Just a wild guess but it might be something stuck in the valve. Air lines are sometimes open to contaminants and they could possibly get caught in the valve.... Perhaps closer inspection of the tire and valve might be warranted.

 

stem

Check the valve stem, it could be loose or damaged. An inexpensive valve stem tool can be had at an automotive parts store.

 

Thanks, Great info about the valve stem. I am guessing that this below is the culprit. I had them on both tires when I bought the bike and never removed them. This thing is supposed to tell you when you are low on air but probably slowly let the air out.

 

Could this be caused by over inflation?

Maybe, but I've run mine at 50 psi several times with no adverse effects.

 

Yeah, but he used thin air, leaks out faster.

 

Cold temps can cause condensation in the air lines to freeze, sticking the valve open.

 

Reinflate the tire and spray it with soapy water. Look very closely for small bubbles forming anywhere on the tire, valve, bead, and around the rim (cracked rim?). If there aren't any bubbles and the pressure holds, great, you had a problem with the valve. If it is the valve, try a new core.

 

Re-inflated, sprayed with soapy water, saw no bubbles, took it for a ride. Looks like I'm good to go.

Thanks for all the help.