Why Use Trailer Tires with a Higher Weight Rating  

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When you change trailer tires of any given size to ones with a higher weight load range, say from a C-rated 175/80-13 tire like # TTWTRTM1758013C to a D load range one like # AM10210, the tire itself will be able to handle more weight but this does not necessarily mean the entire trailer can.

A trailer's gross vehicle weight rating (GVWR), which is the most it can ever weigh when loaded, is a function of all the parts in the trailer, including the coupler, frame, springs, axle, hubs, wheels and finally the tires.

If the tires were known to be the lowest-rated component and you upgraded them to tires with a higher weight capacity then you would be increasing the trailer's capacity, but unless you happen to be the mechanical engineer that designed the trailer you won't be able to know this. You never want to assume anything about trailer capacity and this is why they have a sticker that indicates the GVWR.

There is a benefit to using tires that can handle more weight than they need to. Tires will run cooler when they are operated below their limit. Using D rated tires when C tires will do gives you safety margin by reducing the tires' operating temperature. Since heat is the worst enemy of a tire, reducing the tires' operating temperature is a good thing for safety, meaning you can reduce the risk of heat-related failures.

Trailer tires should always be operated at their specified maximum psi pressure (as shown on the sidewall) and within their weight and speed ratings. You can refer to the two linked articles for more information on trailer tires.

expert reply by: Adam R

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