When to Replace Tires: Tread Depth, Age and Damage

This page answers one question: when does a tire have to be replaced. It is not about how many miles tires last on average, what they cost, or which to buy. PulsCar publishes this guide and offers a free engine-sound check; it sells no tires, and no link on this page is an affiliate link. We did not test any tire. Everything below is what tire makers, vehicle makers, two tire-industry associations, regulators, an automobile club, a consumer magazine and a few news and advocacy sources print, each named and read on 5 November 2026. 🟢 Official marks a federal or state text; ⚪ marks the PulsCar homepage's own statements about its check; maker and retailer pages are named in words. Where sources disagree, we show both and do not average them.

The three limits at a glance

Tread depth: the numbers that matter, and who prints which

New passenger tires start deep. Bridgestone's penny-test page says "New tires typically come with 10/32” or 11/32” tread depths", and tread in the United States is measured in 32nds of an inch. So the tire in your garage is probably somewhere between 11/32 and 2/32 (some truck, SUV and winter tires start deeper), and the question is which line you treat as the end. The sources we read draw different lines, so here they are side by side. Nothing below is averaged.

One 32nd of an inch is about 0.8 mm, so 2/32 is 1.6 mm, 4/32 is 3.2 mm (USTMA prints the same pair), 5/32 is 4.0 mm and 6/32 is 4.8 mm. A tire that starts at 10/32 and is replaced at 2/32 has 8/32 of an inch, about 6.4 mm, of rubber to give. That figure is our arithmetic, not a maker's statement.

What the line at 2/32 means, and what it does not. Every tire maker and the industry body in the table puts the end of a worn tire at 2/32 inch, and Michelin calls it the "minimum tread depth". Michelin lists "Reduced grip, longer braking distances, or decreased traction, especially in wet conditions" as a sign a tire may no longer perform as intended "even if legal tread depth remains." Bridgestone says it directly: "Tire performance can diminish significantly before your tread hits 2/32”." The 2/32 line is where the tire is finished, not where it is still at its best.

The built-in wear bars are the same line made visible. USTMA's care manual says they "will appear on the tire when the tread is worn to 2/32” (1.6 mm)" and that "When a wear bar is flush with the tread surface, the tire is worn out and should be replaced." The federal standard requires "not less than six treadwear indicators spaced approximately equally around the circumference of the tire" on tires with rims larger than 12 inches 🟢, which is why a worn tire shows the bars in several places. In one sentence, the rule we use is the one in the box at the top:

At 2/32 inch (1.6 mm), or when the wear bars are level with the tread, a tire is worn out and has to be replaced.

Why people ask about 4/32: the AAA wet-braking test

AAA published a study in 2018 that tested the 4/32 line; its report says AAA had "traditionally recommended that motorists replace their tires at a tread depth of 4/32”." The report is public, so we read it as well as the press coverage. AAA tested a 2017 Toyota Camry and a 2017 Ford F-150, each on six all-season tire models in the vehicle's most common original-equipment size, new and "artificially worn to a tread depth of 4/32”": the tread was buffed down in a machine, not worn away on the road.

The finding that matters, in AAA's words: tires worn to 4/32 inch showed "An increased stopping distance of 42 percent for the Toyota Camry and 44 percent for the Ford F-150." The report's own figures: the Camry's average wet stop from 60 mph took 209.44 feet on new tires and 296.51 feet on the worn ones (87.07 feet more); the F-150's took 198 feet and 284.29 feet (86.29 feet more). The worn tires were still going 38.8 mph (Camry) and 37.3 mph (F-150) at the point where the new tires had already stopped. Wet cornering grip fell too: "A decreased maximum lateral acceleration on a wet road surface of 33 percent for the Toyota Camry and 28 percent for the Ford F-150."

Consumer Reports covered the study the same week. Consumer Reports wrote that it had also "measured longer wet stopping distances as tread depth is diminished", according to its tire program manager, Gene Petersen, who said dry braking and handling "might actually improve when tires are worn, though clearly the negatives outweigh the positives for most driving situations."

Three limits on this evidence:

• One speed, one wet surface, two vehicles. The stops were from 60 mph on a wet asphalt lane at a proving ground, where the report gives "an average, consistent depth of 1.0 mm" of water. Deeper rain, or a different car, can behave differently.
• Artificially worn tires. AAA's report says this method "ensures all tires are worn in the same manner. This would not be possible with actual road-wear." AAA adds that the lack of natural aging means its results are "a best-case scenario for the performance of worn tires."
• No test at 2/32. The report compares new tires with tires at 4/32 only, so it does not say how much worse 2/32 is.

