What is the biggest size Tire can I fit on my rig?

I'm pretty sure the leading cause of frame rot is unkempt wheel wells. That said, I would go no smaller than 44's. 42's just barely rubbed full bump and lock.

 

I'm loving the sarcasm but it all honestly.

Before you go out and spend your money you need to do a search on this forum and look at the trucks in the build sections.

On a 1st get Tacoma the largest tire you're going to want to run on a daily driver is a 265/75/16. This tire is right at 32 inches. It looks good on trucks with 2.5 - 3.0 inches of lift. If you're running the stock Tacoma wheels you can expect the tires to just barely touch the frame on full lock. Nothing to worry about as it's not going to hurt anything.

If your truck is a 2nd gen the the 267/70/17 is as big as you'll want to go. It too is about 32 inches tall.

 

205/45/16 will work well. Stretch them tires like the hella flush drifters no rubs.