Travel Trailer Tires: Why They Age Out Before They Wear Out

Travel trailer tires fail in a way car tires do not. They age out before they wear out, and the part that goes is the part you cannot see. A tire with most of its tread left can be five years past the point where anyone should trust it, and nothing on the outside says so.

That is the whole problem with travel trailer tires, and it is why tread depth is the wrong test. What follows is what the manufacturers, the regulator and the federal rules actually publish, including the places where they flatly disagree with each other.

How long do travel trailer tires last?

There is no agreed answer, and the disagreement is more useful than a number would be.

Michelin says ten years. Its guidance is to replace tires ten years from the date of manufacture “regardless of remaining tread depth or apparent condition,” with a professional inspection every year after the first five. It applies the same ten year rule to spares. Bridgestone and Firestone share one maintenance manual, and it gives the same pair of figures: inspection once the tire has five years of service behind it, and replacement of anything “more than 10 years old” regardless of condition or tread.

Airstream says five. In a bulletin filed with the federal regulator it states plainly that “if a tire is five years old then it should be replaced.” Its support pages keep the same five year point but add a step, asking for inspection by a tire expert and replacement “even if it has no apparent tread wear.” Same interval, different emphasis, and the bulletin is the blunter of the two.

And the companies that actually specialize in trailer tires publish no age at all.

Carlisle, one of the most widely fitted trailer tire brands in the country, will tell you exactly why tread is meaningless and then decline to give you a year. Its own words: “Remaining tread is not an indicator of tire life as the irregular duty cycle requires that they sit in extended storage under static load conditions often for long periods without tire movement or maintenance, causing the tire carcass (internal structure) to break down, a condition undetected by visual inspection.”

The carcass is the part of the tire you never see. Under the rubber sit layers of fabric cord, usually polyester, and the steel belts. That structure is what holds the air and carries the weight of the trailer, and the rubber is really just the skin over it.

So read that again. The company selling the tires is telling you the failure happens inside the carcass, that storage causes it, and that looking at the tire will not reveal it. Tread wears from the outside, where you can watch it. The carcass goes from the inside, where you cannot. Then Carlisle stops short of saying when.

Maxxis publishes a six year warranty from the date of manufacture, with free replacement inside the first 25 percent of treadwear or twelve months, whichever comes first, and prorated cover after that. It is a warranty window and not a service life. Goodyear names a warranty by product line but its warranty documents would not load for us, and it publishes no replacement age. Jayco and Grand Design owner manuals contain no tire age guidance at all.

So the honest summary is that published guidance runs from five years to ten, the shortest number comes from an RV maker rather than a tire maker, and the people who build trailer tires will not commit to one. What everybody does agree on is that age matters more than mileage and that tread depth will not tell you.

How do you tell when trailer tires need replacing?

Start with the date, because it is the only hard fact on the sidewall.

How do you read the date code?

Every tire sold in the United States carries a Tire Identification Number molded into the sidewall. Federal rule 49 CFR 574.5 sets out how it is built: three symbols for the plant, six for the manufacturer code, and a final group of “four numerical symbols” for the date.

Those last four digits are the ones that matter. The first two are the week and the last two are the year, counted from “the first full calendar week in each year.” The regulation gives its own example: “0109 means the tire was manufactured in the first full calendar week of 2009.”

A tire stamped 2419 was built in the twenty fourth week of 2019. That is the date the clock starts, not the date you bought it.

Why can you never find it?

Because on a trailer it is often facing the axle.

The federal standard for these tires, FMVSS 119, relaxes the marking rule for them, though not for them alone: “Markings may appear on only one sidewall and the entire sidewall area may be used in the case of motorcycle tires and recreational, boat, baggage, and special trailer tires.” Trailer tires are lumped in with boat and baggage tires, and the effect is that everything the rule requires can live on a single side.

A car tire is held to a fuller marking rule on both sidewalls, though even there only the outboard side carries the complete identification number. On a trailer tire there is no rule saying which side gets used, and plenty of builders face the marked side inward.

If you cannot find a date code on the outside of the tire, it is on the inside. You are not missing it.

What else is worth looking at?

Cracking where the tread meets the sidewall, and cracking in the grooves. Bulges anywhere. Flat spots from sitting. Any of those on a tire that is also old settles the question. None of them appearing on an old tire settles nothing, which is the point Carlisle is making.

Check the spare on the same schedule. The federal regulator singles it out: “Spare tires on all vehicles are prone to aging because they seldom get replaced.” A spare that has never turned a mile is exactly as old as the day it was built.

What does the federal government actually require?

Nothing about age. There is no federal tire expiration date, and this is worth being clear about because plenty of writing implies otherwise.

