Switching from a 5.70-8 Tire to a ST175/80R13 Tire on a Boat Trailer

Question:

I want to know if it is possible to take a trailer with 5.70-8 rim and tires to St175/80R13 I was wondering if they make a kit that i can use or if you have any ideas on what can be done to make this happen. I have added some gear to make my little boat heaver and will be taking rides a little further from my local fishing areas and wanted the better tire on the trailer.

asked by: Kirk E

Expert Reply:

You can move to a larger tire size on your boat trailer, however, there are a few factors that you will want to take into consideration before making the switch. The first thing that you will want to keep in mind is that switching to a larger tire will not increase the weight capacity of your trailer. You will still be limited to the weight capacity of your axle.

The next factor to consider is that the tires you currently have on your trailer are 5.70-8 tires. These tires mount on an 8 inch wheel.

The new tire size that you are interested in, ST175/80R13, requires a 13 inch wheel and will not mount to your current wheels. This means that you will need to change the wheels as well. When changing wheels, you want to verify the bolt pattern of your current wheels and choose a new set of wheel that have the same bolt pattern. I have attached an FAQ article on how to determine your bolt pattern for you to check out.

You will also want to make sure you have enough clearance to mount larger tires. Your current tires are 5.7 inches wide and have an overall diameter of about 18 inches. The ST175/80R13 tires are about 7 inches wide and will have an overall diameter of 24 inches. This means the inside of the new tires will sit about 3/4 of an inch closer to your trailer and the top of the tire will sit about 3 inches closer to your fenders. You will want to make sure you have enough room to accommodate the larger tires.

expert reply by: John H