What Happens If you Mix a Radial and Bias Ply Tire on a Trailer

Updated 06/16/2025 | Published 04/29/2023

Question:

I understand its no advisable to mix an R tire with D tires...but why, what could happen? Whats the actual danger? I have a 6foot x12 utility trailer with a single 3500 lbs. axle. My current tires are aged out but I have a new D spare that I was going to put on the ground and buy one new tire. But, my son-in-law just gave me a brand-new R tire. The trailer maybe sees 500 miles a year in short trips. Im just trying to understand why its not advisable to mix the two. Thank you.

asked by: Rex T

Expert Reply:

I'm going to be perfectly honest...the risk is pretty minimal BUT due to the construction differences between bias ply and radial tires the sidewalls do end up flexing differently which could in turn end up with unpredictable ride quality/handling/performance. Is this going to be an issue in normal, non-emergency travelling? Probably not, but if you were going higher speeds and needed to make an emergency maneuver there's a chance the trailer might not handle the situation as well with mismatched tires. I know people mix them all the time and most will never have anything close to a problem. There's even people that use vehicle tires on trailers which is not a good idea at all but it really comes down to how valuable it is being as safe as possible.

expert reply by: Jameson C

6/14/2025

A couple of states from home and in a "have to" situation, I replaced a "D" tire with an "R" some time back. After returning home and not using the trailer for a couple months, I forgot all about it. I've ran the mismatched tires for maybe 1500 miles and had been noticing very uneven wear. The D tire had severe wear on the outer edges (where it was carrying more load). I had also noticed a difference in handling, but hadn't put 2 and 2 together until today when I was buying a replacement tire for the worn D and noticed the D vs R difference. Mismatched might be ok for a spare or very short term use, but you may as well get two that match because the other tire (not the radial) will have a short life once it is running with a radial. I had the same set up as the question: 6x12 trailer with a 3500 pound axle, hauling around 1000 pounds.