Toyota claims 12 inches of ground clearance for the Tacoma, which is physically impossible.

The largest tire they offer is 30.5 inches in diameter. Half of that would be the center of the rear axle at probably 14 inches off the ground (remember tires flex).

Their rear differential holds an 8 inch ring gear, with clearance and material of the diff itself, call it 10 inches in diameter. Take half of that away from 14 inches and you get a maximum 9 inches or so to the bottom of the diff.

I assume Toyota measures ground clearance by driving over a very narrow object and making it clear only the highest possibly spots under the truck. Whatever it takes to sell them.

Edit:

I just found their definition...

Ground Clearance
The distance between the lowest point on the vehicle and level ground.

I guess they don't include the rear diff.