ccww

I live in Oregon where all freeways have heavy aggregate for traction in wet conditions. Unfortunately this also translates to very high levels of road noise in most vehicles and my 2015 E250 Bluetec is no exception. The noise is a dull roar at highway speeds, not a tire sizzle. The experience just isn't commensurate with my expectations for an E-Class. I drive about 800 freeway miles per week and the noise becomes quite wearing eventually.

I know that many forum members have had similar issues with the W212 and I'm quite certain that I've read every thread on the topic at least a few times. Several areas of interest have caught my attention:

Rear Tirewell Area

The most common focus is the rear tirewell area. I've read of forum members applying all sorts of damping and/or absorption materials in the tirewell with remarkably mixed results. Some claim that they realized huge improvements while others claim little improvement. I decided to do an experiment. I filled all the empty space around my DEF tank with towels, except for the DEF heater and AUX battery. I then replaced the trunk cover and my WeatherTech trunk liner, put down about 2" of foam I had laying around on top of the liner, pushed pillows and a comforter up against the back of the rear seats, and then put another comforter over the foam. I figured this makeshift hodgepodge should perform within the ballpark of more permanent but much less bulky acoustical treatment. I then performed a test. I chose three short (about 60-120 second) routes and drove them at 65 mph, each twice. I used the DecibelX iPhone app and while the accuracy may not be great, the precision of the phone and the testing method was good with each run's average measuring within 0.2dB or better of its duplicate counterpart. I then remove the absorbing materials and repeated the six runs. I realized about 0.5dB of improvement with all the materials, not nearly as good as I was hoping for.

I'm not sure if its worth it to continue to pursue noise control in the tirewell area. I don't know if having a DEF tank makes the noise control harder or not, as many of the members reporting improvements removed their spare tires to conduct the treatment. I did tap on much of the sheetmetal in this area and it is mostly non-resonant. This makes me think that a successful solution is more likely based on sound BLOCKING, as opposed to stick-on deadening. If I were to pursue this area further I would likely line the area with Second Skin Audio's Luxury Liner Pro, a noise blocking mass loaded vinyl (MLV) with a foam backing to decouple it from the substrate surface. I would then fill empty space with 3M auto Thinnsulate and then also apply the Luxury Liner Pro on the bottom of my WeatherTech liner. I might even fashion a blocker to go behind the fold-down rear seats. However, considering the poor results of my first test I don't know weather this would be worth the ~$200 cost and time to test it. I would welcome any comments or experience on if I should proceed.

Wheel Wells

Wheel wells naturally come to mind for road noise. I have read that there is no room for acoustic materials between the exterior liner and body. I have also read that little improvement is derived from damping over the exterior liner, which I wouldn't be too keen on anyway. Apparently the interior wheel well areas are very hard or impossible to access. Any information on accessing these areas and if there is any room for acoustic materials would be greatly appreciated.


Suspension

One forum member, @S-Prihadi , has replaced his OEM Sachs shock absorbers with Bilstein B4 and claims an improvement in noise overall. Although I don't know if it is the same kind of high-speed tire roar that is bothering me so much.

Any experiences with suspension and road noise in the W212 would be very useful.

Floorpan Treatment

One member reports having Second Skin products professionally applied to the floor. I suspect this could have a significant impact, albeit at significant cost and weight and a tremendous amount of time to disassemble and reassemble the interior. I believe the seats and center console must be removed to remove the floor carpets. I cannot find documentation for this procedure. Documentation about removing the carpet and/or experiences adding acoustical products under the floor carpet would be great.

Door Treatment

Some members have damped their door panels to improve the performance of the audio system. The door panels are fairly easy to remove. The consensus seems to be that it makes a very small difference in cabin noise, but not enough to justify it only for cabin noise reduction. As such this is lower on my priority list.

