How To Determine Tire Size Needed for 1987 Boat Trailer Wheels

Updated 10/04/2011 | Published 10/02/2011

Question:

tires rotted over the past 2 winters and need replacing so we can move this light wt trailer.. we measured rim diameter to be 9. 4 lug nuts. not sure of width of tire, maybe 4? one side of trailer is sitting on its rim propped up on a stump. Can you advise what tire we need? usually driven 2x/yr - once to camp, once back home.

asked by: Mary

Expert Reply:

If you measured the wheel diameter from the outer edge of one side to the outer edge of the other side and it was 9 inches, it is probably a 8 inch diameter wheel. Wheel diameters are measured from where the tires bead will be seated on the inside of the wheel. If it has 4 lugs it is a 4 on 4 inch bolt pattern. I am including a short video that will show the how the measurements are taken on a wheel.

The wheels I have that are 8 inches with a 4 on 4 bolt pattern will have a width of 3-3/4 inches, 5-3/8 inches, or 7 inches. The wheel width is measured on the wheel from where the beads will be seated, not from edge to edge.

The tire size you will need for the 3-3/4 inch wide wheel will be either the 4.80/4.00-8 or the 5.70-8. For the 5-3/8 inch wide wheel will be 165/65-8. The 7 inch wide wheel will use a 215/60-8 tire size.

I am including a link to a FAQ page that will list the trailer tire sizing. It will list the tire sizes, the rim size they fit, and the weight capacity of the tire.

I am also including links to the tires that we have available in those four sizes.

expert reply by: Jeff D