Converting Tire Size For Bias-Ply Tire To Metric

Updated 05/03/2017 | Published 05/01/2017

Question:

What is the conversion of boat trailer tire 5.30 X 12 bias to radial metric? What are the benifits from switching from bias to radial on my boat trailer tires. My single axle boat trailer carries less than 1000 lbs. Thanks

asked by: Denny R

Expert Reply:

The number 5.30 on your tire is the section width of the tire which means the tire is 5.3 inches wide.

For a comparable radial tire for your boat trailer you can use a tire like part # AM10130. This tire measures 5.7-inches wide. The # AM10130 tire is what I recommend if you switch to a radial tire for your boat trailer. You can calculate the size of the tire width by multiplying the first number of a radial tire by .03937. In this case, the # AM10130 is and ST145/R12. Multiply (145 x .03937). I have attached links to a couple of helpful articles that explains the difference between bias-ply and radial tires and how to measure tires.

A radial tire will run cooler than a bias-ply tire because it has more flex and that gives it better traction and stability. A bias-ply tire has stiffer sidewalls which works better for off-road use.

expert reply by: Jeffrey L