Determining Largest Wheels/Tires That Fit Boat Trailer With ST180/80D13 Tires

Question:

Hi, I currently have ST185/80D13 tires / rims on my boat trailer. I would like to increase the rim / tire size and would like advice on what size I can go up too? Looking at upgrading all tires to radials as I have had a few blow outs last summer. Thanks

asked by: Matt

Expert Reply:

I would be happy to help you determine the largest size wheel/tire you can go to on your boat trailer, but you will need to take a few measurements.

To verify which wheel and tire combination will fit on your specific trailer you will want to measure from the top of your current tires to the bottom of the wheel well, and from the inside of the tire to the frame. You will need a minimum of 1-1/2" from the inside of tire to the frame, and 3-1/2" - 4-1/2" clearance above the tire to allow the suspension to work properly. Lastly you will want to measure the bolt pattern of your current wheels using the included article. You trailer more than likely has a 4 on 4 or 5 on 4-1/2 bolt pattern.

The ST185/80D13 tires you currently have on your trailer have an overall height of 24.7", and a width of 7.3". If your trailer has enough clearance then a ST205/75R15 tire and wheel like the # AM32238B you were looking at would be a great choice. This tire measures 27.1" tall and 8.1" wide. The wheel included in with this combination uses a 5 on 4-1/2 bolt pattern.

If you need a smaller tire then the Karrier ST205/75R14 Radial Trailer Tire with 14" Galvanized Wheel # AM32156 may be a good option as it measures 26.1" tall and 8.1" wide, but would give you the radial tire that you are looking for. The 14" wheel included with this combination uses the 5 on 4-1/2 bolt pattern.

If your leaf springs are currently underneath the axle you could add an over-under kit like the Dexter Trailer Springs Over-Under Conversion Kit # K71-384-00 for 2-3/8" diameter axles or # K71-385-00 for 3" diameter axles which move the leaf springs to the top of the axle giving you additional clearance to add a taller tire.

Keep in mind that adding larger tires or lifting your axles will move the center of gravity of the trailer higher and can cause increased sway.

If you can let me know the clearance your trailer has from the tire to the wheel well, and from the tire to the frame I would be happy to recommend the best option for you.

I included videos for all of the products mentioned for you to take a look at.