Installing larger tires on your Jeep can deliver new levels off-road performance. But you won’t get the full benefit of those oversized Jeep tires until you know how to manage the tire pressure.
First, let’s establish the basics of tire pressure. The volume of air in your Jeep tires supports the weight of your Jeep. Assuming your Jeep’s weight remains constant, the required volume should also be constant — no matter what size tires you are running. What does change, though, is the size of the space where that volume of air is held. And when you put the same volume of air into a larger container, the pressure naturally must be lower.
There are four methods you can use to figure out how much lower the air pressure should be in your new Jeep tires.
Find the maximum pressure that’s noted on the sidewall of your new Jeep tires. Start with that amount of pressure for street driving. If this results in a poor ride quality or faster wear in the center of your tires, make adjustments by reducing the tire pressure.
You can follow the tire pressure guidelines of your tire manufacturer, but only if you know your Jeep’s weight. Load up your Jeep with your gear, and maybe even a few passengers, and take a trip to the scales. You’ll want to record three weights: the weight with your front tires only on the scales, the weight with all four tires on the scales, and the weight with two rear tires on the scales. If you’ve weighed correctly, the front weight and the rear weight should roughly equal the Jeep’s total weight. Divide the front weight by two to get the weight on each tire. Do the same with the rear weight.
For Jeeps that do not have substantial modifications other than the tires, you can use the tire inflation placard and load inflation chart. Identify the recommend tire pressure for your stock tires and then find the weight the tire should hold at that pressure level. Then, use that weight load and your charts to identify the recommended pressure for your new tires. If you need to make adjustments, use this formula: load capacity pounds per psi = tire weight/tire pressure.
The chalk method involves chalking up your tires to identify the size of the contact patch. Start by finding a very flat surface. Then, chalk your tires and drive forward then backwards at least 50’. If the chalk wears only in the center, adjust the air pressure down. Keep making adjustments until the chalk is wearing evenly. You’ll have to repeat this process with each of your Jeep tires.
Once you identify the right street driving pressure for your Jeep tires, you can make adjustments based on your load and the type of driving.