Tire Pressure?

ON ROAD PRESSURE

I have been seeing many requests for how to determine the correct tire pressure for your rig when running on the road and the answers vary greatly. Why? It depends on many things such as the size of the tire, the load range of the tire, the weight of the rig, altitude and other factors. Incorrect pressure can cause premature and abnormal wear on your tires. If you are running stock tires then you can follow manufactures designations but once you increase the tire size that goes out the window.

The best pressure is when the width of the tire makes complete contact with the road as shown in the middle graphic above. The question is: How do I figure out what the best pressure is for my rig?

CHALK TEST

One of the most popular ways is to perform a chalk test by putting chalk on your tire and then run it to see where the chalk is worn (sample pic below). Keep repeating this process until you find the correct pressure for your rig. This is a messy and long process and I prefer to use the TB paper method.

TB PAPER METHOD

What I find is the fastest and easiest way for me is to pull up on a smooth surface, air my tire up where I notice that the outside edge of the tread is not touching the floor. At this point I can easily slide a piece of paper under the tread. I now start to let air out of the tire until the paper is no longer able to go under the outside edge of the tread. At this point, I take an air pressure reading on the tire and that is the optimal pressure for the tire where the tread is completely touching for the width of the tire. I generally do this for the front and the back as there may not be even weight distribution. As you can see, this process is a quick and easy way to find the best pressure for your rig. This pressure will then allow you to have even and consistent wear on your tires.

OFF ROAD PRESSURE

The next question is what is the best tire pressure (PSI) to run when going off pavement. This also depends on what you are going to wheel and what the elements will be. When lowering your tire pressure you are doing two things.

1. allowing the tire to have better grip/traction by being able to grab hold of the obstacle you are crawling over by increasing the footprint
2. allowing the tire to absorb the shock of the bumps when driving off pavement making the ride smoother

So the question is, what is the pressure I should run? I would suggest going no lower than 15lbs per tire, to start! As you get the feel of your rig you can air up or down to the pressure that you feel comfortable with. There are are a few reasons why low tire pressure is bad as shown below.

1. bead could break letting all the air out of the tire when on the trail
2. dirt and gravel can work its way into the bead of the tire and cause a slow leak requiring you to go to a tire place to break the bead, clean it and set it back
3. it lowers your rig so that you have to watch your clearance.
4. you tire could spin on your rim causing you to lose traction.

Have a look at some more detailed pictures of tires at different pressures. Click this link from Facebook.