What Does ST in Trailer Tire Size ST225/75D15 Mean

Question:

Hey Jameson,I need your help in figuring out which is the better choice in replacing my 7.00/15 tires on my 16'tandem axle car trailer.I am currently using a set of Ford factory wheels which are 15x7.The 7.00/15 tires are too narrower for these rims.I'm interested in the following a set of Contender ST225/75R15 range E or Loadstar / Kenda ST225/75D15 range D.Accordingly to the detail of the ST225/75D15 tire it would fit a 15x7 rim. Any help would be greatly appreciated.I have been studying these tires for three nights now. Thanks, P.S. My axles rating is 3500lbs per axle.That might help

asked by: Clarence B

Expert Reply:

ST on a tire size like the Loadstar ST225/75D15 Bias Trailer Tire # AM1ST96 you referenced indicates "special trailer" which means it was designed specifically for use in a trailer application. This type of tire can only be used on a trailer. For more info on trailer tires check out the help article I attached. There's more info on the different trailer tire constructions as well.

expert reply by: Jameson C

Clarence B.

9/30/2019

Jameson C.

9/30/2019

So the first thing we should probably talk about is that you really should not be using passenger vehicle tires and wheels on a trailer. So your best solution is going to be to replace the wheels and tires on your trailer. Vehicles wheels and tires just aren't designed for the vertical weight that trailer see as they had steering axles and acceleration in mind. So a really great solution would be the part # AM32459 for replacements for the trailer. This matches the 5 on 4 -1/2 inch bolt pattern your Ford wheels would have and comes with an ST225/75R15 tire that is going to work really well for you overall and be much safer than what you have. Also has way more capacity than you need for your axles as well. For more info on this wheel and tire combo check out the review video I attached as well.