Hey all. Back from an apparent ban. First off, if l come across as being a know-it-all, l apologize. I do not know everything. On the contrary, l’m not totally confident about any of my techniques. They work. The math is correct. There just isn’t enough reliable information out there on what to base the math on, and there’s some important specs about the cars missing that we would need to properly set up suspension, so we’re stuck trying to find out what to base our math on.
That being said, this has been tested on rally/off road suspension, but l’m sure it will translate to race suspension. The percentage will just change. I figured it out while tuning GRC’S. I was running a certain percentage of my total weight for my spring rates, but as soon as l started tuning a non-grc rally car, my range either wouldn’t be on my scale, or way on the higher end. So, l’d end up going center rate on my non-grc’s, but was just kind of guessing on my GRC cars. I started checking the center rates against my total weight but was all over the place, percentage wise. Or so it seemed. I was taking my percentage from the total weight, but l started working with my individual front and back weight/loads separately(total weight times your front weight percentage, repeat for the rear), and noticed that the center rate on non-grc rally cars were at 31 pct of their respective weight distributions.
So, your total weight times your front distribution percentage gives you the static load on your front. From there, if you go 31 pct, you’ll arrive at the center of your scale. When l reference center scale, l’m talking about weight distribution, with center of the distribution being center of the scale.
I’ll use my VW grc stats as an example since l have most of the specs memorized. As l said, l haven’t done it with race suspension, but l’m pretty confident, you’ll find the same thing going on, just a different percentage…or maybe the same, but it won’t be random, and gives you a reliable baseline. You won’t arrive at center scale with the grc because it runs all the way to like 90 pct of your load up front, and right at 100 rear, but non grc suspension is probably half of that…give or take. This method just gives you a consistent way to get the same load support on the same type of vehicles. For me, it’s 30 pct on rally cars, and 20 on passenger trucks…for now. 33, 25, and 20 will give you a better understanding of spring support and travel, if that information is relevant to your tuning methodology.
VW GRC beetle
Total weight: 2550
Weight distribution: 54% front
2550 x .54 = 1377 - front load
1377 x .31 = 426.87 -front spring rate.
2550 x .46 = 1173 - rear load
1173 x .31= 363.63 - rear spring rate
You can repeat this for the rear, as l’ve shown here, but l prefer dividing by 1.1739 which you get by dividing 54 by 46. I use this for all my weight distributing. You get 363.46 rear. A fractional variance, so you decide which to use, but my preferred method works when distributing anything, really. From alignment to diff bias, which imo isn’t linear. So, it’s worth learning and using.
Common rates rounded:
54/46 - 1.174
56/44 - 1.272
58/42 - 1.383
60/40 - 1.5
Well, that’s it. I don’t see the significance of .31 so, l dropped it to .30, and ended up at .20 on my Raptors, but the point is, if you work with front load/back load instead of total weight alone, you will find a consistent feel, and if you get real sick with it, you can figure your spring travel from here. That’s for another post that l’m not entirely prepared for. I’ve personally gone in circles with frequency, spring travel, wheel travel and all that, and have decided that forza simply didn’t take it that far. As l mentioned, there’s some crucial info missing that you need to get these figures. A-arm and hub measurements to name a couple. Not to mention that l can’t read equations or formulas, but haven’t been motivated to learn them because l realize that the info isn’t available. Hope this is useful to someone.