Hi, Bruce,

No, I wasn't really confusing tire rolling diameter and wheel rim
diameter. With trailer tires you don't get the range of profile
choices like with cars or trucks, so once you pick a wheel rim
diameter you effectively get only one tire rolling diameter.

Now this assumes that you stick with using ST tires on your trailer.
According to my research, ST rated tires are optimized for load
carrying, and an ST tire of given dimensions will carry more load
while running cooler than an LT or a P rated tire of the same
dimensions. Running cool is the key to tire longevity and preventing
blowouts and tread separation.

By the way, radial tires run cooler than bias ply tires, and they also
provide a softer ride for the load, so they are often chosen over bias
ply tires. However, some trailer designs tend to sway when radials are
used, so you've got to be careful when you make your selection.

-John

On Jul 23, 1:58 am, Bruce wrote:
Hi John

You are confusing wheel/rolling diameter and rim diameter.

Bigger rim with lower profile tyre might give you the same axle height as long as you keep to the same tread width. Less
sidewall height will improve swaying, and stability at the expense of transmitting more vibration, and being less
suitable to rough roads. If you do decide to change, I suggest you talk to a specialist - There are an amazing number of
permutations possible.