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Caster settings on a SFA Chevy?

Discussion in 'The Garage' started by sled_dog, Oct 15, 2005.

  1. sled_dog

    sled_dog 1 ton status

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    Alright if my memory serves me right the factory Caster angle on a 73-91 Chevy is 7*. Can someone explain why this is?

    I mean with a load in the bed it will only go more positive. It seems to me we have more then a few degrees of caster to play with to set it up where we want it.
     
  2. Afireinside

    Afireinside Registered Member

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    I dont think caster really changes with a load in the bed.I don't know what the factory spec. is but I would love to.How much are you trying to play with?
     
  3. bernman

    bernman Registered Member

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    depending on how sagged the front and rear springs are you should have 7-8 degrees of caster, that all needs to change once lifted though, and anytime the rear of the vehicle is loaded or lowered the caster will increase
     
  4. BigCountryx

    BigCountryx 1/2 ton status

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    So does anyone know what the minimum amount of caster that is acceptable? As in how many degrees can the front axle be shimmed before caster is unacceptable without spinning the axle tubes.
     
  5. bernman

    bernman Registered Member

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    it depends on where and, how you drive i have about 6.5inches of lift, and about 4 degrees of caster on my blazer, and pinion angle is very acceptable, i think most people will find this acceptable for their rigs.
     
  6. bernman

    bernman Registered Member

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    what are you planning to do with the truck?
     
  7. BigCountryx

    BigCountryx 1/2 ton status

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    I need the truck too have decent street manners.
     
  8. bernman

    bernman Registered Member

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    my truck drives great with 4 deg caster, yours should too
     
  9. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    According the my 1973 GM Service Manual, and my brother, who's a tire wheel engineer for GM who looked up the spec for a '91, the K10 & K20 Alignment specs which matched the ones in my 73 GM service manual, so 1973-1991 K10 & K20 are as follows:

    Caster: +4* Not resettable (well it is sligtly if you use different length schackles)
    Camber: +1.5* Not resettable (well it is with the upper ball joint special sleeve or the camber shim between the spindle & knuckle)
    Toe: 3/16" (exc K10 w/ Full time 4wd= 0")

    Tolerances are as follows:
    Service Check:
    Caster: +/- 1*
    Camber: +/- 3/4*
    Toe: +/- 1/8"
    Camber (Sdde-to-side): 1*
    Caster(Side-to-side): 1*

    Service Reset:
    Caster: +/- 1/2*
    Camber: +/- 1/2*
    Toe: +/- 1/16"
    Camber(side-to-side): 1/2*
    Caster(side to side): 1/2*

    (Service check states: Values within these limits should provice a high level of customer satisfaction and shoud not require resetting
    Service reset states: Values that the vehicle should be set within if it observed out of the service checking tolerace or if it is being aligned due to replacment components or for any other reasons)
     
  10. bernman

    bernman Registered Member

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    i am not referring to any spec guide, i am referring to the hundreds of alignments i have done to these trucks, and most have about 7deg of positive caster in stock trim. some suburbans come clocer to about 9deg.
    due to rear end sag.
     
  11. sled_dog

    sled_dog 1 ton status

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    Hunter spec book says 7*.
     
  12. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    Just telling you what the GM service manual says, and what GM's internal database says. Those alignment machines in the field are notorious for having the wrong specifications. Take your pick.
     
  13. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    I vote for 7 or 8* I got mine set at 8* when the knuckles were put on.
     
  14. Afireinside

    Afireinside Registered Member

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    Can someone please explain to me how caster changes with a load in the rear.
     
  15. sled_dog

    sled_dog 1 ton status

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    when you load the rear the rear sags. The truck pivots on the front axle in that instance and bam the knuckles turn back as the load increases, thus creating more positive caster.
     
  16. Afireinside

    Afireinside Registered Member

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    Could someone please explain a little more.The only way what your saying could actully happen(the way I see it)is if you had longer front shackles and they were at an angle(like running 52s up front).All stock front shackle angles are pretty close to 90* so I still can't picture what you'r saying.Thanks
     
  17. bernman

    bernman Registered Member

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    when you load the rear of the truck, the rear squats down and your trucks frame angles backward, now since your front axle is permantly bolted to your frame via leaf spings, the front axle also leans back (or positive) this is true for all vehicles. the opposite is also true, if you lift the rear, caster will move in the negative direction.
     
  18. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    Who works at an alignment shop and can actually see how much the caster changes on a loaded truck, if at all? Anyone?
     
  19. Afireinside

    Afireinside Registered Member

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    Xs 2
     
  20. monster man

    monster man 1/2 ton status

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    I can see it changing a degree or two, especially if it were a very shortbed like a blazer. But I think it would have to be loaded DOWN, like with a ton of concrete to be noticeable
     

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