Comparing ST175/80D13 Bias Ply Tires to ST175/80R13 Radial Trailer Tires

Updated 06/12/2019 | Published 06/11/2019

Products Featured in This Question

Karrier ST205/75R14 Radial Trailer Tire with 14" Galvanized Wheel - 5 on 4-1/2 - Load Range C

(2390)

$164.03

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

(1556)

$148.76

Loadstar ST175/80D13 Bias Trailer Tire with 13" White Wheel - 5 on 4-1/2 - Load Range B

(2699)

$121.43

Question:

My trailer came with ST175/80D13 tires on 4 1/2inch 5 lug rims. Can I replace those with a ST175/80R13 tire? Looks like the D tires have a much lower load rating.

asked by: Matt

Expert Reply:

The primary difference between special trailer tires ST175/80D13 and ST175/80R13 is the type of construction.

The D in the first tire size indicates bias play construction as with wheel/tire # AM3S050. For the other tire designation ST175/80R13 the R indicates radial construction. The main practical difference between the tire types is that bias ply tires have stiffer sidewalls that make them better suited to rough roads and off-road use while radials have more flexible sidewalls that give them better traction and cornering for highway use.

Either tire type will be available in various weight load ranges. These load ranges are also designated by a letter code. In the bias ply type we have Load Ranges B, C and D and within the radial tire category we offer Load Ranges C and D. All tires in this size appear on the linked page, both bias ply and radials, and all available load ranges. Trailer tires also come with varying speed ratings (yet another letter code!) such as L (good to 75-mph) and M (good to 81-mph).

The right tires for your trailer will have both weight and speed ratings that match or exceed your actual driving requirements. For load range select tires that meet or exceed the trailer GVWR; for example, if a single axle trailer GVWR is 2500-lbs then using two of Kenda wheel/tire # AM31985 which is good for 1610-lbs each will mean that the total tire capacity is 3220-lbs (2 x 1610) and so these tires on such as trailer would give you a weight safety margin of 720-lbs (3220 - 2500 = 720).

expert reply by: Adam R