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Trailer Tire Speed and Weight Ratings


I built a small tear camping trailer on a Harbor Freight Haul Master utility trailer. The wheels have a sticker on them saying warning maximum highway speed 55mph. The tire speed rating is 72m, which according to their owners manual is 81mph. The tires are 12”, wheels have a 4 lug pattern. I don’t know how fast I should go. Do you have an answer?


Helpful Expert Reply:

Trailer tire speed ratings do use a letter code system. A tire rated L for speed means it can be operated up to 75 mph; a tire rated M for speed can be operated up to 81 mph. There are many other speed codes. A trailer tire that does NOT indicate any specific speed rating on its sidewall should be presumed to be rated for 65 mph. If your tires do not indicate a speed rating that is molded right into the tire's sidewall then you should go by what the trailer documentation says.

It is possible your tires have the default 65 mph speed rating but the trailer maker chose to recommend a lower speed (by applying the sticker) for liability reasons. Keep in mind that the manufacturer probably did not intend their item to be converted into a camper.

Trailer wheels like 12-inch 4-lug wheel # AM22318HWTB are not speed rated, but they are load rated for weight. This wheel is rated for up to 1220-lbs, but if it were to be paired with a tire that has a lower weight rating then that lower tire rating becomes the overall limit. If it were to be paired with a tire with a higher rating like # AM10140 (rated for 1520-lbs) then the lower WHEEL rating applies.
When a wheel and tire differ in weight capacities the lower of the two ratings applies to the combined wheel and tire.

I linked our main page for 12-inch 4-lug trailer wheels and tires to choose from. . I also linked some helpful articles and a video on trailer tires.

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