Trailer tires fail differently than passenger tires, and most owners don't find out until they're on the side of the highway. This guide covers what to check, when to replace, and how to choose the right tire for your trailer.
Here's something that surprises most trailer owners: the tread on your tires can look completely fine and the tires can still be dangerous. Trailer tires age out long before they wear out. Unlike a car that puts on 20,000 km a year, most trailers run a fraction of that. A set of boat trailer tires with 40% tread remaining can be 8 or 10 years old, and rubber degrades with time regardless of mileage.
UV exposure, temperature cycling, and simply sitting under load all break down the compounds in the sidewall. The result is internal cracking that isn't visible until the tire fails, often at highway speed with a loaded trailer behind you.
How to check the DOT date code on your trailer tires:
Look at the sidewall for the DOT number. The last four digits are the week and year of manufacture. 1323 means the 13th week of 2023. Most trailer tire manufacturers and transport safety guidelines recommend replacement at 5 to 7 years regardless of remaining tread depth. If your tires have a DOT code older than that, they are candidates for replacement even if they look fine.
Time flies with trailer tires. We've seen customers bring in trailers confident their tires are fine and find DOT dates from 2013. The tread looks perfect. The rubber is not.
When a trailer is stored outside for months at a time, the tires take the brunt of UV exposure. Ozone and sunlight attack the rubber compounds in the sidewall continuously, even when the trailer isn't moving. This is why a trailer that sits parked in the same spot from October to May can have tires in worse shape than one that's been driven regularly.
One of the simplest things you can do to extend trailer tire life is cover the tires during storage. Purpose-built tire covers are inexpensive and block UV radiation effectively. Parking in a shaded area or moving the trailer into a garage during the off-season also makes a meaningful difference.
Store in shade or covered: Direct sunlight accelerates sidewall cracking faster than driving ever will.
Use tire covers: Slip-on covers cost $30 to $60 and can add years to your tire life.
Avoid ozone sources: Don't store tires near electric motors or welding equipment, which emit ozone.
Trailer tires come in two construction types, and this is not a matter of preference. Bias ply and radial trailer tires handle load, flex, and heat differently enough that mixing them on the same trailer creates a dangerous handling imbalance. This is not a guideline, it is a hard rule.
Cord layers run diagonally at alternating angles. Stiffer sidewall that resists lateral flex under load. Runs cooler at lower speeds. Good for slow-speed, heavy-load applications like construction and landscape trailers. Lower upfront cost. Marked ST with no R designation.
Cord layers run perpendicular to the direction of travel. More flexible sidewall, runs cooler at highway speeds. Better tread contact for longer wear. Preferred for highway towing and boat trailers covering distance regularly. Higher upfront cost, longer service life. Marked ST followed by R (e.g. ST205/75R14).
Why mixing is dangerous:
Bias ply and radial tires flex at different rates under load. When one axle has bias ply and the other has radials, the trailer wants to track two different lines. At highway speed with a heavy load, this creates a sway condition that can quickly go beyond the driver's ability to correct. Always replace in matched sets, and if you are unsure what type is on your trailer, bring it in and we will check.
Trailer tires lose pressure over time even when parked. An underinflated trailer tire runs hot, and heat is the primary cause of blowouts. Check cold pressure before every trip and inflate to the maximum PSI listed on the sidewall, not the pressure on your tow vehicle's door jamb.
Trailer tires carry static weight differently than drive tires. Overloading generates heat faster than the tire can dissipate it, which leads to internal failure. Check your trailer's GVWR and ensure your tire load ratings match or exceed the total loaded weight of the trailer.
Look for small cracks running across the sidewall, especially near the rim edge. Minor surface crazing is an early warning sign. If cracks are deep enough to show the cords underneath, the tire needs to come off immediately regardless of tread depth or age.
On tandem and triple-axle trailers, front axle tires typically wear faster due to scrub during turns. Rotating at mid-season extends the life of the full set and gives you a regular opportunity to inspect all tires up close.
Worn bearings cause irregular tire wear and can fail suddenly on the highway. Boat trailer bearings take extra abuse from water immersion. Have them inspected and repacked at least once a year, or more often if the trailer sees regular water launches.
Any time wheels are removed and reinstalled, lug nuts should be re-torqued after the first 50 km. Trailer wheels are susceptible to loosening due to lateral forces during turns. Ted's does a free torque check on all trailer tire installations.
The Freedom Hauler is what we put on the vast majority of trailers that come through our shop. It is an excellent value tire that performs reliably across the full range of trailer types, from light utility and boat trailers to heavier camper and horse trailers, and into heavy commercial applications like dump trailers and construction haulers. If you are not sure what you need, this is where we start the conversation.
Carlstar makes purpose-built trailer tires that offer a meaningful longevity advantage in high-use applications. If you are putting serious kilometres on a boat trailer every summer weekend, or running a commercial trailer year-round, the additional investment in a Carlstar tire can pay off over the life of the tire.
For customers who want a name-brand premium trailer tire, Goodyear is a strong option. Goodyear trailer tires are built for applications where durability and consistent performance across varying load conditions matter, and they carry the brand reliability that many commercial operators look for.