---
title: "How Long Do Tires Last? Tread Is Only Half the Answer"
description: "Tyres run on two clocks: tread is consumed by distance, rubber by time. Federal rules put the build date on every sidewall — here is how to read it, and why a used car is where age catches buyers out."
url: "https://baronauto1.com/car-care/how-long-do-tires-last/"
type: "article"
published: "2026-08-28"
modified: "2026-08-28"
site: "Baron Auto"
disclaimer: "This site is under new ownership and is not affiliated with Baron Auto Emporium dealership."
---

# How Long Do Tires Last? Tread Is Only Half the Answer

> Tyres run on two clocks: tread is consumed by distance, rubber by time. Federal rules put the build date on every sidewall — here is how to read it, and why a used car is where age catches buyers out.

*Detailing & Maintenance · 29 min read · 6,458 words*

## The short version

- Tyres run on two clocks at once. Tread is consumed by distance; the rubber itself is consumed by time. A tyre can pass one test and fail the other, and a used car is exactly where that happens.
- Every tyre sold in the United States carries its own date of manufacture, moulded into the sidewall because federal regulation requires it. The last four digits of the Tire Identification Number are the week and the year the tyre was built.
- NHTSA puts the tread replacement point at 2/32 of an inch, and every tyre has moulded bars in the grooves that show you that depth without a coin, a gauge or an opinion.
- On ageing, NHTSA says some vehicle and tyre manufacturers recommend replacement at six to 10 years old regardless of treadwear — and, more usefully, that you cannot detect ageing by looking at the tyre.
- The wear pattern matters more than the depth. Even wear is ordinary consumption. Uneven wear is a statement about inflation, alignment or suspension, and the tyre is the symptom rather than the fault.
- Nobody registered the tyres on a used car to you. A VIN recall search returns recalls issued against the vehicle; tyres are recalled by brand and tyre line and have to be checked separately.

The honest answer to how long tyres last is that they do not last a length of time or a distance — they last until whichever of two separate limits arrives first. One is tread, which is worn away by rolling and can be measured in a few seconds with a coin. The other is age, which happens whether the car moves or not, cannot be seen, and is the one almost nobody checks.

What makes this worth writing properly rather than repeating the usual mileage estimate is that the second limit is not a matter of judgement. Every tyre in the country is stamped with the week it was made, in a fixed format, by federal requirement. The information is free, it is on the car in front of you, and reading it takes about ten seconds per tyre once you know where to look.

**Figure: How to read the date of manufacture on a tyre sidewall**

Diagram of a tire identification number in three groups, with the DOT certification mark shown separately beside it. The first two groups identify the plant and the tyre; the final four digits are the week and the year it was built.

Every tyre sold in the United States carries this code, moulded into the sidewall under 49 CFR Part 574. Tread depth tells you how much of the tyre is left; only these four digits tell you how old it is, and a tyre can run out of the second while it still has plenty of the first. Worth checking on both sides — the full code is often moulded on one side only.

That code is the subject of the first half of this page. The second half is about everything the code does not tell you: how much tread is left, what the wear pattern says about the rest of the car, and what four tyres considered as a set reveal about how a used car has been kept.

## Two clocks, and only one of them is on the dashboard

Think of a tyre as having two independent countdowns running.

The first is mechanical. Rubber is abraded away against the road surface, faster under acceleration, braking and cornering, faster again when the tyre is at the wrong pressure or the wheel is not pointing where the car is going. This countdown moves only when the car moves, and it is the one people mean when they ask how many miles a set of tyres is good for. It is also, genuinely, unpredictable: the same tyre fitted to the same model can cover wildly different distances depending on the driver, the roads and the maintenance, which is why the mileage figures printed on packaging are ranges wide enough to be nearly useless for planning.

The second countdown is chemical, and it does not care whether the car is moving. Rubber is a compound that reacts with oxygen and ozone, is broken down by ultraviolet light, and is driven along by heat. Manufacturers add antioxidants and antiozonants that slowly migrate to the surface and are consumed there, which is part of why an old tyre eventually develops fine cracking in the sidewall and the base of the tread grooves. That process starts on the day of manufacture and continues in a warehouse, on a shelf, under a car cover and in a garage.

