I had a similar issue last summer. I heard others had new tire squirm and I know personally all LT tire brands are not the same. Had that experience years ago with LT's on Michelin LTX M & S.
My saga. In this case I am on my 3rd set of Continental ContiTrac TR's LT275/70R18's LR E.
The first set where the originals on my F350 in my sig. I bought the truck used with 25,000 miles on it. This is 2007 time frame. I had no problems whatsoever with truck stability with my current camper.
At around 53,000 miles, DW picked up nail in the front tire a week before a 1,000 mile camping trip. Oh man... They are almost gone, so I replaced all 5 tires with new Continental ContiTrac TR's LT275/70R18's LR E. and we set out on the trip with only about 500 miles on the tires. No issues at all. Nothing. This was 2009/2010 time frame.
Then last summer, 2017 time frame I need 5 new tires again due to wear and we have a 1,500 mile camping trip comeing up. Not wanting to change brands or styles I again bought Continental ContiTrac TR's LT275/70R18's LR E. 1 ton truck, 10,000# camper, long wheel base, I know what works and no brand changes if I can help it.
Oh boy, this is very different. We went to a local camping 50 miles from home and their was for sure an instability in the truck. I checked the WD hitch, pressure and it all came up good. I had to deal with it the whole 1,500 mile camping trip. Well, after around 1,500 to 2,000 miles on them, the truck is now back to stable again. It is like they need 3 to 4,000 miles on them to become known stable again.
Something changed in the rubber makeup as in 2009 I had zero issues, now I have a problem.
For us towing campers, we really need a sidewall stiffness index or something as buying new tires can be free for all on brand, style and thread. And now the squirm factor on new tires makes this all that much worse. It's like you have to find someone with about the same truck, camper size and weight and see what they have that works.
Thanks
John
2005 Ford F350 Super Duty, 4x4; 6.8L V10 with 4.10 RA, 21,000 GCWR, 11,000 GVWR, upgraded 2 1/2" Towbeast Receiver. Hitched with a 1,700# Reese HP WD, HP Dual Cam to a 2004 Sunline Solaris T310R travel trailer.