Are ST145/R12 Tires And 4.80-12 Tires The Same Size?

Updated 09/26/2025 | Published 04/19/2025

Question:

I was looking at these tires on your site: Kenda Karrier S-Trail ST145/R12 Radial Trailer Tire - Load Range D, My trailer has tires on them and the size is 4.8.12, Are these the same size? Will they fit on my rims? I wanted to upgrade the tires to a steel belted radial from a bias ply as I am towing a 1000 pound Harley on a 5x8 trailer for 800 miles one way and then 800 miles back. Thank you

asked by: Mark L

Expert Reply:

Hello Mark, thanks for getting in touch. The 145/R12 tires and the 4.80-12 are similar but not exactly the same size.

The 4.80-12 tires are 4.9" wide and 20.7" in diameter when fully inflated.

The 145/R12 tires are going to be about 5.7" wide and 21.3 in diameter.

Both will fit the same 12" x 4" rims.

It may be possible for you to upgrade to the 145/R12 radial tires, but the main thing to consider is the clearance in the wheel well/fender area. You want to have at least 3" between the tire and the fender, and at least 1" between the inside of the tire and the frame of the trailer. The 145/R12 tires would sit about 0.4" closer to the frame, and about 0.3" closer to the fender. So if you can measure your clearance with the current tires, you can know if the larger tires will fit or not. I imagine you should be good but please confirm. As long as the clearance is good, the Kenda Karrier S-Trail ST145/R12 Radial Trailer Tire # AM10130 is a solid choice for you.

expert reply by: Jesse M

Kenda Karrier S-Trail
(click to enlarge)

Jesse M.

9/26/2025

Hey Mark, did you have a chance to measure the clearance with your current tires to see if the Kenda Karrier S-Trail radials would fit? I'm curious to know if they worked out for your trip, as it could help others looking to upgrade their trailer tires.