NHTSA is direct about the practical consequence: most drivers cover enough distance that the tread wears out before ageing becomes an issue, and the risk sits with the people who do not. Low annual mileage, a second car, a classic, a camper or a van used a few weekends a year — those are the cases where the chemical clock reaches the finish line while the tread still looks respectable. The agency also notes that ageing is a greater concern in the warmer southern states, because heat and sunlight accelerate it.

A used car is where these two clocks are most likely to disagree, for a simple reason: you did not watch either of them run. A private seller with a low-mileage car that spent five summers on a driveway is not being dishonest when they say the tyres have plenty of tread left. They do have plenty of tread left. That is not the same claim as the tyres being fine.

## The date is moulded into the tyre

The regulation is 49 CFR Part 574, titled Tire Identification and Recordkeeping. It requires new tyre manufacturers to permanently mould a Tire Identification Number, or TIN, into one sidewall of every tyre they make. For a new tyre the TIN runs to thirteen symbols, split into three groups: a plant code identifying where it was built, a manufacturer’s code that can carry size and brand information, and then the date code.

The date code is the part that matters here, and the regulation is unambiguous about it. In the words of the rule itself, it consists of four numerical symbols, is the final group, and “must identify the week and year of manufacture”. The first two digits are the week, numbered from the first full calendar week of the year, and the last two digits are the last two digits of the year.

NHTSA gives the worked example on its own consumer pages, and it is worth using theirs rather than inventing one: a tyre whose TIN ends 0308 was made in the third week of 2008. That is the whole method. Read the last four digits, split them down the middle, and you have a date accurate to the week.

One point of precision, because it trips people up when they go looking. The letters DOT that sit next to the number are not part of the TIN. Under the regulation the DOT symbol is a separate certification — the manufacturer’s statement that the tyre conforms to the applicable Federal Motor Vehicle Safety Standard — positioned relative to the identification number. In practice it is the landmark you use to find the code, because DOT is the only thing on a busy sidewall that reliably announces what follows it. Just do not count it as one of the groups.

### Which sidewall, and why you may end up on the floor

The regulation requires the full TIN on one sidewall only. Manufacturers commonly mould a partial number on the other side, ending before the date code. This is not an oversight and it is not a defect — it is what the rule permits.

The consequence at a viewing is unglamorous. If the outward-facing sidewall shows a DOT number that stops short of a four-digit ending, the date is on the inward face, and you will have to crouch and get a torch onto the back of the tyre or turn the steering to full lock to swing the front tyres round. NHTSA says the same thing in plainer words: look on both sides, because the number may not be on both.

Check all four, and check the spare if there is one. Tyres are frequently replaced in pairs, so two matching dates on the front and two much older ones on the rear is an ordinary finding rather than a strange one — but you only discover it by reading all four.

### Codes that are only three digits long

If you are looking at a genuinely old tyre — on a classic, a trailer, an unused spare that has lived in a boot well for decades — you may find a date code with three digits instead of four. That is not a misprint.

The original format used a single digit for the year, which worked while everyone could assume the decade. NHTSA amended Part 574 in a 1999 final rule to require four digits instead of three, allowing manufacturers to comply early from the date the rule was published and making it mandatory from July 2000. The stated reasons were better traceability during recalls, easier identification of older tyres, and harmonisation with the European and international standards, which were moving to four digits at the same time.

So a three-digit code means the tyre predates that changeover, which by itself is the only fact you need: a tyre that old should not be carrying a vehicle, whatever the tread looks like. There is a long-standing convention of reading a small triangle moulded after the digits as indicating the 1990s, but the decade is not encoded in the number itself, and you do not need it. Three digits is already the answer.

One more format wrinkle worth knowing, because it produces a shorter number rather than a shorter date. Manufacturers who had been issued the older two-symbol plant code were permitted to keep using it, alongside a shorter overall TIN, until April 2025. Retreaded tyres carry a shorter TIN too. In both cases the date code is still four digits and still the final group, so the rule for reading it does not change: last four, week then year.

### The one-sentence version

Find DOT on the sidewall, read to the end of the number that follows it, and take the last four digits. First two are the week, last two are the year. If the number ends before a four-digit group, you are on the wrong side of the tyre.

## How old is too old

There is no federal expiry date for tyres, and it is worth being straightforward that no such number exists to be looked up. What exists is guidance, and NHTSA states it carefully: as tyres age they are more prone to failure, and some vehicle and tyre manufacturers recommend replacing tyres that are six to 10 years old regardless of treadwear.

