What Size Trailer Tire Replaces an L78-15 Tire on a Boat Trailer

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Question:

My trailer tire is a L78-15 b load range. what tire can I replace it with.

asked by: Steve W

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Expert Reply:

A 78-15 is an older tire size and the metric equivalent is going to be either a 205/75-15 or a 225/75-15 depending on the capacity you need to match the old tires.

A 205/75-15, load range C, # TTWTRTM2057515C, is rated for 1,80 pounds at 50 psi, and a load range D, # AM10245 is rated for 2,150 pounds at 65 psi.

By comparison a 225/75-15 load range C, # AM10251, is rated for 2,150 pounds at 50 psi. A load range D, # TTWTRTM2257515D, is rated for 2,540 pounds at 65 psi. And a load range E, # AM10303, is rated for 2,830 pounds at 80 psi.

The 205/75-15 tires will fit wheels that are 5 to 6-1/2 inches wide (inside where the tire sits, not overall width).

The 225/75-15 tires will fit wheels that are 6 to 7 inches wide (inside where the tire sits, not overall width). I have included some helpful links on trailer tires for you.

expert reply by: Michael H

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Answer 1

Thanks for the photo. Your master cylinder looks like the Replacement Master Cylinder Assembly for Titan Model 60 and Aero 7500 Brake Actuators - Drum #T4395100 or if you have disc brakes #T4820000. I've linked the page to all your replacement…

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Answer 2

This is a common issue with the old Spartan Trailers. Unfortunately we do not have any fenders with that kind of mounting style. The Fulton Single Axle Trailer Fenders #F008574-2 (for white) or the Fulton Single Axle Trailer Fenders #F008584-2 (for…

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Answer 3

What you have is the old letter size tires. An L78-15 was a larger tire which would be most likely a 235/75-15 in the newer metric size. This is not a common size for a trailer anymore but you could go to a 225/75-15. It would be a little shorter and…

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Answer 4

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 5

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 6

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 7

The three most common lug stud sizes for a trailer are 1/2"-20, 9/16"-18, and 5/8"-18. In order to make sure you get the correct lug nuts you need to measure the lug studs on the trailer now as we have no way to look this up for…

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Answer 8

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 9

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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Answer 10

The two sizes you mentioned are pretty similar and fit many of the same 15 inch wheels. The 205/75-15 fits rim widths of 5 inch to 6-1/2 inch whereas the 225/75-15 fits widths that are 5 inch to 6 inch. The 205 is 27.1 inches tall and the 225 is 28.4…

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Answer 11

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 12

Hi Hayden; that bolt pattern is really uncommon but I believe it can be found on some really old Airstream trailers. There are no modern replacements that will match. The best option is to replace the hub with one that has a common bolt pattern like…

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What Size Trailer Tire Replaces an L78-15 Tire on a Boat Trailer

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