Two numbers keep your trailer on the road: the air pressure in your tires and the torque on your lug nuts. Get either one wrong and you lose a wheel or blow a tire. This page has both, pulled straight from the axle and tire manufacturers' published specs.
If you only remember one thing: your tire pressure comes off the sidewall of your tire, not off a chart. Here's why that matters more than most people think.
Trailer Tire Pressure
The lug count on your wheel does not tell you the tire pressure
This is the single most common mistake we see, and it's an easy one to make. People assume a 5-lug wheel means one pressure and an 8-lug wheel means another. It doesn't work that way.
Tire pressure is set by the tire's Load Range — a letter stamped on the sidewall that tells you how much air the tire is built to hold and how much weight it can carry at that pressure. Two trailers with identical 8-lug wheels can take completely different pressures if they're wearing different tires.
It gets one step trickier. Load Range letters have sub-categories, and they don't all run the same pressure:
| Load Range | Ply Rating | Typical Max Cold PSI |
|---|---|---|
| B | 4-ply | 35 PSI |
| C1 | 6-ply | 50 PSI |
| C2 | 6-ply | 35 PSI |
| D1 | 8-ply | 65 PSI |
| D2 | 8-ply | 50 PSI |
| E1 | 10-ply | 80 PSI |
| E2 | 10-ply | 65 PSI |
| F | 12-ply | 95 PSI |
| G | 14-ply | 110 PSI |
| H | 16-ply | 125 PSI |
Look at Load Range D. Depending on whether it's a D1 or a D2, the correct pressure is either 65 PSI or 50 PSI. That's a 15 PSI spread on tires wearing the same letter. Guess wrong and you're running badly underinflated.
Where to find your number
- The tire sidewall. Look for "MAX LOAD ... AT ... PSI COLD." That PSI is your target.
- The trailer's VIN/tire placard. Usually on the driver's side front of the trailer. It lists the tire size and pressure the trailer was built around.
- If the two disagree — someone changed the tires. Go by the sidewall of the tire that's actually on the trailer, and make sure it still meets or exceeds the trailer's load rating.
Run trailer tires at max cold pressure
Trailer tires are not car tires. A car tire is inflated below its maximum for ride comfort. An ST (Special Trailer) tire only reaches its rated load capacity at its maximum cold pressure, so that's where you run it.
"Cold" means before you drive, not before it's been sitting in the sun. Driving heats a tire and raises the pressure, so a tire that reads correct after 40 miles was underinflated when you left. Check them in the morning, in the shade, before the trailer moves.
Underinflation is the number one killer of trailer tires. An underinflated tire flexes more in the sidewall, builds heat, and comes apart — usually at highway speed, usually fully loaded.
Lug Nut Torque
Torque specs are set by your wheel and stud size, not by lug count either. These are Dexter Axle's published figures — Dexter is the most common axle under trailers on our lot.
| Wheel Size / Bolt Circle | Stud Size | 1st Stage | 2nd Stage | Final Torque |
|---|---|---|---|---|
| 12" and 13" | 1/2"-20 | 20-25 | 35-40 | 60-75 ft-lbs |
| 14", 15", 16" (545 / 655 BC) | 1/2"-20 | 20-25 | 50-60 | 100-120 ft-lbs |
| 16" and 16.5" (865 BC) | 9/16"-18 | 20-25 | 50-60 | 140-170 ft-lbs |
| 16.5" x 9.75" (865 BC) | 5/8"-18 | 50-60 | 120-125 | 175-225 ft-lbs |
| 17.5" hub pilot, clamp ring | 5/8"-18 | 50-60 | 100-120 | 190-210 ft-lbs |
| 17.5" hub pilot, flange nut | 5/8"-18 | 50-60 | 90-200 | 275-325 ft-lbs |
| 17.5" hub pilot, swivel flange nut | 5/8"-18 | 50-60 | 60-110 | 150-175 ft-lbs |
Going by socket size instead
If you don't know your stud size, the socket that fits your lug nuts gets you close:
- 13/16" socket — 100-120 ft-lbs
- 15/16" socket — 140-170 ft-lbs
- 1-1/16" socket (common on 17K axles) — 275-325 ft-lbs
How to tighten them
- Start every nut by hand so you don't cross-thread a stud.
- Snug them all to about 10 ft-lbs first, in a star pattern, to pull the wheel flat against the hub.
- Torque in three stages — first stage, second stage, then final — following the star pattern each time. Don't jump straight to final torque; the wheel will seat crooked.
- Use a torque wrench. An impact gun has no idea when to stop. Overtightening stretches studs and warps brake drums; undertightening loses wheels.
- Check your thread stick-out. You want roughly three threads showing past the end of the nut. Less than that and you don't have full engagement.
The re-torque schedule people skip
Re-torque after the first 10 miles, then again at 25 miles, then again at 50 miles. Then check periodically after that.
This is not optional and it is not conservative padding. New wheels seat as you drive — the mounting surfaces settle, and nuts that were at full torque in the shop are loose 10 miles down the road. Skipping the re-torque is behind most of the lost-wheel calls we take.
Re-torque any time a wheel comes off and goes back on, too — after a tire change, a bearing service, a roadside repair.
Download the Charts
- Dexter Axle Product Bulletin #409 — Wheel Attachment and Torque Requirements (PDF) — the full torque table plus star-pattern diagrams for 4, 5, 6, 8 and 10-bolt wheels.
Let Us Handle It
If you'd rather not chase this yourself, our service department checks pressures, torques wheels, and services axles at both lots. We recommend an axle service every 6 months or 12,000 miles, whichever comes first — and the first one is included with a maintenance plan.
Thomasville: (336) 276-0329 | Winston-Salem: (336) 499-9888
Learn more about our service department | Browse our trailer inventory
The specs on this page are published manufacturer figures and are here as a reference. Your trailer's own placard, tire sidewall, and owner's manual always take priority. If something doesn't match, call us before you tow.