Ok so I have an issue.

Every time I go to pump my tires, which I wait a week, and I pump them to 115.

But anyway so I go to pump them and I give them one pump and the Guage says like 120, then another pump and it's like 130. It's completely unpredictable it slowly goes down when I do this.

Am I suppose to let air out before pumping tires?

Is my pump Guage ********?