air compressor for inflating tires

To answer wny pat's question, why do you need a compressor when you already have one on board. Because the on board compressors will typically turn off at 120 and back on around 100 psi. If you need more than a 100 psi in your tires, you have to bleed air to get the compressor to cycle back to 120. It can be a long and frustrating process to Air your tires. I require 120 in the front tires so I use two solutions. One a pancake compressor good for up to 150 when I am at home, and I use an air pressure doubler when on the road . The doubler is a small diaphragm pump that does run off the coach air and it doubles the air pressure. They are made by SMC for use in industrial pneumatic control. Mine fits in the palm of my hand. The only problem is they are not cheap. I suppose they go for 250 now.