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All Wheel drive tire change

With All-Wheel drive, do I need to change all 4 tires (together) if I've injured 1 tire? The dealer said they all need to rotate at the exact same speed, and a tire with 25K miles will spin faster than a new tire, and will burn up my transfer case. Kinda expensive either way! Thanks for any advice...

Comments

  • edited January 2010
    Ask if they can have the new tire shaved down to match the worn tires. This is a service tire retailers now provide just for this problem.

    Tester
  • edited January 2010
    You need to find a shop that will shave a new tire to match the other 3.

    Or give the folks at tirerack.com a call. Good folks to work with.
  • edited January 2010
    It is amazing that they can do that...thank you for the advice. It is a shame to 'shave' a brand new tire, but better than buying [4] new ones! And, a lot cheaper than a new transfer case! Have a good night-- JD
  • edited January 2010
    So are you not allowed to turn the steering wheel either? The outer tires turn faster in a curve.

    God forbid one tire has 5psi more air than the others (the higher pressure will make the diameter about as much larger as the new tire).

    Are you allowed absolutely zero toe in angle? (Toe in makes the front tires rotate slower than the rear tires... much more so than the change in diameter of 25k miles of wear).

    The full time four wheel drive system in your Jeep allows a reasonable amount of slippage between the rotation of the front axle input and the rear axle input.

    This slippage is facilitated by clutches (not unlike automatic transmission clutch packs) that are bathed (and cooled) in automatic transmission fluid.

    This slippage is necessary to prevent overstressing the driveline while driving on pavement, due to the things like toe in, differing tire pressures, slightly different tire diameters, etc. All the things that make the front axle turn at a very slightly different rate than the rear axle.

    Quite frankly, in order to burn these clutches out, you'd have to put go-cart wheels on one axle and drive down the highway in full time 4WD.

    The differing rotation caused by a tire with 25k less wear is not unlike the differing rotation it already deals with.

    Measure the circumference of your 3 tires. You will be lucky if they are within an inch of each other - very lucky if they are within a half inch.

    Bottom line. They don't want to shave 1 tire... they want to sell you 3 tires you don't need!

    $+$$$
  • edited January 2010
    Interesting. I recall these machines many moons ago in the days of bias ply tires. I didn't know they were still around.
  • edited January 2010
    The problem is that differences in tire diameters are constant where turning has a duration of a few seconds. Some AWD units are quite sensitive to differences in tire diameter - some are not. This board has had many, many posts of failed AWD units because of differences in tire diameter - and many of those vehicles have notes in the owners manuals about the subject.

    But some AWD units are pretty insensitive to tire diameter - but it is difficult for a tire shop to know which are which - and since they are usually held liable if an AWD unit fails after replacing a single or a pair of tires, they use universal rules that will prevent damage in ALL situations.
  • edited January 2010

    Who needs a machine??? I had no problem shaving down tires with my 69 Firebird. Ah to be young and stupid again.
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