Tire to Frame Clearance

[Markgyver]

Im trying to figure out on my trailer axle length. How much clearance should I provide between my tire and frame/leafsprings?

 

[Cruiser]

rule of thumb is 2",,

 

[IH8RDS]

I went 1.5"

 

[Markgyver]

So I figure I will go with 2" with 265/70/17 for now and when I upgrade to 285/70/17 it will be about 1.5"