Tyre Pressure Guide: Safety, Fuel Economy & Correct PSI

Tyre pressure is one of the most overlooked aspects of car maintenance in the UK. Studies suggest that around one in four cars is driven with at least one significantly under-inflated tyre. Yet maintaining the correct tyre pressure takes about five minutes, costs nothing (most filling stations have free air), and has a meaningful impact on safety, fuel economy, and tyre life.

Where to Find Your Correct Tyre Pressure

Your vehicle’s recommended tyre pressures are specific to your car, not to the tyre brand. They’re set by the vehicle manufacturer and you’ll find them in two places:

• Inside the driver’s door sill — a sticker or plate listing pressures for different load conditions (normal load vs. full load)
• In the vehicle handbook — usually in a tyre or specifications section

Do not rely on the maximum pressure figure on the tyre sidewall — that is the maximum safe pressure for the tyre, not the recommended operating pressure for your vehicle. The two figures are completely different.

Note that many cars specify different pressures for front and rear tyres. Front tyres on FWD cars often carry more weight and may require a higher pressure. Some vehicles also have different recommendations depending on whether you’re carrying a full load (four passengers and luggage) versus driving solo.

How Often Should You Check Tyre Pressure?

The recommended frequency for checking tyre pressure is at least once a month, and always before a long journey. Tyres naturally lose around 1 PSI per month through the rubber, and more in cold weather (tyre pressure drops approximately 1 PSI for every 10°F / 5.5°C drop in temperature).

Check pressures when the tyres are cold — meaning the car hasn’t been driven for at least an hour, or has been driven less than a mile. Driving heats the air inside the tyre, increasing pressure by several PSI. Checking after driving will give you a false high reading.

Under-Inflation: The More Common Problem

Under-inflation is the more common of the two problems and the more dangerous. A tyre that is 20% below its recommended pressure (e.g. 24 PSI instead of 30 PSI) will:

• Flex excessively, generating heat that damages the internal structure
• Wear the outer edges of the tread faster than the centre
• Reduce fuel economy by up to 3% per badly under-inflated tyre
• Increase the risk of a blowout, particularly at motorway speeds
• Increase stopping distances and reduce handling response

Over-Inflation: The Less Common but Still Risky Problem

Over-inflated tyres ride on a reduced contact patch — just the central portion of the tread instead of the full tread width. This causes:

• Accelerated wear in the centre of the tread
• Harder, bouncier ride with less comfort and noise absorption
• Reduced grip in wet and dry conditions (smaller contact patch)
• Increased sensitivity to road damage and kerbs

Over-inflation by 10% is much less dangerous than under-inflation by 20%, but it still costs tyre life and worsens handling. Check your pressures and keep them within a couple of PSI of the recommended figure.

TPMS: Tyre Pressure Monitoring Systems

Since November 2014, all new cars sold in the UK are required to have a Tyre Pressure Monitoring System (TPMS). A warning light on the dashboard will illuminate when a tyre is 25% or more below the recommended pressure. This sounds reassuring, but 25% is a significant deficit — a tyre at this level is already noticeably underperforming and wearing unevenly. TPMS is a last resort warning, not a substitute for monthly pressure checks.