Pegasus wrote:Billy when you scale a car what side to side weight on the rear do you go for.
Page 15 of my site has a spreadsheet for the wheel loads necessary to achieve equal rear tire loading as the fronts lift. In other words, the RR is going to be very heavy as you sit on the line, but, as the driveshaft torque increases from zero to the value which causes the fronts to lift, the RR and LR loadings will approach the same value.
And, this is why I don't recommend this sort of thing. You only have equal rear tire loading at that final instant. Up to that point, you're most likely going to veer to the left. So, if you set the car up on the scales with equal rear tire loading, you lose performance as the driveshaft torque upsets the loading. If, on the other hand, you put in enough preload to give equal rear tire loading at peak driveshaft torque, you could end up with an ill-handling beast.
Obviously, the ideal arrangement would be to have equal rear tire loading on the scales AND equal rear tire loading for any value of driveshaft torque. But, the only way this can happen is for the car to supply a canceling torque exactly equal to the driveshaft torque.
Let me answer this other post and you'll see that this can be done.
So using scales is a waste of time
No, not at all! I consider wheel scales a necessary investment for any serious dragracer.
SaskCharger wrote:Well then my next question is how to build this asymmetry. The only real adjustments are spring/t-bar, shock dampening or the preloading of one of the ladder bars, right?
Wrong! You're missing one, but it's at the other end of the car. And, with a ladder, this is about all you have! At the front of the car, I would assume you have identical front coilovers. Now, consider what would happen during launch if the RF coilover had a higer rate spring than the LF coilover. As the front of the car lifted, the RF spring would lose more load than the LF. Since the sum of the RF and RR must always be equal (otherwise, the car would be rolling over), that means that most of the weight transfer is going to the RR. And, if you have exactly the right ratio of RF spring rate to LF spring rate, the driveshaft torque value would not affect the rear tire loading.
Of course, you won't find exactly what you want in the spring suppliers' catalogs, but you can get very close. Read Pages 34, 35, and 16 at my site.
(This same sort of thing can be accomplished with the proper adjustment of a 4link. See Page 19.)
Finally, I recommend use of a traction dyno as a final check on your work.http://www.racetec.cc/shope