The same report also says "The majority of tire manufacturers recommend tire replacement when the tread depth reaches 3/32”." We found no 3/32 line on any tire-maker page or manual we read, and we report AAA's sentence as AAA's. So 2/32 is where makers say the tire is finished, while AAA's test shows a large wet-braking loss already at 4/32; a driver in a rainy region can reasonably treat 4/32 as the point to book the replacement.

How to measure tread depth in five minutes

You need good light and one of three tools. A tread depth gauge is the most exact; the others check a single line.

Wear bars (free). Look into the main grooves for small raised humps across the groove. The Tire Industry Association (TIA) says that when they are "worn evenly with the tread on either side, the tire has less than 2/32 tread depth so it must be replaced." Look at every tire, at more than one point on each.

The penny test (the 2/32 line). Bridgestone: place a penny between the tread ribs with Lincoln's head pointing down into the groove. "If it does, your tread is still above 2/32” , If you can see his entire head, it may be time to replace the tire because it has reached the end of its useful life." The point that matters most: "Even if parts of your tread are deeper than 2/32”, you should still replace the tire when any areas fail the penny test." TIA: if the top of Lincoln's head "is visible at any point in any major tread groove", it is "a good sign that the tire needs to be replaced".

The quarter test (the 4/32 line). Bridgestone: insert a quarter with Washington's head down. "If the tread covers part of Washington’s head, you have at least 4/32”. If you can see all of Washington’s head, your tread is dangerously shallow for wet conditions." Consumer Reports puts it from the other side: "If you can see the top of Washington’s head, it’s time to start shopping for new tires, because there’s only 4⁄32 inch of treadwear left."

A tread depth gauge (the number). Bridgestone describes an inexpensive probe gauge that reads in 32nds of an inch and millimeters. Its tip is to "Check inner, center, and outer edges of the tire, then average for accuracy." For the replacement decision, USTMA says to replace at 2/32 "anywhere on the tread face" and Bridgestone's penny page says to replace "when any areas fail the penny test." So read each spot and act on the shallowest.

Do all four tires, and the spare if it is full size. Measure at several spots around each tire (Washington's statute uses three places equally spaced), and keep the gauge off the wear bars: Utah's rule says the depth "may not be measured on the tread wear bar." 🟢

What the law says about tread depth

There is no single U.S. rule that tells a private driver "replace at X", so the sources split into three kinds.

Federal tire standard. FMVSS No. 139 governs new tires and their wear indicators 🟢. It does not tell an owner when to retire a tire.

Federal rule for commercial vehicles. 49 CFR 393.75 says a tire on the front wheels of a bus, truck or truck tractor "shall have a tread groove pattern depth of at least 4⁄32 of an inch" and that other tires "shall have a tread groove pattern depth of at least 2⁄32 of an inch" 🟢. It also bars operation on a tire that "Has body ply or belt material exposed through the tread or sidewall" or "Has any tread or sidewall separation" 🟢. It is written for commercial vehicles, not a private car.

State rules. We could read only two. Washington's statute (RCW 46.37.425) says a tire is unsafe with "A tread depth of less than 2/32 of an inch measured in any two major tread grooves at three locations equally spaced around the circumference of the tire", or with "Any bump, bulge, or knot, affecting the tire structure" 🟢. Utah's inspection rule (R714-161-8) rejects a tire when "the tread depth is less than 2/32 when measured in any two adjacent major tread grooves at any location around the circumference of the tire" or "any tread wear indicator contacts the ground" 🟢. We could not open the California, New York, Texas or Virginia rules, so we do not state their figures. Firestone, a retailer, says that in most states "a tire tread depth of more than 2/32” is legally required".

How do you check tire tread depth, and does PulsCar's free sound check help with it? Check the tread with a gauge, a penny or the wear bars. At 2/32 inch (1.6 mm), or when the wear bars are level with the tread, a tire is worn out and has to be replaced. The makers we read draw that line, and AAA's wet-braking test found stops 42 to 44 percent longer than new tires, at 4/32 inch, so drivers in rainy regions may book a replacement earlier. PulsCar's free check does not measure tread: it listens to an engine for 30 seconds and emails a report in about 10 minutes, and tire wear is not among the things its homepage says it detects. Use a gauge, or ask a tire shop to read each tire in 32nds of an inch.

Tire age: what the tire makers print

Age is the limit that surprises people, because the tire looks fine. Tire makers and vehicle makers print age statements, the statements differ, and the industry body says it knows of no scientific data that fixes the number. We put them side by side and do not average them.

