iRacing provides an exceptionally realistic racing experience that demands a combination of strategic car setup, smart racecraft, and precision driving to be close to the pace. One of the classic cars available on this platform (and one of my all-time favourites) is the Mazda MX5 – renowned for its balance, accessibility, and prolific racing heritage. It’s the car (in the real world) where I learned how to give feedback to my engineer to help him make setup changes that would reduce a particular limiting factor in the entry, mid and exit phases of a corner.
What are the limiting factors to a good lap pace? You’re going to need to understand oversteer and understeer.
Explaining Oversteer and Understeer
Oversteer and Understeer are very recurrent terms you will always hear when talking about car handling.
Whether it’s on the track or the open roads, as long as speed and curves are involved, any car will be prone to one or the other. Certain modifications (setup changes) can be made to cars in order to make them less prone to oversteering and understeering, or can deliberately push them to be more sensitive to either one, in order to suit your personal driving style.
Max Verstappen, for example, is famously preferable to a car that has significant oversteer characteristics. This helps him get the car turned in ready to get on the throttle at the Apex.
In iRacing you will have experienced both understeer and oversteer. Some of it can be adapted to via your driving technique, the rest needs to be adjusted for in your setup.
Oversteer happens when the rear tyres lose grip and slide around, allowing the rear to “over-rotate”. When oversteering, the vehicle will feel like it’s about to spin and will do so if the driver isn’t fast or skilled enough to “catch” it back, with an opposite lock correction in the steering. Oversteer can happen in the corner entry, mid-corner and exit phases of the corner.
If you’re trying to manage a car that seems to oversteer all over the circuit (global oversteer) then you have a few ways to adapt as a driver. If the car is oversteering on entry, you can try to decrease the initial entry speed. You can also try to be smoother on and off the brakes to keep the car more settled. By keeping less weight transfer over the front tyres, you’re allowing the rear tyres more grip. If the car tends to oversteer in the corner entry, there’s a good chance that at the apex, you can “sit” the car down on its rear tyres with a gentle application of throttle.
Of course, you may have oversteer when you get on the throttle, which means the car is not able to squat down enough at the rear or the weight transfer is too slow. We’ll look at how to deal with these scenarios in terms of your setup later in the article.
Understeer, also known as “push” happens when the front tyres lose grip in a turn, causing the vehicle to turn only slightly or not at all compared to the steering input. Turning the steering wheel further makes the front tires slip even more. An understeering vehicle will plow ahead instead of turning, usually sending you straight on to leave the track. Understeer can happen in corner entry, the mid-corner, and in the corner exit.
When you’re trying to manage understeer, you’ll find yourself trail braking for longer into the corner entry, which keeps the weight transfer over the nose of the car for longer. This gives you more grip at the front which, in a generally understeering car is what is required. If you have understeer in the mid-corner, a small amount of understeer is generally acceptable, but if you have too much understeer in this phase then you likely can’t get on the throttle for the exit and you’ll lose time on your lap.
There are driving technique adaptations you can make to deal with the behavioural characteristics of a car. This is essentially what professional drivers do. Rarely are racing cars perfectly setup – you will, over a race weekend, continually make small changes as you learn more about the track and build a corner-by-corner log of what the car is “doing”.
Remember: entry, mid-corner and exit. What does the car “do” in each corner phase? It’s smart to take note of how the car behaves in certain corner types too:
- Hairpin (heavy braking, slow entry, late apex, early throttle)
- Slow to medium speed corner (smooth braking, trailing into apex, gradual throttle input)
- High-speed corner (lift, light brake maybe, throttle on hard)
- See our racing lines article here for more corner types
You’ll very likely discover that the car doesn’t behave in a uniform way, and its balance will be affected by the corner you’re approaching. If you’re approaching a hairpin, then the car will be under heavy braking (weight transfer far forward). Turning the car in too sharply will induce oversteer, which will need correction before you can get on the throttle. This event will cost time, as you likely already know.
Still not sure? Check out this video:
What setup changes can I make to “fix” a limited car?
It’s really important to make sure you’re accurately logging what’s happening in a corner. You can sometimes finish a session, high on adrenaline and very tired, making reconstructing your memory of what the car was doing all the more difficult. So take a measured approach to testing, putting in enough laps to give you an impression of the car’s dynamics before you consider making any changes.
It’s good to write these things down. Chris Haye produced a generic guide to some of the changes you can make below. There’s more options available than this but it’s a good starting point to see how a driver might categorise the features of the car’s performance:
Adjusting the ride height of a race car can have a significant impact on its handling and grip, making it one of the easiest and most effective setup changes to make.
Imagine your car is a see-saw – when you get on the throttle, the weight transfer moves to the rear. When you get on the brakes, the weight transfer moves to the front. If the car is on its nose, the rear has less grip. If the car is squatting on its rear (on the throttle) then the front will have less grip. If the car is oversteering on every corner entry, you might consider dropping the rear ride height. Lowering the front ride height or raising the rear ride height can counter understeer while doing the opposite can counter oversteer in sim racing.
Adjusting the stiffness of the car’s front and rear can have a significant impact on reducing understeer or oversteer, but finding the sweet spot is key. If the car has understeer at corner entry, try softening the front dampers so that they can squat further under braking. This will give you a lot more front grip, at the cost of a little rear grip.
