Need Expert Opinion on Wheel Alignment
 

I recently too my wifes E430 in to have the front end looked at. It was shaking at about 80MPH. seemed to me that either I have a bad shock, wheel out of balance or combination of both.

The car tracks stright as an arrow so I didn't think it was alignment.

I took the car back to the shop I bought the tires and wheels from a little less that a year ago. I also at the time of purchased had them do a 4 wheel alignment.

I was supprised to hear that I now needed 4 new tires and another 4 wheel alignment. WOW!

They showed me the tires while the car was on the rack and sure enough all 4 of them has very bad wear on the inside inch of the tire. It is worth noting that the wear is not on the tread so much as it is more of a 40 degree angle between the tread and sidewall. It almost looks like the tires are rubbing but I dont think that is the case. The tread is starting to separate.I also had them rotate the tires 4 months ago and they mad no mention of any problem at the time. All 4 tires are in this condition.

It is also worth noting that my wife has put 25k miles on the car since the tires were installed. The tread has about 40% tread life left. And nearly all of the miles are freeway for her 40 mile commute to work.

They explained that Mercedes only has toe adjustment and that to fix this I would need to go to a frame guy. However, he also said that it is standard for german cars to have slightly negative camber for better handeling.

Well then why would I fix something that Mercedes intended in the design.

They also said they only did a front alignment and that they adjusted the toe slightly in to compensate for this. I dont understand this. This is why I am looking for someone who can help me. I would like to go back and ask the tires shop some more questions but I need to be more prepared.

I will upload pictures tomorrow!
Pictures Included!!!
### UPDATED ### 09/12/07
I took these pictures today while at a shop that does alignments.Te mechanicput it on the rack and printed out the results. Toe out was something like 3/32 out on both sides. The mechanic said it should be in if anything.

Thanks,
Greg

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RE: Need Expert Opinion on Wheel Alignment
 

Hi Greg,

IMHO this type of tread wear does seem to be prevalent on MB.
I'm also "shocked" by how my owm tyres have worn in this manner although the front tyres also have the outside shoulder worn ASWELL. I don't rotate tyres since this often introduces vibration problems once the rotation has taken place.

There are no sharp edges or "diagonal" shape to any of the blocks on the main tread pattern (on my vehicle) so this suggests the track is OK. How about yours?

Now the key to this is wether the track is REALLY CORRECT.

BE AWARE MB have a special way of carrying out track adjustment for some reason.
It appears that the sills of the car MUST BE horizontal when the check is carried out and this is achieved by loading the vehicle.
Also some models have to be fitted with a "spreader bar" between the two front wheels/suspension members when the check is carried out so that the check is carried out at a known cambersetting.
I'll bet your "local" (non MB) shop didn't do this. In which case the settings that they will have used MAY BE incorrect.
Toe (In/Out or track) changes with Castor angle (the lean backwards of the "king pin" axis) which during measurement is dependent upon vehicle attitude.
MB use a significant amount of Castor angle (self centering).
Camber which is likely negative (out at the bottom) is typical these days BUT this sould not cause just the shoulder to wear but an even "more wear" towards the centerline of the car ACROSS THE FULL TYRE WIDTH.

If four wheel alignment is carried out on either the fronts or the rear I would expect a hard copy document (paper report printed by the alignment equipment) to be presented giving the results INCLUDING a comparison with specification. These results are of course dependent upon the equipment being correctly calibrated and used in the first place!!

So is the track on your car correct?
Can't be sure because it has been altered from original settings either correctly (to counter suspension settlement) or in error. I know that mine is correct.
The equipment usedto set track in the factory is extremely accurate (sets to within 5 minutes) with complexand regular calibration processes to ensure accuracy. Although I ensure my track is correct periodically I insist that adjustment is not carried out without my EXPRESS permission.

Out of interest Iwhat make AND TYPE/SIZE (i.e. Low profile?) of tyre is your car fitted with, does your wife do a full lock reversing manoeuvre getting out of your drive or parking lot every journey...I suspect so.

In which case I believe that this wear is due to the "excessive" castor effect at full lock which although giving good self centering on the steering gives the tyres a hard time when at full lock. (Look at the crazy angle of the wheel at full lock)

Interested in yourresponse.

Stuart

40k miles is in my view a good mileage to have achieved on a set of tyres. S Class knocks them out in a fraction of this.

RE: Need Expert Opinion on Wheel Alignment
 

Stuart,

Thank you for taking the time. You have peaked my interest in understanding the science of alignment.

I have posted pictures of the tire wear while I was at another shop today and told the mechanic I would pay him just to tell me where the alignment is at. He yes and supplied me with a print-out.

Here is what it said:

Left Front:
Camber: -0.8°
Caster:5.5°
Toe: -1/16in

Right Front:
Camber: -1.3°
Caster: 4.8°
Toe: -3.32in

Front:
Total Toe: -5.32in
Steer Ahead: 0.02°

Left Rear:
Camber: -1.6°
Toe: 3/32in

Right Rear:
Camber: -1.7°
Toe: 1/32°

Rear:
Total Toe: 5/32in
Thrust Angle: 0.06°

So according to these measurements it looks obvious that the front toe is off. As far as the track goes, will these numbers tell you anything? Either way I will ask the when I get the realignment. I beleive the tire size is a 235/40 18 if I remember correctly.

Im sure she cranks on the wheel until the power steering pump screams in protest but I feel that the reall damage is the driving about 80 to 100 miles aday on the freeway with excessive toe out.

RE: Need Expert Opinion on Wheel Alignment
 

Hi,

Not sure I am EXPERT assistance!

The figures do appear to suggest the track (=toe in/out) is incorrect however I have not checked to confirm that the comparison data is compatible with MB data.

Were the readings taken in line with MB procedure?

So the conclusion appears to be that the original garage that tracked your car did it incorrectly.

I note however that the RHF Camber is excessive and wonderwhether this front tirehas at some time contacted the kerb? Alternatively the bottom ball joint and bushings should be inspected for wear / age collapse.

I also note that you are on 18" wheels. Low profile tyres are much more sensitive to incorrect camber, and to a lesserdegree toe, due to the square nature of the shoulders. Higher profile tyres e.g. 60 or 70 tend to have much morerounded shoulders. Theadditional width of the tread on the road also amplifies camber issues. IDEALLY toe should be zero at motorway speeds. Toe is usually set to 1/8" in (with rear mounted steering rack) so that any "slack" in the system is taken up. Of course toe is sometimes used to impact cornering characteristics.

Although it is difficult to tell on the pics it looks as though the tyres are at a "legal" minimum depth anyway irrespective of the innershoulder wear. Notethat the rubber compound on the tread is much harderthan the rubber on the sidewall. I suspect that the inner wall/shoulder has been in excessive contact with the ground. Are you sure you have been running at the correct pressures...on a known calibration gauge. In the UK tyre pressure gauges are notoriously inaccurate.

So whats the bottom line...........

Check suspension bushings for wear/settlement.
Establish what might be causing the different Camber side to side.
Reset toe to MB recommendation using MB procedure.
Fit new tyres...possible a different manufacturer.... BUT one recommended by MB.
Ensure pressure are correct.
Inspect for inside shoulder wear more frequently.

Even with all of the above I suspect that you will still experience something similar to this condition next time you tyres are nearingthe end of life.

Sorry I can't be of any moreassistance.

Stuart