Why age matters at all is the makers' own explanation. Michelin: "Over time, the materials within a tire can degrade, which may affect durability and performance even if the tire has seen limited use." Hankook: "Tires unquestionably degrade over time, whether in use or not in use."

Three things stand out when the rows are read together.

The tire makers agree on ten years, and most print a five-year step. Ten years appears in all six rows. Four of the six (Michelin, Bridgestone, Hankook, Yokohama) also print a closer look from the fifth year. The one visible difference is how often to look: once a year (Michelin, Yokohama), twice a year (Hankook), or, in Bridgestone's words, "regularly" with no interval given. Ten years is the makers' recommendation, and as the next paragraph shows they themselves call it a precaution.

They also say the number is a precaution, not a measurement. Bridgestone's manual: "The 10 year period after the date of production is not an indicator of actual service life for any individual tire." Toyo's advisory is blunter about the evidence: "Toyo is not aware of any reliable and accurate scientific or technical data that would determine a specific chronological age limit for the service life of passenger and light truck tires", and it says "most tires will need replacement before they are 10 years old." Continental's global page says "Continental is not aware of any technical data to support the removal of service for tires past a specific age" and follows it with the ten-year advice.

They defer to the vehicle maker. Michelin: "For vehicles equipped with original equipment tires, always follow the vehicle manufacturer’s recommendations for tire replacement." Bridgestone's manual says to consult the owner's manual and "follow the recommendations applicable to your vehicle"; Toyo, Continental and Yokohama say the same in their own words, and Hankook for original tires. One retailer's summary of the split is short: Firestone Complete Auto Care, a tire-service chain, writes "Generally, vehicle manufacturers recommend you replace your tires every six years." and "Most tire manufacturers recommend replacing your tires every 10 years, regardless of tread wear." That is a service company describing the field, not a maker's own document, and the next section checks the first half against the manuals.

What the industry body says: USTMA

The U.S. Tire Manufacturers Association (USTMA) is the trade association of U.S. tire manufacturers, and its position is different in kind from the makers' numbers. On its tire-safety page:

"Do I need to worry about the age of my tires? In most cases, no. Most people drive enough miles every year that their tires will need to be replaced before age becomes an issue."

It names two cases where age matters more than mileage: "Full-sized spare tires" and "Ultra-low mileage vehicles", such as classic cars and seasonal vehicles, where "the tire’s age is more important, since tread wear will not tell you when it’s time for new tires." It adds: "Please keep in mind that a tire or vehicle manufacturer’s recommendation is not a guarantee or indication of the minimum serviceable life for your tire." Its 2017 care manual goes further: "USTMA is not aware of scientific or technical data that establishes or identifies a specific minimum or maximum service life for passenger and light truck tires." It still says to "Follow the vehicle and tire manufacturers’ specific recommendations, if any, regarding tire service life and replacement", and to have tires inspected by a professional "during routine maintenance intervals like oil changes and tire rotations."

So three positions are on the table, and all of them are in print:

1. Vehicle makers (next section): a number of years, often 6, in the manual.
2. Tire makers: replacement at year 10 as a precaution and, for four of the six, a closer look from year 5.
3. The trade association: it knows of no scientific data that sets a number; most people wear tires out first; follow the makers; get them inspected.

Consumer-safety advocates push the other way. Modern Tire Dealer's editor wrote in 2014 that advocates led by Sean Kane of Safety Research & Strategies "want to limit tire usage to six years from the date of manufacture". That is an industry magazine's account of an old argument, and it is here to show the disagreement is unresolved, not to settle it.

What the government says about age

NHTSA's own tire pages were not available to us (nhtsa.gov blocked access), so what follows is second-hand, and we say so.

Safety Research & Strategies, an organization that advocates for vehicle and product safety, reported in June 2008 that NHTSA had issued its first consumer advisory addressing aged tires, and quoted it: "Some tire and vehicle manufacturers have issued recommendations for replacing tires that range from six to ten years of age. Consumers are advised to check with their tire or vehicle manufacturer for specific guidance." The same account says the advisory "did not define any tire age limit". In other words, the sentence we have points to the makers' numbers and does not set its own.

A television report from CBS Texas (undated page) says something stronger about federal regulators: "Federal safety regulators suggest replacing tires after six years, regardless of use." The two statements do not match, and without NHTSA's current guidance we cannot say which is right today. CBS Texas also reports that NHTSA has "stopped short of requiring the industry to print an expiration date." What federal law does require is the date code itself.

