What’s your attitude when you think about boat trailers? Hate? Loathing? Money pit? Nothing but trouble? Trailers are a necessary evil in boating. Either your boat constantly sits on your trailer, or hardly ever, and the trailer languishes out in the sun and weather. It sits on the ground, ignored and neglected until the next haul out or road trip.
Any number of things on a trailer can cause trouble: lights, bunks, brakes, springs, bearings and…tires. If any of these fall into disrepair, they can cause damage, safety risks or citations. This month, let’s look at tires.
Tire Duty Rating
Look at the tire size and rating on your trailer tires. If it starts with a “P,” or nothing, before a three-digit number, it’s a car tire. Don’t use car tires on a trailer. Car tires have more flexibility in their sidewalls than do trailer tires, which have thicker sidewalls. Cars need sidewall flexibility for cornering. Trailers do not; they are always running straight or nearly straight relative to the road. Their sidewall stress arises from vertical compression (up and down).
Always use tires with an “ST” prefix. For larger diameter trailer tires (16-inch and up), you can use LT rated tires (light truck tires) which also have stiff sidewalls. However, you must be certain that the LT tires you select have a load rating that suits the weight of your trailer and boat. Size for size, most trailer tires have more load carrying capacity than light truck (LT) tires.
For any tire you contemplate purchasing, find out the Load Index (numerical code) or Load Range (alphabetic code) and make sure it is compatible with the total weight of your trailer, boat (including full tanks) and gear, divided by the number of tires on your trailer. Include a generous safety factor. Why? Air temperature and tire age are factors. Also, if you have a tandem trailer and blow a tire, will the remaining tires be able to handle the load until you can get to a safe place to change tires?
Inflate the tire when cold to its maximum psi rating molded into the tire. Underinflated tires run hotter and fail earlier. According to BoatUS, underinflated tires are a leading cause of roadside breakdowns.
Check Your Spare
Always carry a spare in good condition and properly inflated.
Don’t let your trailer sit on the ground for long periods of time. Moisture can penetrate the tire rubber and cause a failure. Jack the wheels up and put them on jack stands or put some wood between the tires and the ground. Try to shield the tires from extended exposure to direct sunlight.
When To Replace
If your tread fails the classic Lincoln penny test, it’s time for a new set. Even with great-looking tread, trailer tires need to be replaced after 3–5 years of use. If you use bias ply trailer tires, they fail sooner than radial ply tires, because they do not dissipate heat as well. The industry recommendation is if a tire fails on one side of a tandem-axle trailer, the adjacent tire on the same side should also be replaced, since that tire likely bore excessive weight when the tire next to it failed. When you mount new tires, balancing is optional for most trailers.
Take your time trailering. Do not exceed 65 mph. If you do, you could exceed the rating of not only your tires, but also your rims. A failed tire can damage your rig, but a failed rim can destroy both trailer and boat.
Maintain Your Bearings And Brakes
Although a topic for another day, failing bearings put out enough heat to damage tires. If you have smoked a bearing and have to replace it, your tire probably needs replacement as well. Also, dragging brakes cause both tread wear and heat damage.
Plug repair kits are ok for a temporary fix, but for safety, buy a new tire or take the wheel to a tire repair shop and get it fixed from the inside. Don’t run a plugged tire for very long. Sidewall damage cannot be plugged or patched. Such a tire must be replaced.