Micro Sprint Moment Centers
I've been having some trouble setting up my dirt Micro Sprint. I'm following the chassis manufacturer's setup guide. My car is always very tight, and when I make changes, they have little effect. I would like to find the moment centers of my car, and really know what is going on rather than following an instruction sheet.

I have read and applied the theories in your Stock Car Setup Secrets book for a dirt Street Stock. Have you written a book on Sprints? I haven't been able to find much info on solid axle torsion suspension, and the ideal locations for their MCs in a Sprint. Is there a possibility of a future article in CT?

Thanks in advance,
—Kustra Racing

KR,
In a solid axle suspension, the average height of the ends of the Panhard bar, or locating devise, is the roll center. In your case, the adjustment for heights might be limited.

If you are tight, you can adjust the spring rates of the torsion bars. To free the car up, soften the front bars or stiffen the rear bars, or only the Right Rear bar.

I find that in most Sprint Cars, they run stiffer front spring rates (either coil springs or torsion) than in the rear. There is usually more rear weight in those cars, so it makes more sense to run stiffer springs in the rear. The two suspension systems are the same, unlike in a stock car where the front is a double A-arm.

So, rather than trying to adjust the MC heights, try installing different rate torsion bar springs. If you go to www.circletrack.com and click on the MultiMedia tab, you will find a sway/torsion bar calculator that will get you close to the rates you are running. It uses an average steel coefficient number and yours may vary slightly, but it's the difference in bar rates you are looking for, so it will be OK for your use.

Run all of your torsion bars through the calculator and record their rates. Experiment like I said to soften the front and stiffen the rear, especially the RR, to achieve a more balanced setup. If you find a great combination that makes you fast, don't share that information, or it might end up in the manufacturer's setup sheet.

Cambered Tires for Stock Cars
Hello, my question is go kart racers and Legend racers all swear by cambered and cut tires, how come you don't hear more about this technology for dirt racing or asphalt racing? Is it out there and does it work?

Who would be the leaders in this industry? Any information in this area would be helpful since we have learned we are racing against someone who supposedly has cut tires.

Love the track tech! Thank you,
—Donnie Sullivan.

Donny,
In stock car racing, we can adjust the cambers in the front wheels more easily than with karts or Legends cars. So, the cambered tires make up for not being able to get the correct tire camber.

Since you can adjust your front cambers, and with stagger you will have some rear camber, you don't need cambered tires. They would be way too expensive to build for the larger and heavier cars anyway.

Cutting the tread for a stock tire does help add grip because the grooved tires will roll over on the surface of the tire. So cutting them down adds grip. Dirt Late Model racers often groove and sipe (cut) their tires to add grip, but that is legal in that division. Most asphalt divisions that we know of, outlaw any kind of tire prep.

There is another factor to consider. The karts and Legends cars develop much more lateral force on asphalt and therefore the tires need more camber than a street stock or even a late model car due to tire roll-over.

When I ran a special race in my Sprint laydown kart at New Smyrna Speedway back in the mid-1980s, which I won, I never lifted and went more than 90 mph through the turns. I don't think a Super Late Model can do that.

By the way, racing karts on asphalt tracks with concrete walls is a stupid idea. Never try that at home. If your track does this, ask it to stop. I got lucky.