The next easiest option is to remove the valve core. The valve core screws into your valve stem and can be unscrewed with a simple valve-core removal tool. We also try to install valve caps with a built-in removal tool on all our 4x4s. Be very careful not to drop the valve stem in the dirt when it comes out with all that air pressure behind it. If you do drop it, simply screw the valve cap back on while you're hunting like a maniac for the core, otherwise your tire will quickly go flat and you'll also be hunting for an air tank or compressor.