next time you have a chance try this: In the morning after the car has sat all night go for a drive for say 30 minutes but NOT on the highway keep the speeds below say 100kph back roads kind of stuff.. Then when you know the car is warmed up take it out on the highway and see if it does it.. If it still does it's probably not flat spotting.

ajmerc

I've noticed that the longer I drive around before going on hwy, there's less or no the vibration when I get to the critical speed >100km/h. This morning I had to drive around awhile longer than usual for various reasons before getting on hwy and then there was almost no vibration (very hard to discern) at critical speed and of course the longer on the hwy the less vibration. So that's telling me you are probably right about flat-spotting after sitting. And, by the way, its worse the colder the outdoor temps.
It seems unlikely to be a balance or alignment etc issue if the vibration is not always present or lessens w/ more driving, correct?

ErikM

I'd tend to agree with you. And of course as the temps drop the tires get even harder when they sit and take longer to warm up. I bought one of these kits https://www.stopngo.com/tire-mobility-kit-for-cars/ and will switch out the stock RFT for normal tires.. Plan on ordering my C43 sedan in late December so I can take delivery in the early spring. I'm leasing the car and I'll put the stock tires in the corner of the garage somewhere so I can put them back on when the lease it up. I've done that with my current car and it seems to be the best solution to the horrid RFT..

ajmerc

Additional question: If the vibration diminishes & goes away after warming up & driving for sometime, that means it can't be a bent/damaged rim or damaged, out-of-round tire in which case the vibration would not diminish, correct?

ErikM

It sure wouldn't be a wheel. And a out of round tire isn't going to get mo round. So I'd say flat spotting is it. Of course best way to know for sure is new tires, but that's an expensive experiment

Star4life

it is getting colder in michigan and on morning commute ive noticed a very small vibration. i wouldnt call it harmonic vibration but its a little bit in both the seat and wheel. ive noticed it only on freeway and only for first few miles. once the tires warm up it seems to go away. i will add air pressure to tires to see if thats the issues. they are sitting at 30F and 33R right now which is below spec. I am on 18" oem pirelli run flats.

ajmerc

Sounds similar to mine except I think yours may be less (maybe due to your 18in vs my 19in tires) and I only feel it in the steering wheel - but like you: only at freeway speed 100-120km/h and for first 5-10 miles max.

ajmerc

Ok, so here is the summary from my service appointment today:

All wheels have been road-forced balanced & diagnosed for any wheel damage or tire damage while on the balancing machine and also visually when mounted on the car (I was there for the visual inspection with the service technician). There is no balance problem nor damage to tires or wheels. The service technician that I was dealing with said it must be flat-spotting especially if it goes away after tires warm up and after 5-10 mins on the hwy at hwy speeds. He says it is not uncommon w/ the Pirelli PZero low-profile 19 inch run-flats that I have and I will feel it more pronounced because I choose to drive in Sport+ mode (that has the stiffest suspension setup).

So nothing really can be done about it, but I'm okay with it now that I know what it is and know that once the tires are warmed up, its smooth.

Hope that helps any others w/ same issue.

Star4life

thats what i figured it was. I have the pirelli tires as well. cant wait to get these off and put the michilins on!

5ilver-5urfer

I wouldn't buy that reason if my service tech told me that. I have 19-inch run flat low profile Pirellis on my 4 series as well and they don't have this issue.

Also, the tires are rotating many times a second, how would flat spotting explain the half second vibration, half second no vibration pattern?

Unfortunately, I think we know as little about this issue now as we did before

ErikM

Are the tires on your bimmer the same size as the C43? I had Pirelli's back in the day on a Saab that flat spotted and the car would vibrate for the first 10 minutes or so. My Wife has Continentals on her Acura they flat spot over night.. I have Pirelli P Zero AS that don't flat spot at all. I think flat spotting has everything to do with sizes, brands, RTF or not, Temps, and who knows what else. I do seem to notice that it's mainly folks with 19" Pirelli all season RFT ... For AJmerc how about starting out in comfort or standard see if you perception changes

ajmerc

I experimented w/ Comfort suspension and the vibration is less than in Sport+. And again, it goes away after warming up at hwy speeds.

Jamie Landsman

I’m having the same issue. Most pronounced when between 55 and 62 MPH but not on the gas. Excellerate past 60 and then take your foot off the gas and you’ll feel it as the car slows down. They’ve already changed the bearing but it didn’t help and now it’s in and they are going to try the axle. Apparently Mercedes knows about this issue because the dealer said Mercedes corporate called and asked them to run a very specific test. This car has been nothing but trouble since I bought it. Command screen problems, sunroof rattling, 4 blown tires, a cracked rim (that they couldn’t replace for 6 weeks because there were none available in the whole world!), 3 other rims needed to be straightened, a bad speaker and now this. Thought I was buying the best. Turns out I would have been better offf with nothing. Good luck.

GWSHARK

Nothing substantial to update on my situation, car is going back in next week as issue is still happening, despite me swapping out my run flat 19”s for winters and 18” rims. The ride is significantly smoother and way fewer rattles, but the vibration remains. @Jamie Landsman, did they tell you what the specific test was that they needed to do?