I had 16.5 also odball size, switched to the 16

holy cow man, I don’t need to argue. Do you see “all” in quotations!??

Yeah, 16.5 is a real oddball now.
Look into a wheel/tire package from here:
https://www.tredittire.com/

I always carry two spares now too, especially for a triple axle trailer.
IF I had 16.5s, the main reason I'd go to 16" wheels is it is WAY easier to find a 16" tire that is round, black, and holds air in an emergency, than a 16.5".

FWIW, when I didn't have a spare, and needed to make a trip (borrowed a buddy's brand new enclosed car trailer for a 3 state trip once), I bought an off the shelf wheel and tire from Tractor Supply, and chucked it in the trailer. I kept the receipt, and returned it unused.

Guys, ALL 16" tires are crap these days. Heavy load, 3 axle, tight turn or backing up and a tight turn rips the tread from the casing. Then a few miles down the road ka blam. There goes the stainless fender or some paint off the boat. Ive posted about this is the past. I went with 17.5 s on all my trailers 4 years ago. I have dump trailers, tilt deck lowbed trailers, specialty equipment trailers and a 3 axle gooseneck for my 400SS. NOT one failure in 4 years! These are not cheap I bought 22 tires and wheels as I became fed up with tires blowing up. There are custom wheels now available so the 17.5's are not so ugly. They run 120 psi and the sidewalls are tough. They are a commercial lowbed tire. The overall height is about the same as a 16.

MG-38 your inbox is full

The 16.5 is why I asked the question on size. The older Myco's had those, now everyone has crossed over to the 16's. Look at a number of the trailer tire wheel packages. It may be less expensive to cross over to the 16's. Especially in the long run. If you need to get a tire on the road, almost all the places carry 16's, very few 16.5 anymore. And lets be honest, at some point your going to have to cross over anyway...

M G 38 heres the links I tried to pm you but your inbox is full

https://www.ebay.com/itm/SINGLE-16-X....c100290.m3507
https://www.ebay.com/itm/Firestone-T....c100290.m3507

I agree with you that 17.5" tires are a viable option. However, they are CONSIDERABLY heavier than a 16" tire. This is of note because additional rotating mass is rougher on trailer suspensions, and can cause increased stopping distances.
This all needs to be taken into account when weighing options on whether to upgrade or not.

Yep All that is true. Some pics of tire height. There seems to be about 13 +- pounds difference? 48 vs 61.

i agree with your point but hailing with a 1 ton dually shouldn’t even notice this extra rotational mass... I haul 20k# horse trailer rig all the time, no big deal for a 13,000# boat and trailer.