Your 5-Minute Guide to Checking Tyre Tread & Pressure

Two simple checks you can do at home to improve your safety, increase fuel efficiency, and avoid fines. Here’s how.

Why Tread Depth & Tyre Pressure Are Critical for Your Safety

Understanding why these checks matter will help you remember to do them regularly.

The Danger of Low Tread

Your tyre’s tread grooves are designed to channel water away from the contact patch between your tyre and the road surface. When tread depth falls below 3mm, your tyres’ ability to disperse water diminishes rapidly, significantly increasing the risk of aquaplaning (also called hydroplaning) in wet conditions.

At the UK legal minimum of 1.6mm, your stopping distance in wet weather can be up to twice as long as with new tyres. This is why we recommend replacing your tyres well before they reach the legal limit.

Diagram showing a worn tyre aquaplaning on water versus a new tyre gripping the road.

The Hidden Cost of Incorrect Pressure

Tyre pressure affects the size and shape of your tyre’s contact patch with the road. Under-inflated tyres have a larger contact patch concentrated on the outer edges, causing uneven wear, poor handling, increased rolling resistance (which reduces fuel economy), and a higher risk of blowouts due to excessive heat buildup.

Over-inflated tyres have a smaller contact patch concentrated in the center, leading to a harsh ride, reduced grip (especially in wet conditions), and faster wear in the center of the tread. Maintaining correct pressure can improve fuel economy by up to 3% and extend tyre life significantly.

 

How to Check Your Tyre Tread Depth

⚠️ UK Legal Requirement: The legal minimum tread depth for cars is 1.6mm across the central three-quarters of the tyre. Driving with tyres below this limit can result in a £2,500 fine and 3 penalty points PER TYRE.

The Easy 20p Test: A Step-by-Step Guide

The 20p coin test is the simplest way to check if your tyres are approaching the legal limit. The outer band of a 20p coin is approximately 1.6mm wide—exactly the legal minimum tread depth.
Step 1: Get a 20p Coin
Take a standard 20p coin from your pocket or purse. No other tools are needed.
(Visual: Photo of hand holding a 20p coin)
Step 2: Insert the Coin into the Tread
Select one of the main tread grooves (the deeper channels that run around the circumference of the tyre). Place the 20p coin into the groove.
(Visual: Close-up photo of the coin being inserted into a tyre groove)
Step 3: Check the Outer Band
Look at the coin from the side. If you can see the outer band of the 20p coin, your tread is likely below the 1.6mm legal limit, and your tyres need to be checked by a professional immediately.
(Visual: A clear diagram showing two scenarios: “LEGAL” (outer band is hidden) and “ILLEGAL” (outer band is visible))
Step 4: Check Multiple Areas
Repeat the test in at least three different places around the circumference of the tyre and across its width to check for uneven wear. If you notice significantly uneven wear (e.g., one edge is much more worn than the other), this could indicate a wheel alignment problem.
Tread looking low? Don’t risk it.

How to Check Your Tyre Pressure

Checking your tyre pressure monthly can improve fuel economy by up to 3% and significantly extend the life of your tyres.

Step 1: Find Your Correct Tyre Pressure

Your vehicle’s correct tyre pressures are NOT written on the tyre itself. You can find them in one of three places:
•On the sticker inside the driver’s door jamb.
•Inside the glove box lid.
•Inside the fuel filler cap.

Step 2: Check When Tyres Are Cold

For an accurate reading, check your tyres when they are “cold”—meaning the car hasn’t been driven for at least two hours. If you must check them after driving, add 3-4 PSI to the recommended pressure to account for heat expansion.

Step 3: Use a Tyre Pressure Gauge

Unscrew the dust cap from the tyre valve. Keep the cap in a safe place—don’t lose it.
(Visual: Photo of a hand unscrewing a valve cap)

Step 4: Get Your Reading

Press the pressure gauge firmly and squarely onto the valve stem. The gauge will then display a reading in PSI or BAR. Compare this reading to your vehicle’s recommended pressure.

Step 5: Inflate or Deflate as Needed

If the pressure is too low, use an air pump to add air. If it’s too high, most gauges have a button to release air. Once the pressure is correct, replace the valve cap securely. Repeat for all four tyres.
⚠️ Losing Pressure Regularly? If you find yourself needing to add air more than once a month, you likely have a slow puncture or a faulty valve.

Your Tyre Maintenance Questions Answered

Q: How often should I check my tyres?
A: We recommend checking both tread depth and pressure at least once a month and before any long journeys.
Q: What are tread wear indicators?
A: These are small raised bars of rubber in the main tread grooves. When the tread wears down to the level of these bars, it is at the legal limit (1.6mm) and must be replaced.
Q: Why is my tyre pressure warning light on?
A: This means one or more of your tyres is significantly under-inflated. You should check your pressures immediately. If you inflate them and the light comes back on, you likely have a puncture.
Q: Can I just replace one tyre?
A: It’s best to replace tyres in pairs on the same axle to ensure balanced grip and handling. If you have a 4×4, you may need to replace all four.

Unsure or Don’t Have Time? Let the Experts Help.

If you’re not comfortable checking your own tyres, your tread is low, or you have a persistent pressure loss, don’t leave it to chance. Our technicians at IQ Tyres in Mitcham will perform a comprehensive, no-obligation safety check for FREE.

Book Your FREE Professional Tyre Check →

Or call us now for advice: 07904 962265