Here's how to measure caster. You'll need to start with your rig on level ground, and sitting at ride height. Next, find a machined surface on the inner "C" of the axle housing. Place a straightedge on the machined surface, and place an angle finder on the straightedge. John Currie commented, "Stock caster is about 6 to 8 degrees positive. When you put larger tires and aftermarket wheels on a Jeep, it will often wander and hunt for center as you're driving down the road. We've found that reducing caster to 5 degrees or less will improve centering when you've got larger tires and aftermarket wheels."