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What Air Pressure Should I Run in My Trailer Tires?  


I have a 5 x 8 utility trailer with st205/75d15 6pr tires that say 50psi max. pressure. What happens if I run 40psi in the tires due to not hauling nothing but a 4 wheeler?


Expert Reply:

We recommend that all trailer tires be inflated to the max psi stated on the sidewall of the tire. If the tire is under inflated, the weight capacity is lowered to an unknown amount for that tire.

Although running lower air pressures can improve the ride of the trailer with lighter loads, the weight rating that the tire can carry will be reduced. If a heavier load is put on the trailer without changing the air pressure to the recommended amount, the sidewall of the tire could heat up and may cause a tire failure.

Outside temperature can be an issue in tire inflation. The warmer the outside temperature is the air pressure in the tires will increase. However, in colder weather, air pressure will decrease in tires. If the tire pressure is already lower than the stated amount, tire pressure could decrease more and could cause tire failure. It is recommend to inflate your trailer tires when the tire is cold.

It is recommeded that all trailer tires be inflated to the stated air pressure amount on the tire.

expert reply by:
Jared P



Should the tires of a utility trailer be inflated to max psi before load or should it be adjusted to max psi after load?

Etrailer Expert

Jon G.


Before you load the trailer.



@JonG What if you’ve got your utility trailer filled with a bit of an office type of a structure made out of wood it’s a 3 x 5 trailer and I put my 80 pounds of pressure in the trailer tires after I built the structure is that gonna be OK

Les D.


Under normal circumstances the pressure in a tire remains the same regardless if there is a load on them or not. Since the volume of the tire does not change when under a load (only the shape) the pressure does not increase. In an extreme situation you may see an increase of around 1 psi. So you will want to inflate the tires to their max psi rating when cold and you will be good to go.

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