Note the shape of that sentence. It is not the agency setting a limit. It is the agency reporting that some vehicle makers and some tyre makers set one, and the reason it is phrased that way is that the manufacturers do not all agree with each other. Your own car’s handbook may contain a recommendation; a tyre manufacturer’s published guidance may contain a different one. Both are worth reading and neither is a regulation.

What is not in dispute is the direction of travel, and the single most useful thing NHTSA says on the subject is a warning rather than a number: you cannot detect tyre ageing simply by looking at your tyres. Sidewall cracking, when it appears, is a late and unreliable signal. A tyre can be well through its chemical life with a sidewall that looks perfect, and a tyre can show fine surface crazing from ozone exposure without being structurally finished. This is precisely why the date code exists and why it is the better instrument. It is a measurement rather than an impression.

For a buyer, the practical translation is a series of thresholds rather than a cliff edge:

- **Within the first few years.** Age is not the constraint. Judge these tyres on tread and wear pattern like any other.
- **Approaching the lower end of the manufacturers’ range.** Age becomes a live question. Worth pricing in, worth mentioning, not on its own a reason to walk.
- **Past the upper end of that range.** The tyres are a replacement item on this car whatever the tread depth, and the negotiation should reflect four tyres and fitting rather than nothing.
- **Old enough that the code has three digits.** Not a negotiation. That tyre belongs off the car.

The special case is the spare, and NHTSA singles it out. Spares are the most reliably aged tyre on any vehicle because they are almost never replaced and almost never inspected — the agency’s advice is that even a full-size spare should not be pressed into service as a replacement for worn tyres except in an emergency. On a used car, the spare is also the single easiest date code to read, because nobody has to lie on the ground to do it. Lift the boot floor, read the code, and you have learned something about how the car has been kept as well as about the spare.

### A tyre with no miles on it is not a new tyre

Tyres bought as unused stock, tyres fitted to a low-mileage car, and tyres sold as new from a shelf that has been sitting a long time all carry a date code that started counting on the day they were built. Ageing runs in a warehouse exactly as it runs on a car. If you are buying tyres rather than a car, the date code is a fair question to ask before fitting, and the answer is moulded into the product.

## Tread depth, and what the number actually means

Tread exists to give water somewhere to go. On a dry road a slick tyre grips superbly; on a wet one the tread grooves are the only thing evacuating water from under the contact patch fast enough to keep rubber touching tarmac. As the grooves get shallower they move less water per revolution, so the speed at which the tyre starts to float rather than grip comes down. That is the mechanism, and it explains why tread loss produces no perceptible change at all until conditions turn bad, at which point it produces a large one.

NHTSA’s replacement point is 2/32 of an inch of remaining tread depth. Below that, in the agency’s words, tyres are not safe and should be replaced.

The best way to check against that figure is not a coin at all. Every tyre has moulded treadwear indicators — raised bars running across the base of the main grooves, set at exactly that depth. When the surrounding tread has worn down until it sits flush with those bars, the tyre has reached the replacement point. There is no reading to interpret and no tool required. Look into the groove, find the bar, and see whether the tread around it is still standing proud of it.

### The penny test, the quarter test, and where both fall short

The coin method is the one everybody knows, and NHTSA does publish it: place a penny into the groove with Lincoln’s head upside down and facing you, and if you can see the top of his head, the tyre needs replacing. It works because the distance from the coin’s edge to the top of the head is close to that same 2/32 of an inch.

The quarter version is a common variant rather than an official one. Washington’s head sits further from the edge — roughly twice as far, around 4/32 of an inch — so the test stops the tyre sooner. That is a sensible habit, but be clear about what it is: a self-imposed margin, not a standard. Nothing is failing when a tyre passes the penny and fails the quarter. What you have learned is that the tyre is nearer the end of its tread life than the start of it, which is useful to know before winter rather than during it.

The real limits of coin testing are not about which coin:

- **It reads one spot.** Tread does not wear evenly across the width of a tyre or around its circumference. A single measurement at a single point can miss the worn part entirely, which is the whole reason wear patterns are diagnostic.
- **It gives a pass or fail, not a trend.** A tyre that passes tells you nothing about whether it passes by a wide margin or is a month from the bar. A cheap depth gauge does, costs very little, and is worth carrying if you look at cars regularly.
- **It says nothing about age.** This is the failure that matters on a used car, and it is the whole argument of this page. Tread depth is silent about the date code.
- **It can be defeated by the tyre.** Push a coin into the groove directly over a treadwear indicator bar and you are measuring the height of the bar, not the depth of the groove. Check in the groove between bars.

