There was a run of technology that came along around 1995 where builders tried to eliminate camber change by making the upper arms nearly level. That exasperated the problem. What they were doing wrong was evaluating the camber change by just moving the wheel up and down and not taking into account chassis roll and its affect on camber change.
We quickly went from level uppers to drop snouts once everyone caught on. Nowadays, drop snout might have a little different meaning. We can drop the front of the car by using drop spindles where the spindle pin is located higher up, dropping the whole snout, not just the framerails.
Through all of this, we still need to keep track of the MC and there is a movement away from the extreme BBSS setups to a more soft conventional setup, or SCS. There, I coined the term and intend to use it often.
Dirt Car Setup
I have read your Stock Car Set Up Secrets book front to rear several times and find it very helpful. I have also purchased software programs but have not had much success with the chassis setup so far. I would appreciate your input on some questions.
The car is a metric Monte Carlo Street Stock with 500-plus hp on dirt with 10-inch wide Hoosier 500 tires. This is the first year I have run this car but have had some success with the metrics in the past in different divisions. In response to your "Metric Rear Roll Center" article where you stated that the left-side tires should be nearly the same temp front to rear, does this still apply to a high-horsepower car on dirt?
Would it not be reasonable to see slightly higher rear temps since they are working all the way down the straights also? My temps are nowhere close to balanced but how close should I expect to get them? LF 100 degrees, RF 120 degrees, LR 140 degrees, RR 145 degrees.
I race on a 3/8-mile, medium to high bank dirt track that almost always packs in tight and smooth and takes rubber from top to bottom. It rarely gets dry enough to come apart and get dusty, but instead takes on a black, polished look.
Where should my weight be placed? Is some right-side weight OK or should it all be low left? Currently, 54.5 percent left, 53.5 percent rear, 51 percent cross, 3,150 pounds total. I have about 300 pounds of lead to play with plus the battery. I have some of it high and some on the right side. I installed spindles off a metric Impala with longer upper and lower ball joints and aftermarket upper control arms with fabricated inner mounts.
The problem is the car will get tight unless I am on the gas hard enough to spin the rear tires. If I lift enough to regain rear traction, the car will start a slight push, forcing me to slow down in the middle of the corner. This really surprised me since these are the softest front springs I have ever run and I was expecting the car to be loose, if anything. I've checked several times to make sure the RF is not bottoming out. It's coming close with well over 3 inches of travel, but will only hit on occasion if the track has a rough cushion on top.
Front Roll Center= 3.5 inches high 6 inches left and moves to 2.5 inches high 1 inch left, springs LF 850-pound, RF 800-pound, LR 250-pound, RR 200-pound, and 2.25 inches rear stagger. Are these front springs too soft and causing a problem? Everyone who is trying to help says to stiffen the front up to at least a 1,200-pound RF but I think that will make the problem worse. Do you see any obvious problems and what are some things I should look for? Am I just crazy for trying this in the first place since the guy who built the car had everything just about opposite of what I do now?
I really appreciate any thought you can put into this.
There are several things that jump out at me. First your stagger is more suited for an asphalt car than dirt. You should try to run more stagger up to 3 to 4 inches.
Your track has traction from what you said, and so the g-forces are higher than would be expected of a dry slick track. More force means a tighter car for the same setup, so you need to change the setup. Try a stiffer RR spring. Your front springs aren't too soft unless, as you say, the car hits the track.
The moment center location is fine and your weight distribution looks OK for rear percent and crossweight, but try to lower the moveable weight and move more to the left too. On banked tracks and ones with more traction, a lower center of gravity and more left-side weight helps. And, you're not crazy for trying all of that, you just need to tune it. Once you get the push out of it, things will improve.