Can you change trailer wheel size from 13 inch to 15 inch on the same axle?  

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Yes, you can change trailer wheel size from 13 inch to 15 inch on the same axle if that axle isn't a 2000 lbs axle. Most 2000 lb axles are not rated to use a 15 inch tire. Almost all 3500 lb and up axles can handle 15 inch tires which is most likely what you have, but there are still a few things to consider and check before making this change. A higher trailer can have its benefits of slightly more ground clearance and 15 inch tires gives you the benefit of radial tire options, but a taller trailer has a higher center of gravity and can make a smaller trailer more squirrelly.

One of the biggest obstacles to increasing tire size is clearance. To see if it will work for your specific trailer, you will want to measure from the top of the tire to the underside of the wheel well and from the inside of the tire to the closest part of the frame. You will want to make sure you have an 1-1/2 clearance to the inside minimum and a clearance of 4-1/2 inches from the wheel well for the travel of your suspension. Remember that adding 3 to 4 inches of tire diameter will need to be accounted for, and moving to the 15 inch tire from the 13 inch tire will also add about 1 inch to 2 inches in the width of the tire. When thinking of increased diameter, it is the overall diameter that is important, not just the wheel diameter. While a 15 inch wheel is 2 inches larger diameter than the 13 inch wheel, the tires that fit on a 15 inch wheel add more than 2 inches to the overall tire diameter.

If you don't have enough clearance room, I suggest staying with the 13 inch tires or possibly moving to a 14 inch tire that would allow you to still use Radial tires. Moving to 14 inch tires will still add approximately 2 to 2-1/2 inches to overall diameter and an inch or so in width.

If there is enough clearance then the 15 inch tires I would recommend are the Taskmaster Provider Radial Trailer Tire ST225/75R15 with Load Range E, # TR225LRE, or the ST205/75R15 with Load Range D, # TR20515D. These tires have automotive grade tread with sipes that channel water away for better traction in wet, snowy, or icy conditions. This special trailer TIRE design is strong, durable, and built to handle highway driving. Either tire can be matched with the bolt pattern needed to match your hub. For example, the Provider ST205/75R15 Radial Trailer Tire with 15" Vesper Silver Mod Wheel - 5 on 4-1/2 - Load Range D, is part # MX97FR.

There are 4 possible combinations of measurements for 5 bolt hubs, but two that are more common. You most likely will have 5 on 4-/12 inch or 5 on 5 inch. The way you determine this is measure from the center of one bolt to the center of the next bolt. If the measurement is 2-5/8 inches then you have the 5 on 4-1/2 inch. If the measurement is 3 inches, then you have a 5 on 5 inch bolt pattern to match your wheels to.

Making this change will add height to the tongue of your trailer, so you will want to account for that with a different rise in your trailer hitch ball mount. If you have a 2 inch hitch receiver, you may want to consider something like the Weigh Safe 2-Ball Mount w/ Built-In Scale - 2" Hitch - 4" Drop 5" Rise, # WS4-2. This ball mount has a built in tongue weight scale that will help you stay within the appropriate weights for your hitch and vehicle.

Adding bigger tires will not increase the load capacity of your axle although it may give you a better tire, so you will still want to look at the tire, wheel, and axle ratings and go with the lowest of the 3 when loading. Make sure you stay within the limits of your tow vehicle by checking your owners manual for it's specific ratings as well.

expert reply by: Jason S

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