For a sprint car, that is not an abnormal weight bias (we run a 600 micro, so there aren't a lot of differences); that rear weight percentage is within the range usually encountered. To change it, you can move the seat, or change the length of the links that locate the rear axle. One important thing about scaling a sprint car, as scales are not usually used in sprint car setup, except as a reference to see if something has changed, as after a crash; whether it is a real setup that you use at any specific track or no track at all, develop ONE setup, including the exact amount of fuel in the tank, that you use for scaling. Without the same setup each time you put it on the scales, the info the scales give you, especially with regard to whether or not the car has been tweaked in a wreck, is not particularly useful. So set the suspension up with the blocks in the usual manner, with some specific amount of turns on each torsion bar (or coil spring) at each corner, the same air pressure in each tire, and the same amount of fuel in the tank, as used the very first time you scaled it. This scaling is done without the driver in the car, and is done ONLY to tell you what the chassis numbers are. After you have that, you can put the driver in the car and see what changes and record that, too, if you wish. A good scaling setup is whatever baseline setup the chassis manufacturer recommends, but that is not not necessary, it just needs to be a setup that you have recorded somewhere, so that you can duplicate it each time you scale the car. Unless we had some sort of prang, we put the "scaling setup" on the car before each season to see where we were at, then repeated the scaling a couple of times during the season, and again after the last race, just to make sure there were no changes going on that we had missed. Scaling is not a tool for setting up a sprint car, it's a tool for checking the chassis and locating any changes that may require attention/repair.
This approach is the same for any size sprint car, though we scaled less with the 358s and 410s than with the micro.