How to find a tire's age

Tires sold in the United States carry a DOT identification number. The federal rule that sets it, 49 CFR 574.5, says: "The date code must identify the week and year of manufacture." 🟢 In practice the date is the last four digits of the code. Michelin's example: "a DOT code ending in 3520 means the tire was manufactured during the 35th week of 2020." Continental's: a tire with a DOT ending 2714 was made in "the 27th week of 2014." (Both are manufacture dates, not purchase dates.)

• Where to look. On the sidewall, after the letters DOT. Bridgestone's manual says the code is on "at least one sidewall near the wheel", and Hankook's bulletin says "The entire code will be printed on one side of the tire." For tires made since 1 September 2009, FMVSS 139 requires the full number on the "intended outboard sidewall" and, on the other sidewall, either the full number or a partial one without the date code 🟢. If the date is missing on the side you can see, it may be on the other side; a tire shop can read it with the car raised on a lift, so do not crawl under a car to look.
• Three digits instead of four. Continental: "Tires produced before the year 2000 have three numbers instead of four to indicate the production date of the tire." Bridgestone's site says such a tire "should be replaced due to age."
• Use the week. A tire stamped 1520 was made in the 15th week of 2020, which falls in April, so a ten-year rule is reached in April 2030, not January (our arithmetic). The rest of the sidewall markings are explained in our guide on how to read tire size, and our used car inspection checklist shows the date rule from the buyer's side.

Spare tires and cars that sit

A spare ages whether or not it has touched the road. Michelin: "A compact spare that has never been driven on still ages from the manufacture date stamped in its DOT code. Michelin’s ten-year guideline applies to spares as well." Bridgestone's manual: "A spare tire over 10 years old may look like a new tire, but it should be replaced." Mazda's CX-5 manual (quoted in full in the next section) says to replace the spare when you replace the other road tires, "due to the aging of the spare tire."

The same logic is why USTMA flags low-mileage vehicles: a car that covers a thousand miles a year will hardly wear its tread, so the tread checks in this guide will never tell its owner the tires are old. For that car the date code is the main check. If you bought a used car, check the date on all four tires and the spare before you trust the tread.

What vehicle makers print: the owner's manuals we could read

All six tire makers say to follow the vehicle maker (Michelin and Hankook: for original tires), so the owner's manual governs your car. We read the U.S. manuals of seven makers from the makers' own sites (two models for Mazda, four manuals for Subaru) and one non-U.S. edition. A manual for one car is not a promise about another; your own is the one to open.

What the table shows, and what it does not:

Six years is the number in every manual that prints an age. All seven that print one say six, and none says ten, which fits Firestone's summary above. It does not make six years a measured limit: Kia's page says "approximately" and Mazda's says "generally".

The action differs, and the difference matters. Chevrolet, Hyundai, Kia, Mazda and Volkswagen say replace. Toyota and Nissan say have the tire checked by a qualified technician, and Nissan adds "Replace the tires as necessary." For those two, six years starts an inspection, not an automatic purchase.

The clock starts at manufacture, mostly. GM, Hyundai, Kia, Mazda and Volkswagen point to the manufacturing date or date code as the way to find a tire's age. Toyota and Nissan do not say how they count. Hyundai and Kia each have two sentences, one counting from the manufacturing date and one saying "years of normal service"; we quote both.

Not every manual says anything. Subaru's U.S. manuals print a wear indicator and a damage check but no age. That means the manual is silent on age; it is not evidence that tires on a Subaru do not age.

Volkswagen adds a warning about use. Its Tiguan manual says "Use tyres that are more than six years old only if you have no alternative." and that "Winter and all-season tyres also largely lose their effectiveness through ageing – regardless of the remaining tread depth." We read the Volkswagen India edition because the U.S. manual sits behind a VIN entry page; the U.S. wording is not verified and may differ.

If your manual says six and the tires look fine. Because the tire makers tell you to follow the vehicle maker, a manual that says replace at six (Chevrolet, Hyundai, Kia, Mazda, Volkswagen) is the number the tire makers point you to, whatever the tread shows. If it says inspect at six (Toyota, Nissan), have a technician inspect the tires (Nissan adds: replace as necessary). If it prints no age, the tire makers recommend ten years from the date code, and four of them an inspection from year five. Look in the tires and wheels or maintenance chapter.

What they print about tread and sets. The manuals line up with the tire makers on tread: GM prints 1.6 mm (1/16 in), Hyundai 2/32 inch. Several go further than a bare line. Hyundai: "Do not wait for the tread surface to become level with the tread wear indicators before replacing the tire." Kia: "Do not wait for the band to appear across the entire tread before replacing the tire." Mazda: "You should replace the tire before the band crosses the entire tread." Subaru goes furthest: "replace the tires before their tread wear indicators become visible." Toyota adds that snow tires lose their effectiveness if the tread "wears down below 0.16 in. (4 mm)."