Adjustments using tyre temperature and wear data
Changing your camber settings can increase grip by keeping more of the tire surface in contact with the road. You need to keep an eye on the temperature spread across the tyre surface.
Bear in mind that to get updated tyre temperatures, you’ll need to pit as tyre telemetry data in iRacing is not live.
When it comes to real racing cars, the objective is to keep the tyre temperatures (inside, middle, and outside) as uniform as possible during cornering. This can be achieved through a track-specific quantity of static camber, the latter being adjustable in iRacing setups.
The process relies on your getting the temperature spread of the tyre about equal across the whole tyre.
Here’s a process for that approach:
Before attempting to fine-tune your car’s chassis setup based on tyre temperatures, ensure the tyre pressures and camber are adjusted so that after 5-10 laps of full racing speed, the temperatures on the inside, middle, and outside of each tyre are nearly equal. This ensures the camber and tyre pressures are optimal, leaving only suspension adjustments for fine-tuning the chassis. During this testing phase, increase the air pressure in each tire to reduce friction and increase speed, stopping only when the centre of the tire shows a higher temperature.
For using tyre temperatures in the chassis setup, complete at least 5-10 laps at full racing speed before taking any measurements. Then, stop the car on the pit road without hard braking to take temperatures. After a testing session, take the average of the three temperatures on each tyre. Use these averages to calculate the averages of both left-side tyres, right-side tyres, front tyres, rear tyres, and diagonals (LF + RR, RF + LR). If one tyre’s average temperature is significantly higher or lower than the others, adjust the static weight load to compensate.
With these averages, assess whether the front or rear of the car is losing traction by comparing their respective average temperatures. An end with hotter temperatures indicates a loss of traction. If the average temperature of the front tyres is hotter than the rear, the car is pushing, and vice versa. Further, assess the outside versus inside temperatures, and adjust weight placement or shock stiffness accordingly. If the diagonal average temperatures are not balanced, consider making wedge adjustments to equalize weight distribution. However, keep in mind that wedge adjustments can drastically alter the car’s behaviour and should only be made as a fine-tuning process.
What are the setup options available on the Mazda?
As I mentioned early in the article, I think the MX5 makes for a very good starting point to understand the impact of setup changes on the balance of the car. Just follow one golden rule: make one change at a time.
What do all the iRacing garage settings do?
Cold Pressure: Tyre pressure affects both the responsiveness and the grip of the tires.
Increasing cold pressure: Can lead to less grip as the contact patch (the area of the tire that is in contact with the road) decreases. This can potentially lead to oversteer if the rear tyre pressure is increased or understeer if the front tyre pressure is increased. However, the tires might become more responsive.
Decreasing cold pressure: Increases the tyre’s contact patch, leading to more grip. This could potentially reduce oversteer if the rear tyre pressure is decreased or reduce understeer if the front tyre pressure is decreased. However, the tyres might become less responsive.
Spring Perch Offset: This is essentially adjusting the ride height of the car without changing the spring rate.
Increasing Spring Perch Offset: Raises the car, which shifts the weight balance rearward, potentially leading to oversteer as the rear of the car becomes lighter.
Decreasing Spring Perch Offset: Lowers the car, which shifts the weight balance forward, potentially leading to understeer as the front of the car becomes heavier.
Bump Stiffness: This controls how quickly the suspension compresses under load.
Increasing Bump Stiffness: Makes the suspension compress more slowly, which can reduce grip over bumps and during braking, potentially leading to oversteer in the rear or understeer in front.
Decreasing Bump Stiffness: Makes the suspension compress more quickly, which can increase grip over bumps and during braking, potentially reducing oversteer in the rear or understeer in the front.
Rebound Stiffness: This controls how quickly the suspension extends after being compressed.
Increasing Rebound Stiffness: Makes the suspension extend more slowly, reducing grip when accelerating out of corners, potentially leading to oversteer in rear or understeer in front.
Decreasing Rebound Stiffness: Makes the suspension extend more quickly, increasing grip when accelerating out of corners, potentially reducing oversteer in rear or understeer in front.
Camber: This is the angle of the wheels relative to the ground. Negative camber means the top of the tire is tilted in towards the car.
Increasing Negative Camber: Can increase cornering grip, but decrease straight-line grip. If the front camber is increased, it can reduce understeer, but too much can cause oversteer. If the rear camber is increased, it can reduce oversteer, but too much can cause understeer.
Decreasing Negative Camber: Can increase straight-line grip, but decrease cornering grip. If the front camber is decreased, it can cause understeer. If the rear camber is decreased, it can cause oversteer.
Toe In (rear only): Toe refers to whether the tires are pointed inward or outward relative to the centerline of the car. In the case of the MX5, only the rear tires can be adjusted.
Increasing Toe In: Causes the rear tires to point more towards the centerline of the car, which can increase straight-line stability but potentially decrease cornering grip, leading to oversteer.
Decreasing Toe In (or increasing Toe Out): Causes the rear tires to point away from the centerline of the car, which can decrease straight-line stability but potentially increase cornering grip.
Hopefully, with this information, you’ll be able to take a more informed approach to refine your own setups – it’s well worth practising in the simpler iRacing cars first, the Formula Ford, the Formula Vee and the MX5 Cup. Good luck!