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Tire stagger can be a very frustrating concept in motorsports. I can't tell you the number of times I have watched someone utterly dominate a race but then, suddenly and without warning, begin losing a few tenths per lap. Most times the driver is clueless.
"I just don't know what happened," is an often repeated statement in this scenario. "In the beginning of the race we were so fast, but all of a sudden the handling just went away."
Of course there will be other variables that will cause an ill-handling racecar, but the first place to look in this situation is at tire stagger.
First, we need to define stagger: It is the difference in circumference between the right-side tires and the left-side tires. For instance, if your right rear tire is 86 inches in circumference and your left rear tire is 84 inches, then there is 2 inches of stagger. The best demonstration of stagger is a traffic cone. When one is knocked over, it spins in circles because of one side being much larger than the other.
Sounds easy enough, but problems arise when the car heads onto the track. As the temperatures and air pressures start to build, this has the capability to stretch the tire. Even a stretch of just a quarter of an inch can greatly affect the car's setup. When I raced Karts, there were two things I checked on a regular basis, as much as once or twice every hour, even if I hadn't been on the track. Those two things were the durometer readings to determine the softness of the tires, and the stagger of the tires. I had to stay on top of those two things throughout the race weekend if I wanted any chance to win the main.
When measuring tire stagger, make sure the air pressure is set to the desired level for racing, then use a plastic or cloth tape measure to determine each tire's circumference, measuring at the center of the tire.
Tire stagger can be defined...
Stagger is like money-too much and not used wisely and you can find yourself out of control. Too little and you might end up against a wall with no way out.
Too much stagger results in a loose condition, and it will only get worse. As the right rear tire is sliding and losing traction, it will heat up and build up air pressure, causing the tire to grow and make the car looser. Very rarely does a car start off loose and progress back to a tight condition. That's not to say it can't be done, but it usually doesn't happen that way. Most of the time if it starts off loose, it will end loose, because of the right rear heating up faster than the right front.
Also, having too much stagger can affect straightaway speed. The car will be trying to turn left down the straightaway and the driver will be pulling it back to the right, scrubbing off speed. It is also vital to use nitrogen in tires instead of regular compressed air. Nitrogen allows for a more consistent buildup of air pressure as the tire heats and tries to expand. Compressed air will be inconsistent because of the moisture carried with the compressed air.
Without enough stagger, a car will push toward the outside wall. This causes the right front tire to heat up quickly and intensify the tight condition. Stagger, however, is more important on the rear of the car because the tires (at some point) are connected by the differential and axles. The type of differential determines where stagger affects the car the most. A spool-type rearend, where both axles are locked together all the time, affects the car through the entire turn: entry, apex, and acceleration. However, in a Detroit Locker rearend, where both axles are locked only under acceleration, stagger affects the handling of the car more whenever the throttle is picked up.
Make no mistake about it, front stagger is important as well. But an increase in front stagger may not create that much difference. That's because the front tires are not connected by a solid axle. Front stagger will be most noticeable on the entry of the corner. It will help pull the car down to the bottom of the track when the brakes are applied.
There are some quick fixes for stagger issues. I have always been an advocate of a little more stagger than typically used because it does make a difference throughout the corner. Plus, I like my cars a little more free than most. If you can free up the car enough to where you can rocket through the corner, you can actually exit the corner faster than anyone else. And you won't be giving up that much straightaway speed because of your added speed exiting the corner. However, the problem with that is, again, you run the risk of gaining stagger as the tire heats up. I like to combat this with a little more cross to help tighten down the car, heating up the right front equally with the right rear.
The best thing you can do while at the track to help with stagger problems is to keep a notepad and constantly measure your tires after they c