Replacement Trailer Tires for Size F78-14 Tires on a Boat Trailer

Question

Question:

I have a tandem trailer weighs about 1000lbs which I use to tow my 4000lb bowrider boat. I need to replace the tires which currently are F78-14 ST. What size tires and load range should I consider?

asked by: Kevin

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Expert Reply:

F78-14 is an old size designation and equates to a 205/75-14 tire size so you will want to look at tires in this size. I have included a link to them for you.

Since you will be towing approximately 5,000 pounds gross trailer weight and have 4 tires total on the 2 axles, recommend a Load Range C tire, # AM1ST86, which is rated for 1,430 pounds at 35 psi. Four of these tires will have more than enough capacity to support the combined trailer and boat weight.

I have included a couple of help articles on trailer tires for you.

expert reply by: Michael H

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Answer 1

Your trailer tire size F78-14st is an older tire size. The new label for that tire size is ST205/75D14. They are the same tire basically, but different size label. Your tire size is likely 14 inches instead of 15 inches because to measure the…

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Answer 2

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 3

Light truck tires (LT) are sometimes used in RV applications but generally not on utility trailers. Light truck tires are a type of passenger vehicle tire and as such they are not built with as thick of a sidewall as trailer tires. A thicker sidewall…

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Answer 4

Since both a ST145/R12 size tire, like the Kenda Karrier S-Trail #AM10130, and a 5.30-12 size tire, like the Kenda K353 #AM10068, fit a 12 inch wheel, a ST145/R12 size tire can replace a 5.30-12 size tire. Keep in mind that these tires do have…

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Answer 5

Either one is fine to do. With the Fulton Hi-Mount Spare Tire Carrier part #FSTC1000301 you are not going to be adding a great deal of width to your trailer so the difference is minimum. Giving you my opinion since there is no rule I would Choose the…

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Answer 6

The spare tire can be mounted near the wheel and axle to the frame, but you will want more than 5 inches of ground clearance. I recommend the Extra Offset Trailer Spare Tire Carrier by Dutton-Lainson #DL22145 based on your photo. Every extra inch…

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Answer 7

The psi of your trailer tires will be listed on the side wall. It will list the max psi which is what you will want to fill them to regardless of how much weight you have. For reference, the 4.80 x 12 tires we carry have a 60 psi max for load range B…

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Answer 8

For a 4.80-12 trailer tire, the overall diameter or height is 20.5 inches. For a 5.30-12 it is 21.9 inches. That is a difference of 1.4 inches but you will only see half of that, 0.7 inches, in added height. Please keep in mind that going to a taller…

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Answer 9

If you want to go to the next size up from a 5.30-12 tire you will need to look at 13 inch wheels and tires ST175/80-13. For a wheel and tire combo with 5 on 4-1/2 bolt pattern and radial tire use #AM31985. This tire will be 7 inches wide and 24.1…

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Answer 10

I recently had a similar problem with the LED lights on my flatbed that I have on my 2000 Dodge 3500, except all of the tail lights on the left side of my bed were dim. My issue was a poor ground connection and I would suspect that would be your…

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Answer 11

The 5.30-12 tires, being wider, are going to make more contact with the road. This means that the noise, and heat build up will be higher than a 4.80-12 tire but the rolling resistance will actually be less because the tire is larger diameter. The…

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Answer 12

Load range B trailer tires are going to have a lower capacity than C load range tires. Basically that, psi rating, and the ply rating are the only differences. A higher load range tire would last a little longer than lower load ranges of the same…

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Replacement Trailer Tires for Size F78-14 Tires on a Boat Trailer

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