After a nice long vacation from building setups, I return with this Late Model setup for Irwindale Speedway 2016 Season 4. This setup represents a departure from the way most iRacing Late Model setups are being built right now, and, for me, a return to my earlier methods. With this build, iRacing seems to have gotten some of the aspects of the physics a little closer to science. For a few seasons, the physics involved in tire stagger just didn’t work.
Tire stagger can be calculated mathematically if you know the radius and banking of the turn, the track width of the car, and the circumference of the left rear tire. It is true physics, which is to say that it is a science. There is a definite tire stagger for a given car and a given track. There is not much room for deviation for driver preference or weather condition. Tire stagger (in the real world) is set per track and it’s typically not adjusted much. In the iRacing world, not so much, but they seem to be getting a little closer with this build. You may be saying, “Oh but you’re wrong. We run lower tire stagger on our real race car.” That may be. If you actually do run a different tire stagger on your real race car than what is scientifically correct, you probably either have something else adjusted wrong to compensate for it, or maybe one or more of your input values is incorrect.
With that knowledge, we can begin to base a setup on a given tire stagger. Then we can get the car set to make decent laps. After that, we find the right cambers, gear and fuel load, then tweak the setup to get it feeling right. During the tweaking phase, I keep an eye on the right front and right rear tire temperatures. In the end, I want those temperatures pretty well balanced after ten to twenty laps at race pace (not hot lapping).
This process now works okay in iRacing, but you may find that you have to run the stagger lower than the scientific value. For this setup, it is about a quarter of an inch lower than what was calculated mathematically for this track. I still consider this to be accurate because the input values I have could be wrong. The left rear tire circumference and car track width were taken from some old information and I believe it to be correct. The turn banking was taken from either Wikipedia, iRacing, or an old Irwindale Speedway web page. If it’s wrong, it’s probably very close. The turn radius was measured using Google Maps. I won’t get into details about how that’s done, but I would say that it is accurate enough to get us within one eighth of an inch of the actual scientific tire stagger for a given car on a given race track. All in all, I would say that the scientific tire staggers shown in my tire stagger chart are now correct to within one eight of an inch, but allow one quarter inch just to be on the safe side. If the car is just too loose and nothing will get it tightened up, drop the stagger one click at a time and get it right.
In summary, tire stagger is a great place to start with your setup since it is a scientifically calculable value. Get the tire stagger set to the value, then work from there.
This setup may feel a bit loose until you get accustomed to it. The tire wear is pretty well balanced as long as you don’t abuse the tires. The BIG PLUS about the correct rear tire stagger is that the car turns SO MUCH BETTER. It drives itself through the turns, and that is the purpose of tire stagger. The car turns much better and if you get the rest of the setup right, it’s not really loose at all.