Measure in at least three places across the width of each tyre — inner shoulder, centre, outer shoulder — and at two or three points around the circumference. It takes another minute and it converts a pass or fail into an actual picture of how the tyre has worn. That picture is the next section.

## Reading the wear pattern

Here is where tyres become genuinely valuable to a buyer, because a tyre records the conditions it has lived in and displays them on its face.

Even wear across the whole width means the tyre has been correctly inflated and correctly aligned for most of its life, and that the suspension holding it has been doing its job. That is a good finding about the car, not just about the tyre. Anything else is a pattern, and patterns point somewhere.

**What a tyre wear pattern usually points at**

| What you see | What it usually means |
| --- | --- |
| Centre band worn, both shoulders healthy | Chronic over-inflation. The tyre has been running crowned, riding on its middle |
| Both shoulders worn, centre healthy | Chronic under-inflation, or persistent overloading. The tyre has been running flattened, carrying on its edges |
| One shoulder worn, same side on both tyres of an axle | Alignment: camber or toe outside specification on that axle |
| One shoulder worn on one tyre only | That corner specifically. A bent component, a collapsed bush, accident damage, or a spring or strut that has failed on one side |
| Feathered tread blocks — sharp on one edge, rounded on the other | Toe misalignment. You find this with a hand rather than an eye: run your palm across the tread in both directions and feel the difference |
| Scalloped or cupped patches spaced around the tyre | Suspension damping. Worn dampers let the wheel bounce, so the tyre is unloaded and reloaded as it rolls and wears in scallops |
| A single flat patch | A wheel that locked under braking, or a car left standing long enough to take a set. Usually felt through the steering before it is seen |
| Diagonal wear across a rear tyre | Rear axle alignment, which on most cars nobody has ever checked because most alignments only touch the front |

Two of these rows are about pressure and cost nothing to fix. The rest are about the car rather than the tyre, and that distinction is the one to hold on to during a viewing. A tyre worn on one shoulder is not a tyre problem with a tyre-shaped price. It is an alignment or suspension problem that has been quietly destroying tyres, and fitting new rubber over it buys the next owner the same fault with fresh material on top.

The pressure rows are worth taking seriously in their own right, because inflation is the largest controllable input to how long a set lasts. NHTSA’s own figure is that properly inflated tyres extend the average life of a tyre by 4,700 miles, and that only 19 percent of drivers keep them properly inflated. The agency also points out that the correct pressure is the one on the vehicle’s tyre and loading placard, not the maximum figure moulded into the tyre sidewall — a distinction that catches people out constantly. Checking pressures monthly on cold tyres, rotating in line with the handbook, and having the alignment checked when the wear says so are covered in our guide to [looking after a used car](https://baronauto1.com/car-care/car-maintenance-tips/), which treats tyre pressure as one of the highest-return jobs on the list precisely because it is free.

One caution on tyre pressure monitoring. The requirement is set by FMVSS No. 138 and it runs on date of manufacture rather than on model year, which is a distinction worth keeping straight when a car sits near the boundary — our guide to [what the TPMS light is telling you](https://baronauto1.com/car-care/tpms-light/) covers it, along with the difference between a steady lamp and a flashing one. TPMS is a warning system for significant under-inflation, not a maintenance tool. A car that is not showing a warning light can still be several pounds down all round, which is enough to produce the shoulder wear in the table above over a couple of years. The light coming on means a tyre is already well below where it should be.

## Four tyres as a set: what mismatch tells you

Reading one tyre gives you the condition of one tyre. Reading four, with their dates, gives you a history of how the car has been maintained — and this is where the date code earns its keep a second time.

Tyres are normally replaced in pairs across an axle, so two dates rather than one is the expected finding on a car with any age to it. What you are looking for is the shape of the story the four codes tell:

- **Four codes close together.** One event. Somebody replaced the whole set at once, which is the expensive and correct way to do it.
- **Two pairs, some years apart.** Ordinary. The car was kept properly, one axle at a time.
- **Three that agree and one that does not.** Something happened to one corner. A puncture that could not be repaired, or kerb damage. Worth asking about directly, because whatever hit the tyre may also have reached the wheel, the alignment or a suspension component, and the wear pattern on the neighbouring tyre may already be showing it.
- **Four codes that all disagree.** Tyres replaced one at a time as each one failed, at whatever price was cheapest that week. That is a maintenance philosophy, and it rarely stops at the tyres.
- **Four brand-new tyres on an otherwise unremarkable car being sold.** Not a bonus and not a red flag — a question. New tyres are the cheapest way to make a car feel tighter on a test drive. Ask what the old ones looked like and whether an alignment was done at the same time, because the wear pattern that justified the replacement has just been thrown in a skip.

