Car skips to the side over big bumps
 

Hey guys I have an 06 S55 I have spent about 15k wholesale replacing many things to make this car run and drive the way it did new. One thing I've noticed with this car is when on the freeway hitting a bad bump the car will skip to the side. I rebuilt the front end but haven't touched the rear end as I was told it was good. Keyes MB did claim to do a 4 wheel alignment a couple months ago but I noticed no difference.. This is my fourth S and the only other one that did this was my 08 550. I've been searching for days and have seen the issue crop up a few times but haven't found any solutions. My tech said he took a crowbar to the rear sub bushings and they flexed within spec, but I'm wondering if they should flex at all.. other than the dealer not aligning it correctly I'm at a loss. I'm about to just have the rear end rebuilt to rule it out but would prefer to know and fix the precise issue.

Any help is appreciated!

Could be your abc reaction over big bumps , I've noticed my cl will do this

Hmm what would cause that? I remember my 08 S550 had it too and that was Airmatic then my 2010 S550 was issue free

Jack up each rear corner in turn, so the wheel is clear of the road.

Grab the wheel and try to shake it up and down hard. It shouldn't move, but I will place a small wager that one of them will move up and down freely a few fractions. That would probably be due to a worn strut top rubber bush. Happens quite a lot. Only solution is to replace the strut I'm afraid, so good luck.

nick

That makes a bunch of sense. My old 05 S55 would do that and the PAX front had a torn bush.

Thanks for the info. I know the rear pass side abc strut was replaced a couple months ago so I assume their struts have new bushings? Which makes me wonder. If they can replace the bushings why can't we? Also would the top bushings make the car skip like that? Also what about those pieces that guys add in?

That was me.


Attachment 360026


You can add a rubber washer to the top of the strut top bush to take up the slack caused by the wear of the bush. It's a cheap, quick, easy fix that makes a big difference to an old car, but unfortunately it only works on the front. The rear strut top bushes are quite different, and you can't do anything with the bush. Tragic.

Nick

Thanks Nick I just called Arnotts asking if their rebuilt struts have new top mounts and they have to contact their engineers and let me know. I assume they must be as they couldn't sell them bad but the fact they can't be replaced yet they sell rebuild struts confuses me. As for the fronts, is that a decent fix or does that still compromise ride quality? Do you think this is probably the cause for this skipping to the side? I've searched for this issue and have only found one or two cases across multiple boards which surprises me. Thanks again!

Just thought I'd give you an update guys.. when you buy an Arnotts strut you are getting a USED upper mount!! In other words buy from the dealer if you want it right/to last... :(

Whaaaat?

YGTBKM!!

Yup.. Arnotts messaged their engineers and they said "at this time" they are using the best cores they have.......

Hey Nick,

Do you think it could be from the front struts too? Those spacers you use to stop the play on the front struts does that make the ride as good as struts with no issues? Is it an easy job? I just had the dealer align it will it need to be done again? Thanks for all your help!!

Both of my CLs have done this, and it's from the upper rear strut mounts. I have lived with it, as the cost of replacing two complete, otherwise good working struts is too much just to eliminate that sideways kick over uneven surfaces.

Wow that's good to know. I have a new Arnotts on the pass side rear only a couple months old but now that we know they are used that's iffy.. but maybe I just need one

I recently noticed this on my CL, too. I was a bit unsure what to think about it. I'll try the mentioned method next time I change the tires.

Hey Nick,

I took the car out on the freeway tonight and noticed a few things.. yes it happens over bumps but it seems worse when I hit cracks in the road or certain road that walks the car.. once even the steering wheel turned pretty quick on its own when it happened. Those time there really wasn't any bumps, yet sometimes I can hit good bumps and have no side to side feel.. also keep in mind I just had the front end rebuilt with all new OEM parts and the dealer re leveled and four wheel aligned it.. would the strut mounts still be the cause? I'm thinking whatever this is is in the front and the back too. Thanks for your help because I'm lost!! This makes the car kind of scary on the freeway.

Hi Chris

Bad strut bushes can have a profound effect on the car's ride and handling, though it does depend on the circumstances. Strut bushes have little effect when going slowly, or when the road is smooth, or when the bumps are long, or when the surface isn't broken with cracks and pot-holes, or if you have tires with tall sidewalls. In other words, when the suspension isn't doing much.

