ST205/75R15 Travel Trailer Tires: What The Size Means And Which Load Range To Buy

If you own a single- or tandem-axle travel trailer built in the last twenty years, there is a good chance it is wearing this size. It is the default fitment across a huge swathe of the market, which is why it is also the size people search for directly rather than searching for a brand — you walk out to the trailer, read the sidewall, and type what it says.

The useful news is that in this size the field is deep and genuinely competitive. The less useful news is that the shelf is full of load range C tires sitting next to load range E tires at similar prices, and those two are not interchangeable in either direction. So this page is mostly about the sidewall, and only then about which tire.

Reading ST205/75R15, character by character

After the size you will see something like 107M or 107N, and then a load range letter. The three-digit number is the load index, the letter after it is the speed symbol, and they matter more than the tread pattern ever will.

Load index and speed symbol: the load index is a coded maximum load per tire (107 is about 2,149 lb; 111 is about 2,403 lb). The speed symbol is a maximum sustained speed — M is 81 mph, N is 87 mph. Neither is a target. A trailer tire run near its load and speed ceilings in summer heat is the classic setup for a blowout.

Load range C, D and E in this exact size

Load range is the whole decision. It describes how much the tire can carry at its specified cold inflation pressure, and the letters correspond to what used to be called a ply rating.

Multiply by the number of tires on the ground to see what this buys you. A tandem-axle trailer on load range C has roughly 7,280 lb of tire capacity; the same trailer on load range D has about 8,600 lb; on load range E, about 9,600 lb. Your trailer’s GVWR has to sit under that number with margin, and the margin is what keeps a hot highway afternoon uneventful.

The rule going down is absolute. Never fit a lower load range than the certification label on the trailer specifies. That label states the tire size, load range and cold inflation pressure the trailer was built around, and it is the only document that matters in a dispute.

The rule going up has a condition. Stepping from D to E in the same size is a common and sensible upgrade for a trailer that runs near its GVWR — but the extra capacity only exists at the higher inflation pressure. A load range E tire inflated to 65 psi carries roughly what a D carries. So before upgrading, read what is stamped on your wheels. If the rims are rated to 65 psi, fitting 80 psi tires and inflating them to 80 psi loads the wheel beyond its rating, and the wheel is now the weak part. Rims in this size are commonly rated 50, 65 or 80 psi, and there is no way to know which you have without looking.

Which of the five, and why

Goodyear Endurance (load range D, 107N). The premium answer and the tire most often named by owners replacing a failed original set. You are paying for a major manufacturer’s build quality, a published warranty, a real dealer network, and an N speed symbol rather than M. Sold individually, and a set of four is a real amount of money.

Carlisle Radial Trail HD (load range D, 107M). The sensible default. A genuine ST radial with the same 2,149 lb per tire as the Goodyear, widely stocked so a roadside replacement is actually findable, at a noticeably lower price. The M speed symbol means 81 mph, which is not a constraint for anyone towing sensibly.

Maxxis M8008 Plus (load range C, 6-ply). The best reputation per dollar in this size, and the one to read the label for — this is a load range C tire, so about 1,820 lb per tire. On a lighter single-axle trailer that is correct and the tire is excellent. On a 7,000 lb tandem it is not enough, no matter how good the tire is.

Free Country load range D (107N). Load range D at a price many load range C tires ask, with a curb scuff guard. The honest framing is that you are buying the right load rating from a brand with far less published history than the two above, and budget ST tires are the ones most often reported failing on long hot runs.

Free Country HD load range E (111N, set of four). The upgrade option: about 2,403 lb per tire, sold as a set, at a price close to four load range D tires individually. Buy it if your trailer runs near its GVWR and your wheels are rated for 80 psi. Otherwise it is weight and harshness you are not getting paid for.

Three things that matter more than which brand you picked

Age beats tread, every time. Trailer tires almost never wear out — they age out, sitting in one position in the sun between trips. The sidewall carries a four-digit date code at the end of the tire identification number: week and year of manufacture. Most guidance puts the replacement point somewhere between three and six years regardless of how much tread is left, and a tire with deep tread and a 2018 date code is not a good tire. How long trailer tires last goes into what actually drives that.

Pressure is the single biggest controllable. Inflate to the cold pressure on the trailer’s certification label for the load range fitted, check it cold before every trip, and never bleed pressure down because the tires “feel hot.” Under-inflation is the leading cause of trailer tire failure, and the sidewall flex it causes generates exactly the heat that destroys the tire. The psi guide covers it properly.

You will not notice a failure without help. You cannot feel a trailer tire going down from the driver’s seat, which is why a TPMS is the most useful accessory a trailer owner buys. And when the trailer is parked for weeks, tire covers slow the UV damage that ages the sidewall in the first place.

And if your placard says 225, you are on the wrong page. The other common travel trailer size is ST225/75R15, which is wider, taller and sold in load range D, E and G rather than C, D and E. The 225/75R15 page covers that ladder and answers the swap question properly — the short version is that fitting 225 where the label says 205 is a clearance and ride-height change that raises no rating.

What this page is, and is not

We have not road-tested these tires. The figures above are read from the published load and marking requirements in FMVSS 109, each maker’s published specifications, and the current retailer listing data our price pipeline reads automatically. Load and pressure figures given by load range are the common published values for this size and do not replace the marking on the specific tire you buy — read your own sidewall. Our scoring method is on how we pick.

If you want the field ranked rather than the size explained, the travel trailer tire roundup is the page for that. If you are weighing ST against LT tires for a trailer at all, ST versus LT handles that argument, and the trailer essentials hub has the rest of the first-trailer gear.