I went to change my old Tyre to news. But later when I pick up and went to servo for pressure checking. Because it look bad, if Tyre look alright. I wouldn't check the pressure. the 3 Tyre was nearly fk the rim. And one seem to be in good psi. Then put a hose in. Wow, don't know what happen there. All 3 Tyre below 22psi. But the one that look right was in the correct psi. Next day after work, looking at the Tyre. 2 of the Tyre were were below 22psi. Then pump with air compressor that connect to car lighter plug. Took it back to a shop. Then they check. Nothing leaking. But one of the guy ask me. Where do you check the pressure and I say servo. He says never pump your Tyre or check pressure at servo because the psi will be off and servo will never give a correct psi. Then I been told to bring back the car next day to check pressure. And went back next day. Check all pressure is correct. I don't know, what happen there. If anyone could explain that would be great. The thing is that. After I pump my Tyre at servo and close the value. I can see compare to the one I didn't pump yet. It different. And next day check Tyre without air compressor. I notice the different straight away. If it the servo compressor not good. Then how can I notice the different on Tyre rise height.m even straight away. So help me. What happen there.