Determining If ST185/80R13 Tires On 2008 Fleetwood Saratoga Can Be Replaced W/ ST225/75R15 Tires

Question

Question:

I have been running with 185 80R13 on this Fleetwood Saratoga since I bought it in 2016. The loaded weight of the trailer max is 3500 with 400 on the tongue. Tire life has been short and I have had a few flats - more than normal for how well I maintain it. I do put the trailer through the skids boondocking, gravel roads, highway speeds, long distance trips, etc.. My question is whether I can upgrade my wheels and tires to 225 75R15 on this trailer. It seems like the wheel well can accommodate another two inches easily but Im not sure. Thanks

asked by: Bryan

0

Expert Reply:

I would be happy to help!

It may be possible to replace the ST185/80R13 tires on your 2008 Fleetwood Saratoga with larger tires, but your current tires are 24.7" tall and 7.3" wide where the ST225/75R15 tires you mentioned are 28.3" tall and 8.9" wide so you will need to take a few measurements.

You will need to measure from the top of your current tires to the bottom of the fender, and from the inside edge of your current tires to the frame rail.

For these larger tires to fit you will need at least around 4.75" clearance above your current tires, and at least 2" clearance between the tire and frame for these larger tires to fit. If you have the clearance, then the Kenda Karrier ST225/75R15 Radial Trailer Tire w/ 15" White Spoke Wheel - 5 on 4-1/2 - Load Range D # AM32545 would be a great option for you.

If you do not have enough clearance above your tires there are still a few options.

The first is lifting your trailer to get the additional clearance. If your trailer has leaf spring suspension you would use an over-under kit that moves the axle from above the leaf springs to underneath the leaf springs. This would lift the trailer by the diameter of the axle plus the height of the spring stack. Since you mentioned having a GVWR of 3500 your trailer likely has a single 3500lb axle which would use the # K71-384-00.

If you do not want to lift your trailer the other option would be going with a slightly smaller tire. I recommend upgrading to Karrier ST205/75R14 Radial Trailer Tire w/ 14" White Spoke Wheel - 5 on 4-1/2 - Load Range D # AM32161 instead as they are 26.1" tall and 8.1" wide so they will be closer in size to your current tires, but have a higher load rating.

The # AM32161 have a load rating of 2200lbs per tire at 75 PSI, so they will be more than enough for your 3500lb trailer.

I included videos of the products mentioned for you to take a look at.

expert reply by: Samuel C

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Answer 1

I recommend going with the 13 inch Loadstar ST185/80-D13 Bias Trailer Tire, #AM1ST79. This tire is the same size as the tire you currently have on your pop up camper. These tires have a capacity of 1,725 lbs at 65 psi. With trailer tires you will…

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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

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 4

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 5

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 6

Your math is correct in your trailer weight load example. If a fully-loaded tandem axle trailer weighs 4000-lbs then each of the 4 tires will bear 1/4th of that load, or 1000-lbs. In this case a tire rated for 1300-lbs would provide a good safety…

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Answer 7

To find the load capacity for your axle you should look on the trailer VIN plate or sticker that lists the VIN number. The weight rating of the axle should be listed on that same plate or sticker. Also, the axle could have a tag or plate on it that…

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Answer 8

To determine the size of the hub assembly you need to purchase you have to determine which bearings are in the old assembly. If the old assembly has L44649 inner bearings, you would use the hub you chose #8-258-5UC1. If the inner bearings are marked…

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