Use the tire pressure recommended by Toyota.  Look at the label on the
side of the driver door.  Forget what the tire max PSI says.  Check
the spare too.

This has been posted on here before. The consensus on it at least one of
the times it was asked was to inflate ( or deflate) until the tread has
full contact. One way to tell this is to drive in a straight line across
some wet pavement. Then look at the tire contact the wet pavement.
Another method used was to put chalk marks across the tread and drive in
a straight line and check for even wear of the chalk. Here is a site on
tires:  http://www.1010tires.com/tech.asp?type=tires_general#airpressure
Scroll down to the pressure heading. here is a link to a Tacoma forum:
http://www.tacomaworld.com/  You may be able to find more info there.
Or, if you register you may post there for free.

FWIW I am running 36 front and 34 rear on my '99 Tacoma with the tires I
have on it now, with no load in the rear, in order to get proper tread
contact. This is different than I ran in the previous tires.

Fill the tires to the pressure indicated on the sticker inside the driver
side door.

 If they are the stock size and load rating tires as OEM, use the
recommendations on the doorpost or glove box sticker.

 If the tires have been changed from stock or the vehicle is loaded
differently (camper on permanently), go get a copy of the Load &
Pressure chart for those tires (out of the tire maker's catalogs) from
the tire dealer.

 Get the axle weights or wheel weights at a truck scale - if it isn't
a "Certified Weight" most will do it for free or real cheap.

 Or load the truck up with "stuff" for recycling, and get the wheel
weights off the Recycling Center truck scale on your way out.  You get
the weights, and you even get paid (for the stuff you recycled).

 Once you have the wheel weights and the printed L&P chart, it's easy
to see what the real proper pressure is.

 --<< Bruce >>--