Acoustic Laminated Glass

Laminated Safety Glass with Acoustic Film (839) was an available option from the factory. I have spoken with my local dealer and might be able to order this glass from Germany. Between the glass, retinting, and installation the cost is significant, if not prohibitive. I'm certain this does reduce noise transmission through the window, but the question is what kind of noise is transmitted through the windows? My guess is more wind and traffic noise than tire roar, so this is likely something I would do after making a decent dent in the tire roar noise by addressing other issues.

Door Seals

I know the door seals eventually wear out and will allow sound into the cabin. However, mine are fine on visual inspection and I only have 32k miles. Also, there are no easily identifiable noise hot-spots that would indicate an area of poor sealing. Instead the sound just seems to be coming from everywhere.

Any comments or experience with reducing W212 road noise would be greatly appreciated. Obviously there are a lot of possible strategies as detailed above. I'm currently a bit discouraged at the failure of my initial experiment and trying to decide what to try next.

DFWdude

Before I spent hardly any of the money suggested for these mods, I would trade the W212 for a wallowy land barge, like a Cadillac sedan.

Or I would assemble all the road warrior tunes I could find on an SD card, and turn up the volume...

Or I would move to Arizona.

I get the impression that no car will ever be quiet enough for you. Can't imagine driving 800 miles a week in a boat anchor SUV. But at least you will sit far above the offending aggregate.

ChrisB

A clever autistic engineer should devise a noise cancelling system.

ccww

I'll readily admit that I'm a bit sensitive to noise... That said, judging from the history on this forum being bothered by road noise in the W212 doesn't seem to be limited to just me. It also just seems louder than a luxury sedan of this caliber should be. My partner's 2012 Ram 1500 has significantly less road noise.

DFWdude

There's a smart phone app for that... "White Noise Generator"

DFWdude

Well it's a compromise. Soften the suspension so it wallows like a Caddy, but quiet... Or provide the sporty suspensions all of us want at the expense of some road noise.

On interstates here in TX, the road noise is very sedate... or the sound system is too loud. I like my R&R

LILBENZ230

I, too, doubt that you will ever be satisfied - but I don't think it is the car's fault here. My E350 is very quiet. But how do you correct for road conditions? I actually don't think a softer-riding land barge like some old Cadillac would even help here. I would do some research on getting the quietest tire possible and otherwise not spend a lot of money chasing what is basically a road quality issue. You can't really compare the E-class to a Ram - you're sitting so much further away from the tires/road in the Ram than in the E. So maybe Bob is right that a taller, higher-riding vehicle would be better suited to your particular sensitivities?


Edit: You should take a commute in the MX-5 for a few days to appreciate the E.

ccww

You and @DFWdude are both probably right about me not ever being satisfied. And the W212 is a pleasantly quiet car on a smooth road, unfortunately those are very rare here in Oregon with the aggregate. Even after fresh paving they're back to being noisy within 6 months of wear.

Higher-riding vehicles definitely aren't to my taste. And unfortunately I want to have my cake and eat it too with the tires. I'm running Michelin A/S 3+ as I love the grip. However, I will say that they are significantly quieter than the stock run-flats, albeit surely not the quietest tires in the world.

Car and Driver measured the W213 with Acoustic Comfort Package as 7dB quieter than the W212 E350 at 70 mph, so it is possible in a car of this height. I do wonder how much is simply transmitted through the W212 suspension and can't be effectively blocked, however.

LILBENZ230

Can't really compare the W213 to the W212 either. I mean yeah they're the same height, but there is no way to really account for what might have changed in the complete ground-up redesign. I think the acoustic glass would not help in your situation as it is road noise instead of wind noise.

The tires you are running around roundly criticized for being loud. They are good tires, and get good reviews, but I ruled them out because of how loud they are known to be. Have you thought about Continental DWS06? I almost always run these on my cars - MX-5 the exception - and have always found them to be a good balance of performance in dry/wet (little snow here in the south), longevity (about 30,000 miles on average on the staggered Benzes I've always had), and comfort/quietness.

