The transport industry has, in the past, been quite precious about using retread tyres on their applications. Often it has been with good reason, possibly based on bad experiences in the past, or questions over the perceived levels of quality or safety attached to the tyres in question. But times – and technologies – have moved on somewhat, and the operator and fleet managers find themselves facing an ever-growing choice of options when it comes to retreads. The drive is being led by the major manufacturers themselves, who realise the need for sustainability and a desire by fleets to be seen to be more environmentally aware.
For example, the message from Bridgestone is that fleet operators who are eager to shrink their carbon footprints should take another look at running on retread tyres, if they are not already doing so. Opting for retreads could give them an edge when tendering for work because they can cite their use as proof of their commitment to minimising their environmental impact; a vitally important consideration so far as many customers are concerned.
One of the ways the global tyre giant is encouraging operators down the retread path is by investing nearly £5m in its retread tyre factory in Bourne, Lincolnshire. The move is part of a three-year programme where production will be increased and the product range will be revised and refreshed.
At present the Bourne plant makes 70,000 retreads a year. However, the total could increase to up to 100,000 units a year over the next five years, the company predicts. Executives point to the extensive use of recycled materials in the retreads Bourne produces. “It’s a good example of the circular economy at work,” says Andrea Manenti, Bridgestone north region vice-president responsible for the UK and the Republic of Ireland.
Around 75% of the material used to make a new tyre is reused when a retread is built, with 32kg of rubber and 14kg of steel recovered. Building a retread swallows up to 70 litres less oil than making a new tyre, while as much as 80% less CO2 is emitted while it is being manufactured.
QUALITY ASSURANCE
One thing that Manenti is keen to insist is that the reuse of content does in no way, shape or form, result in a poorer quality product. “Inspection processes such as shearography, nail-hole detection and inflation testing have resulted in quality retreads that are every bit as good as new tyres,” he says. “There are multiple inspection stages making the quality checks on the finished product as comprehensive as they get.”
Shearography works rather like an ultrasound scan. It analyses the tyre’s core structure in order to identify any defects that may be lurking under the surface, invisible to the naked eye.
Running on retreads can contribute to shrinking tyre costs per kilometre by almost one-third, compared with relying solely on new tyres, Manenti contends. While tyre labelling has yet to be applied to retreads, Bridgestone is anticipating its introduction, with the company suggesting that its retreads deliver a level of on-highway performance and dependability that nigh-on matches what is on offer from its own range of brand new tyres.
The investment programme has been crafted to pivot Bridgestone’s UK retread range away from pre-cure retreads in favour of their hot-cure stablemates. Hot-cures make up 80% of the UK retread truck tyre market, yet pre-cures made up 60% of Bourne’s output up until recently.
The reason is not hard to discern. Bridgestone bought US-based retreader Bandag in 2009 and continues to use its brand name. Bandag based its business around pre-cures, which explains the bias in favour of them until now. That bias is fast-diminishing as Bridgestone responds – somewhat belatedly – to UK market sentiment. Pre-cures had shrunk to 40% of factory output at the time of writing, with hot-cures now dominant. “We’re growing the hot-cure range and we’re retiring some of the pre-cure products,” says Bridgestone service operations business partner, Mike Howling.
HOT ON THE HEELS
The investment plan has resulted in eight additional hot-cure presses being installed. A new hot-cure rubber extruder and two new buffing machines have appeared, too, along with related ancillary equipment.
The arrival of new kit has been accompanied by the launch of a new hot-cure range under the Bandag Hotread banner. Seventeen new hot-cure variants are breaking cover this year, with eight already available.
The Bandag Hotread line-up being rolled out includes the M-Drive 001 drive-axle tyre in 295/80 R22.5 and 315/80 R22.5 sizes and the R-Trailer 002 trailer tyre as a 385/65 R22.5. Smaller sizes are not being neglected, with 265/70 R19.5 and 285/70 R19.5 drive-axle fitments among those well on their way to the party. In a nod to the 50-year-old plant’s roots, Bourne still uses the Bulldog branding on some of its products.
The performance that the Hotread newcomers offer is several rungs up on what was available from their predecessors, Bridgestone insists. For example, the R-Trailer 002’s rolling resistance is 5.7% lower than that of the hot-cure R168, the company claims; it offers 7% more mileage and delivers a cost-per-kilometre reduction of up to 4%. Its features mirror those of a new TBR Duravis R-Trailer 002, it adds.
PLANT SPECIFICS
Acquired by Bridgestone in 2005, and spread across three adjacent sites, the Bourne factory operates for 24 hours a day, five days a week. The company confirms that the 60-strong labour force could expand to 75 as output grows.
In 2022 alone, Bourne recycled 4,400 tonnes of scrap tyres and 520 tonnes of rubber dust, says Bridgestone. This equates to savings of 4m litres of oil, 2,000 tonnes of rubber, 900 tonnes of steel and almost 4,000 tonnes of CO2 emissions compared with the equivalent production of new tyres, it claims.
The factory’s new machinery is more productive than existing equipment, says Bridgestone, and less CO2-intensive. The buffers consume 25% less energy, the presses 15% less, and the rubber extruder 10% less.
Says Manenti: “There’s been a big focus on making retreads more efficiently, with reduced energy consumption.” Some 25,000 UK buses run on retreads, says the tyre maker, along with 70% of supermarket trucks.
GLOBAL SUSTAINABILITY
Boosting the benefits of retreads is in harmony with Bridgestone’s stated aim of achieving greater sustainability in everything it does. For example, at the same time as helping with the production of sustainable natural rubber in Southeast Asia and West Africa, the tyre giant is investing in the development of an alternative to natural rubber involving a plant called guayule. It can be grown in dry areas of the globe – and could potentially be used as a source of biofuel.
Bridgestone wants the whole group to use 100% sustainable materials and be carbon-neutral by 2050 – and aims to increase the share of recycled and renewable materials in its tyres to 40% by 2030. It is also working with Michelin in a joint initiative to increase the use of recovered carbon black in new tyres.
As things stand, less than 1% of all the carbon black used in new tyres worldwide comes from recycled end-of-life tyres, says Bridgestone. Increasing this percentage will reduce the industry’s reliance on petrochemicals, it adds, without any performance trade-offs. Furthermore, using recovered carbon black in new tyre production cuts CO2 emissions by up to 85% compared with the use of virgin materials.
THE PRODUCTION PROCESS
To create a hot-cure retread, new rubber is applied to the circumference of the casing which is then placed in a press which moulds on the tread pattern. It does so at a pressure of 14bar and a temperature of 155°C maintained for up to 90 minutes.
With pre-cures, ready-formed treads supplied in 10m-long rolls brought in from a Bridgestone plant in Belgium are applied to casings using an extruder/builder. Each roll is sufficient for three tyres.
Once the tread has been applied the tyre is placed in a rubber bag, all the air is evacuated from the bag, and the tyre is cured in an oven at 115°C for four hours.
Hot-cures undoubtedly look better than pre-cures, and can be difficult to distinguish from their new equivalents. They are said to be slightly cheaper, too. Pre-cures are said to last longer, however, because of the density of the tread rubber employed.