Front wheel tube slowly leaks air After I changed tires to conti 4 seasons in my road bike, the front wheel has been leaking air very slowly. I've changed tubes some 3 times already, and it keeps happening (after a couple of weeks). The tube will keep some pressure for about 3 to 4 hours before it's noticeable. Submerging the tubes in water doesn't help to find leaks, and the back tire is fine. I checked several times and found no sharp objects inside the tire. 

The only thing I did find a bit weird was that the rim tape was not exactly on the center on one point, and would not stay in the center easily (it kept climbing the inner wheel).
There are two ways for air to leave a tube - an actual slow leak in the rubber or a faulty valve.

Since you've checked the tube and changed it. this could be a technique thing where you're pinching the tube creating a small hole that is not big enough to show up in a water test.

Try inflating your naked tube to a pressure of about 10 PSI.  It will double in diameter, and could burst if you go too high.   Mix some dishwash liquid into your lukewarm water to help break surface tension.  Put the tube into the water, starting at the valve, and work around the whole thing.  Flex the tube back and forth and take time.

A slow leak is hard to find, but its probably there somewhere.

Last chance is your tubes are all super-light and the air can permeate the surface.  If this is the case, buy heavier tubes.