The tire staggers on this page are fairly accurate. I would estimate they are within +/- 1/8 inch. If you start with these staggers on the rear (and on the front is recommended) you may find the car to be extremely loose on exit and possibly in the middle of the corner. In most cases, it can be adjusted out using springs, shocks, bars, etc. It’s easier to say, “I’ll just adjust the stagger until it feels right.” That is probably a mistake.
It’s pretty clear that iRacing has done a good job on the physics. It’s just as clear that the physics is a little off. Here is what I can tell you: When I’m able to make setups using the stagger settings in this chart, and get them adjusted out, I get more compliments on my setups than when I just set the stagger by “feel,” and I can tell that the setups work better. So, as a setup builder, you can build better setups if you try to at least get close to these staggers. If you can’t seem to get there, you will just have to lower the stagger a little and compromise. iRacing is great, but iRacing physics is not perfect.
There are many settings in the iRacing garage that are trial and error. You have to set them, try them, change them, try them again, until you find what works best. To me, that is the most tedious, frustrating, and boring thing about iRacing, but if you’re going to run advanced setups, you’re going to have to do it to be fast. Fortunately, tire stagger is one thing that can be calculated mathematically. The calculation may not always be perfect, but it is pretty close.
The stagger chart below was made using Matt Holden’s Stagger Calculator after I remeasured all the tracks using Google Earth. If you’re curious about the differences in my measurements, I’ve included that information below the chart. I’ve always found Matt’s Calculator to work pretty well when I’m looking for the right stagger for a given track and given car. You need a certain set of data to calculate tire stagger:
- Track banking in degrees
- Turn radius in feet
- Track width aka tread width (the distance between the outside edge of the tires)
- Left rear circumference
Since iRacing doesn’t provide all of this data, you have to scrounge it up for yourself. The only one that is easy to find is track banking. I believe I have included all of the relevant short tracks and cars.
Update 12/4/2016: I remeasured the radii on each track. In this measurement I attempted to use the racing line which changes some aspects of the measurement. Specifically, I measured the radius of the path that the right side tires would typically follow in race conditions. This increased the radius slightly on a few tracks, in turn making the calculated stagger slightly lower. Also, iRacing has provided the correct track width for all of the cars except the Street Stock. I don’t have updated information on any tire circumferences, but all tires vary in circumference due to differences in manufacturing and of course the air pressure used. For now, I am going to provide a range of staggers to use on the Street Stock on the tracks where there is actually a difference. The track width I originally found for the Street Stock was 65 inches. Stock Camaros from that era were not that wide and the track width was slightly wider in the front than in the back.
I’m sorry Dave, the data that is called here appears to be missing from my system tables. Please go to Discord and let Jeff know. Thank you.
When I made this calculator, I decided to meticulously remeasure all of the track turn radii available using Google Earth. I found that some of my measurements were different from Matt’s. I came up with a standard process for making the measurements. I won’t get into the measurement details, but I will tell you where my measurements differed from Matt’s.
- I measured Bristol’s turn one and two radius at 284 feet. Matt measured it at 242 feet. If you use Matt’s measurement, you’re going to want to raise your rear tire stagger one or two clicks from what I have in the chart.
- Here are the measurements I took at Concord: Turn 1 radius, 287 feet, turn 2, 334 feet, turn 3, 235 feet – turn 1 banking, 14°, turn 2, 11°, turn 3, 14°. Since turn 2 is the key to this track, the correct stagger setting for that turn is important. On the chart, I include a range. The first number is the low end stagger (for turn 2). The second number is the high end stagger (for turn 3). I suggest a stagger setting somewhere in this range, and I would lean toward the lower end.
- I measured Iowa’s turn radius at 479 feet. Matt’s measurement was 540.2 feet.
- I measured Langley’s turn radius at 245. Matt measured it at 273, making his stagger calculations slightly lower.
- My radius measurement at Lanier was 224 feet, just slightly higher than Matt’s measurement which was 218.4 feet. I also differ on the banking used for the stagger calculation. Lanier has graduated banking with 5° at the bottom of the track and 11° at the top. Matt uses the 11° number, but cars don’t run a high line at Lanier, therefore the correct banking would be 5°, making the correct stagger setting slightly higher, but only of little or no mathematical significance.
- I measured Martinsville’s turn radius at 200. Matt measured it at 242.6. I spent some time remeasuring to verify my measurement. Another source I found lists the radius at 187 feet, but I think I’ll go with my measurement. One possible reason for these variations could be due to the way that I measure. I measure in the racing line. It’s not significant where tire stagger is concerned, but it’s worth noting that while some sources say that the banking is 12°, the Martinsville Speedway websites lists it at 11°.
- I measured New Hampshire’s radius at 445 feet. Matt has it at 375 feet. According to the New Hampshire Motor Speedway website, 375 feet is the turn radius measured on the inside. I made my measurements in the racing line. The banking is variable from 2° to 7°. Since the cars run around the middle of the turns, I used 5° for my stagger calculation.
- I measured the radius at New Smyrna Speedway at 225. Matt measured it at 267.2. The banking is given as 23°. This seems high to me but the New Smyrna Speedway website has the same information. Wikipedia, however, lists the banking as 18-20 degrees. In terms of tire stagger, I’ll stay with the 23° number.
- I measured the radius at South Boston Speedway at 225 feet. Matt measured it at 251 feet.
- I measured Stafford’s turn radius at 257 feet. Matt measured it at 309.8 feet. Another source of unknown reliability has Stafford’s turn radius at 235 feet. This may be measured at the bottom of the track. Since I measured it as a tighter turn, my stagger calculation comes out slightly higher than Matt’s.
As you can see there were quite a few differences. In no way do I imply that my measurements are more accurate. These can be measured in different ways. For the most part, I measured the turns tighter than Matt did, so my stagger chart shows higher stagger with a couple of exceptions. If you feel the stagger is too high, bump it down a couple of clicks.
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