Very slow leak

Darwins Child

The passenger front tire on our '14 touring sport loses about 3 psi per month. This is not a great problem except that within two months, depending on when the first significant snowfall comes to Edmonton, I'll be backing our vehicle into our garage for its winter storage position -- the passenger side as close as possible to an outside wall.

If the tire goes flat over the winter, which may very well happen, I'd have a heck of a time getting an air line onto the tire valve and I might have to drive the vehicle forward a few feet to get access and I don't want to do that on a flat tire. (Would perhaps three rotations be a terrible thing to do?)

So today I took the wheel off the vehicle, increased the pressure from 32 psi (I had pumped it to 35 psi about a month ago) to 40 psi, and sprayed soap solution all over the tire's tread, bead area (with the tire lying down) and valve stem. In short, I could find no leak.

The tire has been plugged once at some point during its 9800 kms. I gave special attention to that plug with the soap solution and it does not appear to be leaking, but, again, this is a very slow leak and maybe it is so slow that soap solution will not detect it.

I'm now considering taking the wheel (which is still off the vehicle) to some tire place that has a dip tank, but I doubt if they're going to find the leak, either.

None of the other OEM tires has lost even 1 psi all summer. Do some tires allow air to permeate through the rubber?

Is there some new device that will "sniff out" a very slow leak in a tire?

Any advice on how to proceed would be welcome.

Thanks.