Now updated with information from New Tire Model (NTM)
I still use the Setup Tweak Guide a bunch.
The default iRacing Indycar oval setups carry a lot of wing and are quite stable to drive. The problem is they’re also a lot slower than folks are generally running in the series.
Over the last few seasons there have been some great setups posted in the forums, while some were very very fast, I found a lot of them to feel funky, twitchy or downright dangerous.
This guide is an attempt to outline how to adjust the car and what makes a fast setup. This is a community effort and I’ll post updates as folks chime in.
Normal range for the front springs are 500 – 1000 lbs, in 25 lb increments
As well as helping to set the ride height and rake, springs help with mitigating body roll along with the shocks and ARBs. Stiffer springs make for more responsive handling with softer springs helping with grip.
A lot of fine tuning is done with the bump and rebound of the shocks on the circuit and teams spend a lot of time with it. What they have that we don’t is telemetry showing where the tires are losing traction.
I have some base bump and rebound settings that feel pretty good. I’ll work on the track, turning laps and looking for things that can be helped.
Some folks are just running 0’s all round for bump, rebound. I’m still trying to find a balance where I can have some adjust-ability in the car.
Anti Roll Bars
The front Anti Roll Bar ties the front wheels together and controls how the wheels work together through the turns. Both the front and rear ARB’s are adjustable in cockpit.
A stiffer front ARB will help when changing direction and initial turn in.
The latest thinking is to run more camber on the front left than required to get even temps. This helps drag the car into the corner and helps with general handing. I try to keep right front temps within 10 degrees across the tire with the inside being a little hotter than the outside.
Caster effects the twisting of the chassis as the wheel is turned. Caster rotates the front geometry as the wheel is turned. More caster helps with turning the car at the expense of rear grip.
Toe In/ Out
Toe In – helps with straight line stability
Toe out – helps with initial turn in
While a little is good, more is not always better. Excessive toe in/ out will greatly affect tire wear.
The majority of the setups I’ve seen have been running a +7 -7 Rear steer setup. Feel free to jump in if you’ve played with this setting.
Rear Springs 400 – 600
Arb – limit body roll
Tries to torque the bar when turning
Rear cambers help the car turn in conjunction with the amount of rear steer dialed into the setup. I aim for a little higher temps on the inside of the track, so outside of left rear and inside of right rear. If the temp spread is higher than 10 I’ll stand the tire up to try and even out the temps.
As low as you can get it without dragging too much. Ride height is more determined by rake … see below.
Rake is the difference in ride heights front relative to rear. More rake (bigger difference between rear and front ride height) = looser car, Less rake = more understeer. The key is trying to balance the car and be able to control balance during the fuel burn by using the front and rear anti-roll bars in conjunction with the weight-jacker.
There a couple of schools of thought on oval rake settings. A high nose, will lower the rear wing and may allow for a reduced wing angle and a higher top speed while sacrificing a little handling.
It’s a matter of balancing speed with drafting, you need a car that is fast alone and while in the pack as the majority of the tracks featured on the IndyCar schedule have drafting to a greater or lesser extent.
Tire pressures (updated for NTM)
Tire acts a spring, with softer tires generally offering increased grip. With the updated tire model (NTM) it’s more about tire wear than even temperatures as it was with the old tire model.
Although it’s quite ok to have uneven tire temps, as long as the tire wear is more even having an inner or outer temperature significantly different to the other two temperatures could mean that the tire isn’t being used to it’s fullest.
Tire pressure increases with temperature, which also affects tire grip. One to the things I try to achieve is good balance over a fuel run. After running several laps (preferably at least 10) take a look in the garage at the hot tire pressures, a front pressure significantly higher then the rear could mean you are using that end of the car up faster and will likely lead to understeer. The opposite of course holds true for the rear.
More to come …
Locking up the rears usually leads to a quick swapping of ends and the air being filled with expletives. While a rearward bias will help you turn the car getting into the corner, too much will lead to bad things.
While on short ovals such as Milwaukee you will use brake to help rotate the car, a rearward brake bias will make life difficult when coming into the pits.
The weight-jacker is a setting somewhat akin to wedge on a stock car. The main difference is that the driver can adjust weight-jacker while on the track. There are even rumours of some drivers adjusting weight-jacker in between corners to get the most out of a lap.
Increasing weight-jacker makes the car looser. The weight-jacker goes from -15 to 15. Bear in mind that the setup keeps the last weight-jacker settings and can cause a setup to fail tech in the garage.
I try to get the car setup to where it’s a smidge free with the weight-jacker set to 0. When I leave the pits or at race start, I’ll set it to -1 to add a little push to the car for the first lap while the tires are cold.
Important to note that just 1 click of weight-jacker can have drastic effects on the amount of over/ understeer in the car. It’s a brave soul who will click it more than once at a time.
The rake tends to increase as the fuel burns off which leads to more over-steer through the run. This can be countered by increasing the weight-jacker as the race goes on. I tend to increase the weight jacker by 1 click every 6 – 10 laps depending on how much the car is pushing on corner exit.
The front ARB also can be lowered or rear ARB raised as the run goes if fitted.