The date codes also let you audit the seller’s account, which is the part nobody expects. If an invoice or a verbal claim puts the tyres at a year old and the codes read four years earlier, the tyres were not new when they were fitted. That may be entirely innocent — old stock, or used tyres bought deliberately — but it is a discrepancy between a document and the car, and those are worth surfacing while you are still deciding.

Two more mismatch cases are about grip rather than history. Mixing different tread patterns or different brands across a single axle means the two ends of that axle have different grip characteristics, which shows up under hard braking and in the wet rather than on a gentle test drive. And a size that does not match the vehicle’s placard is a separate issue again, affecting speedometer accuracy, load rating and sometimes the stability control calibration. If you want to know where the correct size actually lives — and why the VIN is not the place to look it up — our guide to [tyre size by VIN](https://baronauto1.com/vehicle-history/tire-size-by-vin/) covers that question in full and this page will not repeat it.

Used tyres deserve a specific mention because they are cheap and they are common. A second-hand tyre can be a perfectly reasonable purchase and it can also be somebody else’s problem sold on. The decisive advantage over almost any other used component is that this one carries its own age, stamped on by law, so at least one of the unknowns is not unknown. Read the code before you agree to anything.

## All-season, winter, summer, and what is actually fitted

NHTSA sorts consumer tyres into a handful of categories, and the distinctions matter more on a used car than on a new one because you are inheriting somebody else’s choice.

All-season tyres are the default on most cars sold in the United States. In NHTSA’s description they handle a variety of road conditions and have some mud and snow capability — the operative word being some. Winter tyres are more effective than all-seasons in deep snow, because they use a softer compound that stays pliable at low temperatures and a tread pattern designed to bite. Summer tyres are the opposite specialisation: warm-weather tyres that, again in the agency’s own terms, are not designed to operate below freezing or on snow and ice. All-terrain tyres sit mainly on four-wheel-drive vehicles as a compromise between road manners and rough ground.

What this means at a viewing is a set of questions the tyres answer for you:

- **Winter tyres on a car being sold in summer.** Very often means there is a second set of wheels somewhere, and it is worth asking whether they are included. It can also mean the winters were fitted and then simply left on, in which case they have been wearing quickly through warm months and the tread reading is less impressive than it looks.
- **Summer tyres on a car in a cold state.** Fine if the car is a second vehicle stored for winter; a real limitation if it is meant to be daily transport. This is worth knowing before the first frost rather than after.
- **A mixed set across the four corners.** Two winters and two all-seasons is a genuinely poor combination, because the grip balance front-to-rear changes depending on the temperature that day.
- **Aggressive all-terrains on a road-going crossover.** Tells you something about the previous owner’s intentions, and usually means more noise and a shorter tread life than the car came with.

On markings: tyres intended for winter service carry a symbol of a mountain with a snowflake inside it, applied by manufacturers to tyres that meet an industry severe-snow traction test. The older M+S marking, for mud and snow, is a much weaker signal and appears on plenty of ordinary all-season tyres. If winter capability is the reason you are buying a particular car, the mountain-and-snowflake symbol is the marking to look for, and it is on the sidewall alongside everything else discussed on this page.

## The recall nobody is going to tell you about

This is the part of Part 574 that has nothing to do with dates and everything to do with used cars.

The stated purpose of the whole regulation, in its own opening section, is to make it possible to notify purchasers of defective tyres so they can act. That is why the identification number exists at all, and it is why the rest of the rule is about registration: manufacturers must supply registration forms to their dealers, and dealers selling new tyres must either hand the buyer a form with the full identification number already recorded on it or submit the buyer’s details themselves. The registration form is even required to carry a specific sentence explaining why: in case of a recall, the manufacturer can reach you only if it has your name and address.

Now follow that chain onto a used car. The regulation treats a motor vehicle dealer who sells a used vehicle equipped with *new* tyres as a tyre dealer, with the registration duties that go with it. A used car sold on the tyres it already had triggers nothing at all — and a private sale, which is how an enormous number of used cars change hands, sits outside the tyre registration system entirely.

