As you'll recall I've had an ongoing alignment problem with my E430 Sport which only began when I paid the dealer to align it at it's first service as a precaution. Prior to that it showed no unusual tire wear at all .

They re-aligned it twice, but I asked that they check it a third time, as now I was getting excessive tire wear on the inside edge of the right front tire.

So, I had the dealer re-check the car the other day and according to the printout (which I have) everything is within spec EXCEPT the caster. It's a bit on the negative side of tolerance, but nearly the same on both sides.

Spec is positive 5.37 degress +/- .5 degrees. Mine is set at 4.5 degrees on the left and 4.7 degrees on the right. Now my question, could this cause any unusual tire wear on the inside or outside edges?

The caster shouldn't cause tire wear!! However if you remember I suggested that once tires have a abnormal wear pattern they will continue to wear unevenly. One of the problems with radial tires is uneven wear. Most tire companies recommend rotation every 6-7.5k miles. Even Michelins will wear unevenly if they aren't properly cared for. AT the dealer I worked for the alignment "machine" had to be recalibrated every 9-12 months(& it is one of the best!!) Could that be the problem?? Is there any good alignment shops in the area that can check your alignment & print out the finished spec. sheet?

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MERCEDES BENZ MASTER GUILD TECHNICIAN
ASE MASTER TECHNICIAN
27 YEARS M.B. TECH

Caster in not generaly considered to be a wear angle. Especialy a the low degree that you are at. High degree setting ie.10deg and above can cause some wear. Mostly with agressive type cornering. I dont think that this is contributing to your problem.

Thanks for your replies. The shop foreman at the dealership has been very helpful with this issue. During our conversation he told me they have their Hunter machine calibrated every 6 months and that he was as certain as was possible that it was accurate. When they had re-alignmed it previously he admitted the rear toe was out and that probably was why the tire was showing some unusual wear on the inside edge, as it had been rotated rear to front.

I think MB Doc is right and I'll look for another shop that can give me a second opinion.

The aggravating thing about all of this is that the alignment, wheel position, etc. had been nearly perfect beforehand, and all I wanted to do was to ensure I wouldn't experience unnecessary wear. It seems by having them align it I caused the precise problem I was trying to avoid! @#$%!

Basic alignment adjustments:
front camber and caster.
front and rear toe.

if all of these are ok, what should not be overlooked is when the caster sweep is done, the included angle (SAI) should be checked. If these do not match from side to side you can consult a chart to show you what is BENT.
one bad pothole can do it. I got a good Toyota chart from a GM tech that used to also work on Toyotas...

good luck

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... (cont)
After replacement of the rack, I notice much better directional stability and apparently reduced wear. Has yours been checked?

Jerry,

(previous message truncated)

The dealer elected to replace the steering rack in my new E430 as a little surprise at my first A service. While I had noticed it drifted a little at high speeds... I chalked it up to the E's usual traits. The dealer just "tossed in" a new rack when they saw uneven front tire wear at 8K miles... and the result is much more stability. I trust that by now your dealer has looked at the rack very carefully, but who knows?

One thing I am getting from all of this is "If it ain't broke don't fix it". I have had customers come in and say "I need an oil change and rotate the tires and alignment" I always ask if they need the alignment or if they just want me to check to see if the tires are wearing abnormally or the steering wheel is off center.

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Benzmac:
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

In my case I simply asked for routine "A service" with 7K miles on the clock. The dealer says, "Hey you need a new steering rack, by the way". The resulting car is much less prone to drift at speed. Jus' wonderin' who else may be in need a a little steering rack replacement!

I'm not alignment expert (thought i use to work in a garage and did some alignments with a Bear unit). Would tire pressure be a factor in uneven tire wear? Just though i could help and cover all your bases.