I can certify that this technique of adding a few PSI to the tires DOES WORK!!! My first job out of college was at the General Motors Proving Grounds in Milford, MI, northwest of Detroit. Given the often wet and very variable temperatures in southeast Michigan, due to the proximity of Lakes Erie and Huron and to a lesser extent Lake Ste. Clair, puddles of water that would freeze overnight when the weather cooled, often resulted in cars parked at the proving grounds becoming frozen in the “puddles”!!! Given that the surface area of a typical tire “below the rim,” being 200 to 350 sq. in., only 5 psi would result in half a ton of force against the ice!!! Ice may be tough to break or chip, but exposed to significant force, it is very brittle. When an air tank was not available, “plan B” was to reduce the tire pressure 10 to 12 psi, pile salt around the edge of the tire, and add a couple cups of water. In a relatively short time, this would release the tire and enlarge the “hole” sufficiently that the vehicle could be “pulled” out. This was an often used technique since the typical circumstance at GMPG was for the front tires to be frozen in a “trough” of ice in the “gutter” at the curb of a parking area where snow and/or ice had not allowed the water to drain. Since nearly all the cars were rear wheel drive (I worked for GM from 1972 to 1975), we could then simply back the cars out of the “ice ruts”!!! Since the caller’s problem was “frozen” rear tires on a front wheel drive car. this technique would have been appropriate. You then simply need to drive carefully and relatively slowly to a service station to “refill” the tires!!!