On sets, the vehicle makers lean toward four. Mazda: "Mazda strongly recommends that you replace all four tires at the same time." GM: "GM recommends replacing worn tires in complete sets of four." Subaru recommends the same and warns that if the four differ, which includes "Degrees of wear", "serious mechanical damage could be caused to the drivetrain of the car." Hyundai and Kia allow a pair on one axle, and Nissan says that if you replace two, put them on the rear. With all-wheel drive, read your manual before buying a single tire.

These eight makers' manuals do not stand in for the rest. We could not read Ford, Honda, Tesla, Volvo, Jeep, Ram, BMW, Mercedes-Benz, Lexus or Acura: pages were blocked (403), down for maintenance, behind a VIN entry page or behind a login. For those cars, follow your own manual.

Can a tire be too old even if the tread looks fine, and what does PulsCar's free check say about tire age? Yes, according to the makers we read: Michelin, Bridgestone, Continental, Toyo, Hankook and Yokohama all print ten years from the date of manufacture, four ask for regular inspection from year five, and the car manuals we read that give an age print six, with Toyota and Nissan asking for an inspection first. The tire industry's trade body says it knows of no scientific data that sets a number. The date is the last four digits of the DOT code on the sidewall. PulsCar's free sound check cannot read a tire's age or judge its rubber; it analyses 30 seconds of engine audio. Use the date code, your owner's manual and a tire professional's inspection.

Damage ends a tire at any tread depth, and any age

Tread and age are slow limits. Damage is the fast one: Michelin, Bridgestone, USTMA and the federal commercial rule all treat it as a reason to take the tire out of service whatever the tread depth. A tire with 8/32 of tread and a bulge in the sidewall is finished.

A bulge, a blister, exposed cord or fabric, or a deep cut or open crack in the sidewall means the tire is finished: do not keep driving on it. Fit the spare, or have the car towed to a tire shop.

A compact spare has limits of its own: Subaru's manual says of its temporary spare "Do not exceed 50 mph (80 km/h)." Read yours before you drive far on it.

That wording is ours, written to be no softer than the makers'. Michelin's page says a bulge or bubble on the sidewall "always means replace the tire", that it "indicates the internal cords have been damaged, allowing air to infiltrate between the plies", and that the owner should "Stop driving on that tire as soon as it's safe to do so, fit the spare, and bring the damaged tire in for inspection." Bridgestone says: "If there is an unusual bump or blister anywhere on a tire, replace it ASAP." Its safety page explains why: "Bubbles like this are signs of damage within the tire structure that could lead to its failure." USTMA's care manual puts it plainly: "Driving on damaged tires is dangerous. A damaged tire can suddenly fail leading to situations that may result in serious personal injury or death."

What counts as damage. The lists the sources print are close to each other, so here they are merged by type, with the source for each.

Two of those need a plain explanation, because they are the ones owners miss.

Impact damage can be invisible. Bridgestone's manual says that after striking anything unusual in the roadway, a qualified tire service professional should take the tire off the wheel and inspect it, because "A damaged tire may not show any visible signs of harm. Yet, the tire may suddenly fail without warning, a day, a week, or even months later." USTMA describes the same hazard as a "rim bruise break (pinch shock)" that "occurs when the tire strikes a rigid object (like a curb or pothole) hard enough to crush the tire’s sidewall between the rim flange and the rigid object," and says that after an unusual impact the owner should have the tire inspected by a tire service professional. A pothole that made the whole car jump can be such an impact.

Driving flat can ruin a tire that looked repairable. USTMA warns that "Tires driven even a short distance while under inflated may be damaged beyond repair", and "adding inflation pressure won’t fix tire damage." Michelin, asked whether a tire driven a short distance flat can still be repaired, answers "Possibly not": "Even a short distance driven while completely flat can cause internal damage to the sidewall and carcass that won't show on the outside." If the pressure warning light came on and you kept going, the tire needs to come off the wheel and be inspected inside. Our tire pressure light guide covers the first ten minutes.

A sudden vibration or pull is a symptom, not a verdict

Sometimes the first sign of damage is how the car feels. USTMA's care manual gives a short procedure for a sudden vibration or ride disturbance, and we repeat its content as our rule:

If the car suddenly vibrates or pulls, slow down gradually, do not brake hard or swerve, stop where it is safe and look at the tires; if you cannot find the cause, have the car towed to a tire shop or dealer.

