I have 6 boat trailers in my backyard, they all use the same bolt pattern wheels. I also have a spare for my trailers, which is a factory Ford Mustang wheel complete with the Mustang logo center cap. I did a google search (Oh NO, am I wrong AGAIN?

), no I am not. 5 on 4 1/2".

... "reversed" means just that.....back in the olden days it was really racey to cut the center out of your wheel and flip the hoop over so they hung out ferther...or looked more "deep dish". I had reversed wheels on my Whitchcraft trailer and they hung out to far, the lip of the fender would contact the tread on the tire.
So I was curious and just took a good look at my 6 boat trailers and 3 of them had reversed rims and 3 did not have reversed rims. The stock wheel size for a older boat trailer is 14" X 6". The stock offset has
about 2 1/2" backspacing and the reversed wheels have
about 3 1/2" backspacing. 3 1/2" + 2 1/2" = 6". Back spacing is measured from part of the wheel where it butts up against the brake drum or spindle (depending on whether or not the trailer has brakes) when it is mounted to the inside side of the wheel when the wheel is mounted on the trailer. Reversed rims make each tire stick out about an inch more than the stock back-spaced or non-reversed wheel. With these measurements you can determine which type of backspacing you want on your trailer by measuring your trailers spindles/brakes compared to the center of the fenders of the trailer.

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