What Size Radial Tires to Replace Existing B78-13ST Load Range B Tires on Boat Trailer

Question

Question:

I currently have B78 13ST Load range B on my trailer. FRom what I have read I think I would be better off with a radial tire. Will you tell me the tire size I should purchase. Should I also replace my non-radial spare? Thank you

asked by: Bill C

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Expert Reply:

The B78-13 tire you have corresponds to a ST175/80-13 tire size. Radial tires are an excellent choice. They tend to run cooler than bias-ply tires, which will lead to longer tire life.

If you are needing the tire only, we offer that size in a radial load range D (1610 lb capacity @ 65 psi) or a load range C (1360 lbs @ 50 psi). The load D tire is part # AM10210, the load range C tire is part # AM10199.

If your present wheels have a 5 lug on 4-1/2 inch bolt circle, we offer a load range D radial tire on a galvanized wheel, part # AM31994 or a load range C # AM31952.

If your bias-ply spare is still in good shape, you can continue to use it but I wouldn't recommend using it for anything other than emergency use.

Keep in mind, these tires measure 24.1 inches in diameter and 7 inches wide. When upgrading to modern size tires, be sure you have enough room in the wheel well to accommodate this tire size.

expert reply by: Mike L

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Answer 1

The existing B78-13ST tires on your Bass Tracker Boat Trailer are essentially the same as a modern 175-80R13 size. Because of this the new tires will fit your current wheels without issue so unless they are just in need of replacement you can hold…

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Answer 2

A trailer tire size 175/80-13 will replace either an A78-13 or B78-13 trailer tire. A 175/80-13 is going to have 3 load ratings: B at 1,100 pounds at 35 psi, C at 1,360 pounds at 50 psi, and D at 1,610 pounds at 65 psi. This size will have a diameter…

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Answer 3

The B78-13ST is an obsolete tire size that's no longer used. A 175/80-13 is the closest modern tire size. The #AM10210 tire you looked at is a 175-80-13 with a D load range radial tire that has a 1,610 lb capacity at 65 psi. You'll want to…

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Answer 4

Even though I cannot comment specifically on the grease you used because I am not familiar with it, I can tell you the best grease for trailer bearings is a a grease with a rating of GC-LB, which just means it is made to withstand very high…

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Answer 5

Trailer wheel bearings are specific to the spindle that is installed on the axle that is on your trailer. You will need to safely support the trailer, remove the wheel and tire, remove the grease cap, remove the cotter pin and washer that secures the…

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Answer 6

In order to determine the torque rating for the lug nuts on your trailer you will need to know check out the chart I attached that shows all of the torque specs for all the trailer lugs available based on stud size, wheel material and wheel size.

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Answer 7

The difference between an load range C and load range D tire in the same size is the capacity and psi rating. The two tires will still have the same dimensions and fit on the same wheel. The D rated tire has a higher capacity. For a ST175/80D13 like…

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Answer 8

Hello Robert, thanks for reaching out. If you have grease zerks on your spindles, you would want to slowly add grease until it starts coming out of the spindle or the front of the hub. Do not force too much grease in and overfill or you can blow out…

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Answer 9

After you've packed the bearings and assembled everything, carefully slide the hub assembly onto the spindle and install the outer bearing. Install the spindle and tang washer and run the spindle nut down finger tight, then rotate the hub back…

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What Size Radial Tires to Replace Existing B78-13ST Load Range B Tires on Boat Trailer

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