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Thread: Scalloping Tire Wear Diagnosis

  1. #1
    500E Terminus Illuminatus DerFuror's Avatar
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    Scalloping Tire Wear Diagnosis

    I successfully diagnosed a tire wear situation caused by a steering linkage issue & (although non-500E) am passing on the results which may save time & hassle for anyone running into a similar situation.

    Problem: Right front outer tire wear only (Accelerated scalloping of outer edge).
    Cause: Loose/worn idler arm bushing (frame end connection)

    A friend brought a 1998 BMW 740il series in yesterday to find out why only the outer edge (approx 1.5 inches) of the right front tire was scalloping. His distress was heightened because all tires are relatively new; the car had a recent alignment & a follow-up alignment (which made no real corrective difference). Also, having rotated right side tires, two tires were now affected by the progressive scalloping.

    The car is in overall quite good shape, having relatively new steering control components such as tie rods, control arms, etc (factory stickers are still present on many components) and wheel bearings.

    Safely placing the front end up on jackstands, I tested for wheel horizontal & vertical loose play. There was audible horizontal loose play. I then went underneath the car to trace the culprit along the steering linkage while my assistant horizontally rocked the wheel back & forth.

    I easily discovered the problem was being caused by the idler arm connection on its frame-side end. Loose or worn idler arm bushings will cause front end shimmying. I was extremely happy that the problem wasn’t related to a more PITA component and location. The owner is capable of doing the repair & afterwards can still get a complimentary warranty realignment.

    Be aware that the attentive alignment tech should have inspected & discovered this problem beforehand (having had two opportunities to do so). That dealership missed out on a service opportunity & now will be doing a second gratis realignment after component r&r.
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    " Destination ???, It's the ride that takes you there! "
    1993 500E W124.036 040/271
    1965 220b W111.010 Heckflosse

  2. #2
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    gerryvz's Avatar
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    Re: Scalloping Tire Wear Diagnosis

    Thanks for this. Yes, idler arm bushings are an often overlooked culprit for front-end issues, including audible clunking over bumps and such.

    A word to the wise ... DO NOT get non-factory idler arm bushing repair kits (i.e. Febi, Meyle, etc.). GET ONLY FACTORY IDLER ARM BUSHING REPAIR KITS.

    I have a spare kit for my E500 sitting on my workbench in the shop. I was able to slightly tighten up my existing idler arm bushing to cure a very slight front-end clunk at the end of the summer. But it is very likely only a matter of time until this bushing kit needs replacement. On the E500E, clearance from the top is an issue, so have your eyes wide open going into this job if you are going to DIY. It has been discussed on this forum a couple of times.

    Is your friend's iL a chick magnet, too?!?

  3. #3
    500E Terminus Illuminatus DerFuror's Avatar
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    Re: Scalloping Tire Wear Diagnosis

    Quote Originally Posted by gerryvz View Post
    Is your friend's iL a chick magnet, too?!?
    Nah, even with the extended length...Dullsville.
    " Destination ???, It's the ride that takes you there! "
    1993 500E W124.036 040/271
    1965 220b W111.010 Heckflosse

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