Proper Trailer Tire Inflation — Why It's Different from Your Truck Tires
Inflate trailer tires to the maximum cold PSI stamped on the sidewall — always. Unlike passenger car tires where you run under max, trailer tires should be at their maximum rated pressure. Under-inflation is the #1 cause of trailer tire failure. Check pressure when the tires are cold (driven less than a mile) with a quality gauge.
Why Trailer Tires Are Different
On passenger cars, running tires at the max sidewall pressure is often too firm for ride comfort and causes center tread wear. On trailers, the dynamic is completely different:
- Trailer tires carry static loads — the tire must support the full weight of the trailer without the comfort flex engineered into car tires
- Trailer tires don't steer — there's no need to optimize for handling feel or comfort, only for load capacity and heat management
- The load capacity rating stamped on the sidewall is achieved at maximum inflation pressure — running under-inflated reduces the tire's effective load rating
- Under-inflated tires flex excessively, building heat. Heat is the #1 cause of trailer tire blowout.
How to Check Pressure Correctly
- Check When Tires Are Cold
Tire pressure increases as tires heat up during use — typically 4–6 PSI above cold pressure after highway towing. Always check and set pressure when tires are cold: parked overnight, or driven less than a mile at low speed. Checking pressure on a hot tire gives you a reading 4–8 PSI higher than the actual cold pressure, causing you to under-inflate.
- Use a Quality Gauge
Cheap stick gauges can be inaccurate by 5+ PSI. Use a dial gauge or digital gauge and verify it against a known-good reference periodically. At 65–80 PSI (common for Load Range D/E trailer tires), accuracy matters.
- Inflate to Max Sidewall PSI
Find the "Max Load XXXX lbs at XX psi Cold" marking on the sidewall. Set the tire to that PSI. All four tires should be at the same pressure if they're the same size and load range.
- Check Before Every Trip
Tires lose 1–2 PSI per month naturally, and more in temperature swings. Check before every trip of consequence. A 10-minute pressure check prevents a roadside blowout.
Typical PSI by Load Range
| Load Range | Typical Max PSI | What You'll See |
|---|---|---|
| C (6-ply) | 50 psi | Light utility and cargo trailers |
| D (8-ply) | 65 psi | Most common — dump, equipment, enclosed trailers |
| E (10-ply) | 80 psi | Heavy duty trailers |
The exact max PSI is on the tire sidewall. Always use that number — the table above is typical, not universal.
An under-inflated tire carries less load than its rated capacity, flexes more, and builds heat. Heat breaks down the rubber compounds and belt adhesion — causing a blowout, often with no visible warning. Many trailer tire blowouts happen on tires that are only 10–15 PSI under their rated max. At highway speed, that's enough to cause loss of control.
Seasonal Pressure Changes
Tire pressure changes approximately 1 PSI for every 10°F change in temperature. A tire at 65 PSI on a 70°F day will read about 58 PSI on a 0°F Michigan winter morning — 7 PSI under spec, which is significant. Check and adjust pressure when the season changes, particularly when moving from warm to cold months.