Strut bushes have more effect on short length, small-amplitude, high-frequency bumps because the damper becomes stiff when the wheel moves quickly, and the bumps tend to by-pass the spring /damper, and get absorbed by the bush instead (and the tire of course).

These are the sorts of bumps that tend to excite a resonance/oscillation in the suspension's unsprung mass. The sprung mass is the car itself, while the unsprumg mass is the wheels, tyres, brakes and suspension. Just as the sprung mass bounces up and down on the springs and dampers at a frequency of roughly one hertz, the unsprung mass is also excited by higher frequency bumps, more like ten hertz.

The strut bushes have little bearing on the primary resonance, but they play a much greater effect on the unsprung resonance, especially on modern cars which tend to have soft bushes, and they have to control this high frequency resonance. If the bushes wear, they don't control it effectively, and the wheel can shake up and down as the unsprung mass bounces up and down against the compliance of the tires and the bushes.

The thing with a resonance like this is the energy is alternately stored in kinetic energy as the wheel moves up and down, and in potential energy as the bushes are compressed, which is typical of oscillating systems. When a wheel hits a sharp bump, the bush is compressed, and the stored energy is released as the bush relaxes. If the bush is worn and slightly collapsed, it can relax far enough to go slack, and then it's no longer controlling the unsprung mass. It hardly controls it at all.

When you drive down a bad road at speed, that is full of small, short, sharp bumps, the wheels can bounce up and down at high frequency, without either the damper of the bushes controlling it properly. That makes the car feel crashy and shaky, but it also makes the suspension feel like a blur, like you've got a horrible, rough ride, but you're also disconnected from the wheels. It's horrible, but again not something that you're really aware of on very smooth roads.

The first time I encountered this I thought my subframe bushes or suspension arm bushes were worn, but they were all fine. It was difficult to pin, but it all became clear once I started experimenting adding spacers to the front bushes, which you can tackle relatively easily.

No, you don't have to have alignment re-set.

Regards, Nick

Thanks for the info Nick! What threw me was going over the road with a long crack and how it felt like the car was on a long rail all of a sudden following this road.. it just didn't seem like it was bumping at all but I figured it could be at the wheel without me knowing as the strut isn't pushing the wheel down like it should. I tried searching for the directions on how to install the spacers but maybe I'm not using the right keywords. Do you know the link? Also if memory serves me didn't you or someone else discover where the spacers could be bought instead of made? Thanks again!!

I think most well-used W215's and W220's will suffer from this problem, and it can be easily fixed. The improvement to the ride and handling is really worthwhile on broken surfaces.

On the rear strut, the bush appears to be bonded to the metal mounting. I don't think this causes problems as readily as the front, but the bush can come free due to corrosion or bonding failure. The only solution I found was to replace the strut. Buy a good used one off ebay, and its not too expensive or difficult (as long as the so-called quick-release connector isn't seized).

I cut some small doughnuts out of a 10mm rubber sheet and put them under the top bush nuts. You need a stout 35mm pin spanner. Don't even need to lift the car up - in fact its better if you don't.

The ride is much better now. You can't do the same trick with rear struts unfortunately.

Attachment 359973


Its an angle grinder type of spanner that you need; not a C spanner.

You can't use adjustable ones; they're not up to the job. Ask me how etc.

You use the spanner to undo the large flat nut on the top of the front strut, in the centre. You remove the electrical connector first.

Don't jack the car up - you need the weight on the wheel to stop the rest of the strut from spinning round (which may damage the hydraulic pipe).

Attachment 359974

I'm afraid that getting the strut off is often difficult. You have to remove the electrical connector at the top, plus the hydraulic connector at the side, plus the mechanical bits. The worst bit is that the hex grub nuts at the bottom of the strut are often corroded and seized. Heat helps, otherwise just remove the transverse control arm.

The easiest way to get a rubber bush/spacer is by searching for an M20 rubber washer on ebay. Check the diameter of the bush itself, and you should be able to find something 3mm thick quite cheaply and easily.

Nick

Thanks Nick! I am not sure I understand I am not familiar with how the struts look. So you take the top nut off with the spanner and then you mentioned taking the strut off. So does the car have to be jacked up then to remove the strut? Also, those M20 washers, do you think those are as good as the ones you made? Thanks again for your help! Also I'm almost positive my front mounts are bad but is there an easy way to check them? Thanks!

Look at this on eBay http://www.ebay.co.uk/itm/360582863882

Here are some that say 3mm

Sorry, I was trying to remember what I did, which was indeed to take the struts off. It's absolutely not necessary, it's just that I usually do things the hard way before I find the easy way.

