Different PSI Listing for Two Tires on Boat Trailer

Updated 09/05/2017 | Published 09/01/2017

Question:

I have a trailer with two Trail America ST175/80D13 B78-13ST tires on it it is a two tire trailer for my boat, they are the tires that came with the trailer. The odd thing is one says 50PSI and the other says 35PSI. All other writing is the same. The one that says 35PSI looks low, plus I know I dont want two tires inflated differently. Is it likely that the 35PSI is a misprint? I asked the dealer I got the boat and trailer from, they got it all directly from the manufacturer and said misprints are common. Id drive it to a tire dealer but it is 35 miles to the nearest town. Hope you have some advice thanks

asked by: John W

Helpful Expert Reply:

While it's possible that there is simply a misprint regarding the maximum psi for the tires on your boat trailer, I recommend checking the sidewalls again, specifically for their load range identifier.

Based on my research, a 175/80D13 tire with a Load Range C will typically have a maximum psi of 50, while a Load Range B tire of the same size will have a maximum psi of 35. The load range of a tire indicates its horizontal and sidewall strength. This will correlate to the amount of weight each tire can safely handle at its maximum psi. Since these psi values happen to be the two numbers you found listed on the tires, it's very possible that the load ranges for the two units are actually different.

The load range is usually listed just after the tire size on the tire's side wall. On your metric tire, there should be an "LRC" to indicate a load range C or "LRB" to indicate a B load range. If both tires do a show a load range C, then I recommend filling both tires up to 50 psi. I have also included an article on reading a tire's sidewall that you might find helpful.

If you do find that the load range on your two tires is different, you will want to replace them as soon as possible. For a load range C tire, I recommend the Provider ST175/80R13 Radial Trailer Tire # TTWTRTM1758013C. This tire has a maximum load of 1,360 pounds at 50 psi and an excellent maximum speed of 81 mph. I have attached a short video on this tire for you to check out.

expert reply by: Chris R