What’s the difference between ST and LT tires (and why LT tires don’t belong on boat trailers)?

When it comes to boat trailers, tire choice isn’t optional. Trailer tires must be ST tires, which stands for Special Trailer. ST tires are purpose-built to handle the unique stresses of towing — something LT (Light Truck) and P (Passenger) tires simply aren’t designed to do.

Why ST Tires Are Required for Boat Trailers

• Designed for Trailers, Not Driven Axles
  ST tires are engineered specifically for use on boat, utility, and cargo trailers. Unlike LT or P tires, they’re built to carry heavy loads on non-powered axles that don’t have the benefit of steering or braking traction.
• Higher Load Capacity
  For the same size, ST tires can carry 10% more load than equivalent LT tires and 40% more than passenger car (P) tires. That extra capacity is crucial when your tires are supporting the full weight of the boat, trailer, and gear over long distances.
• Stiffer Sidewalls to Reduce Sway
  ST tires have reinforced, thicker sidewalls that control trailer sway and withstand the vertical load of towing. LT tires, by comparison, have more flexible sidewalls meant for ride comfort, not stability.
• Heat Resistance
  Because trailers put constant vertical pressure on their tires, ST tires are built to better resist heat build-up — one of the leading causes of blowouts during towing.
• Speed Rating Considerations
  Most ST tires are rated for speeds up to 65 mph, unless otherwise marked. This aligns with typical safe towing speeds. LT tires may be speed-rated higher, but that doesn’t make them safer — it makes them less durable under the load conditions of a trailer.

Why LT Tires Don’t Belong on Boat Trailers

LT (Light Truck) tires are designed for SUVs, vans, and pickups. They perform well under mixed driving conditions, offering traction, handling, and ride comfort. But they lack the load-handling capacity and sidewall strength that a boat trailer demands.

• Lower Load Ratings: LT tires cannot carry as much vertical load as ST tires in the same size.
• Flexing Sidewalls: More flex equals more heat and faster wear under trailer loads.
• Risk of Premature Failure: Using LT or P tires on a boat trailer increases the risk of tread separation, blowouts, and sway.

The Bottom Line

For safe towing, never substitute LT or P tires for ST tires on a boat trailer. While they may look similar, their internal construction and load ratings are very different. ST tires give you the extra strength, load capacity, and stability you need when hauling thousands of pounds of boat and trailer down the highway.

Venture Tip: Always check your tire’s sidewall for its ST designation and inflate to the manufacturer’s recommended PSI to get the maximum performance and lifespan.