What Size Trailer Tires Will Replace B78-13 Trailer Tires

Updated 05/14/2014 | Published 05/13/2014

Products Featured in This Question

Karrier ST175/80R13 Radial Trailer Tire with 13" White Wheel - 5 on 4-1/2 - Load Range C

(1593)

$126.21

Karrier KR03 ST175/80R13 Radial Trailer Tire - Load Range C

(2521)

$89.76

Karrier KR03 ST175/80R13 Radial Trailer Tire - Load Range D

(2519)

$107.94

Loadstar ST175/80D13 Bias Trailer Tire - Load Range B

(4020)

$69.13

Question:

I have a trailer with a 16ft. boat that have been sitting in my carport for the winter and the tires are both flat. They were kind of cracked from sun damage before but this was the last straw I guess. They have been sitting on the rims well at least one of them for about 6 months. Do I need to get tires with rims or without rims? What are my tire options? Thanks,

asked by: Krista

Expert Reply:

I was able to zoom in on the picture you submitted to see that the tire size you have is B78-13ST. A trailer tire size 175/80-13 will replace a B78-13 trailer tire. You would not need a new rim, just tires.

A 175/80-13 is going to have 3 load ratings: B at 1,100 pounds at 35 psi part # AM1ST74, C at 1,360 pounds at 50 psi # AM10199, and D at 1,610 pounds at 65 psi # AM10210. This size will have a diameter of 24.1 inches. This tire size will fit on a 4-1/2, 5, or 5-1/2 inch wide wheel like what you should have.

If you choose tires rated higher than your axle, you still have to go by the axle weight capacity. If you choose tires rated lower than the axle capacity, then you need to go by the tire capacity. I have included some links to tire FAQ articles for you.

expert reply by: Jameson C