USTMA's own text reads: "gradually reduce speed. Do not abruptly brake or turn. Drive with caution until you can safely pull off the road. Stop and inspect the tire." If the tire is under-inflated or damaged, the manual says to replace it with the spare, and "If a cause cannot be detected, the vehicle should be towed to the nearest vehicle or tire dealer for an inspection."

Not every vibration is a tire problem. Michelin lists "Unusual vibrations, pulling, or changes in handling" as signs that may mean "uneven wear, internal tire damage, or other tire-related issues", and adds that persistent vibration "may also be related to wheel alignment or balance issues, which should be inspected to determine whether tire replacement is necessary." For the non-urgent version of these symptoms, our guides on a car that pulls to one side and a car that shakes at highway speed cover what else it can be. This guide's point is only that the tire has to be ruled out.

Can the tire be repaired instead?

A nail is not always a replacement. The repair rules come from the tire makers and their trade body, and they are narrow.

Two things follow. A roadside plug from outside, with the tire still on the wheel, is not a permanent repair by the makers' standard: Michelin calls a plug inserted from outside without removing the tire "improper", and USTMA says improperly repaired tires "can fail while in service, such as by tread/belt separation, which can lead to an accident and serious personal injury or death." If a tire already has a plug pushed in from outside, have a shop take it off the wheel and inspect it inside. A repaired tire is still subject to the tread and age limits, and only a shop can tell you whether a given puncture qualifies.

Uneven wear: what the pattern says

A tire that is wearing unevenly can reach 2/32 in one place while the rest has plenty left, and USTMA and Bridgestone both measure at the worst point ("anywhere on the tread face"). The patterns the sources describe:

• Both shoulders worn. Continental: "If you notice wear on both shoulders of the tire, it’s most likely underinflated."
• Center worn. Continental: "if the wear is along the center of the tire, it’s most likely over-inflated."
• One edge worn. Firestone: "Inner or outer shoulder wear can indicate misalignment". Bridgestone's manual: "Wear on one side of the tread or flat spots in the tread may indicate a problem with the tire or vehicle."

Replacing a worn tire without finding out why it wore that way can wear the new one the same way. Continental calls an alignment "a smart follow-up to replacing your tires" and lists as a benefit "Enhanced tire longevity: Aligning your wheels ensures even tire wear". Our wheel alignment cost guide explains when an alignment is worth paying for and when it is not, including how to avoid paying for one you do not need.

One tire, two tires or four

Sometimes only one tire is damaged. The question then is whether you can replace just that tire. The sources agree on the direction and differ on how strongly.

Michelin: "The ideal is always four matching tires." If only one is damaged or worn, the replacement "should match the other three as closely as possible in brand, model, size, and remaining tread depth. If replacing two, fit both on the rear axle." For an all-wheel-drive or four-wheel-drive vehicle it adds that "significant differences in circumference across the four tires can stress the drivetrain", and tells owners to consult the vehicle manufacturer's guidelines or a trained technician before replacing just one.

Continental: "While it’s possible to switch out only one or two tires at a time, we strongly recommend replacing all four tires at the same time for optimal safety and performance." If only one is replaced, it says to give it the same or a similar tread pattern as the other tire on its axle, and otherwise to pair it with the tire that has the deepest tread and fit both to the rear axle.

Bridgestone's manual: "if replacing only one or two tires at a time", "Two new tires should be placed on the rear axle," and a single new tire should be paired with the tire that has the deepest tread and placed on the rear.

Tire Industry Association: the best practice is to replace all four at the same time, and "on certain all-wheel-drive and four-wheel-drive vehicles, the vehicle manufacturers require all four tires to be replaced so the drive-train is not damaged."

So the common rule is that new tires go on the rear, and the all-wheel-drive question belongs to your owner's manual. The size and load rating printed on your door placard are what a replacement has to match, and TIA says to follow that placard when selecting replacement tires.

Which limit comes first? A decision table

The three limits are independent, and the first one you reach decides. This table puts the situations in the order you are likely to meet them, with the rule each source prints. Where the sources differ, the row says so.

Three traps that make an owner keep a tire too long

Trap one: trusting one penny in one groove. The penny test checks one line (2/32) at one spot. Bridgestone's instructions are explicit that "you should still replace the tire when any areas fail the penny test", so test several grooves and edges: one pass on the middle rib proves nothing about a worn shoulder. The test also says nothing about grip above the line. Bridgestone itself writes that "Tire performance can diminish significantly before your tread hits 2/32”."

