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rear wheels: camber adjustment...?

20K views 24 replies 7 participants last post by  samosali 
#1 ·
hello

for the 1999 S420, is there a camber adjustment for the rear wheels?

showing negative camber (wearing across inside of tire)...


thank you...
 
#2 ·
Not that I know of

My S500 was wearing out the inside of the rear right tire when I purchased it but didn't know about that until well after I purchased the car

No amount of wheel alignment would fix it and the mechanic who did the alignment could not find any worn or bent arms etc

Ended up replacing the rear sub frame and mounts

All good now
 
#3 · (Edited)
Interesting!
After completing a lot of work on the rear suspension components, I am yet to drive to the alignment stand and check the angles.
I might be wrong, but as I recall, at least one of the links in the back uses eccentric washer which should be for setting either camber or toe.
On the parts diagram it is #164.

Again, I am yet to see what the alignment tech will say, and I am eager to learn the answer myself.

Steve
 

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#4 ·
Having just gone through this myself (replacing all the control arms in the rear plus inner and outer control arm bushings, I took mine into an alignment shop. I was surprised how close it was.

The tech there said there was no camber adjustment. But having bought new eccentric bolts (highly recommended, as the old ones were worn), we set out to adjust the camber. It was a bit of a struggle, having to loosen a few other bolts.

But it can be done. I guess I was lucky as the subframe was not bent. IIRC, mine was out something like 0.5 degree.

But it was only at my insistence, and getting in the pit with the tech that I got it done.

Cheers
 
#6 ·
The forward upper arm has a bolt and eccentric washer where it attaches to the subframe. That's where we adjusted the camber. We also loosend the outer lower control arm bolt where it attaches to the wheel carrier. Found that that made easier for the camber to be brought into alignment.

Of course the toe-in is adjusted by the forward arm.

As I mentioned before, the alignment shop was insistent that only the toe-in could be adjusted. But I carried with me a print out of the alignment specs so I could show them that the camber was out of spec. And once they allowed me to climb under the car with them and pointed out the eccentric washer on the control arm, the agreed it was adjustable.

Cheers
 
#7 · (Edited)
Thanks for your response. Please use the diagram and clarify the following:



1. By forward arm, you mean part #140. Or #92 ?
2. By bolt and eccentric washer where it attaches to the subframe, you mean parts #158 and #164. Or #110 and #107 ?
3. By outer lower control arm bolt where it attaches to the wheel carrier you mean part #149. Or #98 ?

Steve

PS IIRC, access to bolt #98 will require removal of the rotor/caliper, as well as messing with bolt #68. I hope this is NOT what you had to do to set the camber right.
 
#10 ·
Steve,

Back in Dec 2016 you wrote:
"Updated part numbers for suspension bushings?
Gentlemen:

First, I would like to acknowledge forum members Alter, shimshon, bbirdwell, bnZE430/1999, NZJay, and especially G-AMG for several great threads on suspension updates. "

So I try to help out as I can.

Second, you are correct, I did have a typo and missed a zero as the correct rear outer carrier bushing is 2203520227.

Lastly, I was writing my comment to Eric since he was having a tire wear issue and I believe this carrier bushing is an overlooked part often in need of replacement.

Seth
 
#14 · (Edited)
Thanks Thom. Your links may have been due, but replacing them is unlikely to get the camber right on its own -- even if you mark the position of the eccentric washer, new vs old part will introduce another variable in the geometry -- alignment will be called for anytime suspension is overhauled.

I am hoping Peter will come back and answer the question. This is important for all of us who will have to get the cars aligned properly.

Best regards,
Steve
 
#15 ·
Sorry. This one slipped my mind.

My PSE pump caught fire the other day when I was driving. Have to spend some quality time with it.

The rear link (62) is what we used to adjust the camber. It has the eccentric bolt on it to make the adjustment.

After playing with 140 link for the toe, we then adjusted 92 to bring the camber out a bit more.

Cheers
 
#16 · (Edited)
Sorry. This one slipped my mind.

My PSE pump caught fire the other day when I was driving. Have to spend some quality time with it.

