In some racing series the car setup (tire pressure, fuel load, camber, caster, spring rate, etc) is fixed and some series they are open. In a fixed setup series, every driver has to use the exact same setup. What this means is that you can compare driver vs. driver without tuning getting in the way. If one driver is 1 second faster than another, it’s because that driver is actually better at sim racing. Once you go to open setups, that may not be true. Here, equally skilled drivers may be separated by setups. Now you may argue that the driver who can craft setups is better off than the driver who cannot, and I agree, but 95% of drivers in an open setup race didn’t do their own homework, they download setups created by other drivers.
So what happens when you drive a downloaded setup? Not everyone prefers the same car behavior. Some of the really fast drivers can balance a car on a knife’s edge. If that’s not you, you might find yourself spinning a lot. Heck, even some of the iRacing baseline setups are difficult to drive. A few years ago, the Spec Racer Ford was easy to drive but in 2020, the back end is too lively for most drivers. Learning how to tame that behavior is important or you won’t have any fun in what is otherwise a really great car.
So what exactly are you tuning for? The very basics are the following.
- Direction of the track
- Length of the race
- Oversteer vs. understeer
Every tire has an optimal temperature where it gives the best grip. Changing your tire pressures so that all 4 tires have optimal grip is the first place to tune. Most tracks are asymmetrical with more time spent turning one direction than another. The iRacing baseline setups are balanced. So you can always get a little bit of extra speed just by making your tire pressures asymmetrical left-right.
For short races, you don’t need much fuel. Minimizing fuel load lightens the car and that makes a measurable difference in lap time. Always take the minimum amount of fuel needed for the race, which may be more than the minimum allowed. Running out of fuel while leading a race is a special kind of failure.
Changing the balance from oversteer to understeer can make a car go from undriveable to telepathic to undriveable. There are many factors that affect how you perceive and adjust to weight transfer. In order to gain balance, you sometimes have to remove grip from one end of the car or the other (it’s easier for me to think of removing grip than adding grip). This can be done with tire pressures, anti-roll bars, brake bias, and spring rates. I usually start with brake bias to dial in trail-braking to my tastes. I do a lot of trail-braking, so I often have to move brake bias forward. For adjusting mid and late corner behavior, I change tire pressures (higher to reduce grip and rolling resistance). I generally set my ARBs on the soft side and since most of the cars I drive don’t allow changing spring rates, I don’t bother with those.
I suck at tuning. Really, I have no excuse for that. I could spend a lot of time studying and experimenting and I’d become good at it. But I just don’t have the passion for it. I love driving, like data analysis, and don’t want to be bothered by the rest (tuning, building, maintenance).