Tire Question

P

Pat Anderson

New member
For my tire gurus out there, we just bought a cargo trailer that came with no spare tire. I have two spares for the boat trailer.

The cargo trailer tires are ST205/75R15, and the boat trailer tires are ST225/75R15.

I know the 205 and 225 numbers, which is the only one that is different, refers to the width of the tire from sidewall to sidewall (thanks, Google!).

So my question is whether there would be any problem using one of my boat trailer spares as a spare for the cargo trailer, even though is 20 mm wider, since the height and diameter are the same.

I would appreciate any feedback, thanks!
 
The 75 is the aspect ratio which mean the section height is 75% of the width. This says the tire radius is slightly larger. You would have a taller tire as well as wider tire but if the cargo trailer is a single axle trailer I would not be concerned with using it as a spare. Certainly better for same size tires but used as a spare to get out of a situation I would not worry.
 
I found this article very informative. Here are a couple of paragraphs copied and pasted.

The Goodyear Endurance tires on my boat trailer are Load Range E and so-called "10 ply," but it appears there are not actually 10 plies. They also have six lug nuts, so would be unusable on the cargo trailer anyway.

The cargo trailer tires are ST205/75R15 Load Range D. There are five lug nuts with a 4.5" bolt pattern. So as long as I get an ST205/75R 15 Load Range D tire on a rim with five lug nut holes and 4.5" bolt pattern, I should be OK without worrying about plies, correct?




Today's load range/ply ratings do not count the actual number of body ply layers used to make up the tire's internal structure, but indicate an equivalent strength compared to early bias ply tires. Most radial passenger tires have one or two body plies, and light truck tires, even those with heavy-duty ratings (10-, 12- or 14-ply rated), actually have only two or three fabric plies, or one steel body ply.

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Special Trailer Service Tires
Special trailer service tires are often available in multiple load ranges. The appropriate load range is identified immediately following the size's rim diameter in Tire Rack's descriptions.

ST-metric sized special trailer service tires will be branded with their load range (load range D or LRD) on their sidewalls and list their appropriate load range letter in their descriptions as ST205/75R15 LRD.
 
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