Tyres and legal tread depth: a pre-purchase safety check

Tyres are easy to overlook when a used car is polished and parked in a showroom, yet replacing four tyres can change the real purchase cost. Check tread, pressure, size, damage, age, matching and uneven wear before you sign. The legal minimum is not the same as a comfortable safety margin, and a car that passes an MOT can still need tyres soon.

This guide is a visual and budgeting checklist, not a substitute for a qualified tyre inspection. Never crawl under a car or stand in traffic to check it.

Check all four tyres

Turn the steering to inspect the front tyres and use a safe position to view the rear. Look for cuts, bulges, cracks, exposed cords, puncture repairs and objects in the tread. A damaged sidewall needs professional attention and should not be ignored because the tread looks deep.

Read the size, load index and speed rating on each tyre and compare them with the vehicle handbook or approved specification. Different sizes front and rear can be correct, but four random sizes are not. Ask the dealer to explain any mismatch.

Check the spare wheel, repair kit, locking-wheel-nut key and tyre-pressure monitoring system. Put missing equipment in the order form.

Tread depth and uneven wear

Use a tread-depth gauge if you have one or ask a tyre specialist to measure it. Check across the width, not only in the centre. Wear on one edge can indicate alignment, suspension or pressure problems. A single low tyre may be a symptom rather than the whole problem.

The legal threshold for cars is set out in the Highway Code and MOT guidance, but do not wait until a tyre is at the legal limit. Wet braking and cold-weather grip can be affected before that point. Ask for the measured depth in millimetres and record it.

If two tyres are near replacement, price two. If all four are old or mismatched, price a complete set and a wheel-alignment check.

Pressure, age and storage

Tyre pressure should be checked cold against the manufacturer’s label, not judged by sight. Ask when it was last set. An over- or under-inflated tyre can wear unevenly and affect handling.

Find the date code and ask how the tyres were stored if the car has been standing. Age alone does not establish that a tyre is unsafe, but cracks, hardening and poor storage deserve an inspection. Do not buy a car on the assumption that new-looking tread means new rubber.

An electric car may be heavier and have different approved tyres. Check the exact specification, especially if the dealer has fitted replacements.

Interactive guide

Tyre check before buying

Record the condition and cost before making an offer.

Buying an EV or performance car

Ask whether tyres are approved for the model and whether acoustic foam or a load rating is required. High torque can increase wear if the car has been driven aggressively. A low-profile tyre may cost more and be more vulnerable to pothole damage.

For a performance car, check wheel rims for buckles and ask about alignment. For a van, confirm load rating and commercial-vehicle requirements.

Long journeys and winter travel

Check tyres before a motorway trip and before travelling to a colder country. Winter-tyre rules may apply outside the UK even though there is no universal UK changeover date. Check the destination’s requirements and carry the equipment specified for the route.

Do not fit a mismatched pair simply to save money. Ask a tyre centre for advice and keep the invoice.

At handover

Photograph tyres, wheels, pressures if displayed and any damage. Get replacement dates, brand, size and warranty in writing. A “new set before collection” should appear in the order form with the correct specification.

Use Car Dealer Finder to compare dealers by area. Tyres are a small part of a vehicle’s appearance but a large part of its safety and first-year cost.

Read the sidewall as well as the tread

Record the tyre size, load index, speed rating, construction, brand, model and any marked rotation or inside/outside direction. Compare all four wheels with the specification in the handbook or on the vehicle label. A tyre can have legal tread and still be the wrong size, damaged or unsuitable for the axle.

Look for cuts, bulges, exposed cords, cracking, nails, valve damage and objects lodged in the tread. Check the inner shoulder, not just the part visible from outside; use a torch or ask for the car to be lifted by a qualified person. Do not drive on a tyre that appears unsafe simply to complete the viewing.

Interpret uneven wear

Wear on one edge can point to alignment, suspension, inflation or load issues. Wear across the centre can suggest over-inflation, while both shoulders may indicate under-inflation, but a visual pattern is not a diagnosis. Ask for a professional inspection and check the tyre-pressure record. A new tyre on one side can hide an older problem on the other.

Check the age and storage history of the tyres. The date code is useful evidence, but age limits depend on condition and use rather than a single universal number. Ask when the car was stored, whether it spent long periods outdoors and whether the spare or repair kit is present. Include replacement timing in the ownership budget.

EV, hybrid and performance considerations

Electric cars can deliver high torque and carry substantial weight, so tyre load rating, efficiency, noise and manufacturer approval may matter. Compare the exact specification for the vehicle rather than assuming a generic tyre is acceptable. Ask whether the car has a tyre-repair kit, space-saver or no spare wheel, and how roadside assistance handles a puncture.

On a performance or four-wheel-drive vehicle, check whether tyres must match by axle or across the car. Ask a specialist about tread differences and the effect on driveline systems. For winter travel, confirm the law and insurance position for the countries you will visit; UK requirements do not automatically answer an overseas journey.

Buying used with a tyre plan

Ask the dealer to write “four tyres replaced” with size, specification and brand into the order form. If only two are changed, record axle and tread depth. Request the pressure set at handover and the date of the inspection. Do not accept “good tyres” as a measurable promise.

Photograph tread and damage when collecting the car, then recheck pressure after carrying a load. Keep receipts and alignment reports. Tyres affect braking, steering, range and noise, so their cost belongs in the first-year calculation alongside tax, servicing and insurance.

Ask for measurements, not reassurance

If the dealer says tyres are acceptable, ask for tread readings across the inner, centre and outer sections and the inspection date. Measurements are useful only when the gauge and location are clear, but they are better than a description with no evidence. Note whether the tyres are all-season, summer or winter and whether the spare follows a different specification.

After purchase, check pressures when the tyres are cold and follow the vehicle label rather than a number found on a generic website. Recheck after a heavy load, a long journey or a puncture repair. If the steering pulls, the car vibrates or a pressure keeps falling, stop treating it as normal wear and arrange a qualified examination.