But someone else may be able to recommend an even quieter tire.

ccww

Thank you for the Continental DWS06 suggestion. I'm definitely open to trying other tires when these need replacement, although I would like to stay in the ultra high performance all season category, like the DWS06 and A/S 3+. I've heard mixed things about the A/S 3+ noise with some claiming its terrible and some not. They are definitely quieter than the OEM runflats. Tirerack rates both the DWS06 and A/S 3+ exactly the same for noise, 8.2, but who knows how reliable those numbers are as most of the raters don't have many points of comparison.

LILBENZ230

A lot of reviewers of the AS3+ claim it is loud. I don’t doubt it is quieter than runflats (those are awful) but my gasoline version has a spare and is currently riding on new versions of the OE continentals (which suck). I will be going with DWS06 when these are done. Just 7100 miles on them so far.

But I’ve also been doing research to see if there’s a quieter tire option. Oddly enough I broke my windshield by accident recently during a wiper blade change and it got replaced with a Fuyao replacement which I was initially against, but it turned out the car is quieter now than before.

ygmn

Change tires.... they are causing issues since they areon the road
May tale several brands and models to find what you like.

My guess is a super duper sport tire that wears quickly would be quiet since more tread on road and soft rubber.
Would suck in rain though.

Also change to smaller wheel and get bigger sidewall tires that are quieter....
Then go to stearo shop have them strip inside of car and install dynomat stuff everywhere as it acts as sound insulation.
Foam does not attenutae sound that much.

PS 3dB change is what stereo nerds say is what is noticeable..
anything less does not compute in ears.

nc211

OP - if utter silence is your goal, then Lexus is your brand most likely, but at the cost of driver engagement. I've had two Lexus sedans in the past, an LS400 and a GS430, each with the V8 engine. Both were buttery smooth and church mouse quiet. On the LS, that was fine because it was really a big boat cruiser. But on the GS, it neutered the intent of a relatively sporty sedan. I ultimately replaced it with a VW GTI (Mk5) for some enjoyment in the process of driving. The E 350, in my opinion, is kind've in that GS territory and I enjoy 99% of the sounds it makes. I do understand your point though, it is a little elusive to look at it and not think it'll be a quiet as the Lexus counterpart. But, that's not a bad thing for folks like myself.

I suspect the trunk indeed. The suspension aspect transmitting road noise into the cabin is also a culprit. This is where Lexus achieves their quietness via thick rubber bushings on every single connection point. That rubber is the difference maker. Yes, insulates noise and vibration, at the expense of driving engagement through the steering wheel and sense of understanding what the car is doing at all time. I can tell you, I feel totally fine and confident in driving my E 350 in a downpour rain storm, and totally numb and a bit frightened in anything Toyota related (and I have one of those too still, a 2013 Highlander). The Highlander is insanely smooth and quiet, and I totally hate it in any kind of rain.

Tires - I have yet to ever have a complaint about Michelin tires on any of my cars, ever. I've had the Dunlops, Perilli, Bridgestones, etc. I have the OE Continentials on the E350. Whenever one of my cars needs new tires, I have never been disappointed with paying a little extra for Michelins as the replacement. I replaced the Perilli's on my current MK7 GTI with the Michelin A3's, and man what difference in road noise and overall feel of the car. Cruises far better than before. I've had them on there now for two years and 25k miles. I will stick with them for that car without question. And that thing is basically a coke can with a turbo slapped on it!

atraudes

It doesn't really help you, but when I had the liner off for other reasons, I lined the rear hatch of my wagon with Kilmat and it made a tremendous difference. I'm going to have to line the spare wheel well too...

pierrejoliat

I went from driving S classes to E classes, it was a definite change in ride and noise quality, my E's don't have air ride, I have had the Conti DWS and the Conti DWS06, great in the snow especially noticeable on the 2WD. When I got my 13 it was noticeably louder tire noise than my 12 so I replaced the Michelins with the DWS06"s much quieter. Anyhow, up here in the rust belt we used to undercoat our cars, most people don't bother with this any longer, cars up here used to show rust after 3-4 years, now they make it 8-10.
Undercoating quiets things down immensely and it still can be done, I bet in eastern Oregon. I've seen the undercoating places in eastern Washington state, but that was 5-6 years ago. I was working in Bellingham. {which is NW WA.}

Tom in Austin

Interesting discussion ... just drove new E and S models yesterday and noticed that the E was nice and quiet on smooth pavement then got quite loud over a stretch of coarse roadway. The S over the same area was so quiet I couldn't even tell I was driving over the coarse pavement.

