What can happen?

[Selahdoor]

What can happen if I run 4 ply tires on my f250?

Truck is empty. Never has more weight in it than maybe 400 pounds.

I don't tow anything.

What is likely to happen?

 

[towcat]

ply rating and actual ply are two different animals.
you should run tires equivalent to the axle rating of your truck.
anything less is illegal. Noone will notice until you get into a wreck and the accident investigation shows you were using an underrated product and you're now in deep-doo-doo

 

[slashbike]

Don't forget that your truck weighs somewhere around 6000 lbs. Add you, fuel, and load and you use up your tire's rating pretty quickly.

 

[IDIoit]

not to mention weaker tires will make your rig ride like dog doodoo.
ever run a truck with 4 tires @ 10 psi?

 

[Selahdoor]

I got a set of brand new studded snow tires. Correctly rated for the truck.

They make a HUGE difference!

The kid that owned the truck before put huge tires on there. It drives, steers, and turns, much better, with the correct size on there.