After long search-well 30 minutes-15inch LT tires load E/116

I'm guessing maybe the OP is running at a higher speed than the 65mph rating for the Maxxis tires. Also unless you have 6 lug rims, I don't think anyone makes a 16" rim for a 5 lug bolt pattern. If you only have 7K split between 2 axles on a 5th wheel, it must be a super small under 30ft 5th wheel. Have you actually weighed your 5th wheel to see what the actual weight is??