Inner tire wear/Upper Control Arm

ImperialPunk · Feb 29, 2012

I recently had my 78 300D in to the mechanic to have the oil changed and in the process he discovered that the front tires are worn down to the cabling on the inside. His diagnosis was that the upper control arms and bushings need to be replaced. Does this sound right? I'm fairly sure it's not alignment, because I had it aligned last September (when it was in the shop last).

Secondly, is replacing the upper control arms an involved process? I've found the parts I need online and I'm pretty handy, so I guess I'm wondering if I can do it myself. I'd hate to get halfway through the project only to realize that I need some special MB doohickey tool to complete it and that I shoulda just taken it to my indy mechanic in the first place.

Thanks!

jusme · Feb 29, 2012

I did one in my 1980 300D, drivers side. It was a breeze. If you use a floorjack under the LCA, you can get to the sweetspot that allows the removal of the hardware. It will just "float" in there. Use a quality jack!

300Dman · Mar 1, 2012

There is no special tools needed. With the exception you may need something to pop the Ball Joint out of the upper Steering Knuckle. A genericTire rod puller may work or in your cas a Pickle Fork because you are not concerned with damaging the Ball Joint Boot. That could be a free rental from Autozone.

However, changing the Arms could mean you may need to have a Wheel Alinement when you are done.

You might also want to replace the 2 Rubber parts on the tip of the Sway Bar; 2 per side. The tip of the Sway Bars have also been know to be rusted out. (There is a repair for that; it involves cutting the end of the bar and replacing it with a part that needs to be welded on.)

I was able to remove and install my new ones with no problems; but, only Hang-up I have read concerning the Job is some have had the Bolt rusted inside of the Arm and have had to Saw through the Bolt/Arm to get it off.

That info is somewhere below:
Repair Links
DIY Links by Parts Category - PeachParts Mercedes ShopForum

PeachPartsWiki: Do It Yourself Articles - Mercedes Vehicles

Rmac58 · Mar 1, 2012

^ Good advice.

You don't need that self made tool, the spacer to set, if necessary, the ball joint, I use an open end wrench the same depth.

300Dman · Mar 1, 2012

You might want to recheck thoes threads at the other Forum to besure that the Tire Wear Pattern matchs up with a Upper Control Arm Issue.

ImperialPunk · Mar 14, 2012

For posterity:

Did the job, took about two hours, was easy as pie.

nedro · Mar 14, 2012

sorry I missed this. Upper arm may have been bad, but that does not cause both front tires to wear on the inside. The car was running toe-out quite a bit to cause this. Did you do a simple tape measure check of the front wheels before doing the job?
Did you at least do it after the upper arm R&R?
That last question was stupid since I know you had it aligned after replacing a front end part. My apologies.

Inner tire wear/Upper Control Arm

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