Our C350 suffered from horrendous road noise in spite of having very-quiet Pirelli P7 Cinturato tires. I've been gradually adding sound deadening throughout the car in all the places discussed in this thread and have made some nice headway, but when we go over certain types of pavement the noise comes back with a vengeance. And when you get the carpet and interior trim pieces out you can see Mercedes made very little effort to insulate the interior - there's molded foam on the underside of the carpet and a couple thin fibrous pieces here and there and that's it.

It appears to me Mercedes has designed or tuned the 'lesser' models to do very well on high-quality road surfaces. But once you get onto broken or coarse pavement, it all goes bad and my wife says in despair, "I thought Mercedes was a luxury car!". I read somewhere once that German roads are very smooth and well-maintained and this may be a factor in Mercedes' approach to suspension tuning and sound insulation.

SteveE400

I am one of the owners who noted significant noise reduction when I "filled" the spare tire well of my W212 with fiberglass insulation, such as what is used inside home walls. I wrapped the spare in 4-inch insulation, then stuffed more into all the spaces in the tire well, just leaving the aux battery and its wiring exposed. Personally, I did notice a major drop in tire noise.

I also notice a change in road noise when I change from my winter WeatherTech mats to my summer carpet mats. Much quieter in summer.

Oh, and some of our roads are much quieter than others. They have recently re-paved much of the interstates around Chicago in concrete. The old asphalt roads are far quieter than the concrete. Some stretches of the concrete are so loud that I am always worried that I am losing a wheel bearing. . .

I have to agree with @nc211, Lexus is "The Quiet One." After my W201 MB, I had 3 Lexus autos - an LS400, an ES300 and a LS430. Each of them was far quieter than my W212, BUT at a cost. If you want to ride somewhere, buy the Lexus. If you want to drive there, buy the MB. Lexus makes great cruisers. MB cars are much more engaging.

ccww

Thanks very much to all for the thoughtful responses.

@ygmn , I already have the stock 17" wheels and I'm not going any smaller or narrower. At least I have no complaints about the ride being too harsh as some with larger wheels on this forum do.

I've been in Lexuses and they do have the kind of hushed ride I enjoy, but I very much agree with the comments about driver engagement. I would much rather drive a MB and live with the noise or attempt to remedy it myself. The detached driving of almost anything from Toyota just isn't for me.

Interesting idea on the undercoating, @pierrejoliat . I can definitely see how it could help with road noise. I don't know anything else about the procedure though. Are there any long term concerns or any concerns with a shop not familiar with MB doing something deleterious? Any idea of the weight addition?

@Tom in Austin , your observations are very consistent with mine. The car is beautifully quiet on very smooth roads. The wind noise is good and even my diesel engine is very quiet when cruising. I like the diesel growl anyway. However the noise on rough pavement is highly intrusive. I'm very interested in your treatment of your C350. What areas have you found to be most beneficial? What kind of materials are you using? Any advice from what you've learned so far?

@SteveE400 , I reckon your fiberglass significantly outmatches my experiment with comforters and towels in terms of absorptivity. Perhaps that is why you've realized a greater gain. I'm not comfortable filling the DEF tank area entirely with heat insulation, but there does seem to be a consensus that this area is a sonic hot spot. I'm considering taking more of a blocking approach and using a foam-decoupled mass-loaded vinyl (MLV) barrier between the trunk floor and my WeatherTech trunk liner and anywhere else that looks like it needs it. Did you ever take any measurements of your improvement? And do you always get the improvement or is it drowned out on the worst concrete highways?

pierrejoliat

I had a 13 Lexus RX350, road/wind noise was loud, the Highlander is more luxurious. I put the Pirelli Cintaurato's on and it was quieter but swayed a lot, very sloppy. my buddy has the LS460 it's quiet but still sloppy.