You just have to remove the top washer/bush, and it's best if you don't jack the car, as that keeps the weight on the strut and helps to stop it spinning when you undo the top nut.

Best to drill out the blind holes so that the pin spanner pins can go in deep and engage properly. Even with a proper, non-adjustable spanner, it's still quite difficult.

Make sure you don't turn the strut when to undo the washer, so that you don't damage the ABC hydraulic hose connection.

Nick

Thanks Nick. Is there a way to confirm they are indeed bad by looking at them?

With weight on wheels, if you can see a gap between the washer bush, and the wheel arch pressing that it sits against, then I guess you could just go ahead an fit an additional rubber washer. It's not a guaranteed method though.


Nick

Hey there I am still not sure I understand where the problem is.. I found this picture. Do the bushings go under that puck looking thing? What if we were to cut them and stuff them in and then epoxy the cut? I'm not sure I am completely clear on taking it apart.

Hey Nick,

It seems we both replied at the same minute lol! So I just popped my hood and they definitely look like there is a big gap in them. I am sorry to be asking so many questions but I just don't understand. I am assuming the washers go between the piece that you use the scanner on and the strut tower.. you can see the marks where the piece bottoms out on it. I guess my question is, once you put a scanner on that piece after removing the connector then what do you take off? Does that piece twist off with the scanner and then it's just a shaft that you drop the washers down onto? Is this going to ride as good or am I better off buying two new struts? I don't want to spend thousands of dollars if I don't have to but I want it right and I want to be able to drive it without dying when I surge into the other lane lol!

I see a pretty big gap there between your strut tower and the bushing
Attachment 359947

why don't you just buy some m20 rubber washers , slice a cut in them and coat them in epoxy in one side , then slip them between the strut tower and existing bushing , to close up that open
gap ? Should take all of ten seconds

Thanks that's what I was thinking but when on the freeway and just hitting uneven road without bumping the car will surge to the side.. so if the strut is causing that it's because there is no down force on the tire I'm thinking.. if that's the case I would need to put enough so there is pressure on them right? I'm wondering if this fix is going to even work for the issue I'm having. With how bad the freeways are here and this being a scary issue being slingshot into the next lane I'm wondering if I should just spend the money and replace them.. if the bushings would solve it and ride the same I'd rather go that route but I can't have my family drive in a car that shoots to the side like this.

Chris,

The looseness in the bushings does not affect the down-force on the tire. Adding the rubber washers will not change the down-force on the tire. The full weight of the car is sitting on the struts.

The ABC cars do not have antisway bars. They depend upon the hydraulic struts to control the body movement of the car at all times.

If the top bushings are worn, so that there is space between the bushings on the top of the strut and the tops of the strut towers, there will be looseness when the body moves up. If the car hits a ridge in the highway that runs along (not across) the road, the front tires may try to follow the ridge. (Suspension engineers call this "trolley-tracking", since it was first very noticeable when the early cars ran parallel to the trolley tracks commonly found in the streets then.)

If the suspension bushings are all firm and tight, the ABC suspension has no problem controlling the small movement, and it is not noticeable. With the clearance between the bushings and the body that your car shows, when the front tire hits the ridge and tries to follow it, the looseness lets the body move in lateral roll, and that small movement is magnified to a noticeable amount.

If you could simply hold the steering wheel rock-steady, the movement would almost instantly damp out, and the car would hardly move off-line. Unfortunately, virtually no one can just hold the wheel steady and ignore the small movement. Everyone automatically tries to correct for the movement, and when the car almost instantly settles, the driver's correction is usually much larger than the car's initial movement. The driver than tries to correct his correction, and over-corrects in the opposite direction. The result is what aeronautical engineers call "PIO" - Pilot Induced Oscillation.

If you do as several folks have suggested, and add firm rubber washers to fill the gaps and eliminate the looseness, the car should drive much better.

(A "scanner" is an electronic device to check for trouble codes in the car's diagnostic system. A "spanner" in the USA is a flat wrench that uses (usually) two protruding steel pegs that fit into holes in a threaded plate to loosen/tighten the plate like a nut. In the UK and associated countries, a "spanner" is what we call an open-end wrench.)

I converted my S600 to coilovers, so I have a complete set of not leaking 78k mile struts I'll sell cheap. I'll take a look at the tops and see what shape they're in.

