Of course they were the 10 ply E1 load rating they went on a 2500HD GMC. I have yet to tow the trailer with them but I have had Defenders before on my 1500 before I upgraded both truck and trailer but I am confident they will be quite stable while towing. I never had a compliant with the Firestones sidewall stability either so I am not trash talking them, I just like the Defenders better for the better traction and stopping grip. Just my opinion but reading testimonials like this may help out some people in deciding.