ST145/R12 Trailer Tire Recommended PSI and Load Guidance

Updated 09/15/2026 | Published 09/07/2026

Question:

I have a ST145/r12 tire. Wanting to know the best tire pressure to run with a max load of 500lbs.

asked by: steve h

Expert Reply:

Hi Steve, the safest recommendation is to run your ST145/R12 trailer tire at the maximum cold PSI listed on the tire sidewall, even with a 500 lb load.

Trailer tires are designed to carry their rated load at the specified pressure, and running them underinflated can create extra heat and sidewall flex, which is exactly what you want to avoid when trying to prevent a tire failure. For example the Kenda Karrier ST145/R12 Radial Trailer Tire and Wheel, part # AM35354, specifies 65 PSI at all times.

That should give you the best chance of keeping the tire running cool, wearing properly, and tracking the way it should without having to guess at the pressure based on your cargo weight.

Do you know exactly which tire you have?

expert reply by: Heather A

Steve H.

9/11/2026

thank you

Heather A.

9/11/2026

@SteveH no problem at all Steve, let me know if you need anything else!

Mike

9/12/2026

@HeatherA Been running them 2 to 3 years without issue and have held up and the wear is even and minimal so far. No complaints on them and have basically switched all my small trailers over to them.

Todd

9/12/2026

Run it at the recommended pressure and thre will be no issue

Rick T.

9/12/2026

Hi Steve I've had them for over a year now, I wish I could give you some usefull input, but all I can say is they have been a great bunch of tires so far, gonna take them on a 3000 mile trip in a few months. That will tell the story for me, but I would buy again as of right now!

Carl U.

9/13/2026

Mine are on a utility trailer hauling a zero turn mower, so the weight is similar to yours. I mow as a side job, so I'm towing 3-4 days per week. Over 2,000 miles so far this year. I always run the max pressure with no problems.

Heather A.

9/15/2026

@CarlU Thank you for joining the conversation Carl! Love to hear these are working out well for your side gig. How's the zero turn working out for you?

Carlu

9/15/2026

It's a Cub Cadet, and I love it!

Heather A.

9/15/2026

@Carlu Wow that's a nice one!

Darrell

9/13/2026

I use them ona boat trailer so i run them alittle less than recommended pressure to give some added suspension. Its a light jon boat so there has been no issues or complaints on how the boat rides or the wear on tbe tires. Best choice to spend alittle more on better tires!