Four Digits on the Sidewall: The Used-Car Tyre Audit Most Buyers Skip

Most used-car checks start at the paint and end at the odometer. The tyres get a quick kick, a nod, and maybe a comment about how much tread is left. That's a mistake. A car can look sharp, drive straight, and still be sitting on four pieces of rubber that are old enough to vote.

Here at Hyde Motors, we'd rather you spot that before you sign than discover it on a wet A-road in November. The good news is that you don't need a garage to do it. You need a torch, a phone, and about ten minutes.

Tread depth is only half the story

UK law says 1.6mm across the central three-quarters of the tread. Most sensible drivers replace well before that — around 3mm for decent wet-weather grip. But tread depth tells you how much rubber is left, not how old it is.

Rubber ages. It hardens, it perishes, and it can crack from the inside out. A tyre with 5mm of tread can still be a liability if it has spent years baking in the sun or sitting on a forecourt. That's why the date code matters as much as the depth gauge.

Where to find the DOT date code

Look for the letters DOT on the sidewall. After that you'll see a string of characters, and at the very end there's a four-digit number. That's the date.

The first two digits are the week of manufacture. The last two are the year. So 3221 means the 32nd week of 2021. A three-digit code means the tyre was made before 2000 — on a used car today, that's a museum piece, not a spare.

The catch is that the DOT code is often only on one side of the tyre. If you can't find it on the outer face, shine your torch into the wheel arch and look at the inner sidewall. It's awkward, but it's not a job that needs a jack. A phone camera on a short video can help you see round the back of the wheel without kneeling in a puddle.

The ten-minute forecourt audit

Bring a torch — your phone light will do at a push — and work around the car methodically. Don't just check the front tyres because they're easy to see.

Check all four tyres and the spare. Note the four-digit date on each one, plus the brand and tread pattern. You're looking for three things: age, mismatch, and condition.

Age is straightforward. Four tyres from the same year or a year apart is normal. A mix of 2018 and 2024 tyres on the same car suggests someone has been replacing them one at a time as they failed, which is not automatically bad, but it's worth asking about.

Mismatch matters more than many buyers realise. Different brands across an axle, or a winter tyre paired with a summer one, can affect grip and handling. It's not an MOT failure in itself, but it's a clue about how the car has been maintained. Check the sizes too — they should match the vehicle handbook and ideally match across each axle.

Condition is where the torch earns its keep. Look for cracks in the sidewall, especially near the rim. Look for bulges, cuts, and chunks missing from the tread. Kerb damage on the alloy is common; deep gouges in the tyre wall are not something to ignore. Run your hand around the tread — carefully, in case of sharp debris — and feel for uneven wear. A tyre worn bald on one edge points to alignment or suspension work that may be due.

While you're down there, check the valve stems for cracking and ask whether the car has a tyre pressure monitoring system. If it does, make sure no warning light is glowing on the dash when you start it.

What the dates actually tell you

There's no UK law that says a tyre must be replaced at a set age. The MOT doesn't fail a tyre simply because it's old. But most tyre manufacturers and motoring bodies suggest that tyres should be inspected closely from around five years and replaced by around ten, even if the tread looks fine.

On a used car in late 2026, a tyre stamped 2016 is a decade old. It might have passed an MOT last week, but it's still a candidate for replacement. A set of four matching tyres from 2022 is a much better sign.

This is where the maths gets real. A car with plenty of tread can still need hundreds of pounds of rubber if the sidewalls are cracked or the dates are old. Use that in your negotiation. Ask for a quote from a local tyre fitter and factor it into your offer, or ask the dealer to replace them as part of the deal. Get the agreement in writing, including the dates of the new tyres.

Run-flats, space savers and winter rubber

Run-flats need a closer look. Check that the car is actually meant to have them, that they match across the axle, and that there's no sidewall damage. Some run-flats can't be repaired after a puncture, and they're not cheap to replace. If the car has a space saver, check its date too. Many are original to the car and have never been used — which means they're also very old. A space saver is a temporary get-you-home wheel, usually limited to around 50mph, so don't treat it as a full spare.

Winter tyres are another one to read carefully. They're brilliant in cold, wet conditions, but the compound is softer and they can age just like any other tyre. If a car is being sold in summer with winter tyres fitted, ask why. It's not a deal-breaker, but it's a question worth asking.

Questions to ask before you sign

Ask the dealer for the date codes on all four tyres. Ask whether any have been replaced recently and whether they have matching brands and patterns. If something looks old or cracked, ask for it to be replaced before collection — and get the new date codes in writing. If the answer is vague, budget for tyres yourself.

A used car is a collection of parts, and the tyres are the only ones touching the road. Give them ten minutes with a torch and you'll know more about the car than a shiny bonnet ever tells you. Straight advice, no drama — that's the Hyde way.