Thanks for the info Wally! When you talk about the movement being minor I take it you mean when the bushings are good, right? As the other night the steering wheel jumped pretty good when it trollied on a crease in the road.. do you think cutting some firm washers and putting them in there as tight as I can is less of an alternative to trying to get the nut off with the spanner? Is there any performance loss to going the bushing route vs replacements? Is the strut now moved up higher than it was meant to be going to cause issue? When you look at mine from the inside of the towers they are raised very high vs how they look in the picture.. Thanks again for your help and great explanation!!

Thank you very much but I'm afraid I need to run the AMG struts.

Hey guys I just spent the money and bought two brand new struts. The dealer gave me 30% off so I paid $1300 each. I just want it done right.

huh? S600/s55/s65 abc struts are the exact same part

I thought the AMG had different suspension? On Arnotts the late vin cars are different part numbers vs the early numbers are the same

My Dealer doesn't sell New Struts anymore. They sell New/Refurbished now. Is that what you got ??

No.. they sell the refurbished and want to push those but they can get the brand new ones.. they had to order them from Germany for me. I saw all the screens etc. If your dealer said that then they just didn't want to get them from Germany.. my friend was saying why not just buy the refurb for a few hundred less.. but after Arnotts said they can't even replace the upper mounts and that they just use the best cores they have and that theirs already have a little gap already I started to wonder if the company that rebuilds them for MB does the same thing.. they may not, but I didn't want to take the chance plus with the new ones I can keep my struts so if I sold them to Arnotts as cores or to someone else who wants to put the bushings in them I'll be at the same price as refurbs but I'll have brand new.. seeing as I'm replacing perfectly good struts just because of the upper mounts buying new seemed very important.. all my buddies who one works for MB and owns these cars too and one owns the biggest MB specialist shop in town and the others work there all thought adding washers was a joke.. they referred to it as more Mickey Mouse repairs from the internet lol and usually they are more on the liberal side of playing it safe than sorry so I decided to go this route.. every one of them said the same thing.. it's my life riding on those struts and putting spacers in there could just make the already weak upper mount give more. No idea if that's a possibility, the washers may have been great..

You made the right decision!! I would personally never micky mouse anything on a mercedes let alone struts but a lot of people here do it so to each their own. Getting new struts is the best way and I am at the same stage right now with my two front ones but my dealership will only sell the refurb so I am looking at the New Bilsteins since I will not get arnotts. Anyhow good luck with yours.

Thank you very much! I hope you work yours out too!

Well, MB specialists always know best ....

My front struts on the 65 look just like that. They have 57k miles on them. Does that gap indicate they're shot? I was looking closely a while ago, and thought that's the way they were supposed to be??? :confused:

Yes that means they're shot like mine.. really stupid design.. the upper strut mount is what fails.. If you have 57k on them then that tells me it's the age and weight on them that wipes them out maybe.. who knows maybe they redesigned them.. I'll know when they come in from Germany but I doubt it..

So ...... did that fix the original problem?

I haven't gotten them yet. They are coming from Germany. I should have them this week and will let you guys know how it goes.

Side to side in the rain as well
 

guys, thanks for this post... I have been having the same problem and it is scary!!! My car does it over bumps and in the rain it feels as though I will have an accident by jumping into another lane!!! Cmpcpro, please let us know asap the results! Thank you so much for your feedback!!!

Racer: glad to help!

Hey guys my brand new struts were installed today! What a difference! I haven't driven it enough on the freeway to say it's resolved but I will this weekend. However the front end is brand new maybe a few hundred miles on it and it still felt like it had play going up my driveway or hitting bumps and now it's nice and tight! The old ones have clear play in the upper mounts now that they are in the box. I will say though after looking at the old ones in the box I think using the washers would probably solve the problem. You would be losing a bit of travel but probably not enough to notice. I'll keep you guys posted after the freeway trip!

Great to hear. Just picked up mine yesterday from the dealership. Mine are the remanufactured ones though. Hopefully i will be as happy as you :)

Hey guys, so a quick update. The car feels a lot better and no more hitting a bump and having the steering wheel rip out of my hand however hitting certain lines in the road and I still get a bit of the problem but it seems to be coming from the back now.. it seems the backs will need to be replaced. The sad part is one of them was replaced just a few months ago with an Arnotts and obviously with them being used that is no help. The front end feels great though!! The only thing on the front that isn't new is the rack.. even though it still feels very tight.

same issue