If you’re shopping for a used boat, there’s a pretty good chance you’ll be shopping for trailer tires sooner or later. No other tires withstand so much neglect, abuse, and degradation through disuse as they do.
Trailer tires sit in one spot for long periods, which leads to flat spots and UV damage. They also get dragged over and across more curbs in one boating season that most car tires do in their lifetimes. What’s more, in the case of dual- or triple-axle trailers, many of them get dragged across the pavement laterally in tight turns. They lead a hard life and they do an important job — getting your boat to the water — so when it comes time to replacing them, get something at least halfway decent.
Here’s the kicker. The best used boats are those about two to four years old — right about the time trailer tires are supposed to be replaced — so there’s a pretty good chance you’ll be in the market.
The first thing to understand is that trailer tires are different from car tires. Same goes for the wheels. Trailer tires have no offset, which means the flange where the wheel bolts to the hub is in the linear center of the tire tread. This distributes the load evenly across the tread surface.
When shopping for tires, those little letters and numbers on the sides have meaning. For example, let’s look at a sidewall with ST235/70R15 nomenclature. ST indicates “special trailer,” which is what you want. P235 or LT235 would designate a tire for a “passenger car” or a “light truck,” respectively. Thus the P and LT. The number 235 refers to the tire’s metric width at the widest point of its sidewall. The number 70 refers to the aspect ratio, which in this case means the sidewall is 70 percent of the tire’s width. A 60 would mean the sidewall is 60 percent of the tire’s width, and so forth. The letter R means it’s a radial, and the number 15 refers to the diameter of the wheel.
In terms of selection, you have many options, but don’t go cheap on trailer tires. Think of all those boats stranded on the side of the road with flat tires. Those owners either bought cheap tires or didn’t replace them in time. Don’t be that guy. I’m not suggesting you spring for top-of-the-line Michelins, but do realize that chintzy trailer tires can ruin a weekend.
Replace them in pairs if you can’t afford to replace all four. Also, be sure to buy radials. They’re better in every measureable way. They wear better, ride better, and absorb jounce better than a bias-ply ever could. Bias-ply tires cost less, but it’s false economy compared with a radial tire.
Trailer tires are rated for a maximum amount of weight they can carry at maximum air pressure. For example, if your boat and trailer weigh 4,000 pounds, each tire on a dual-axle trailer must exceed 1,000 pounds of load carrying capacity.
You don’t have to know everything about what you want in a trailer tire, but it does help to know what you don’t want. Show up at the tire store with enough information that the service adviser can help you. So when you find a great deal on a used boat, don’t let the prospect of buying trailer tires discourage you.