Jimbo1980

Hi all, Picked up a 65 plate A1 S line TDI at the weekend, very pleased with it overall but suddenly got a warning about loss of pressure in rear passenger side tyre. No problem, looked up the correct tyre pressure online and the general consensus seems to be 29 PSI for rear. Attached my air compressor and it's showing 42 PSI! Seems a bit excessive? Also, if it's already over inflated why would it be showing loss of pressure? Any and all help greatly appreciated. Jim