What Is Load Range C on a Trailer Tire? | Tire Code Decoded

Load range C marks a trailer tire built to carry a moderate load, usually in the old 6-ply-rating class, with capacity tied to its size and PSI.

If you’re asking what is load range C on a trailer tire, the plain answer is that it is a load class. It tells you how much weight the tire is built to carry at a stated cold inflation pressure. On most trailer tires, load range C lines up with the old 6-ply-rating class, not six physical plies inside the casing.

That little C matters because it shapes payload room, air pressure, and the kind of trailer the tire fits. But it is only one part of the sidewall story. Tire size, tire type, wheel rating, and the trailer’s axle numbers still decide whether the tire is a match.

Load Range C On A Trailer Tire In Plain Terms

A load range is a strength class. Think of it as the tire’s carrying bracket. A C-rated trailer tire usually sits above B and below D. That makes it common on utility trailers, boat trailers, pop-up campers, and lighter travel trailers that do not need the extra air pressure or carrying room of D or E.

The old ply language still sticks around, so you will hear people call load range C a “6-ply rated” tire. That does not mean the tire has six actual fabric layers. Modern radial trailer tires use different materials and build methods. The letter is what matters when you compare carrying class.

A Sample Sidewall Walk-Through

Take ST205/75D14 C. Read it left to right. ST means Special Trailer. 205/75 is the size. D means bias construction, while an R in that spot would mean radial. The final C is the load range. Change only one of those pieces and the carrying number can move a lot. That is why two tires with the same C can still carry different loads.

What The Letter Changes In Daily Towing

When the load range goes up, the tire can usually carry more weight and take more cold air pressure. That can steady a loaded trailer and add more room under the axle rating. But the gain is tied to the exact tire size and model, not the letter by itself.

• Weight room per tire: A C-rated tire can carry more than a B-rated tire in the same basic size family.
• Cold inflation ceiling: Load range C often runs more PSI than lighter classes, though the sidewall gives the final number.
• Casing firmness: More air and a firmer casing can calm sway on a loaded trailer, while an empty trailer may feel harsher.
• Wheel and valve limits: A tire is only half the setup. The wheel and valve stem must be rated for the pressure you plan to run.

Read The Whole Sidewall, Not Just The C

Trailer owners get into trouble when they shop by letter alone. Read the whole sidewall and the trailer placard together. That full read tells you what the tire is, what it can carry, and what pressure it needs when cold.

Sidewall Marking	What It Means	Why It Matters
ST	Special Trailer tire	Built for trailer duty, not as a passenger-car substitute.
205/75R14 or 205/75D14	Size and construction	R means radial, D means bias; size changes the load figure.
Load Range C	Carrying class	Usually the old 6-ply-rating class in trailer fitments.
Load Index	Numeric weight code	Pairs with tire specs to show the rated load.
Max Load	Most weight one tire can carry	You need enough total capacity across the axle, with room left over.
Max PSI Cold	Highest cold inflation listed	The wheel, valve stem, and placard need to line up with it.
Speed Symbol	Rated speed class	Trailer tires have speed limits just like tow-vehicle tires.
DOT Date Code	Week and year of build	Age matters even when the tread still looks fresh.

Continental’s page on how to read a tire sidewall states that load range ties back to ply-rating language, and Carlstar’s Sport Trail LH spec table lays out how one C rating can land at different load numbers once the size changes.

Where Load Range C Fits Among Trailer Setups

Load range C sits in the middle of the small-trailer market. It is not the lightest class you will see, and it is far from the heavy-hauler end. That middle spot is why it turns up so often on single-axle utility trailers, boat trailers, and lighter campers.

C is not a quality grade. It is not “better” than D or “worse” than D on its own. It simply matches a lighter job. A tire can be exactly right at C when the trailer, wheels, and cargo all line up. It can be badly undersized once extra batteries, water, tools, or denser cargo creep into the build.

The trap is treating C like one fixed weight number. It is not. A small 4.80-8 C tire and a ST205/75D15 C tire both wear the same letter, yet their rated loads are miles apart. Size and construction change the number.

Load Range C Size Examples

On Carlstar’s bias-ply trailer line, a few load range C sizes land here. These figures work well as a reality check, not a universal chart for every brand or every radial tire.

Tire Size	Rated Load	Max PSI Cold
ST175/80D13 C	1,360 lb	50 PSI
ST185/80D13 C	1,480 lb	50 PSI
ST205/75D14 C	1,760 lb	50 PSI
ST215/75D14 C	1,870 lb	50 PSI
ST205/75D15 C	1,820 lb	50 PSI

That spread tells the story. The letter C gives you the class. The size gives you the real carrying number. Read both, every time.

When Load Range C Is The Right Pick

Load range C makes sense when the trailer’s loaded axle weight leaves decent headroom under the combined tire rating and the placard already calls for a C-rated tire. In that situation, staying with the original class often keeps the trailer balanced the way it was built.

• Single-axle utility trailers carrying mowers, lumber, or household loads within the trailer’s rated limit.
• Boat trailers built around smaller to mid-size boats.
• Pop-up campers and lighter campers that left the factory on C-rated trailer tires.
• Replacement jobs where the wheel rating, valve stem, and axle tag all line up with a C-rated setup.

When C Is Too Little Tire For The Job

If your trailer spends every trip close to the tire’s max load, you do not have much room left for heat, road shock, or cargo creep. That is where trouble starts. A tire that looks fine on paper can be working too close to its ceiling on the highway.

• Your loaded scale weight lands near the tires’ combined rated load every trip.
• You added heavier gear, water, racks, boxes, or denser cargo since the trailer was new.
• You run long highway miles in hot weather with little cushion left.
• The trailer placard or axle label already calls for D or E, yet someone fitted C-rated tires anyway.

Do not jump to a higher letter without checking wheel rating, rim width, valve stem rating, and trailer clearance. More PSI on an underrated wheel is bad news, even when the tire itself can take it.

Mistakes That Trip People Up

• Buying by letter only. Load range is one data point, not the full answer.
• Ignoring construction. A bias-ply C and a radial C can carry different loads in different sizes.
• Guessing on pressure. Use the placard, the sidewall, and the real loaded weight of the trailer.
• Forgetting the wheels. Tire pressure, wheel rating, and valve stem rating need to agree.
• Trusting tread alone. An older tire with decent tread can still be due out because age and heat take their toll.

Checks To Make Before You Buy Or Tow

1. Read the trailer placard. Start with the size and load range the trailer maker listed.
2. Read the old tire sidewall fully. Note the size, load range, max load, max cold PSI, and build date.
3. Weigh the trailer loaded as you actually tow it. Guessing is where bad tire choices begin.
4. Match the wheel and valve hardware. Do not raise pressure beyond what the wheel and valve stem can handle.
5. Leave room, not a razor-thin match. A trailer tire works better when it is not pinned against its ceiling on every trip.

Load range C is not a mystery code once you read it in context. It tells you the tire’s carrying class, usually the old 6-ply-rating bracket, and it only makes sense next to size, max load, and cold PSI. Get those numbers lined up with the trailer placard and your real loaded weight, and the right tire choice gets a lot easier.