Not Sure......

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  • Mod66x
    Senior Member
    • Nov 2009
    • 102

    #1

    Not Sure......

    Not sure we're to ask, so decided to ask here! When scaling a car or truck for dirt does cross% play any part of the process? Or just worry about lr bite and your left% and rear%. Trying something new on dirt and not sure we're to start. Full frame (3 x 4 frame rails), 2x3 front and rear clips (rear is ovER rail), 3 link with steel tube qc, 5x5 hubs, weight is 2800 with driver and no lead. Added 90 lbs to right frame to get 54.6 left% rear is 52.1%, LR bite is 105.
    Lf spring 500 rf 550
    Lr 250. Rr 225
    Any recommendations. ....
  • TheJet-09
    Senior Member
    • Jul 2013
    • 1616

    #2
    Cross % is typically something you only hear referred to in the asphalt world, at least from my experience. In dirt you'll usually hear/talk about left side%, tail weight (rear %), and bite (amount LR is heavier than RR). Where and what are you racing (a Sportsman type car? Tires? Engine?)? Is it coilover or conventional type springs?

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    • Mod66x
      Senior Member
      • Nov 2009
      • 102

      #3
      15 x10 steel wheels on Hoosier D-35s, coilover, 355 with Holley 500cfm carb, will be running in a sportsman division until division grows (if it does), T-10 trans with 3 disc clutch. 1/2 mile track semi banked. This was a South East Super Truck(asphalt)...
      Attached Files

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      • drtrkr244
        Banned
        • Dec 2007
        • 1024

        #4
        I have converted an asphalt mod to dirt so I have a little exp with this.I would swap those front springs, because ur going to need to be much tighter.I would also increase rear % to 54. Try moving the lead as close to the rearend as possible, even right behind it, if that's what it takes.You can start with that and then look at raising motor/fuel cell if you don't get enough side bite. Good luck!

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        • bob75
          Senior Member
          • May 2007
          • 2814

          #5
          cross is lr bite

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          • hpmaster
            Banned
            • Aug 2009
            • 1088

            #6
            Back in the day, I was told by CJ Rayburn that crossweight was to be within 2 or 3 percent of your left side weight. If he still believes it or not I do not have a clue. One of my older still very competitive friends swears by 2 percent MORE than left side numbers, he has raced pavement and dirt for over 30 years now. I have not worried about crossweight in years.

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            • Matt49
              Senior Member
              • Jun 2007
              • 3123

              #7
              Originally posted by bob75 View Post
              cross is lr bite
              Partially true. More of one certainly means more of the other but how the numbers correlate differs depending on left% and rear%.
              Cross% actually makes way more sense to track as it takes the entire weight of the car into account where as "bite" doesn't.
              In other words, 100 lbs of bite in a 2300 pound car will provide VERY different handling characteristics than in a 2800 pound car.
              If you keep the cross% the same...not so much...

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              • Mod66x
                Senior Member
                • Nov 2009
                • 102

                #8
                How is cross also lr bite? When cross is a combination % of rf and lr of total weight and lr bite is the difference of weight between rr and lr....

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                • Matt49
                  Senior Member
                  • Jun 2007
                  • 3123

                  #9
                  Assuming total car weight is the same, more bite=more cross and more cross=more bite. There's no way to make just one corner of a car heavier without adding weight. And even just trying to add weight to one corner usually results in changes to the opposite corner.

                  If you saw down one leg of a table, the opposite leg is the one most affected by it.
                  Last edited by Matt49; 08-05-2014, 10:07 PM.

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