Compatibility of Combining R Tires with D Tires on a Trailer

Updated 09/29/2014 | Published 09/27/2014

Question:

Is it ok to have a spare r number and the trailer having d tires on it ?

asked by: Makers F

Expert Reply:

It's fine to use a radial-type tire as a spare (a tire with "r" in its size code) with a trailer that has Bias ply "d" tires but for a short distance in the event of a flat tire. But mixing tires is not recommended for everyday use because their internal construction is different.

•R: Stands for radial construction, meaning the tire's body plies branch out from the imaginary center of the wheel.
•D: Stands for diagonal or bias ply construction, meaning the tire's body plies crisscross.

Only special tires (ST-type) tires should be used on a trailer; never passenger car tires; always inflate to rated PSI pressure as noted on the sidewall. Although, some 5th wheels come with LT-type tires. Beginning of a tire size: Stands for "Light Truck-metric," meant to be used for vehicles capable of hauling heavy cargo and pulling large trailers.
I linked a couple of FAQ articles on tires for you as well.

expert reply by: Chris B