What Happens If Your Tyre Pressure Is Higher or Lower Than Recommended?

Tyre pressure is one of those things many drivers check only when the tyre looks visibly flat. But even when a tyre looks perfectly normal, its pressure can be too high or too low.

The pressure recommended by the car manufacturer is not an arbitrary number. It is selected based on factors such as the vehicle's weight, tyre size, handling characteristics, fuel efficiency, ride comfort, and load capacity.

So what actually happens when you drive with tyre pressure above or below the recommended level?

What Happens When Tyre Pressure Is Too Low?

When a tyre is underinflated, more of the tyre's sidewall flexes as it rolls along the road. This creates more resistance and makes the tyre work harder.

One of the first things you may notice is that the steering feels heavier, particularly at lower speeds. The car can also feel less responsive because the tyre isn't maintaining its intended shape as effectively.

Underinflation can also increase rolling resistance. That means the engine has to work harder to move the vehicle, which can affect fuel efficiency.

The bigger concern, however, is heat.

A significantly underinflated tyre can flex more than intended, generating additional heat as you drive. Excessive heat buildup can contribute to tyre damage and, in severe cases, increase the risk of tyre failure.

Does Low Tyre Pressure Reduce Mileage?

It can.

When tyre pressure is below the manufacturer's recommended level, the tyre generally has greater rolling resistance. Your engine therefore needs to use more energy to keep the vehicle moving.

The actual change in fuel consumption depends on how far the pressure has dropped, the vehicle, driving conditions, tyre type and several other factors.

So if your car suddenly seems to be returning worse mileage, checking tyre pressure is one of the simple things worth doing before assuming there is a mechanical problem.

Can Low Tyre Pressure Affect Tyre Wear?

Yes.

An underinflated tyre tends to put more stress on its outer tread areas and sidewalls. If you consistently drive with incorrect pressure, the tread may wear unevenly.

You may eventually notice that the edges of the tyre are wearing faster than the centre.

Uneven tyre wear isn't just an appearance issue. It can shorten the useful life of the tyre and mean you need to replace it sooner.

What Happens When Tyre Pressure Is Too High?

Now let's look at the opposite problem.

When a tyre is overinflated, it becomes stiffer because there is more air pressure inside it. The centre portion of the tread can carry more of the load than the tyre was designed to under the recommended pressure.

This can change the way the car feels on the road.

The ride may feel harder, and bumps and imperfections in the road can become more noticeable because the tyre has less ability to absorb them.

Does High Tyre Pressure Improve Mileage?

You may sometimes hear that increasing tyre pressure improves fuel economy.

There is some truth behind the idea that lower rolling resistance can reduce energy consumption, but that doesn't mean you should deliberately overinflate your tyres.

The recommended pressure is a compromise between factors such as rolling resistance, handling, comfort, tyre wear and load capacity.

Running significantly above the recommended pressure simply to chase better mileage can create other problems.

Can High Tyre Pressure Reduce Grip?

It can affect the tyre's contact with the road.

An overinflated tyre may have a smaller effective contact patch, depending on the tyre and vehicle. This can change the way the car responds, particularly during braking and cornering.

That doesn't mean the car will suddenly become impossible to control. But tyre pressure is part of the vehicle's overall handling characteristics, so deliberately running substantially higher pressure than recommended isn't a good shortcut for improving performance.

Does High Tyre Pressure Cause Uneven Tyre Wear?

It can.

When a tyre is significantly overinflated, the centre portion of the tread can experience greater wear than the outer sections.

Over time, this can produce a noticeable difference in tread wear across the width of the tyre.

So both extremes can cause problems:

Too low: greater wear toward the edges.

Too high: greater wear toward the centre.

Maintaining the manufacturer's recommended pressure helps the tyre operate closer to the conditions it was designed for.

What Is the Correct Tyre Pressure for Your Car?

This is where many drivers make a mistake.

The correct pressure is not necessarily the maximum pressure printed on the tyre sidewall.

The tyre sidewall typically includes information about the tyre's maximum permissible pressure or other specifications. Your car manufacturer's recommended operating pressure is different.

Look for the recommended pressure on the vehicle's tyre-pressure label, which is commonly found on the driver's door frame or door pillar. It may also be listed in the owner's manual.

Depending on the vehicle, the recommended pressure can differ between the front and rear tyres and may also have different recommendations for heavier loads.

Should You Check Tyre Pressure When the Tyres Are Hot?

Ideally, check tyre pressure when the tyres are cold.

Driving causes tyres to heat up, and the air pressure inside them increases as the temperature rises. If you measure a hot tyre and immediately adjust it based on the cold specification, you can end up setting the pressure incorrectly.

A good habit is to check your tyres before a long drive, ideally after the car has been parked for several hours.

Does Weather Affect Tyre Pressure?

Yes.

Tyre pressure changes with temperature. As the surrounding temperature changes, the air pressure inside the tyre changes as well.

This is one reason you may notice a difference in tyre pressure between cooler mornings and hotter conditions.

It doesn't mean you should constantly adjust the pressure every time the temperature changes. Instead, check the tyres periodically and maintain them according to the manufacturer's recommended cold pressure.

What About Carrying Extra Passengers or Luggage?

Your car's recommended tyre pressure may include different specifications for normal loads and heavier loads.

If you're taking a long trip with several passengers and a fully loaded boot, check the manufacturer's recommendations rather than guessing.

Some vehicles specify a higher pressure for heavy loads because the tyres are carrying more weight.

The important thing is to follow your specific vehicle's recommended figures, not a generic pressure number from another car.

How Often Should You Check Your Tyre Pressure?

You don't need to check it every time you start the car, but leaving it unchecked for months isn't a good habit either.

Tyres naturally lose some pressure over time, and small leaks, temperature changes, punctures and valve issues can cause additional pressure loss.

Checking your tyre pressure about once a month and before long trips is a useful routine. If your car has a tyre-pressure monitoring system, pay attention to warnings rather than ignoring them.

Can You Drive With the Wrong Tyre Pressure?

A small difference from the recommended pressure doesn't necessarily mean you need to stop the car immediately.

But if the pressure is significantly too low or too high, it should be corrected before continuing normal driving.

A tyre that is visibly underinflated, rapidly losing pressure, damaged, or showing signs of a puncture should be inspected rather than simply inflated and forgotten.

What Is Worse: High or Low Tyre Pressure?

Neither should be treated as a normal driving condition.

Very low pressure can increase rolling resistance, heat buildup and tyre wear, while excessive pressure can affect ride comfort, handling and tread wear.

The safest approach is not to choose between the two. Keep the tyres at the pressure recommended by the vehicle manufacturer.

Final Thoughts

Tyre pressure might seem like a small maintenance detail, but it affects much more than how the tyre looks.

Too little pressure can increase rolling resistance, heat buildup and uneven wear. Too much pressure can make the ride harsher and alter the tyre's contact with the road.

Instead of relying on how the tyre looks or using the number printed on the tyre itself, check your vehicle manufacturer's recommended pressure and measure it when the tyres are cold.

The right tyre pressure isn't the highest or lowest number. It's the number your car was designed to run.