Tire review and qustions

So our trails here just opened yesterday. Went out for the first time on my 26" Evo’s. I had them set at 7lbs. I noticed they wander on the hard pack roads I was running. I mean my grizz was side to side on the trail. I was like WTF here. Checked tire pressure and they were still at 7lbs. Also I noticed that if I hit rocks at any kind of speed, I could feel the rock hitting the center part of the rim, like the tire had squashed down. I never had these issues on the stock tires. Anyone else notice this on these tire?