The rear link (62) is what we used to adjust the camber. It has the eccentric bolt on it to make the adjustment.

After playing with 140 link for the toe, we then adjusted 92 to bring the camber out a bit more.

Cheers
I will have to ask you to perhaps revise your response. link #62 is NOT going to affect camber. It must be #92.
Also, you didn't answer the most burning question -- which bolt? If #98, then it will require removal of the rotor/caliper, as well as messing with bolt #68.

Please confirm/correct.

Steve
 
#17 ·
Steve, all

I jacked up the rear today and pulled pieces off to get some pics.

First off, you need a special tool to do the adjustments on the eccentric bolts. The eccentric bolts (68, 98, 149) have a very special socket head. It's a triple square, not a torx (Tork are 8 point, triple square are 12 point). The only place I could find the socket and bit were King Tony tools in the UK. That was fun ordering them in. The first pic is how I welded up the bit to fit in the confined space behind the rotor shield.

There are two adjustments that should be made to alter the camber: the forward and the rearward upper arms (92 and 62 respectively). Both of these attach to top of the the spindle with eccentric bolts. I took a shot of these from above the rotor shield. The rear arm is on the left side of the pic; the front arm is on the right side. Altering these does not seem to effect the toe very much. This pic was taken from the drivers side of my LHD.

The rear arm (62) I adjusted by using the special tool I welded up from the triple square bit. It's a bit crude, but it fits in the really tight space behind the rotor shield. In the middle picture, the forward arm adjustment is made from the right side. Sorry I couldnt get a clear picture of the head of the eccentric. You can see the nut fitted to the bolt on the left side of the arm. For this adjustment, you don't have to remove the wheel, caliper or rotor. The 3rd picture shows the adjustment for the forward arm as seen from the outside of the dust shield. For identification, the wrench is sitting on the rear arm.

The forward arm (92) is adjusted by taking off the caliper and rotor, adjusting, then replacing the rotor in order to mount the alignment mirror.

I know that both of these affected the camber, as I was watching the display of the alignment machine in real time from the pit under the car. Neither the caster or the toe were affected much for adjusting either of these arms.

The toe is adjusted by eccentric bolt 149 on arm 140.

I hope this helps someone. It's not complicated. The hardest part was getting the eccentric bolts and the correct bit for them. It's a 10mm triple square.

Cheers
 

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#18 · (Edited)
Thanks for the update. I will save your write up. Just as I feared. Getting to those bolts will require lots of ground work.

BTW, Torx bits are star-shaped, 6-pointers. Very common, but I don't recall too many on the c140.
The HZN bits (triple square, 12-pointers) are rare, but fairly easy to source in the US.
Audi uses them a lot and I have a set. The axles on the MB, as well as the head bolts also call for HZN drivers

Inverse torx (E-bits or E-torx) are the rarest of all. I cannot recall seeing a single one on my MB.

Steve

PS On the background of this picture showing the worn outer LCA bushing, you'll see the bolt (should be #149) on the diagram. It is a regular 19mm hex. I did not see any eccentricity to it when I undid it...wonder why...you said toe is adjusted by that bolt, is yours also a regular hex?
 
#19 ·
Steve,

It's 11 pm here. Lions and hyenas are wandering around the compound this time of night, so it's not safe to go out and check. I'll go out under the car in the morning.

But, according to memory, and the diagram, it should be an eccentric bolt. That is where the toe is adjusted. Hard to believe on a car with such low mileage as yours someone had already been in there.

I'll post a pic of mine tomorrow.

Cheers
 
#20 · (Edited)
Thank you!
I found a better picture of the bolt in question (#149) in its unperturbed state. Pretty sure no one has been there before me. If memory serves right, it is a grade 8 bolt.

I was under the impression that the bolts where the links connect to the subframe have eccentric washers which is how the adjustment is done. The front LCA is like, for sure. The attached picture no.2 is a low-res, but the two vertical tabs on the subframe and the eccentricity of the washer are visible.

I cannot find any pictures of the extracted bolt. I think I would have noticed something unusual, but this will not be the first (or the last) time I have been wrong.

Always good to learn something new.

