Max psi ... inside the door or tire sidewall?

Installed BF Goodrich T/A KO tires on my '07 Taco. The sticker in the door says to inflate to 29 psi but the sidewalls say 50psi max. My tire guys installed the tires at 28 psi and the truck drove like shit on the street. Gas milage was horrendous. I pumped them up to 45psi. Now they drive 100% better.

What's correct? I don't want to f up the tires!

 

inside the door pressure is intended to give a comfortable ride on stock tires.

If you value peformance of the tire more than a cushy ride, or go with an aftermarket tire or size, the pressure listed on the door is fairly useless.

your new tires will handle whatever is listed on the sidewall. though the max is going to be overkill, and cup the tread as they wear down.

 

Do the chaulk test to determine the proper pressure for your tires. It will vary by vehicle and by tire.

 

Too low or too high you will compromise traction, wear and braking distance. You will get better gas mileage over inflated because your tire will ballon in the center and thus you reduce rolling friction. Your goal with the chaulk test is to get even contact across the tread, increasing traction and creating even wearing (provided your alignment is within man. specs)

 

Use the chalk test - but the number on the door is closer to right than the number on the sidewall. You'll get great MPGs by over inflating, but you'll give all that money back by wearing out the center of your tires too fast.

 

They use the door jab inflation numbers for liability reasons unless you specifically tell them otherwise.

I've found 38 PSI to be the perfect balance on most tires.

 

The door jamb psi numbers are for the P rated tires your truck came with. LT rated tires require more psi than P rated tires with everything else being equal (same size). So once you switch to LT tires, you can ignore the door jamb.

There seems to be a million different opinions out there for what air pressure is best for X size tire on X vehicle. I've done plenty of searching and found this guide from Toyo that makes selecting a good starting point much easier.

On this link, there's an inflation table link that will download the file in PDF format. Lots of reading if you want to understand better, but I'll break it down to basics.
http://toyotires.com/tires-101/load-and-inflation-tables

1. Somewhere around page 14, you can start looking for the stock type/size tire that came with your vehicle. Check your door jamb for the recommended tire pressures, and find those pressures on the columns next to your tire size. It may not be exact, but you should be able to calculate what yours might be.

2. Take note of the load weight listed for your stock tire/pressure. Some are different for front and rear.

3. Keep scrolling down till you find your new tire size. Find the column with the closest load weight to your stock setup, then scroll up to see what psi matches it. Again, it won't be exact, but should be pretty close.

When I did this for my 285's, it said 35 psi would be about right. The chalk test proved that this was almost dead on. I ended up with 36 psi after chalking them. For the 255's I'll be putting on, it says 43 psi will be what I need. So I'll start around 45 psi and chalk it from there.

EDIT: The chart was right on again. Turns out my perfect psi is 42psi with the chalk test.

 

To get the most longevity out of your tires....you want to make sure they are contacting the roadway EVENLY. Too little or too much tire pressure will cause your tires to wear prematurely.

29 is a bit too soft for me personally.... I run around 32psi. A happy medium between comfort, tire wear, & gas mileage.

Anything higher than that...my kidneys start rattling.