So the tyres on the car you are about to buy are registered, at best, to somebody who no longer owns them, and quite possibly to nobody. If those tyres are recalled, no letter is coming.

There is a second gap alongside it, and it is one people routinely fall into while doing exactly the right thing. NHTSA’s recall lookup searches vehicles by VIN or licence plate and returns unrepaired recalls issued against that vehicle. Tyres are searched on a different tab, by brand and tyre line, because a tyre recall is issued by the tyre manufacturer against a production range rather than against any car. A clean VIN check is therefore not evidence of anything about the tyres. It never was designed to be. The vehicle side of that search is set out in our guide to [open recalls on a used car](https://baronauto1.com/vehicle-history/how-to-check-a-car-for-open-recalls/), and it remains the highest-value free check anyone can run. The tyre search is a separate errand on the same site, and you need the brand and line off the sidewall to run it.

While you have the VIN in hand it is worth spending the couple of minutes to [look up what the record says about the car itself](https://carcheckervin.com), because title branding, reported mileage history and past damage are the questions no amount of kneeling next to a tyre will answer.

## What to do at the viewing

Tyres reward about five minutes of deliberate attention, and almost nobody spends it. Here is the order that gets the most out of that time.

Do it before the test drive, while the tyres are cold and while you are still allowed to be slow and unhurried about it. Take a torch, and be prepared to crouch.

- Read the date code on all four tyres and the spare. Turn the steering to full lock to bring the front sidewalls into view, and check the inner face if the outer number stops short of a four-digit ending.
- Write the four codes down. The pattern across the set is more informative than any single one, and you will not remember them.
- Look into the main grooves for the treadwear indicator bars, and check whether the surrounding tread still stands proud of them.
- Check depth in three places across each tyre, not one. Inner shoulder, centre, outer shoulder.
- Run a hand across the tread in both directions to feel for feathering, which the eye misses entirely.
- Look along the sidewalls for bulges, cuts, kerbing damage and cracking, on the inner face as well as the outer.
- Note the brand and tyre line, so you can run the tyre recall search later.
- Compare the size moulded on the sidewall against the placard on the driver’s door jamb.
- Check the pressures if you can, and check the spare’s pressure too — a flat spare is a small thing that says a lot about the car’s upkeep.

Tyres and brakes are the two consumable systems a buyer can genuinely assess without tools, and they are worth doing in the same walk round the car, since you are already at each wheel with a torch. Our guide to [how long brake pads last](https://baronauto1.com/car-care/how-long-do-brake-pads-last/) covers the other half of that inspection, including what pad and disc condition can and cannot be judged through a wheel.

What tyres cannot tell you is what is happening structurally underneath them. A wear pattern says an alignment or a suspension component is out; it does not say why, and the difference between a worn bush and a bent subframe from an unreported collision is a difference of thousands. That is what a lift and a professional eye are for, and the list of things worth asking for is in our guide to the [used car pre-purchase inspection](https://baronauto1.com/buying-guides/used-car-pre-purchase-inspection/). If you found a wear pattern, name it explicitly when you book the inspection, because it turns a general look into a specific question.

## Putting it in the price

Tyres are a bounded, knowable cost, which makes them one of the easier things to handle in a negotiation. Four tyres and fitting is a figure you can obtain from a local supplier in a phone call before you go and look at the car, and it converts a vague misgiving into a number both parties can discuss.

Be honest with yourself about which finding you are pricing, though, because they are not equivalent:

- **Tread near the bar, even wear, recent date codes.** Ordinary consumption. Price in a set of tyres and move on. Nothing here says anything bad about the car.
- **Plenty of tread, old date codes.** Also a set of tyres, and the harder conversation, because the seller can see tread and cannot see age. The code is on the tyre and it is not a matter of opinion, which is what makes this a discussion rather than an argument.
- **A wear pattern.** Not a tyre price at all. Price the diagnosis and the repair, and treat the tyres as the consequence. Fitting new tyres without fixing the cause simply restarts the clock on the same damage.
- **Sidewall damage, a bulge, or a cut into the structure.** That tyre is finished today, not eventually.