Keep us updated on your work.

Best regards,
Steve
 
#23 ·
This is for Samosali,

Just to add a bit more to this thread.

Reference the picture of the rear suspension adjustment points from another thread. Here is shows the camber adjustment is made by the hex head bolt and eccentric washer where the forward upper link meets the frame. In post #20, he shows both the hex bolt and the eccentric washer and plate on the frame used to make this adjustment.

Now, when I did the job, there were also two eccentric bolts with 12 point (triple-square or XZN) recessed head bolts. These are found where both upper links attach to the top of the hub carrier upright.

Now, look at the pics of the brake backing plate I posted in #17. There is a hole in the backing plate from the factory where you can see the head of the eccentric bolt from the forward upper arm. To my mind, the reason the factory put that there was to make adjustments to the camber as well. it is possible that the frame attachment point of the forward arm is for gross adjustments, and the upright attachment point is for finer adjustments.

What I found at the alignment shop was that we could not get the camber correct until we adjusted the rear upper link. That adjustment point is what I had to make the special tool shown in post #17. The attachment point for the rear link has the bolt head at the rear of the upright, and there is no space for a bit and a wrench. I had to take an XZN bit I received from the UK and grind most of it off and attach it to an old sway bar link to get the wrench in there. That adjustment was what brought my camber in line.

It may be that my subframe was bent, and that the original adjustment points could not bring the alignment in enough. I just don't know. But it would seem obvious to me that the factory intended for the camber to be adjusted at two points. First, at the frame mount of the upper link. That does not require removal of the caliper or the rotor.

But if that adjustment is not enough, then you have to remove the caliper and rotor and get the the adjustments on top of the upright.

I hope this helps. It's the least I could do for your help in getting my ventilation system operational.

Cheers
 

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#24 · (Edited)
Now, when I did the job, there were also two eccentric bolts with 12 point (triple-square or XZN) recessed head bolts. These are found where both upper links attach to the top of the hub carrier upright.

Now, look at the pics of the brake backing plate I posted in #17. There is a hole in the backing plate from the factory where you can see the head of the eccentric bolt from the forward upper arm. To my mind, the reason the factory put that there was to make adjustments to the camber as well. it is possible that the frame attachment point of the forward arm is for gross adjustments, and the upright attachment point is for finer adjustments.

What I found at the alignment shop was that we could not get the camber correct until we adjusted the rear upper link. That adjustment point is what I had to make the special tool shown in post #17. The attachment point for the rear link has the bolt head at the rear of the upright, and there is no space for a bit and a wrench. I had to take an XZN bit I received from the UK and grind most of it off and attach it to an old sway bar link to get the wrench in there. That adjustment was what brought my camber in line.
I respectfully disagree. Have not done an alignment yet, but have spent countless hours searching and reading and I think your take on where the adjustments are to be made is not correct.

The bolt you're accessing by removing the rotor, and the one you showed in post #17 is pictured here:



This is the bolt pointed with the blue arrow on the attached pictures.
One needs to mess with it in order to replace the link, but it is doubtful that it can do anything for the camber, as it is NOT eccentric.

Correct me if I am wrong, but the adjustments should be made at the subframe side via the bolts I referenced in an earlier post and have shown with red arrows pointed at them.

Best regards,
Steve
 
#25 ·
This is for Samosali,

Just to add a bit more to this thread.
Thanks, Peter, very much. I appreciate it. Actually i read this thread today very briefly from beginning to the last post. As you probably noted I stopped with action called "rear axle renewal". MB mechanics told me that everything is fine and i believe them because car drives perfectly smooth and straight, no tire wear.

According to what I have read here I am happiest person in the world that I do not need to touch these things. I am only an amateur mechanic, I even do not have basic tools like bushing removers, etc.

I was told by one mechanic recently that no. 122 is for camber adjustment but this info does not count anything because i do not trust him. On the other side he was self-confident.

I can support Steve's words that 12-leg bolt (HZN) holds torsional bar link. I guess it is an ordinary bolt without any other function, at least it is so in my memory. all i did in rear suspension is replacing torsional bar links and springs.
 
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