Ziebart is one of the companies in the undercoating business, they train employees well. they do inside the doors, whole underside of car and use 3-5 gallons @18- 20 LBS. a gallon, so not much weigh addition, Last car I had done was my 2007 S550, it was quiter but that car was quiet from the start, interestingly, not as quiet as my 2003 S500 which was louder than my 93 S500 which was like a tomb, both undercoated by Ziebart. anyhow it was 400 dollars in 2008 and they sprayed 5 gallons in and under that car. Millions of people used to undercoat their cars, never heard of a problem. In the Cleveland snowbelt, rustproofing was mandatory.

In a related story, I designed equipment for a Coke plant south of Atlanta, they put the control room next to the pump room and it was really loud, we went to the local car audio store and bought this really thin sound deadening material and did all the walls and doors, I was shocked how much quieter it was, it was a lot, can't remember the brand, sorry.

I've been on your roads, it's bigger aggregate, way louder, they do the same thing in Wisconsin and Minnesota except the roads are red colored!

ccww

Thank you very much for the information, @pierrejoliat . Doesn't look like Ziebart is in Oregon but I'm adding undercoating to my list of things to research.

LILBENZ230

Like @Tom in Austin , I had a 2014 C350 Sport. I find my 2016 E350 Sport to be significantly quieter than the C, though, on the same roads.

pierrejoliat

I quickly googled it and found six places Oregon who do undercoating, you are correct, none of them Ziebart.

I also agree as you move from C to E to S you get more quiet, my first Benz was a 91 190 E, then I got the 93 S500, kept that and got a 2001 C240, loved that C.

ccww

The coating is on my list of options, but I think I will try some internal damping first. 3-5 gallons at 20lb/gal adds up if I also add 50-100lb internally.

Right now I am recovering from some injuries from a motorcycle accident and not able to take apart the inside of my car or cut damping materials. However in about a month when I'm more able I'm going to add some constrained layer butyl rubber and aluminum damping to the tirewell and trunk area (like Second Skin Dampifier). Then I'm going to make MLV and foam barriers to go under the WeatherTech trunk mat and behind the rear seats. Possibly some 3M auto Thinsulate where it'll fit. If that helps I'll start thinking about doing the cabin floor and doors, although the former in particular is much more involved in terms of disassembly work.

Does anybody know where it is safe to put insulating materials with respect the aux battery and DEF hardware in the spare tire well? Does the area have or need any airflow?

DFWdude

If weight is a concern (it is) then I would use carpet underlayment (padding) rather than sound deadener bought by the gallon. Carpet padding is lightweight, easy to cut with scissors, and easily shaped into confined areas. A generous layer over the lower trunk bits and under the OEM carpeting should make a difference.

You have a diesel, so if you also have one of these covers over your trunk Aux battery (below), then that answers your question about airflow. If genuine Mercedes parts can cover the battery, then you can do so yourself with other materials...

ccww

I'm willing to add a decent bit of weight. 100lb no problem. But obviously there are reasonable limits. I do think I will be focusing on MLV to block the road noise. The E is already built pretty solidly and doesn't suffer from excessive panel resonances that need much additional damping. Absorption is very difficult at these frequencies as demonstrated by the failure of my test with lots of towels/blankets/pillows/foam in the trunk.

I suppose my question more specifically is can I put insulation under that trim cover? Like packing 3M Thinsulate around the battery and the other stuff under there? Or leave the trim and preserve the airspace under it?

On a tangentially related note, that trim piece you pointed out doesn't fit very well on my car and it's always bothered me. The edges and holes don't line up precisely. Is this the case for anybody else?