Advice: What's in a retread

By far the best known name in truck and bus tyre retreading is Bandag and, in April 2019, the company’s Wacol (Qld) factory produced its 10 millionth retread under Bridgestone’s ownership.

Bridgestone Australia purchased Boral’s tyre operations in 2000, including Bandag and the production facility in Wacol, Queensland. Bandag is now the only producer of tyre tread in Australia and New Zealand, exporting to Fiji, Papua New Guinea and the Asia Pacific region.

Top quality truck and bus tyres aren’t cheap and, provided they’re operated correctly, can be retreaded multiple times. This reduces the number of tyres entering the waste stream, which saves operators money and is much kinder to the environment.

A Bandag retread uses significantly less water and energy to produce than a new tyre, as well as 68 per cent less oil.

Bandag retreads are a core component of Bridgestone’s commercial product mix, complementing the range of Bridgestone and Firestone drive, steer and trailer tyres with equivalent retreaded products, including low rolling resistance compound options and a newly-developed severe-service compound for refuse and metro bus operators.

Bridgestone and Bandag have made a multi-million dollar investment in sustainability measures at the Wacol production site, with capacity to store more than one million litres of rainwater and the installation of solar panels.

As well as reusing tyre cases, the Bandag retreading process sees shavings from old tyre treads recycled. The Wacol facility’s shavings are supplied to locally based A1 Rubber for reuse in products such as the rubber flooring Bridgestone uses in its retail stores.

The Bandag operation retreads more than 400,000 truck, bus and trailer tyres each year through its company-owned factories in Australia and New Zealand. Bandag also has 30 franchised and licenced stores.

Bridgestone Australia General Manager of Retread Business, Greg Nielsen, took us on a tour of the Bandag Wacol factory.

The process is two-edged, with worn tyres coming into the plant for examination and preparation for retreading, in parallel with the ingredients for making different sized and different-compound rubber treads.

Bandag uses as much recycled material as possible and is constantly investigating methods of reducing retread costs.

The tread production involves ‘cooking’ the various tread components, after careful weighing of the ingredients, to meet the desired tread characteristics.

From this process the tread is extruded into a long strip of the thickness required to suit different applications and moulded with the desired tread pattern.

While the tread manufacturing process is taking place, in another section of the Wacol factory, customers’ worn tyres are separated into batch sizes and very carefully examined for fitness for retreading. Each casing is visually examined inside and out for obvious faults or inclusions, such as nails.

The next stage is an electrical inspection, using a coiled-wire ‘wand’ that checks for non-visible faults.

The next inspection is ‘shearography’, with the casing in a vacuum, while lasers measure any surface anomalies and produce an animated visual of any defects.

At any point in the inspection processes a casing can be judged unfit for retreading and rejected.

If the casing passes all these tests it progresses to an automated buffing machine that grinds off the original tread and accurately profiles the casing for retreading.

The advantage of a mechanical buffer is that it produces consistent shape and finish, ensuring a truly-round, correctly-shaped base for the new tread.

At this point there’s yet another inspection, after which any remaining damage, such as rust in under-tread areas, is treated.

The next step is application of Bandag’s unique bonding-rubber ‘cushion’ to the casing. This slightly ‘tacky’ coating is optimised for adhesion to the new tread.

Tread application is done by an operator on a building machine that calculates and pre-cuts the correct tread length for that particular casing. The operator ensures correctly aligned fitment, before sticking the tread ends together and stapling the spliced joint in place.

The now-assembled retreaded tyre is fitted into an elastic, rubber ‘envelope’, with bead locking rings and an air valve. A vacuum pump sucks air from the envelope, tightly pressing the tread in place, before the tyre enters an autoclave, for curing.

Some hours of heat-soaking later the finished Bandag tyre is given a unique identification number that’s recorded at the factory and marked on the inside of the casing.

At the same time a letter is ground off the tyre brand name, signifying that it’s been retreaded: the number of ground-off letters shows the number of times the casing has been retreaded.

Some critics of retreading cite the number of failed tyres on the nation’s roadsides, but as a grizzled Bandag employee told me years ago:

“If you can see any carcase wire in those blown-out tyres, don’t blame a retread, because there’s no wire in a tread!”