How Much Closer Will an ST185/80-13 Size Tire Sit to the Frame than an ST175/80-13 Size Tire

Question:

My current tire is a ST 175/80R13 rated at 1360 #. I would like to upgrade to the Kenda LodeStar ST 185/80D 13 to get the 1710 # rating. My current tire has about 1/2 inch clearance between the frame and the inner/upper tire edge. Will the 185 clear the frame? The major use is offroad gravel/dirt low speed carrying a heavy 2000# plus trail Caterpillar tractor from job site to jobsite with some asphalt. I am concerned about sidewall toughness from rocks and sticks. If I buy the wheel + tire set it comes mounted with high pressure valve stems?

asked by: Lee

Expert Reply:

The Loadstar ST185/80D13 Bias Trailer Tire # AM1ST79 that you referenced has a section width of 7.2" while a ST175/80R13 Radial Trailer Tire, like the Provider # TTWTRTM1758013C has a section width of 6.97". If we just round the 0.23" difference in distance to 0.25" or 1/4" (for the sake of easy math) that means that the larger tire size will sit about 0.125" or 1/8" closer to your trailer frame.

If you measured that 1/2" distance with your trailer loaded then it will clear your trailer. However, if you measured the 1/2" distance with the trailer unloaded you may want to load it up and measure again. Since trailer axles have a natural arch to them this can slightly affect how the tire sits in relation to the trailer frame when loaded/unloaded. Please also keep in mind that trailer setups may vary with what a safe distance consists of.

Since it looks like your current tire has a Load Range C rating (1,360 lbs at 50 psi) you may just want to go with an ST175/80-13 size tire with a Load Range D rating (1,610 lbs at 65 psi). For this option we have the Kenda Karrier # AM10210 which is a Radial tire or the Kenda Lodestar # AM1ST77 which is a Bias tire. Radial tires are better for highway use while bias tires are better for off road use like what farm equipment would require. Going this route would give you a higher weight capacity and would ensure that it fits.

All of our tire/wheel combinations come with a valve stem that is rated for the manufacturer's recommended psi rating for the tire.