Can 4.80-12 Size Trailer Tires Be Changed to 4.80-8 Size

Updated 08/03/2020 | Published 03/18/2015

Question:

I have a boat trailer with 4.8-12 wheels and tires, I was wondering if I could downsize to 4.8-8 and what the speed rating was on these tires.

asked by: Cody

Expert Reply:

The difference in overall diameter between 4.80-8 and 4.80-12 size trailer tires is about 4-1/2 inches. A smaller tire will clearly not create a clearance issue around fenders where a larger size could. The two tires' widths are fairly close to one another - 3-3/4-inches for the 4.80-8 and 4-inches for the 4.80-12. Here again a slightly narrower tire will not create fit problems.

But you will want to be sure that the lower load capacity of the smaller 8-inch tire will still be enough for your trailer's gross weight rating. A 4.80-8 tire in Load Range C has a capacity of 760-lbs at 90-psi pressure while the larger 12-inch 4.80-12 size carries a Load Range C rating of 990-lbs at 90-psi. If a single axle trailer was switched from the larger C-rated size to the 4.80-8 size the overall weight capacity for the trailer would drop by 460-lbs - 2 times the 230-lbs difference per tire.

If the lower capacity is enough for your load then the weight rating is not an issue. Please note that in cases where the wheel and tire carry different ratings, such as with the Kenda 4.80-12 Bias Trailer Tire with 12-inch White Wheel # AM30620 that you referenced, where the wheel is rated to 1660-lbs but the tire is rated to only 990-lbs, the lower 990-lb rating for the tire becomes the overall limit.

Another thing to consider is that the smaller tire diameter means your trailer deck will be about 2-1/4-inches closer to the ground. You will need to evaluate whether this will be enough ground clearance. You may also need a new ball mount with less drop to keep your trailer level when hitched. I included a link to our ball mount page and to a helpful article on ball mounts.

Trailer tires are rated for a maximum speed of 65-mph unless otherwise stated by their manufacturer. They should ALWAYS be inflated to their maximum rated psi pressure as noted on the sidewall since their weight rating depends on this full inflation.

I have linked you to a series of helpful articles on tires which may be of interest to you.

expert reply by: Adam R

Rick

7/27/2020

I have a light weight boat trailer And fixed up to carry a canoe. The tires and rims are 4.80x12. They are in bad shape. A friend gave me two 4.80x8 rims and tires. The trailer weighs more then the canoe. Both sets of tires are 4 hole rims. The canoe and trailer never go more than 50 miles and I don’t speed. Will they work ok?

Chris R.

8/3/2020

As long as the combined capacity of the smaller tires is still higher than the loaded trailer weight, they will work okay. Just note that they will lower the trailer height by a couple inches.