My 99 Deville has 48k miles and the oem tires. The front ones look new and the rears were good enough for me to pass NJ inspection.
I’m running the recommended 30 all around. The tires are squealing like crazy around turns at slow to moderate speeds, any ideas? Thanks.

Squealing can be caused by anything from road surface and temperature to tire composition and temperature. Smooth asphalt, polished brick, and some concrete textures squeal like crazy.

About the only thing you have any control over is speed and pressure. Look at the fine print on the sidewall to find out the maximum cold inflation pressure. Probably between 38-41 psi. With the tires cold inflate them to 35 psi using a good dial gauge. See if that helps. (Your ride may get a little harder.)

Your tires are balding. They may look fine but at 48k you need new ones.

It may be out of alignment if the pressures are OK.

Thanks for the advice guys