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some DW info w/links

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by jimmy88, May 5, 2002.

  1. jimmy88

    jimmy88 1/2 ton status

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    Learned a lot more than I can put in this post and the Jimmy’s to do list ain’t getting any shorter, so here’s some of what I’ve learned to date. Hopefully it will help some of you solve your DW problems.

    I’ve talked to BFG tires, Dana (Traction Tech Division), ProComp tires, Interco tires, Skyjacker, emailed Rancho, and others, as well as doing searches on the web. GM and Chrysler told me to see the dealer and would not forward my questions to an engineer. I’d still like to talk to an automotive engineer and maybe that will happen. Most of those I contacted thought DW was rare and didn’t know much, if anything, about it. Its been a little disappointing, since there seems to be no single major cause DW and not much interest in the problem from the automotive community as a whole. Here is the response from Rancho which pretty much sums up the situation:

    Dear Jim,
    Thank you for your interest in Rancho products. Probably the biggest cause
    of violent front shimmy other than a problem with the balance or roundness
    of the tires and wheels or worn components is not enough positive caster.
    This situation can be made worse if the truck is lifted and the front axle
    is rotated with shims to lessen the front pinion angle to help straighten
    the front driveline. In addition, this angle is not usually adjusted when
    aligning a stock vehicle so may not be corrected if the truck is aligned by
    someone not familiar with these vehicles and often the alignment is not
    checked after lifting straight axle trucks.


    At this point I have to agree with Rancho that tire/wheel balance and run-out, worn or damaged parts and alignment settings are the leading factors in DW. While steering stabilizers or panhard rods may help minimize the problem, they can only do so much. Its going to come down to getting your tires/wheels balanced and round, the suspension tight and the alignment settings right for what tire and suspension your running. Once all that’s REALLY been taken care of, I’ll bet the majority of the severe DW will be gone. Just my 2 cents and worth about that much, so check out the links and decide for yourself.

    Here are links to some good info.

    EXCELLENT WHEEL BALANCE AND ALIGNMENT INFORMATION:
    PDF file 1.07MB takes some time to download but well worth it.
    www.ingallseng.com/terms.htm

    Interesting but scary camber shim (looks like it might transfer the spindle load to the studs):
    www.trucktires.com/library/publications/periodicals/RealAnswers/97V1Issue3/Doctor_expl.htm

    (Note the inside the tire balancing weight patch)
    www.tirerack.com/wheels/tech/centerb.htm

    Tire term definitions:
    www.sae.org/automag/scrubradius/


    Here is what different alignment sections list as possible causes for shimmy:

    Wheel and Tire Assembly Lack of Dynamic Balance
    Wheel and Tire Assembly Runout (Lateral)
    Incorrect Caster (too much or too little positive caster)
    Incorrect Toe
    Defective / Worn Suspension or Steering Components
    Worn Tires
    Under or Over Inflated Tires
    Excessively Loose Wheel Bearings
    Steering Gear Loose


    I got a ex corporate guy suppose to be hooking me up with info (off the record, of course, stupid liability crap and all). We’ll see.
     
  2. m j

    m j 1/2 ton status

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    so basically you cannot run swampers.
    they dont come round
     
  3. TwoCrowsDesign

    TwoCrowsDesign 1/2 ton status

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    Good read Jim, thanks for doing the research.

    John
     
  4. jimmy88

    jimmy88 1/2 ton status

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    When I talked to Interco the tech guy didn't know too much, he said they don't make all their tires in house and he would have a tech from Dennman?(my first thought was the ground hawg people, should have asked) call me, but that never happened. Figure that would have been an intresting discussion. I didn't know that BFGoodrich sold the tire line to Michelin either, guess you never really know who really makes your parts.
     
  5. Thumper

    Thumper 1/2 ton status

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    Well, thats what I said a while ago. The Swampers on mine caused the DW big time, but the radials didnt cause it at all. But, when I adjusted the toe to compensate for the change in Bias to radials, it stopped the DW with the Swampers. Then when I swapped back to the radials, I adjusted the other way. If I forgot to adjust it, the DW would come back with either tire.
    Mike
     

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