How Much Can Tire Size Be Safely Increased

Question:

Replacing my 5 lug 4.80-12 trailer tires. What’s the largest tire I can go with? Thinking about a 5.30-12 or 5.60-12. Lots of room under the fender and inside the axle. Radial or Bias? I drive over 65 sometimes.

asked by: Tony

Expert Reply:

How much larger in size you can go will depend on how much clearance you have between the top of the tire and the underside of the fender when the trailer's at full load. You want to see a minimum of 3 inches. You won't want the tires to be so wide that they rub the trailer frame on the inside or extend past the fenders on the outside.

Most of the trailer tires we carry are rated for a maximum safe speed from 65-81 mph. Consistently operating them at speeds higher than what they're rated for will cause excessive heat build-up that can dramatically shorten the life of the tire.

Radial tires generally run cooler, so going that route would be recommended. A 145/80-12 tire like part # AM10130 is a radial that'll be about an inch wider and a 1/2 inch larger in diameter. The tire has a 1220 lb capacity when correctly inflated to 65 psi.

If you went up to a 13 inch wheel, you might be able to use # TA43RR which is on a 5 lug/ 4-1/2 inch bolt circle rim. The tire has a 7 inch tread width and a 24 inch diameter, and has a 1360 lb capacity when correctly inflated to 50 psi.

Keep in mind that going with a tire that has a higher load rating will NOT increase the load bearing capacity of your trailer. You'll still need to abide by the capacity of the lowest rated component, be it the axle, springs, spindles, etc.

expert reply by: Mike L