Any Issues Going from a ST175D13 Bias Tire to a ST185D13 Radial for 19Ft Boat Trailer

Updated 03/03/2017 | Published 03/02/2017

Question:

I mistaqkenly purchased to new ST185D13 radial tires for my boat. When I got it back from the shop I realized it had ST175D13 Bias tires on it. I measured and I have 3 inches of clearence currently to tire fender. The trailer mechanic said I should be running bias over radial for stiffer sidewalls. Should I return these and pickup the correct set? At one time I thought it had St185D13 on it. Boat is a 19foot Key West with 115 Yamaha Boat motor, trailer and gear I figure around 2500lbs. Also if i keep the radials that means my spare will be a ST175D13. Is it ok to drive a short distance say less than 50 miles with a smaller tire on one side and a bias and radial on opposite sides. Thanks

asked by: Mike

Expert Reply:

If your original tires size was ST175/80-13, like # AM1ST79, the new tire will only be 5/8 on an inch taller and 13/32 on an inch wider. As long as you have the clearance, the height of the new tire will not be an issue.

As for the difference between a radial and bias tire, I recommend a radial tire especially if you are doing a lot of highway towing. Bias tire do have a stiffer sidewall over many radial tires, but the issue with bias tires is they cannot dissipate the heat like radial tires.

When a tire is fully inflated to the specified psi and is traveling down the highway, that tire will heat up due to trailer load and road friction. Radial tire can dissipate the heat better than bias tires and in turn will last longer. Heat damage is the number one reason for trailer tire failure.

As long as you only use the spare as a spare and travel a short distance les than 50 miles, you will not have any issues.

expert reply by: Jared P