What the National Highway Traffic Safety Administration publishes on its consumer page is a report of what other people recommend: “Some vehicle and tire manufacturers recommend replacing tires that are six to 10 years old, regardless of treadwear.” That is the agency describing the industry, not setting a rule.

Its research went further. The Tire Aging Test Development Project measured what happens to rubber over time and found hardness and cross link density going up while tensile strength, elongation and flex properties went down, all of it consistent with thermo oxidative ageing.

In durability testing the agency reported that “the laboratory roadwheel test results for used tires often exhibited a trend of decreasing time-to-failure with increasing mileage and/or age.” Its report to Congress is more cautious still: “about half of the six models of used tires exhibited a trend of decreasing time-to-failure in the roadwheel test with increasing service life when compared to new versions of the same tires.”

Note the hedges. About half of the models, and a trend rather than a rule. The agency has measured the chemistry of ageing directly and found a pattern in how aged tires fail on the test rig, but it stops well short of a clean relationship, and it has never set a maximum service age.

It does single out vehicles like ours. Infrequently driven, low annual mileage, parked in sunlight, stored badly, warm climates. A travel trailer ticks most of those in a normal year.

What is the difference between ST and LT tires?

ST stands for Special Trailer, and the difference is not simply that one is better.

Federal rule FMVSS 110, which covers vehicles rated at 10,000 pounds or less, says trailers “may be equipped with ST tires, FI tires, or tires with a rim diameter code of 12 or below.” Heavier trailers fall under FMVSS 120 instead, so check your own weight rating before applying any of this. Either way it is permission, not a requirement, and it is worth reading carefully before anybody tells you the law demands one or the other.

The structural difference is the one nobody mentions. Special trailer tires are certified under FMVSS 119, written in 1971. Most of the radial tires on the truck pulling the trailer are certified under FMVSS 139, which came out of the TREAD Act and phased in through 2007, and which adds tests 119 does not have, including a low inflation performance test and an aged tire endurance test. The tires on the back half of your rig are held to an older standard than the tires on the front half.

Carlisle argues against fitting passenger or light truck tires to a trailer, and its reasoning is about sway rather than strength: “Passenger or truck tires, with their more flexible sidewalls, can result in trailer sway problems. The stiffer, heavy duty sidewalls of ST tires are designed to control and reduce sway problems.”

That is a tire maker defending its own category, and it is also a coherent argument. A trailer has no steering and no driver input to correct with. Sidewall stiffness is doing work there that it does not do on a car.

How fast can you tow on trailer tires?

The sixty five mile an hour figure that gets repeated everywhere was never a federal rule, and on current tires it is out of date.

Carlstar publishes the convention: “If the tire is not marked with a speed symbol, the default speed rating for trailer tires is 62 mph.” It also puts the familiar numbers in the past tense: “In the past, most trailer tires were rated at 62 or 65 mph.

Today, some of our tires are rated at 87 mph (N), some at 75 mph (L), some at 65 mph (J: ST tires) and some at 62 mph.” Goodyear said at the Endurance launch in 2017 that the whole line carried an N speed symbol, which is 87 miles an hour, and every size we checked still does. Maxxis publishes N across the M8008 Plus range as well.

Then Carlstar says the thing worth quoting twice. First, on what a rating means: “speed ratings are test speeds and not recommended driving speeds. The ratings apply only to the tire itself, and not a particular vehicle.” Second, on what to actually do: “We recommend driving no more than 60 mph when towing a trailer.”

A tire manufacturer telling you to tow slower than its own tires are rated for is the most useful sentence in this whole subject. Worth being clear about who is speaking, though: Carlstar is Carlisle, and the same company supplies the tread quote, the inflation advice and this speed advice. It is the most forthcoming voice on this page, not three independent ones.

What load range do you need?

Load range is a letter, usually C, D or E, and it is not a fixed weight. It is size specific and it only means anything paired with a pressure.

The federal standard for trailer tires requires the letter to be molded on, alongside a line reading “Max load ____kg (____lb) at ____kPa (____psi) cold.” It never defines what the letters mean. That definition lives in industry tables rather than in the rules.

What you can rely on is the pairing. In the same size, a higher letter means a higher maximum pressure and therefore a higher load. Maxxis publishes the M8008 Plus in load ranges C through E with maximum pressures from 50 to 80 psi and maximum loads from 1,360 to 3,420 pounds depending on size.

Airstream gives a worked example on the most common travel trailer size: “A Goodyear Endurance ST225/75R15 tire inflated to 80 PSI (MAX.) has a load capacity of 2830 lbs.” Goodyear publishes the same figure for that tire, at load index 117.

