I had a problem with the rear suspension system. Could not seem to pump it up or determine the pressure in PSI that was in the system. Well I hadn't done enough research to know that you do not use an air compressor to put air in and that it requires a low pressure hand pump in order to not damage the system. That said, I got lucky. In troubleshooting I found that the core in the Schrader valve was damaged and air was not getting through the lines and into the shocks. When I unscrewed the valve core the suspension lowered down. Put a new core in and was able to restore the air system and get it pumped up to the 36 PSI I needed for 2-up on the trike. Works great now - I'm lucky - easy fix!!