Are you struggling with handling imbalances in your track car? There could be many factors causing this, but have you considered the relationship between tyre pressure and handling balance?
In this article, you’ll learn how and why simple tyre pressure changes can make a significant difference in your car’s handling balance. And the best bit? Tyre pressures are one of the easiest setup changes to make on your track car.
By creating experiments to make simple tyre pressure adjustments, you can quickly explore different setup changes, develop your driving and, ultimately go faster whilst having more fun. What is not to like! There’s even a nerdy suggestion at the end to to speed up this whole thing, if you’re feeling brave…
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Understanding Tyre Pressure’s Impact on Handling Balance:
Changing your car’s tyre pressure alters the vertical stiffness of the tyre, similar to adjusting springs and anti-roll bars (arb’s).
These changes affect the distribution of lateral load transfer that your tyres experience during cornering, which has a primary influence on your car’s handling balance.
You might be surprised to learn just how much changing your tyre pressures affects this stiffness. According to this study, increasing tyre pressure from 26 psi to 34 psi (1.8 to 2.3 bar) resulted in a 15% increase in vertical stiffness.
While a tyre is just one component in the suspension, it can have a significant impact – particularly as your tyre pressures will change during the time you are on track (and you can learn what hot tyre pressures to target here.)
To make this a bit clearer, you can consider this through a quarter car model.
The Quarter Car Model
A “quarter car” model helps you understand the relationships between the road, tyre, wheel, spring, damper, and chassis on one corner of your car. The big box at the top represents the car, followed by a spring and damper, then the wheel, and finally, the tyre touching the slightly bumpy road.
A tyre is typically ten times stiffer than the spring on your car, so its influence is not going to be as significant as a spring change, but it’s also far from having zero impact.
Building on from this insight, you can then consider the relationship between tyre pressure and handling balance.
Achieving Better Handling Balance with Tyre Pressure Adjustments:
Although this may compromise your overall grip potential, attaining a superior balance can often justify the trade-off, as a more confident driver can extract a faster lap time.
So there you go.
Your challenge is to put together a testing plan to try different tyre pressures over a number of runs and record your results using any data you have and including driver feedback.
If you’re up for a bit (a lot!) of maths however…
Simulating Tyre Pressure and Handling Balance:
If you’re confident enough to build a simulation, you can play with this kind of stuff all day without even going near a race track.
The diagram below shows one output from a complex simulation model that I built for my racecar. It displays the “understeer gradient” in the three images on the right:
The understeer gradient is the measure of a car’s understeer or oversteer, which can be influenced by the stiffness of the springs, arb’s, and tyres.
In this case, we were just looking at the change in the arb on understeer gradient.
In other words, what change to the mid-corner handling balance could we expect (and by how much) by changing the arb setting.
The diagram on the left shows the level of understeer gradient achievable with different front anti-roll bar settings.
You can observe similar effects by altering tyre pressures front and rear, which changes the vertical stiffness, and I’ve found can help you fine-tune your car’s handling balance.
Tyre pressure plays a crucial role in your car’s handling balance.
By experimenting with different tyre pressures, you can give yourself more confidence and improve your vehicle’s performance on the racetrack.
I often see people aiming for the same target hot pressures all round but trying different combinations will help you understand more about the tyres influence on your handling balance.
Always stay within your tyre manufactures recommended pressures but good luck experimenting and let me know how you get on!
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