Took my bike to my LBS for a check up and while I was there I had them install some new tires. Once I got home I wanted to adjust the pressure and noticed that they gave me a different tube on the rear with what looks to be a schrader valve but it has a screw top like a presta?? And I can't seem to work it right, using my pump, I pump 3 times and it says 120 then continues to drop. I can't seem to be able to read what the pressure is. I don't like it Does anyone know what kind of valve it is and am I doing something wrong?