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How to Set the Correct Tire Pressures in ACC

Every time you head out of the pits, chances are you’d feel your tires first. A common question that faces every driver is “Are these tires correct enough to be driveable?”, and that simple question is ever so crucial for racing. So what is the fuss about tire pressures in ACC and is there a “right pressure window” for each car? Short answer, yes. Long answer, read on!

Importance of Correct Tire Pressures

Back to our driving example, we know that an overinflated tire has the tendency to; burst, leak some air out and feel super hard in terms of ride comfort. Similarly, an underinflated tire will feel more bouncy and soft but increase tire wear significantly and increase fuel consumption. The same translates to racing. So much so, that even a single PSI of pressure above or below the optimum number can cost you 5-6 tenths of a second in lap times.

Regarding ACC, the most critical factors that contribute to optimum tire pressures include weather, track temperatures, air temperatures, brake temperatures, type of session and the car itself. There are many more nuances, some smaller than the others, but they nonetheless contribute to the overall picture.

If you manage to get the right pressures for your tires during an event/session, you will be able to maximise your car’s performance and make your life much easier. If you thought incorrect steering setups cause unruly cars, inaccurate tire pressures are equally stubborn.

Identifying Tire Pressure Factors in ACC

Whether you are an amateur or a professional sim driver, there are many cues displayed throughout ACC to help you understand your car as much as possible. Tire Pressure is also a very mappable reading in the game. First and foremost, it is essential to understand the units and measure air pressure in a tire.

Air pressure is measured in Pascal (the SI unit), PSI and bar, but we will stick to PSI as it’s the standard unit used for measuring tire pressures. Getting your PSI number for each tire correctly right down to the decimal values should be your ultimate goal.

Optimum Tire Pressure

In simple terms, optimal pressure is the tire pressure you need to have when starting a hotlap (in qualifying), or the tire pressures you need to maintain after your formation lap in a race. Calculating optimal pressure values is easier during practice. Start with a baseline pressure value and complete a few laps (minimum 3). Note your tire pressure and compare it to the optimum windows (given below) based on the tire compounds. Try inflating your tires to a value that allows you to reach the optimal pressure in the given amount of time.

Understand How the Tyre Works

A tire offers variable grip, shock absorption, rolling resistance and tire wear depending on the tire pressure (and of course, tire compound). A higher PSI value results in a tire having less dampening, low wear, short-term grip and less rolling resistance.

The inverse is true for lower PSI values. Your suspension will have more bounce, but your tire life and grip reduce while tyre wear and rolling resistance increase. A technical note; the DHD2 compound (2018-19 tracks) has better grip outside the optimum range while the DHE compound (2020 tracks) has the best grip when in the optimum range.

Pay Attention to All Temps

This might sound a little generic but holds for all temperature readings. Track temps, tire temps, brake temps and the weather dictate how your tire pressure behaves. Colder temps reduce your tire pressure compared to the pressure you had in the pits while heat and hotter temps, in general, will increase the pressure inside the tires.

Use the HUD

The tire display widget in the HUD option displays your tire temps and pressure for each tire along with the brake temps. A green tire (around 80-85 degrees Celsius with a working range of 75-95 degrees Celsius) is a perfectly heated tire, and the optimum tire pressure should be achieved at this state. But displaying temps is just one feature of the HUD. It also shows you the shape of a tire.

If the middle band is curved inwards, it means your tire is under-inflated, and tire wear is more on the exterior. If the middle band is longer than the sidebands, it means your tire is overinflated, and tire wear is concentrated in the centre. Make sure your tires are green and that all bands are equal.

How to Adjust Tire Pressures and When

All cars have variable tire pressures, and it depends on driver preferences quite a bit. But ultimately, each car has its sweet spot where the PSI levels are just right for it to churn out maximum performance.

In technical terms, we call this the optimum pressure. Depending on the scenario, you’d be required to increase or lower the pressure. Automatic and Preset Setups are always available, but they don’t offer the maximum results. Hence, custom setups are the way to go and you can find custom setups for each car over at Coach Dave Academy!

Dry Conditions

The most common session conditions will be dry and during the day. Generally speaking, the only factors that affect you here are track temps and air temperature. Higher temperatures will cause tyre pressures to increase rapidly. Hence, filling air lower than the optimum tire pressure is the way to go.

In lower temperatures, it will be more challenging to get the heat into the tires and have a slightly higher tire pressure than optimum is best practice.

Optimum Tire Pressure Windows

CategoryCompoundPressures (in PSI)
GT3DHE (2020)27.3 to 27.8
GT3DHD2 (2019)27.5 to 28.0
GT4DHE26.8 to 27.4

Wet Conditions

A lot of things change when the conditions turn to wet weather racing. Changing your car setup to wet is not the only thing required, and adjusting tire pressure is one of the tricks. Since we expect the track and the ambient temperatures to be lower than typical values, heating the tires will be a huge issue, not to mention water, flowing or standing which will rapidly cool the tires.

It is advised to inflate your tires slightly over the optimum range to ensure the high pressure is maintained even when the tires are cold.

Optimum Tire Pressure Windows

CompoundPressures (in PSI)
Wet DHE (2020)29.5 to 31.0
Wet DHD2 (2019)29.5 to 31.0

Changing Conditions

Changeable weather is the biggest foe of any sim driver. It is difficult to predict the exact conditions for any given instant of your session. A lot of guesswork is required, which then takes practice and data to fine-tune your setup accurately.

A simple trick would be to predict the direction of the weather. If it is heading from dry to wet, expect temperatures to fall and hence, inflating your tires at a higher pressure will give you more grip and control as the weather changes.

Similarly, a drying track will cause your tires to heat up quickly, so staying on the lower end of the optimum range will help you. As these conditions cannot have a fixed optimum window, we can only say “practice makes perfect”. Try out a range of tire pressure setups in varying conditions for many different events using The Sim Grid’s Daily Racing option.

Time of Day

This one isn’t all that significant, mainly because most events have a fixed time slot. When it comes to endurance or dusk and dawn events, the time of the day can influence your tire pressures. Colder tracks need more tire pressure and vice versa.

As a general rule of thumb, for every 1 degrees Celsius of increase/decrease in ambient temperature, decrease your tire pressure by 0.1 PSI and vice versa.

Track temperatures, conversely, have an impact on your tire temperatures, particularly meaning you will then need to consider your car’s cooling (such as brake ducts) in order to keep tire pressures within the optimum window.

And that concludes our lecture on tire pressures! These four tyres may seem unimportant in how much air they hold, but the effect of even the slightest differences can cost you precious seconds over a stint. You can find more information on this and everything ACC on Coach Dave’s Academy. You can also sharpen your skills by heading over to The Sim Grid!

This article was written by Rudra Mehta, with editing from Grant Campbell

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