Tire pressures are a crucial element of any car’s set up. Tires are your contact point with the road, so getting them to work properly is crucial. An important factor to consider then is how to set your tire pressures, especially for racing and track days.
Your ideal tire pressures will depend on your driving style, the weather and the type of car you’re driving. You will need to test to find your perfect tire pressures. When changing tire pressures, do so by 1 psi at a time. In the wet, increase your normal tire pressures by about 6-8 psi.
In this article we will discuss the variables you need to consider when setting your tire pressures correctly both for track days and for racing events. We are also going to go over some general guidelines so that you know exactly where to start.
Why Are Tire Pressures Important?
For this article we are going to assume you are on track with performance tires. These will give you better grip and will also be able to handle the higher pressures. Always remember to refer to your tire manufacturer’s guidelines to ensure you are using the right tire pressures.
Point Of Contact
The primary reason why your tire pressures are so crucial is due to the fact that the tires are the only part of the vehicle that contacts the road. So, they essentially must interpret what you as the driver are doing with steering and accelerating or braking. They then ‘pass’ this information to the road, making the car do what you want it to do.
Drivers often change complicated settings on their set ups when they struggle with the car. Usually they’re trying to find the perfect balance between oversteer and understeer. Although these issues can be resolved by adjusting the chassis set up, often it’s as straightforward as running on the wrong tire pressures, so never neglect this seemingly small set up component.
All About Grip
Tire pressures can change how much grip your car has and how long that grip lasts. You can use different tire pressures to change the amount of time it takes for your tires to heat up and even overheat. So, let’s go over the basics of tire pressure and how you can use it properly.
General Tire Pressure Basics
Tire pressures have an operating window in terms of temperatures and PSI. This window is the pressure and the temperature that will give your tires the right amount of grip. Your tires will not have the same PSI or temperatures at the end of the session as when you started though, and this is important to remember.
It means that your tires have a ‘cold’ pressure and a ‘hot’ pressure. The cold reading is when the tires have not been used yet. The hot reading is when you have just come off the circuit and your tires are hot from friction caused by the track.
Hot vs Cold
Your hot pressure reading will be higher than the cold pressure reading. Imagine that you are about to go out on track, and you set your tire pressures to 40 PSI on all 4 tires. After a couple of laps around the track you come into the pits and you immediately check your tire pressure gauge.
You will notice that your tire pressures are a fair bit higher than what you set them at initially. This is because when the tires start to heat up (caused friction between the rubber and the road) the tires expand, thus putting more pressure on the tire walls. There is no more air inside the tires than at the start, but the air inside them is just moving around a lot faster, causing the higher pressure.
4 Different Readings
You will also notice that all of your tire pressures will give different readings. This variance may be as small as 0.1 PSI. This is because all 4 tires work at different rates depending on the circuit you are driving on. For example, if you are driving on a circuit with a majority of right-hand corners, you will find the left side tire pressures to be higher because they are working harder.
Usually you will find the higher the tire pressures, the more grip you will have earlier in the session. They will heat up faster and so will also reach their correct working temperature much quicker. This makes higher pressures the perfect choice for sessions like qualifying or track days where you won’t be pushing the car constantly, but rather you will be looking for one fast lap at a time.
The drawback here is that these pressures will mean that the tires tend to overheat much earlier, and they will be losing their grip after a few laps, for example in race conditions. In addition, your tires will also wear out faster due to the higher temperatures.
You also can’t push your tire pressures too high; the car will become unstable because there is less tire contacting the circuit. There is also a maximum limit on PSI, which varies depending on the tire manufacturer. I would recommend checking this before you start.
Think Of A Balloon
The best way to describe this is by thinking about a balloon sitting on the floor. When the balloon is filled up with too much air, there is less of a contact area between the rubber and the floor, as the rubber is stretched. There’s also the risk of the balloon bursting when pressure is put on it.
Lower tire pressures will give you the opposite result. These tires will take longer to heat up and reach their correct temperatures. So, you will need to go the first few with less grip before the tires really start to work properly.
Good For Racing
This means these pressures are ideal for racing conditions. You will start to find more speed the longer you are driving, rather than your lap times becoming slower the more you drive. Driving on these cold tires at the start of a race can be challenging for newcomers, so make sure you are used to driving in low grip conditions
Going back to the balloon example: when it is slightly underinflated, there is more rubber touching the floor as it is less stretched (larger surface area is equal to more grip). It also becomes harder to burst a balloon that is underinflated.
Remember that all tire manufacturers have different operating temperatures, so the PSI may be different from Michelin tires to Bridgestone tires for example. Most manufacturers have all of this info on their website of recommended tire pressures.
The Compound Effect
Different compounds also have an effect on the tire pressures you should run them at. In general, harder tire compounds will require higher pressures than soft compounds. Wet weather tires are also different, which run at higher pressures than dry compound tires. You only need to worry about these when you have racing tires fitted to your car, as general road tires do not have different compounds.
How The Type Of Car Affects Tire Pressures
Weight And Speed
The type of car that you are taking out for a track test or even for a race will make a difference in the required tire pressures. This is because a heavier vehicle will be harder on its tires for example. The speed of the car is also crucial, specifically the cornering speeds. If you have a car that can corner faster, you will need to adjust your tire pressures accordingly.
