The economics of the heavy trucking industry rely on the retreading industry to keep their tyre costs down. Truck tyres are commonly retreaded twice. However, trucking firms monitor their tyre performance closely. Tyres are rotated through steer, drive, and trailer positions, to maximise their life and the number of retreads they can attain.
The casual observer may think that this is not desirable, because of the strips of rubber that can be seen alongside the main trucking highways. But it is not the retread that has separated; it’s the casing components that have separated, which can be seen from the strands of steel wire attached to the rubber tread strips.
Retreading bonds a new tread compound to a freshly prepared surface of the old tread. The process, called ‘buffing’, presents a scored creped clean surface to the new rubber. New retread rubber can then be applied using unvulcanised rubber spirally wound around the tread, precured with a bonding layer sandwiched between the old and new, or unvulcanised strip rubber with a bonding layer on its underside. All systems have their advocates. The bond of new rubber to the old is quite strong, and service reliability of the retread is not usually a problem. Trying to get the last bit of life out of a tired casing is.
Aircraft tyres are retreaded using the spiral wrap hot application process, and six or seven times is quite normal. The casing inspection standards are quite rigid though, as you can imagine.
Nowadays, passenger retreads do not enjoy the same acceptance. Several factors have influenced this:
- Casing mileage has been doubled with the introduction of steel belted radials compared to bias ply.
- Motorists’ expectations have risen regarding performance. Motorists realise the difference that a set of good tyres can make to their car.
- Casing reliability standards deteriorated, considering that the retreaded radial was expected to do four times the life of a new bias ply tyre.
- The relative costs and efficiency of manufacture of new tyres lowered the cost difference between the two processes. Similar things happened to the engine reconditioning industry.
However, when times get tough and the pocketbook can’t meet the cost of new tyres, retreads are always there, and are infinitely better than a bald tyre once it starts to rain.