And keep the whole subject in proportion. Tyres are visible, measurable and replaceable, which puts them among the least frightening things you can find on a used car. The expensive unknowns leave no mark on the rubber at all: what the title says, whether the mileage on the dash matches the mileage in the record, whether a serious repair was ever declared. None of that is visible from a crouch beside a wheel, and it costs very little to [check the title and mileage record before you commit](https://carcheckervin.com). Do the tyres first, though. They are free, they take five minutes, and they are the fastest way to find out whether the car in front of you has been looked after or merely cleaned.

Wear patterns are the other half of reading a tyre, and they describe the car rather than the tyre. Our guide to [wheel alignment and what tyre wear tells you](https://baronauto1.com/car-care/wheel-alignment-cost/) sets out which pattern points at geometry, which at pressure, and which at a worn part that an alignment cannot fix.

## Common questions

### How long do tyres last?

There is no single interval, because two separate limits are running at once. Tread is consumed by distance and depends heavily on driving style, road type, inflation and alignment, so the same tyre can cover very different mileages on different cars. Age is consumed by time regardless of use: NHTSA notes that some vehicle and tyre manufacturers recommend replacement at six to 10 years old regardless of treadwear. Whichever limit arrives first is the one that ends the tyre, and on a low-mileage or infrequently used car that is usually age.

### How do I read the date on a tyre?

Find the letters DOT on the sidewall and read the identification number that follows. The last four digits are the date of manufacture: the first two are the week of the year, the last two are the year. NHTSA’s own example is a number ending 0308, which means the third week of 2008. If the number you are reading does not end in a four-digit group, you are looking at the partial number on the wrong sidewall — the full number is only required on one side.

### When should I replace my tyres?

On tread, when the surface has worn down level with the treadwear indicator bars moulded into the grooves, which sit at 2/32 of an inch — the depth NHTSA gives as the point at which tyres are not safe. Before that, replace on evidence of damage: cuts, bulges, exposed structure, or a wear pattern severe enough that the tyre cannot be saved. On age, replace against your vehicle handbook or the tyre manufacturer’s guidance, using the date code rather than appearance, since NHTSA is explicit that ageing cannot be detected by looking.

### Do tyres go off if the car is barely driven?

Yes, and that is the case the date code is most useful for. Ageing is a chemical process driven by oxygen, ozone, ultraviolet light and heat, and it continues whether the tyre is rolling, parked or sitting on a shelf. NHTSA specifically flags low annual mileage, recreational vehicles, collector cars and any vehicle that is not driven regularly as the situations where ageing becomes the binding limit, and notes that the problem is worse in hot southern climates. Spare tyres are the extreme case, because they are almost never replaced.

### Is the penny test reliable?

It is reliable for the one thing it does, which is telling you whether a tyre has reached the replacement point at a single spot. It is not a measurement, it gives no sense of how much margin remains, it can be defeated by placing the coin over a treadwear indicator bar, and it says nothing whatever about the tyre’s age. Checking the moulded indicator bars is quicker and needs no coin, and a cheap depth gauge measured at several points across the tyre gives you far more than a pass or a fail.

### Should mismatched tyres put me off a used car?

Not by themselves — replacing tyres in pairs is normal and produces two different dates on a well-kept car. What matters is the pattern across all four. One odd tyre among three that agree usually means a single corner was damaged, which is worth asking about because the impact may have reached the wheel or the suspension. Four codes that all disagree suggests tyres were replaced one at a time on price, which tends to describe the wider maintenance approach rather than just the tyres.

### Will a VIN recall check cover the tyres?

No. NHTSA’s VIN and licence plate search returns unrepaired recalls issued against the vehicle. Tyre recalls are issued by tyre manufacturers against production ranges and are searched separately, by brand and tyre line, which you read off the sidewall. There is a further wrinkle specific to used cars: the tyre registration system that exists to notify owners of recalls is built around new tyre sales, so the tyres on a used car are typically registered to a previous owner or to nobody, and no notification is going to arrive in your name.

## Sources and further reading

- [49 CFR Part 574 — Tire Identification and Recordkeeping](https://www.ecfr.gov/current/title-49/subtitle-B/chapter-V/part-574)
- [NHTSA TireWise](https://www.nhtsa.gov/tires)
- [NHTSA recall lookup](https://www.nhtsa.gov/recalls)
- [NHTSA Office of Defects Investigation complaint database](https://www.nhtsa.gov/nhtsa-datasets-and-apis)

Recall, complaint and safety-rating figures on this page were retrieved from the federal databases above on August 19, 2026. Federal data changes — re-check any VIN before you rely on it.

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