What’s the Relationship Between Air Pressure and Traction?
The pressure of your vehicle’s tyres sets the weight distribution across the tread pattern. With the manufacturer’s recommended tyre pressure (often found on the tyre placard in the driver’s side door jamb), your vehicle is most stable.
When a tyre is not correctly inflated, it loses its stability. In turn, this affects your handling, cornering, and stopping distance. Incorrect tyre pressure also causes tyres to wear unevenly, meaning they need replacing more frequently.
From the type of wear on your tyres, we can tell whether you underinflate or overinflate:
- More wear in the centre of the tread means your tyres are overinflated
- More wear on the outer edges means your tyres are underinflated
Tyres lose traction when the shape of the tyre becomes deformed and the tread becomes uneven.
Here’s a table that explains the increases and reductions in factors as a result of tyre pressure:
|Under Pressure||Recommended Pressure||Over Pressure|
|– Performance||+ Performance||– Traction|
|– Safety||+ Safety||– Safety|
|– Response||+ Even Wear||+ Tyre Damage|
Does Letting Air Out of Your Tyres Improve Grip?
You may have heard that letting some air out of your tyres improves grip. The logic is that the more of the tyre touching the ground, the better the traction. Though friction is what grips your tyre to the road, it does not depend on the surface area.
There’s an equation to measure friction. The pressure on your tyres is equal to the force divided by the area of contact. Therefore, an increase in the surface area of your tyre touching the road due to deflation is counteracted by the reduced pressure. The friction (and therefore traction) doesn’t increase.
Though your underinflated tyre will have no effect on your tyre’s traction, it will have a negative effect on your steering and stopping distances. You don’t want this in normal conditions, never mind on a slippery road.
What Can You Do to Improve the Grip of Your Tyres in Slippery Conditions?
In Australia, there are 5.4 road-related deaths per 100,000 people each year. Most of these are single-vehicle accidents rather than collisions. After long periods of hot and dry weather that are broken by heavy rainfall, the roads become extremely dangerous. When you take your car out in these conditions, you may as well be driving on an ice rink. So, what can you do to stay safe and improve tyre grip on the roads?
The number one thing you can do to stay safe in slippery conditions is to be a sensible driver. Always maintain your tyres in good condition, ensure they are correctly inflated, and:
- Increase the distance between yourself and other vehicles
- Make gentle turns and slow down for a corner
- Don’t brake if the vehicle aquaplanes; instead, pull off the accelerator and concentrate on steering through
What Causes Tyres to Lose Grip?
Tyres lose grip on the road due to a lack of traction. Here are some reasons your tyres might lose traction:
- Overbraking: By braking too hard, you can cause your wheels to lock up
- Oversteering: By steering too hard, you can cause the back end of your vehicle to slide out
- Over-acceleration: Applying too much power when accelerating leads to wheel spin
- Speeding: Driving too fast in slippery conditions causes a lack of traction
What Do the Experts Have to Say?
Tyre and vehicle manufacturers will all tell you the same thing when it comes to letting the air out of your tyres to improve grip. Bridgestone’s advice is:
“Underinflated tyres do not provide better contact with the road. Plus, it increases the amount of wear and tear to not only the bottom but also the shoulder of the tyres.”
Do your tyres keep deflating? Have you noticed uneven tread wear? Feel free to contact us to book an appointment or ask any questions you may have.
Keeping your family and fleet safe on the road,