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Will 175/80-13 Tires Fit in Place of 185/80-13 Tires on a Cox Tilting Boat Trailer


I am replacing radial sized p185/80-13 mounted on a 5 on 4.5 wheel. Its on an old steel COX tilting boat trailer that carries a 19 foot ODay Mariner centerboard sailboat that weights 1350 lbs. I dont know the weight of the trailer. Will a 175/80-13 radial with D rating handle the load? I am new to trailering and therefore dont know how to assure myself otherwise.


Expert Reply:

First, if your current tires have a P in front of the size that indicates they are likely passenger vehicle tires which should not be used on trailer due to the differences in construction. If they are trailer tires, they should have ST in front of the size.

A 185/80-13 is a trailer tire size. Check the trailer tongue for a plate that lists the capacities and should also list the tire size the manufacturer uses for the trailer. That is the size you would ideally want to stay with.

Both a 175/80-13 and 185/80-13 will fit the same size wheels (4-1/2 to 5-1/2 inch wide) and they are about the same diameter (between 24 and 24-1/2 inches).

The major difference is the capacity. A 175 tops out at 1,610 pounds for a load range D, # AM10210. A 185 tops out at 1,725 pounds for a load range D, # AM1ST79. If you go with the smaller size you need to be sure that it can handle the gross trailer weight.

Since the two different sizes will fit the same wheels you do not have to also replace the wheels. But if you want to I recommend # AM3S339 for a 185 with aluminum wheel or # AM31998 for a 175 with aluminum wheel. Aluminum is corrosion resistant and looks sharp. Both wheels have a 5 on 4-1/2 bolt pattern.

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