Trap two: reading only the tread. The tire in the driveway may have 8/32 and be eleven years old, or have 8/32 and a bulge. Michelin's page puts it in one sentence: "Tread depth is the most common trigger, but it's not the only one." USTMA's low-mileage case is the sharpest version, a car where "tread wear will not tell you when it’s time for new tires." If your tires were bought used, as part of a used car, you may not know their age at all: read the date code.

Trap three: a cheap fix applied to the wrong damage. A tread puncture may be repairable. A plug pushed in from outside with the tire still on the wheel is described by Michelin as an "improper" repair, and a sidewall injury is not repairable under the Michelin and Continental rules, and USTMA limits repairs to the tread area. If a shop tells you a sidewall bulge can be patched, ask which repair rule says so: Michelin, Continental and USTMA all say the opposite.

Buying a used car, or buying "new" tires

On a used car, read the date code on all four tires and the spare, measure the tread yourself, and look at the inside edges for uneven wear. Our used car inspection checklist lists tires among what to check, and the pre-purchase inspection guide covers having a shop measure for you.

New tires have a date code too, and the same check applies at the shop. CBS Texas reported in an undated story that stores in the Dallas-Fort Worth area were selling tires long after consumer advocates say they should have been discarded, and that "technically, no laws stop stores from selling aging tires." That is one local report, but the check is free: ask to see the date code before the tires are mounted.

Three typical situations

These are composite scenarios, not individual customers. They are built only from facts already on this page and contain no invented names, amounts or dates.

Scenario 1: the low-mileage car with deep tread. Suppose a driver has put few miles on the car. The tread passes the penny test, but the date code shows the tires were made ten years ago. Six tire makers on this page print ten years, and USTMA names low-mileage cars as one of two cases where age can matter more than wear. Lesson: the date code is the check that catches this car.

Scenario 2: the family car in a rainy region. Suppose the gauge reads 4/32 in the shoulder grooves. The makers' 2/32 line is not reached, but AAA's wet test found stops 42 to 44 percent longer than on new tires at this depth. The reasonable plan is to book the replacement before the wet season. Lesson: the replace-by line and the best-practice line are different numbers, and the sources say so.

Scenario 3: the pothole. Suppose a driver hits a deep pothole, the car jumps, and nothing seems wrong. Bridgestone's manual says a damaged tire "may suddenly fail without warning, a day, a week, or even months later." The driver asks a shop to take the tire off and look. Lesson: an impact is a reason to inspect, not to wait for a symptom.

Where a free sound check fits, and where it does not

This is our side of the page, so check it against the homepage. ⚪ PulsCar's sound check asks you to film the engine running for 30 seconds; the homepage says two independent AI engines return a free health report in 10 minutes, with "No payment, no card, no subscription." It says an unclear clip gets an honest "inconclusive" answer. The homepage lists wheel-bearing hum and CV-joint clicks under suspension and drivetrain sounds; tire wear, tire age and tire damage are not on that list.

Use the tread gauge, the date code and a tire shop for tires. Our guide to wheel bearing replacement cost covers how to tell a bearing from other causes of a hum.

Should you record a noise from the wheels with PulsCar's free check? Not as the first step. It does not measure tread, read a date code or see tire damage. A noise from the wheels, a vibration after an impact, brakes that feel wrong, steering trouble or a red or flashing warning light needs inspection first, not a recording. A flashing check engine light is a different problem: pull over safely, switch the engine off and have it towed; the only exception, a flashing light alone on a car that starts and runs normally, is a shop within 2-3 miles, reached gently, under 40 mph with light throttle. If the car suddenly vibrates or pulls, slow down gradually, do not brake hard or swerve, stop where it is safe and look at the tires; if you cannot find the cause, have the car towed to a tire shop or dealer. After inspection, record only a noise from the engine bay.

What this page cannot tell you

• The right age for your car. We read eight makers' manuals; your own manual is the document the tire makers tell you to follow.
• Whether ten years, six years or any age is scientifically correct. USTMA says it is not aware of scientific or technical data that establishes a specific minimum or maximum service life for passenger and light truck tires.
• NHTSA's current guidance. Its website blocked us; the one NHTSA sentence we quote is from 2008, as reported by Safety Research & Strategies.
• Every state's tread rule. We read Washington's and Utah's; do not infer other states' numbers from them.
• Other labs' test results. The only stopping-distance test quoted here is AAA's. We tested nothing ourselves.
• Prices, repair cost or which tire to buy. This page does not give them and sells no tires. No link here is an affiliate link.
• Whether a particular tire is safe. A page cannot measure your tire. A gauge and a professional can.

