Changing Boat Trailer Tires from 20.5x8x10 to 175/80-13 Size

Updated 04/10/2015 | Published 04/09/2015

Products Featured in This Question

Kenda 205/65-10 Bias Trailer Tire with 10" Galvanized Wheel - 5 on 4-1/2 - Load Range E

(7215)

$140.27

Kenda 205/65-10 Bias Trailer Tire with 10" White Wheel - 5 on 4-1/2 - Load Range E

(7486)

$137.22

Question:

want to change out my 20.5x8x10 to your st175x80rx13 tires. i have a 1997 magic-tilt trailer with the dual axles springs with about 4inch of clearance with the present tires. its for a pontoon boat if that makes a difference and drive about 5000 miles yearly.

asked by: Tom M

Expert Reply:

Your current 20.5x8x10 size trailer tires have an overall diameter of just over 20-inches. The modern metric designation for this size is 205/65-10, an example of which is # AM3H490.

The tire size you want to switch to, 175/80-13, has an overall diameter of 24-inches. This size tire will not give you enough clearance. At minimum you want the current 4-inches of tire-to-fender clearance to allow for suspension travel.

Also these two tire sizes do not fit the same wheel size. A 20.5x8x10 tire fits only 6-inch wide rims while a 175/80-13 tire will fit rims widths of 4-1/2-, 5- or 5-1/2-inches. The two linked articles will give you lots of useful information on trailer tires.

If you want to upgrade your current tires' capacity you may be able to use a higher-rated load range tire than what you have now. For example, the highest-capacity load rating in your 205/65-10 size is a Load Range E, examples of which you can see on the link provided. We offer tires with wheels in this size and rating with two bolt patterns, 4-on-4 and 5-on-4-1/2.

For example, part # AM3H480 is a white 5-on-4-1/2 wheel with a Load range E bias ply tire. This item is rated for a 1650-lb load at 90-psi inflation. Trailer tires should always be inflated to their maximum pressure as noted on the tire sidewall.

expert reply by: Adam R