I honestly don't think any of my suspension components are bad. It's a 134k mile 06 LX470. I've taken care of it and flushed the AHC fluid recently.
Do you think an out of round tire, which causes vibration, could cause tire cupping on that tire AND the tire across from it?
If that's the case, which I find believable, then what has happened in my situation is this: The original new tire which is on the rear, is out of round. The vibration from that bad tire causes cupping on itself and the tire across from it. So, now the previously good tire across from the out of round tire is also cupped and causes it's own vibration. The bad tire is replaced with a new tire which will now in turn begin to cup itself because of vibration.
Does this sound feasible??
Weak shocks, which you cannot tell just by looking at them, will allow the the axle to move up and down while you drive over the slightest bump in the road.
The springs support the weight of the vehicle, the shocks press against the frame and the axle pressing the axle down doing their best to hold it to the ground, they do NOT help hold up the vehicle contrary to popular belief.
If you had no shocks every time you hit a bump the axle would compress the spring and the tire would come off the ground. The body would bounce up as the spring was compressed, the axle drops back to the ground, the body then comes back down, the spring does it’s spring action pushing the body back up, then the spring is attached to the axle and then pulls the axle up, tire comes off the ground and so on.
Every time a rotating tire comes off the ground and lands there is extra wear on that spot of the tire that hit the ground, once that spot becomes big enough the tire will naturally bounce on that spot, the spot becomes larger.
The same tires cupping on the same axle are because they are connected to the same axle, so whatever happens with one tire happens to the other just not as pronounced.
If you have a GoPro mount it under the truck recording the offending tire, drive around and watch what happens.
I cannot speak to the AHC and it’s effects, but I can speak to the effects of weak shocks, and your problem sounds EXACTLY like weak shocks.
As for tire pressure, there is no “proper” tire pressure, manufactures put the tire pressure on the door for the tire that came on the car and to give the best compromise in ride, handling and fuel economy for a single person and no extra weight in the car using the OE tire.
I run my tires at 50psi in the summer, 40psi in the winter because a “softer” (less air) tire runs warmer than a “harder” (more air) tire, this aid’s in snow and ice traction by melting the snow and ice and making it sticky, but I do not sacrifice to much in mpg because I do not lower the pressure to low, if I ran a even lower tire pressure I’d have even better winter traction.
Snow tires are made of a softer rubber that runs hotter so it grips better, that’s why you can’t run snow tires in the summer, they get to hot and wear really quickly.
A tire with more air in it runs cooler, increases mpg but gives a harsher ride.
Remember the whole Ford/Firestone tires exploding deal? Ford recommended to low of a tire pressure to increase ride comfort but the tires were overheating, so they failed, people lost control and died.
And I’m just throwing this in here for s***s and giggles, I never rotate my tires, ever, and they weather check and leak before the tread wears out.
Tire rotation was a thing that needed to be done with bias ply tires because they did not wear evenly and the tire manufacture process was not as good as it is now.
You need new shocks.