You will also need to adjust your tire pressures based on where the weight of the car sits. For example, if you have a car with its engine in the front your tire pressures will be different to that of a rear engine mounted car. In addition, front wheel drive cars will also be different from rear wheel drive cars.
These are important variables to consider because it will tell you where you need to start with your tire pressures. If you have the wrong tire pressures you could upset the balance of the car, or even suffer a tire failure.
Example Tire Pressures
The table below gives some example ranges of tire pressures based on the powertrain in the car.
|Type of Vehicle||Tires||Pressure (PSI)|
|Front engine/front wheel drive||Front Rear||40-45 30-40|
|Front engine/rear wheel drive||Front Rear||35-40 30-40|
|Mid/rear engine||Front Rear||35-45 35-40|
Weather Conditions And Tire Pressures
Temperature Is Key
Tire pressures are extremely sensitive to weather conditions. You may have noticed that your correct tire pressures and grip levels fluctuate according to the weather and the ambient temperature around the racetrack. This is because heat in the tires will cause the pressures to rise. Keep this in mind if it is a hot day or if the temperatures around the track change throughout the day.
This is important because your tire pressures will rise as you drive, but also as you move on throughout your day at the track, as the ambient temperature around the track will be changing. This will also change the pressures you need to run in order to maintain maximum grip. Always keep an eye on the temperatures and the weather conditions throughout the course of your race day.
Monitoring The Weather
If the day heats up, you will want to keep your tire pressures lower in order to ensure that their temperatures don’t become too high while you’re on track. Another factor to consider is that any kind of temperature change will affect your tires, for example if your car is sitting on the grid with the sun heating up the tires. Make sure to account for these kinds of things before the race.
Conversely, it might be a cold and overcast day, and the temperatures around the track stay the same throughout the entire day, or even decrease as the day goes on. You will need to set your tire pressures higher than usual so that they can heat up quicker.
For wet conditions and rain, it is recommended to increase your tire pressures by 6-8 psi. This helps to prevent aquaplaning. Wet weather conditions are the opposite to dry conditions. You actually want less of the tire’s surface toughing the road. Higher surface area causes water to push underneath the tires and lift them resulting in aquaplaning.
Your driving style will determine which tire pressures work or you and which don’t. This is based on how aggressive or how smooth you are with your steering, braking and throttle application. Furthermore, you can adjust your tire pressures to give you the set-up preferences that you like on your car. Refer to the guidelines below:
|Adjustment||Decrease Oversteer||Decrease Understeer|
|Front tire pressure||Lower||Higher|
|Rear tire pressure||Higher||Lower|
Testing To Find Your Preferred Pressures (Especially For Racing)
Like most setups in racing, it’s crucial to find the adjustments that work for you. Your driving style will determine whether you take better care of your tires and how you can control the temperature in your tires. Your driving style could even determine how long it takes your tires to wear out.
Smooth vs Aggressive
It depends on how smooth or aggressive your driving style is. It’s important to find your own tire pressures, rather than asking another driver. Doing so can give you a guideline to work with, but at the end of the day, it might not work for you.
It’s best to use a day of testing to find out which tire pressure settings work for you, and which don’t. Start each run on track by making notes of the weather conditions and the temperatures. Having these notes will help you to quickly check back in the future.
Shoot For Consistency
You should not be trying to set your fastest ever time in this session, but rather try to understand how your tire pressures are affecting your car’s performance, and also to see which suits your driving style best. Aim to be consistent. Try to also test different racing situations like qualifying laps or even a full race length to see if your tire pressures are working.
Start with higher tire pressures, like 45 PSI. Focus on when your tires reach their perfect grip levels and when they start to lose grip. You can use your lap times to see exactly when this happens. The more consistent your lap times are the better, as it will be easier to see when your tires start working as the lap times get faster.
If you are able to set laps within a tenth of a second of each other, you will see a clear difference in your lap times where you have cold tires at the start of the session and where your tires are overheating at the end of the session.
Once you get back into the pits, get a hot tire reading. This will give you an indication of how much your pressures change while out on track. This amount could vary depending on the weather and the track conditions.
Decreasing The Pressure
With each run you should drop the PSI down by 1. Keep taking the pressures down with each run until you find the lowest pressures you can. When your lap times become slower than usual, you have found the lowest possible pressures you can run on. Remember that lower pressures can mean it takes longer to get up to temperature. Make sure you get the tires working before you give up on your run.
Once you have found the perfect spot for your cold PSI measurement go up by half a PSI to see how that affects your lap times. From there you can fine tune to find your ideal spot. Once you have found this you will know in future where you need to start with your tire pressures for a race weekend on a track day.
Write down the information those tire pressures gave you. For example, on the 45 PSI run, I found that the tires warmed up about 4 laps into the session, and they started overheating after around 16 laps. You can enter all of this info into an easy to read spreadsheet like this:
|PSI||Switch On Lap||Drop Off Lap||Fastest Lap Time||Temperature|
Find this data out for yourself in an easy way so that you can quickly check it in the future. So, when you’re in the middle of a race and there’s a sudden change in the weather conditions, you can quickly check back on your notes and know which PSI range you need to be in.
Tire pressures are important to get right. If you have the wrong pressures you will struggle to maintain control of the car and it will be difficult to drive. You will need to do some testing and spend some time on track to find the tire pressures that work for you. Once you find your baseline, it will be easy to refer back to it and adjust accordingly in the future.