Could you be driving with an illegal tyre? Hankook demystifies jargon to keep you safe
Only 39% of UK drivers are aware of the legal minimum tyre tread depth of 1.6mm, meaning 61% of drivers could unknowingly be on the road with unsafe or even illegal tyres. In fact, research also shows that up to a quarter of vehicles could have illegal tyres.
“It’s a startling figure, and it highlights a significant knowledge gap that could compromise driver safety”, explains Mark Eatwell, Technical Services Manager at Hankook Tyre UK.
Road users may be embarrassed to admit they don’t know as much about their cars as they feel they should, and as a result, Hankook wants to take the confusion out of tyre jargon and instil confidence in drivers with a simple guide for consumers.
“Understanding tyre terminology might seem daunting at first, but it can make a big difference in maintaining safer vehicles, cutting unnecessary running costs, and making informed decisions when purchasing or replacing tyres”, Mark adds.
Below is Hankook’s go-to guide to demystify some of the most common tyre-related terms so drivers can hit the road knowing their vehicle is safe and roadworthy.
Hit the road, rolling
Tyres are the only point of contact between the car and the road. They influence everything from handling and braking to fuel efficiency and their condition has a direct impact on safety.
“Whether it’s ensuring correct pressure, monitoring tread depth, or understanding what the sidewall markings mean, having these basics down could reduce wear and tear, lower fuel consumption, and even help you avoid hefty fines for non-compliance”, explains Mark.
He decodes some of the key tyre jargon you might encounter.
1. PSI (Pounds per square inch)
PSI is a measurement of air pressure inside your tyres. Maintaining the correct PSI is essential for tyres to perform optimally. For instance, if the pressure is too high, the tyres wear unevenly and can reduce grip; if it’s too low, it increases rolling resistance, which can lead to excessive fuel consumption and overheating of the tyres.
A car’s tyre-pressure monitoring system (TPMS) tools measures tyre pressure and will flag to the driver when pressure is low; keeping the tyres properly inflated will help with fuel economy and improve the handling of the vehicle, so it’s best to not ignore these warnings.
“If you want to check your tyre’s air pressure, you can usually find the recommended PSI for your vehicle in the owner’s manual or on a label inside the driver’s doorframe. Most petrol stations have air pumps to check and adjust your PSI, making it easy to keep your tyres in tip-top shape”, explains Mark.
Another term that may crop up here is ‘bead’ – the area of the mounted tyre that sits against the wheel rim, forming an airtight seal. “The bead is crucial for keeping the tyre securely seated and maintaining proper inflation”, explains Mark.
2. Tread depth
Tread depth refers to the measurement of the grooves in the tyre’s surface. These grooves are critical for dispersing water from underneath the tyre, maintaining grip, and preventing skidding, especially in wet conditions.
“The legal minimum tread depth in the UK is 1.6mm across the central three-quarters of the tyre’s width and around its entire circumference. It’s a good idea to check your tyres regularly using a tread depth gauge or the simple “20p test” - if the outer band of the coin is visible when placed in the groove, it's time to replace that tyre”, advises Mark.
When replacing tyres, drivers may come across the term ‘run flats’. “These are tyres specifically constructed to allow limited driving, usually up to 50 miles at reduced speeds, after a puncture. This gives you time to reach a service station without needing an immediate roadside repair”, explains Mark.
3. Sidewall markings
The sidewall of a car tyre is like its ID card. It contains a string of letters and numbers that identify the tyre’s size, load index, speed rating, and more.
For example, the marking “205/55R16 91V” breaks down as follows:
205 – The width of the tyre in millimetres
55 – The height of the tyre’s sidewall as a percentage of its width (aspect ratio)
R16 – The tyre’s construction type (radial) and diameter of the wheel in inches
91V – The load index (how much weight the tyre can carry) and speed rating (the maximum speed the tyre can safely handle)
Deciphering these digits can help ensure consumers are buying the right tyres for their car.
4. Rolling resistance
Rolling resistance is the force that slows a tyre as it rolls, caused by the tyre pressing and rubbing against the road.
Tyres with low rolling resistance are designed to reduce energy losses as the tyre rolls, making the car more fuel-efficient.
“This term often comes up when shopping for eco-friendly tyres, as tyres optimised for lower rolling resistance can reduce your car’s carbon footprint and those rising fuel bills”, explains Mark.
5. DOT code
The DOT code is a series of letters and numbers that indicates where and when a tyre was manufactured. The last four digits represent the week and year of production (e.g., “1525” means the tyre was made in the 15th week of 2025).
“Tyres older than six years might not perform as well, regardless of outward appearance. Checking the DOT code can help you ensure you're not purchasing old stock that could compromise your safety”, adds Mark.
6. Alignment, tracking and balancing
It may sound like a smart navigation tool, but tracking refers to the angle and direction that tyres are set to, or it’s wheel alignment. As Mark explains, “As your tyre hits kerbs or speeds through potholes, they can turn away from a straight position and when this happens you might notice a dragging to one side when steering, uneven tyre wear or, in extreme cases, vibration through the steering wheel.
“Proper alignment helps tyres wear evenly and ensures the vehicle handles as it should, particularly when steering or cornering.
“Wheel balancing, on the other hand, is all about making sure the tyre and wheel assembly rotate evenly. If a wheel is out of balance, you might feel vibrations at certain speeds, which can cause uneven wear and potentially damage your suspension.
“Both alignment and balancing are essential for a smooth, safe ride and can extend the life of your tyres.”
Keep calm and drive on
Understanding these terms equips road users with the knowledge to regularly monitor their tyres for wear, pressure issues, and damage. This not only keeps them safer but also helps their tyres last longer. Plus, staying on top of tyre maintenance can prevent potential fines for non-compliance, such as having insufficient tread depth.
As Mark adds: “Tyres are your car’s most important safety feature, yet they are often overlooked and having insight into tyre terminology and maintenance will help you stay safer on the roads. Simple steps like checking your tread depth or ensuring the correct PSI can be the difference between a safe journey and an avoidable accident.
“Tyre jargon doesn’t have to be intimidating. By understanding key terms and checking your tyres regularly, you can ensure your vehicle is safer, more efficient, and less costly to run. Take a few extra minutes to give your tyres the care they deserve; you’ll thank yourself later”, he concludes.