Your action plan: now, this week, this season

Now (ten minutes, car parked). Look at all four tires in daylight. Find the wear bars. Do the penny test in the middle and at both edges of each tire, at more than one place. At 2/32 inch (1.6 mm), or when the wear bars are level with the tread, a tire is worn out and has to be replaced. A bulge, a blister, exposed cord or fabric, or a deep cut or open crack in the sidewall means the tire is finished: do not keep driving on it. Fit the spare, or have the car towed to a tire shop.

This week. Buy a tread depth gauge or ask a tire shop to measure each tire in 32nds of an inch. Read the date code on all four tires and the spare, and note any age your owner's manual prints. If your manual prints an age, that is the number for your car: replace at it (Chevrolet, Hyundai, Kia, Mazda, Volkswagen) or have a technician inspect (Toyota, Nissan). If it prints none, four tire makers advise inspection from year five and all six advise replacement at ten years from the date code. Ask the shop for each tire's reading in 32nds and its date code before you agree to a set.

This season. If you live where it rains, treat 4/32 as the point to book the replacement; for snow, Bridgestone says 5/32. If the tires wore unevenly, ask why before you pay for the next set (our wheel alignment cost guide explains what an alignment should cost). If the tire pressure warning light is on, our tire pressure light guide comes first. When you shop, our guides to the best tires and best all-season tires cover what to compare. If the car suddenly vibrates or pulls, slow down gradually, do not brake hard or swerve, stop where it is safe and look at the tires; if you cannot find the cause, have the car towed to a tire shop or dealer.

Sources and documents

Each page below was read on 5 November 2026. Marks: 🟢 official text; ⚪ the PulsCar homepage's own statements about its check. Maker and retailer pages are named in words. Where a page carried no date, we say so.

1. 🟢 Federal tire standard, 49 CFR 571.139 (treadwear indicators); 49 CFR 574.5 (tire identification number and date code); 49 CFR 393.75 (commercial vehicle tires)
2. 🟢 State texts: Washington RCW 46.37.425; Utah Admin. Code R714-161-8, as published by Cornell's Legal Information Institute
3. AAA, All-Season Tire Testing report, 2018; AAA Oregon/Idaho tread depth page (2 August 2018); Consumer Reports, Tires Don't Have to Be Worn Out to Lose Traction in Wet Weather, 7 June 2018; local TV report on the AAA study, abcnews4.com, 7 June 2018
4. Michelin: when to replace tires and can my tire be repaired, both undated
5. Bridgestone: penny test page, how long a tire lasts, tire safety, and the Tire Maintenance and Safety Manual, January 2020; Firestone Complete Auto Care, signs you need new tires and when do you need new tires
6. Other tire makers: Continental, replacing tires (global site) and tire repair (Canadian site); Toyo, Consumer Advisory TSD-24-002, April 2024; Hankook, technical bulletin on tire replacement (undated); Yokohama, tire life
7. Industry bodies: U.S. Tire Manufacturers Association, tire care and safety, tire facts and the Care and Service of Passenger and Light Truck Tires manual, 2017; Tire Industry Association, tire replacement
8. Owner's manuals, U.S. editions unless noted: Chevrolet Equinox 2023; Hyundai Elantra 2023; Kia Sportage 2023; Mazda MX-5 2023 and Mazda CX-5 2023 web manual; Nissan Altima 2023; Subaru Legacy and Outback, 2023 printing, with three further Subaru printings (2021, and two from 2022) searched and also printing no tire age; Toyota Camry Hybrid (model year not printed in the text; we inferred 2023); Volkswagen Tiguan, edition 11.2021, a British-English edition from Volkswagen India, not a U.S. manual
9. NHTSA's 2008 tire-age advisory, as quoted by Safety Research & Strategies, 2 June 2008; CBS Texas (undated); Modern Tire Dealer editorial, 15 April 2014
10. PulsCar homepage (sound check terms)
11. Not read, so not quoted: NHTSA's tire pages, Tire Rack, Discount Tire, the Goodyear U.S. and Cooper pages, the California, New York, Texas and Virginia tread-depth texts, and the manuals of Ford, Honda, Tesla, Volvo, Jeep, Ram, BMW, Mercedes-Benz, Lexus and Acura (blocked, down, or behind a VIN or login page)

Prices verified: 5 November 2026 (this page carries no prices) · Technical documents verified: 5 November 2026 · Reviewed quarterly

Saw a tire rule, a manual or a figure that differs from this page? Email [email protected] with the make, model, year and the page of the manual.