300E (W124) alignment running out of range?
 

I have a 1993 300E 2.8 whose front tires are wearing out the outer edges really fast. It had a 4 wheel alignment several months ago but no help. The MB indy shop that I frequent checked it out and told me that the alignment is already at the extreme positions and cannot be further adjusted. He recommended that the control arm be bent to correct the alignment problem. He claimed that this is a common issue among W124 since the range of adjustment is pretty small and we'd easily run out of range by now with the suspension sag over time. Does this sound right? I did a search and found no posts on this issue.

Thanks,
Ying

I'm not an alignment specialist, but I a have a solid understanding of the basic principles.

If your issue is suspension sag, then the problem is CAMBER. And it seems to me that the INSIDES of your tires would be more likely to wear due to spring sag, than the outsides. Plus if your suspension sag is beyond the adjustment limits of your control arms, then you need new springs -- or thicker pads if you're not already at the max.

How does the car track (drive down the road)? Is there any vibration at highway speeds.

What you're experiencing (outer tire wear) is a classic sign of excessive toe-in. Any tech who knows which end of a screwdriver to use knows that, so we have to assume that your guy has already checked the toe-in, and that it's within spec. (Although we shouldn't Ass-u-me.)

I'll let one of the professional techs chime in about bending control arms (yow) and the notion that it's common practice. Frankly, I've never heard of it... and it doesn't seem to make much sense to me.

Again, if your suspension is sagging to the point that you need to bend your control arms, something is wrong! Ask yourself this, "Did the control arms come pre-bent from the factory?" What you need to do is restore the suspension to factory spec.

I'd get a second opinion. Are you sure this is an MB specific shop. Sounds questionable.

Just my 2 cents...arguably worth that.

Jeff Pierce

I've never done an alignment on a 124, but I've done plenty others. I've never seen a Benz that didn't have gobs of adjustment available for dialing in the alignment. Until one of the Benz pros says different, I'd avoid bending anything.

Can you post the alignment measurements so we can see where the problem is?

I concur with Mr. Pierce. I think it's time for a new shop.

The car started life with negative camber on the front tires - they tip inward at the top, rather then standing straight up and down. As the car ages and the suspension settles, the front will develop additional negative camber. As you can imagine, negative camber wears the inside edge of the tires, not the outside.

I'm assuming you don't have positive camber. If so, the tops of the tires would be sticking out of the wheel wells, dumbo style. Failing that, only excess toe-in will cause the outside tire wear.

Time for a second opinion. Of course, maybe you just drive around corners really fast.

- JimY

There is no vibration up to 75mph (I don't usually drive faster than that) and the front end doesn't pull in any direction. Unfortunately I didn't ask for any measurements when the alignment was done. The shop who recommended bending the control arm was a different shop than the one who did the alignment and couldn't do the bending themselves, so maybe it's case of incompetency here.

Any recommendation for an alignment or general MB shop in the San Jose CA area?

Thank you for all the insights. I was suspicious myself and now I have confirmed it. This forum has been of great help to me.

For a w124, the shop MUST use the mb spreader bar...

A regular shop will put the car on the rack and set the alignement to the specs WITHOUT the required spreader bar. Then, at highway speeds the alignment toes out and the car wears the tires.

The important place to start on alignments and the MB techs on this list helped me! I set the adjusters all to the center of their position. Front end has a bunch of alignment adjustment. Only possible way I'd belive that is IF your car has been in a hard collision.

Most ppl take seem to have the best luck with a good MB dealership doing the alignement or a shop which KNOWS mb's.

Michael

Go to the dealer. It will only cost you about $30 more, and you know it's done right.

It's money well spent. Alignments on these cars last for years... some say decades.

Jeff Pierce

Wheel goes into positive camber when turning?
 

I thought about this alignment going out of range issue all over again and thought that something else might be wrong. Indeed today I noticed that when the front wheels are turned to one side, the inner wheel (e.g. left wheel when turning left) goes into positive camber very significantly, to the point where the inner edge of the tire is not touching the ground (when the car is stationary). The outer wheel seems ok, when observed with my untrained eyes. What's the problem here?

I think this is the reason why the front tires are wearing out badly in the outer edge.

Thank you very much for all the help.

Ying

No problem. MB uses a high caster angle, and that naturally causes what you're seeing. The specification on my car is over 10 degrees.

Same here. It's the way the car is. The only way to minimize it is either take it easy going around corners or rotate the tires to try to even out the wear. I do the latter more than the former, but still, every set of tires I've ever changed out on the car has always been with the outer shoulders worn bald with tread on the inner shoulders.

Alignments only are as good as the condition of the suspension. A first step to diagnosing any alignment problem is to inspect suspension and steering components for out-of-tolerance. This includes ball joints, struts, tie-rod ends, and idler-arm and A-arm bushings. Wear in any of these items can cause alignment on the road to be dramatically different from that found or adjusted on an alignment bench.

Steve

If it is normal that when the front wheels are turned to one side, the inner wheel goes into a fairly large positive camber, then wouldn't it be unavoidable for the outer edge of the tire to be worn out quickly? The couple of recent posts and my own experience seem to agree with this conjecture. My lowly VW didn't do that. Why would MB choose such a design? Is this not adjustable (beyond the normal alignment adjustments)?

Thanks,
Ying

No. This condition only exits near lock, so it is during low-speed maneuvering. Unless you fling it around in parking lots, it will make a miniscule contribution to tire wear. Some 99% of driving is done with the wheels nearly straight ahead, so alignment in this condition is the most critical.

Steve

Alignment angles are measured and adjusted when the vehicle is at rest. But, they have to work when the vehicle is in motion. Alignment specifications generally aim for a compromise between tire wear and vehicle stability. If alignment specifications were such that each wheel had 0 camber and optimal toe regardless of steering angle, the tires would show minimal wear, but the vehicle would have very little on-center stability, and you would not enjoy having to constantly correct the steering inputs in response to every bump or groove in the pavement. Not to mention the safety hazard involved with dynamically unstable steering.

Yes, you can adjust the caster angle on a Benz, but not so far as to significantly change the camber changes in turns.

I am also not yet convinced that your edge wear is being caused only by camber changes in turns, unless you drive only in circles.

MB when properly aligned -stay aligned- and have great tire life!

I like the mb rec-balls steering. It's mellow on center for highway driving and high speed, yet it's non-linear nature still responds bigger response.


Michael