So, after reading through this thread I went to Mavis Tire to look at there selection of ST235/80R16 tires, and magic, they were all speed rated as (R) 106 mph with two of them carrying a (Y) 186 mph rating including the Carlisle Radial Trailer. I'm impressed, but I don't think the Ram is up to it.
This was the New Port Richey, FL store website.