Originally Posted By: Billbert
Retreads were more popular when a typical passanger or light truck tire lasted only 10,000 Miles. Now that tires typically last 40,000 Miles plus, The tire casing is usually to fatigued to retread.
Retreading for typical passenger car and light truck tires became obsolete when radial tires came out in the 1970s.
In days of old, when tires were built with criss-crossing nylon, rayon or cotton cords for their internal strength - such as the "4-ply nylons" that were so popular in the 1960s - it was possible to retread or "recap" them by buffing off the old tread rubber, applying a new layer of uncured rubber, placing them inside inverse-treaded hot molds and expannding them out to press new treads into the rubber with thick inner tubes carrying high pressure air inside them. The heat of the molds cured the rubber and bonded it onto the old tire casings. Radials cannot be expanded into molds with high pressure inside them like that because their under-tread steel belts hold their dimensions and prevent it.
Radials lasted so much longer than the former style when they were first introduced, literally 40,000 - 50,000 miles instead of 10,000 - 12,000 miles for a new or retreaded set of 4-ply nylon tires, that the demise of the old "recapping shops" went largely unnoticed by the motoring public.
The form of retreading that survives to this day involves basically gluing on new rubber treads and using a wrap-around process to apply pressure from the outside inward to bond them to the casings. It is not economically viable to do this for passenger car tires, considering the cost of buying new radials and how long they last, but it is still popular for large, special purpose tires. The "Bandag" process has been used for a long time to retread truck tires, for instance.