The number that has to clear is your axle rating divided between the tires on that axle, with the trailer loaded the way you actually tow it. Not the empty weight on the brochure.

What pressure should trailer tires run?

Here the sources genuinely disagree, and you should know that before somebody tells you the answer is obvious.

Carlisle says run the sidewall maximum: “Maintain air pressure at the maximum PSI recommended on the tire sidewall.” It also names the failure mode, and it is the one that ends trips: “Under inflation is the number one cause of trailer tire failure.”

Bridgestone says the sidewall number is not a recommendation at all: the figure there “only indicates the greatest pressure permitted for that tire,” and running at it “could make them wear faster or compromise your traction or braking abilities.” It points owners to the placard on the vehicle instead.

Goodyear once published load and inflation tables telling owners to inflate to the tire carrying the heaviest load on the axle. That guidance lived on its RV tire site, which no longer exists, and its current consumer pages simply point to the vehicle placard. Worth knowing if somebody quotes the old tables at you: they are no longer published.

The federal rule sits behind Bridgestone here. On trailers rated at 10,000 pounds or less, FMVSS 110 makes the placard the vehicle manufacturer’s statement of recommended cold inflation. Above that rating the equivalent requirement is in FMVSS 120. On a trailer the placard figure and the sidewall maximum often land in the same place, because trailer builders tend to specify a tire at close to its rated capacity. That is not a rule and no manufacturer states it, so treat the placard as the authority and Carlisle’s position as Carlisle’s.

Two practical numbers from Bridgestone that are easy to forget. A tire loses “approximately 1 pound per square inch (PSI) of tire pressure every month” on average, and “for every 10 degrees F change in ambient temperature, tire pressure will change by approximately 1 PSI.” That second one runs both ways, but it is the cold direction that catches people out. A trailer that came out of storage in March at the pressure you left it in November is not at that pressure any more.

Check them cold, before towing, every time. Travel trailer tires punish this more than car tires do, because nobody drives them daily and notices. If you would rather know while moving than find out afterwards, our guide to setting up TPMS on a travel trailer covers what the sensors weigh and where the repeater goes.

Why do campers keep having blowouts?

Put the sourced facts next to each other and the pattern is not mysterious.

• The tires are certified to an older standard than the ones on the tow vehicle.
• They spend most of their life stationary under load, which Carlisle says breaks down the carcass invisibly.
• They lose pressure sitting, roughly a psi a month, and more as it gets cold.
• Under inflation is what Carlisle names as the number one cause of failure.
• The one test most owners run, looking at the tread, is the test the manufacturer says does not work.
• The date code that would tell you the real answer is often molded on the hidden sidewall.

Travel trailer tires are not fragile. They are used in a way that defeats the checks people know how to run.

The five picks

Five lines, all shown in ST225/75R15 so the numbers sit side by side. That size is an example, not a recommendation. Match the size, load range and pressure on your own placard and sidewall, because the right tire for one trailer is the wrong tire for the next one.

Every figure below comes from the manufacturer rather than the retailer, and that distinction is not academic here: Amazon’s own spec table gives the Maxxis a load capacity of two pounds. The more important thing they have in common is what none of them publishes. Not one of these five states a replacement age.

What they publish instead are warranty windows. Maxxis six years from the date of manufacture, Carlisle two years from the date of purchase, and those are coverage limits, not advice about when a tire stops being safe. Two of the five publish no warranty terms that can be reached at all. That gap is the argument of this whole article, and no maker on this page closes it.

Restful RV is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.

One pattern is worth naming before you go looking. Search this size for anything above load range E and almost everything that comes back is a private label with no technical documentation behind it, no published spec table, no warranty you can read, sometimes no stated load index.

Carlisle and Maxxis publish nothing above load range E in ST225/75R15, and we could not find an above-E Endurance either. The owner who needs more than an E is pushed out of the documented brands entirely, which is worth knowing before you assume the choice is yours to make.

The other thing to watch for is the listing that borrows a name. Search for the Goodyear Endurance in this size and one of the first results is a two pack sold by eCustomRim whose title begins with the word Fits. It is not a Goodyear. Read the brand line, not the title.

What it comes down to

Find the date code, on the inboard sidewall if it is not on the outboard one, and write the year on something you will still have next season. Set your own replacement age with the published range in front of you, knowing it runs from five years to ten and that no trailer tire maker will pick for you.

Check pressure cold before every trip, against the placard. Load the trailer the way you tow it and make sure the axle rating divides into tires that can carry it. And tow at sixty, because the company that makes the tires says so.

None of that is expensive. All of it is more reliable than looking at the tread. Tires are the part of the towing system that touches the road first, and the RV towing guide covers how they connect to the hitch and brakes.

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