Load Range D is better for most highway trailer applications — its 8-ply construction handles heavier loads and sustained highway speeds more safely than the 6-ply Load Range C rating.

The letter on a trailer tire sidewall indicates ply rating and maximum load capacity at a given PSI. Load Range D tires carry roughly 1,760 lbs per tire at 65 PSI on a standard ST205/75D15 size, compared to approximately 1,520 lbs for the same size in Load Range C. For utility and garden trailers running light loads at moderate speeds, Load Range C is adequate. For boat trailers, car haulers, or anything pushed consistently near max weight at highway speeds, Load Range D is the right call.

  • Load Range C trailer tires are 6-ply rated; Load Range D trailer tires are 8-ply rated.
  • ST205/75D15 Load Range D tires are typically rated to approximately 1,760 lbs per tire at 65 PSI.
  • ST205/75D15 Load Range C tires are typically rated to approximately 1,520 lbs per tire at 50 PSI.
  • Bias-ply trailer tires in both Load Range C and D carry an M speed rating — maximum 81 mph, safest below 65 mph.
  • The "D" in a tire size like ST205/75D15 indicates bias-ply construction, not Load Range D — these are two separate designations.

How to Choose

  • Pick Load Range C (6PR) if: your utility or garden trailer runs well under 1,500 lbs per tire at moderate speeds on local roads.
  • Pick Load Range D (8PR) if: you're hauling a boat, car, or heavy cargo trailer on the highway anywhere near the tire's weight limit.
  • Pick Load Range D if: your trailer sits loaded for extended periods — 8-ply construction handles static load stress better than 6-ply over time.
  • Pick Load Range E if: Load Range D still leaves you within 10–15% of the per-tire weight rating — heavier fifth-wheel or gooseneck setups need the additional headroom.
  • Stick with Load Range C if: you're running a MERXENG 4.80-12 trailer tire on a garden cart or small utility rig where total trailer weight stays below 1,800 lbs combined.