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Thread: Tire cupping anyone?

  1. #1
    Z8 Addict Z8doc's Avatar
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    Question Tire cupping anyone?

    My Tires have worn evenly since owning the car, routine alignment checks, wheel balancing and air pressure (normal air, not Nitrogen). Had the performance package installed 6 months ago with no sign of abnormal wear at installation except what you would expect for the negative camber of a BMW. Less than 2000 miles since the installation of the PP.

    I have been preparing for the installation of the Brembo Big Brakes and new wheels and was looking over my tires with my tire supplier today. There is significant tire cupping on the inside edge of right front and minor cupping on the left front tire. The rear tires, wear bars are exposed evenly with no abnormal wear despite 2 degrees of negative camber in the rear.

    Cupping can have multiple causes including poor tire balance, bad wheel bearings, bad front end bushings or my fear.... bent suspension parts, namely -- front strut or frame?

    Tire wear is something that occurs exponentially... meaning that you even if something is out of round like a tire or wheel balance, the wear over the first 10,000 miles will be minimal but you will get moderate to severe wear in the next 5,000 miles due to degredation of the molecular bonds in the rubber.

    Questions are, a] is this cupping something that has been caused by something done at the time of the PP installation? or b] the progression of a previous unrecognized problem like a wheel bearing(s) going bad or control arm bushings needing replaced (I do have 43K miles) or tires that were poorly balanced or c] a slightly bent frame that was unrecognized by the inspection process (the right front fender does bend in ever so slightly?

    Any one else noticed any tire cupping on one or both front tires after PP installation?
    Best Regards,

    Jeff
    61995 Silver /// Rot - Original Owner
    Z8 Club of Germany e.V. #102

  2. #2
    Could you post some pix or diagrams, I've never heard of this before, but I guess it is always good to be aware of new things!
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  3. #3
    Z8 Addict Z8doc's Avatar
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    Andrew,

    Here is a link that decribes the various patterns of tire wear and possible causes.

    http://www.procarcare.com/includes/c...dtirewear.html

    I am sure you have seen some of these wear patterns before but maybe just never though much about what they might mean. (Incidentally, just an FYI since I know your love of the 2 wheeled vehicles -- tire cupping on a motorcycle is generally considered normal if it occurs on both sides of the tire, if it occurs on only one side, abnormal).
    Best Regards,

    Jeff
    61995 Silver /// Rot - Original Owner
    Z8 Club of Germany e.V. #102

  4. #4
    Wow, that looks rather scary, is it as pronounced as the diagram?
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  5. #5
    Z8 Addict Z8doc's Avatar
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    Actually, the right front tire is nearly like the diagram and yes, scarry looking for sure. I have been having some increased "shimmy" in the front at around 45 - 55 mph of late that nearly goes away (like a wheel that needs balanced) but then returns again around 85 mph. Also, the car seems to want to track / drift to the right as well.

    Not sure if this is a serious problem or just a wheel out of balance and alignment. I plan on having it evaluated thoroughly when I take the car in soon to have the brakes done. Since the rotors will be off, it is easy enough to see if the RF wheel bearing is bad or not at that time. That fix is only a few hundred dollars including labor.

    Hopefully, it is just a wheel alignment / balance issue and can be easily corrected.

    My dealer is the last one to have aligned my car at the time of the inspection. I have had problems with them not being able to get the car aligned properly when they originally did my Dinan upgrade, even though they have a Hunter machine.

    Because of that, even though I will have them align the vehicle after the brakes, I will get a second alignment done at an independent shop once the whole job is done (tires, wheels, brakes). The independent shop I used last time has a Hunter too and does 4 wheel alignment on high end cars (local Ferrari club uses them). They successfully corrected the problem before when I had the suspension upgrade so they will be my verification. I did not have them recheck it after the dealer did it at the time of the inspection 8 months ago and probably should have.
    Best Regards,

    Jeff
    61995 Silver /// Rot - Original Owner
    Z8 Club of Germany e.V. #102

  6. #6
    At your mileage, and bearing in mind the use you've put the car thru at the track and on other high speed runs I'd suggest popping in new front bearings because they are such an easy thing to do while everything is off and out, plus it may well help sort out the issue - it certainly can't hurt.

    I also think it is much better to get your alignment done by a specialist shop, sadly in my experience most dealers have the kit, but get the tea-boy to work the Hunter as an after thought. A Hunter machine is only as good as the person operating it. Setting up a car right takes experience, time and pride, rare things to find in the alignment bays at big dealerships.
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  7. #7
    Z8 Addict Z8doc's Avatar
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    I understand the "tea boy" statement as a generality but the suspension mechanic at my dealership is a 10 year BMW veteren and only does suspension work and alignments. However, he is not a certified Z8 mechanic nor has the dealership sent him to get Z8 training so some nuances he may not know. I had already decided to do the wheel bearing too because as you pointed out, easy to do now and the milage.

    I agree and although this alignment endeavor will cost me double (one at the dealer and one at the specialist) but there may be a lag between the first and the second, I have to have the dealer do one first. Oh, well, the price of being sure.

    I can not get either the Motul or Super Blue locally so I will more than likely go with the Super Blue since the Amber 200 they make is to the same specification which make switching out easy.

    Thanks for the help and I will post once the job is complete and I have the pictures.
    Last edited by Z8doc; June 25th 2007 at 00:08.
    Best Regards,

    Jeff
    61995 Silver /// Rot - Original Owner
    Z8 Club of Germany e.V. #102

  8. #8
    Z8Mania
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    Jeff, if you brake really hard does the car pull to one side really hard?

  9. #9
    Team Z8 KenZ8's Avatar
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    Jeff, have them look very closely at the control arm bushings. My shimmy symptoms were very similar until they were replaced. When they inspected them the first time, they did not notice hairline tears. When they reinspected (after rebalancing the wheels twice, road force balancing the wheels, replacing the rotors, pads, and basically rebuilding the calipers), they chose to pull the bushings, at which time they disintegrated in the mechanic's hands. The damage was not readily visible, and the car had much lower mileage than yours. The result has been no more shimmy.

  10. #10
    Z8 Addict Z8doc's Avatar
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    Jerry,

    It pulls a little to the right under hard braking but mainly just wants to drift right while driving. I have to constantly correct to the left to go straight. It is not a hard fight but just something you have to do. Does that make sense?
    Best Regards,

    Jeff
    61995 Silver /// Rot - Original Owner
    Z8 Club of Germany e.V. #102