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Will an ST225/75-15 Fit In Place of a 31x10.5R15LT Tire on a Boat Trailer


My problem is I have truck tires and rims on a tandem boat trailer. A farmer owned it before me and he had these tires and put them on for his short hall to the lake. Now I need to change them and need help. I have 31x10.5r15lt tires on 8 inch wide rims bolt pattern 2 5/8. My questions are: 1 This tire will only go to 7 inches, can it be used on 8 inch rim? What is the potential problem , if any? 2 Can a truck tire safely be used on a trailer? If not, why not? education of a consumer 3 Any suggestions? Thanks for your help. By the way, your phone person was a great help and I appreciated her help.


Expert Reply:

Wheel width can only be measured with the tire off of the wheel. You will measure from bead seat to bead seat. That will be from the inside of the inner wheel flange to the inside of the outer wheel flange, not from edge to edge of the wheel. I have linked a video that should help.

If you measure and find you actually have an 7 inch wide wheel then you can use tire # AM10256. Any given tire has a certain range of wheel widths that it will fit. Going too large or small means the tire will not fit properly and will not hold air so you would not be able to sue this tire on an 8 inch wide wheel.

Some trailers and RVs use light truck tires so it is not uncommon but I can't say I have seen them on a boat trailer before. I would stick with ST tires (special trailer). Trailer tires are built with a thicker sidewall compared to passenger vehicle tires. This allows the trailer tires to handle more vertical load.

Trailer tires also need to be inflated to the max psi indicated on the trailer tire. If under inflated the thicker sidewall leads to excessive heat build up.

You mentioned a 2-5/8 bolt pattern so I assume that you measured from the center of one hole to the center of the adjacent hole. That would mean you have a 5 on 4-1/2 bolt pattern. I have linked a help article on measuring for bolt pattern.

If you do have a 5-4-1/2 bolt pattern and need to switch to different wheels you can use wheel and tire combo # AM3S862 for a steel wheel or # AM3S874 for aluminum. Both tires are rated for 2,540 pounds at 65 psi.

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