Moved from the Ask Mike section as it's not a complicated issue.
It's not an issue of tightening them; it's an issue of wear and tear. I doubt that tire size contributed as much as (usually) cranking of the torsion bars and the increased angles on the inner tie rod ends. I wore out my first rack due to having the front end cranked up too high. My current rack has play in it on the passenger side and that play is internal to the rack. It is not the rack mounts.
You should independently verify what's wrong if you can. Jack up the front end and support it via the frame. With a friend, grab a front tire and wiggle it back and forth and look for the movement. You might see the whole rack moving, which means mounting brackets are worn out. You might see movement at the inner tie rod end, which could mean new tie rods are needed. Or, like me, you might see the inner shaft of the rack moving meaning a tired rack. You do need to move the inner tie rod boot to see this area.
Worn components can lead to significant tire movement here which accelerates other wear and tear including on your tires. If there's a lot of movement I would not ignore it.
