Maintaining correct tyre pressure is one of the simplest and most important aspects of vehicle maintenance. Incorrect tyre pressures compromise safety, increase fuel consumption, accelerate tyre wear, and can lead to catastrophic failure. This guide explains everything UK drivers need to know about tyre pressure. ## Finding Your Recommended Tyre Pressure Your vehicle's recommended tyre pressure is displayed on a sticker located inside the driver's door jamb, inside the fuel cap door, or in the owner's handbook. Do not use the pressure stamped on the tyre sidewall as this is the maximum pressure, not the recommended pressure. Typical recommended pressures for passenger cars range from 30 to 36 PSI (206 to 248 kPa) for front tyres, and similar for rear tyres. Many vehicles have different recommended pressures for front and rear axles, particularly performance cars and some four-wheel-drive vehicles. If you carry heavy loads or regularly tow a trailer, the recommended pressure may increase. Look for load-specific pressure information in your vehicle handbook or on the door jamb sticker, which typically shows pressures for normal and full-load conditions. Winter tyres require slightly lower pressure than summer tyres because they are designed to operate at lower pressures. Check your tyre or vehicle manufacturer guidelines for winter tyre pressures. Typically, reduce pressure by 2-3 PSI compared to summer tyres. ## How to Check Tyre Pressure Tyre pressure should be checked at least monthly and before long journeys. Check pressure when tyres are cold because heat from driving causes air to expand and gives artificially high readings. Remove the valve cap from the tyre valve, press the gauge firmly onto the valve stem, and read the pressure display. Compare against the recommended pressure. Add air if pressure is too low, or release air if too high. Tyre pressure gauges vary in accuracy. Dial-type and digital gauges are generally more accurate than stick-type pencil gauges. Many motorway service station air pumps have built-in gauges, though these vary in reliability. After adjusting pressure, replace the valve cap to prevent dust and moisture from entering the valve and causing slow leaks. Consider upgrading to brass valve caps with rubber seals for better protection. ## Effects of Under-Inflation Driving with under-inflated tyres is the most common tyre pressure problem and the most dangerous. Even tyres 5-8 PSI below recommended pressure significantly increase the risk of tyre failure. Under-inflated tyres flex excessively in the sidewall area, generating heat build-up. At high speeds or with heavy loads, this heat can cause the tyre structure to fail, resulting in sudden deflation or a blowout. The AA reports that tyre-related factors contribute to around 1,200 road casualties annually in the UK. Fuel economy suffers significantly with under-inflated tyres. The Rolling Resistance of under-inflated tyres is substantially higher, increasing fuel consumption by 5-10% in some cases. Over 10,000 miles, this can add £100-200 to your annual fuel bill. Tyre wear is also affected. Under-inflated tyres wear more quickly and wear predominantly on the outer edges of the tread. This pattern is distinctive and recognisable with a little practice. ## Effects of Over-Inflation Over-inflated tyres are less common but equally problematic. Excessive pressure makes the tyre contact patch smaller and concentrated in the centre of the tread. This reduces grip, particularly in wet conditions, and makes the ride harsh and uncomfortable. Over-inflated tyres wear rapidly in the centre of the tread while leaving the outer edges barely worn. This pattern is the opposite of under-inflation wear and indicates excessive pressure. The reduced contact patch from over-inflation compromises braking distance and handling. The vehicle may feel nervous and unstable, particularly on uneven road surfaces. ## Tyre Pressure Monitoring Systems Since 2012, all new cars sold in the EU and UK must be equipped with a Tyre Pressure Monitoring System (TPMS). These systems alert the driver when tyre pressure drops below 25% of the recommended pressure. There are two types of TPMS. Direct systems use pressure sensors inside each tyre that transmit real-time pressure data to the car's computer. Indirect systems use the ABS wheel speed sensors to detect when one tyre is rotating faster than others, indicating reduced pressure. A TPMS warning light is a legal requirement to address immediately. If the light comes on, check all tyre pressures as soon as possible and inflate to the correct pressure. If the light persists after inflation, have the tyre inspected for slow punctures or TPMS sensor faults. TPMS sensors require battery replacement when the battery fails, typically every five to seven years. Sensor replacement costs £40-100 per sensor plus fitting, depending on the vehicle and sensor type. ## Frequently Asked Questions **Should I adjust tyre pressure for motorway driving?** For sustained high-speed motorway driving, some manufacturers recommend increasing tyre pressure by 2-3 PSI above normal settings to account for the increased load and heat generation. Check your owner's handbook for specific guidance. **Do nitrogen-filled tyres need less pressure checking?** Nitrogen-filled tyres lose pressure more slowly than air-filled tyres because nitrogen molecules are larger than oxygen and leak through tyre rubber more slowly. However, nitrogen tyres should still be checked regularly. The performance difference is modest and nitrogen filling is generally not worth the cost. **How does temperature affect tyre pressure?** Tyre pressure drops approximately 1 PSI for every 10-degree Celsius drop in temperature. This means cold winter mornings can reduce tyre pressure significantly. Check pressures more frequently in winter and add a few PSI extra to account for expected temperature drops. **Can I use different pressure in front and rear tyres?** Some vehicles are designed to run different front and rear pressures, particularly performance cars and some four-wheel-drive vehicles. Always follow the manufacturer's specific recommendations. Do not assume front and rear should be the same.