100 years of retreading: Michelin gives truck & bus tyres several new leases of life

• Retreading is more cost-efficient, resource-efficient and sustainable
• In 2023, almost all MICHELIN truck and bus tyres are retreadable
• MICHELIN Remix process sets standards in quality, safety and mileage

Michelin is marking 100 years of retreading truck and bus tyres – with around 30 million worn tyres given a new lease of life at the Michelin plants in Stoke-on-Trent, UK and Homburg, Germany.

That's 30 million fewer tyres that had to be recycled in the region, corresponding to 1.5 million tonnes of raw materials saved and almost 3.5 million tonnes of CO₂ that hasn't been polluting the environment. This demonstrates the tangible environmental benefits of retreading truck and bus tyres.

"Retreading is a more sustainable and environmentally friendly process than new tyre production and an integral part of Michelin’s offering for haulage companies, own-account operators and both coach and bus fleets. Our customers expect economical solutions that result in cost savings and support them in making their contribution to sustainable transport. Retreading, together with regrooving, delivers this and more," says Andrew French, B2B Sales Director at Michelin Tyre plc.

Since the company was established, Michelin has contributed to advances in mobility with numerous innovations, especially in the road transport industry. As early as 1923, Michelin began to offer retread truck tyres, setting a precedent for its focus on sustainability. This allowed the company to extend the service life of its tyres – leading to greater conservation of resources and lower costs for customers. Thanks to their quality, MICHELIN tyres were also easier to repair and retread.

The next major innovation followed in 1930 with MICHELIN Metallic: instead of textile layers, the company used metal layers in its heavy vehicle tyres, which were much more resistant to damage. And, thanks to their more robust design, they were suitable for retreading up to three times.

100 per cent the same as the original
With the invention of the radial tyre, Michelin set a new standard in terms of durability, safety and fuel economy for tyres at the end of the 1940s.

In the following years, Michelin adapted it for trucks and buses. 20 years later, the company developed the MICHELIN Remix process – with the Remix name standing for REmould, MIchelin, Radial, with the X being used by Michelin as the official designation for a radial tyre.

This makes it possible to renew the tread with the same Michelin materials, technologies and manufacturing processes as in the production of new tyres. The MICHELIN Remix process also follows the original design – meaning a MICHELIN Remix tyre delivers the same performance in terms of safety, traction and grip – another breakthrough.

Demand for retread tyres continued to increase, leading to the expansion of production to the Stoke-on-Trent plant in 1968.

Sustainability improvements
Retreading delivers tangible environmental savings during manufacturing, helping to conserve valuable raw material resources.

On average, only 20 kg of raw materials need to be added to the casing to manufacture a MICHELIN Remix tyre, compared with a new tyre which requires around 70 kg of materials. This means that a retread truck or bus tyre consumes up to 70 per cent fewer raw materials than a new tyre.

Extrapolated to 100 retread tyres, this means a saving of up to five tonnes of raw materials and more than six tonnes fewer CO₂ emissions.

High casing acceptance rate for retreading
MICHELIN truck and bus casings are designed from the outset to have multiple lives in service and to be retread at least once. Nevertheless, every tyre is subjected to a strict inspection and verification process by skilled professionals before the retread process begins.

All casings pass through a visual, tactile and X-ray inspection process upon arrival at the factory, a further shearographic inspection of the casing surface.

Up to 90 per cent of MICHELIN truck and bus tyres delivered for retreading meet the criteria of the initial inspection. Whether or not the tyre has been regrooved has no impact on its acceptance for retreading. 

After this verification, preparation and machining, the casings receive new treads and sidewalls before being cured for around 90 minutes in a mould at temperatures of up to 200 degrees Celsius, which gives them their final tread pattern. The amount of rubber and the quality of the mixtures are identical to those used to make new tyres, guaranteeing a constant thickness of rubber between the bottom of the tread pattern and the protective layers.

Finally, after being remanufactured, all tyres are subject to a final quality inspection which involves inflation to 140psi to confirm the product’s integrity. Tyres which have had any casing repairs carried out also go through a secondary test, which sees 50,000 Volts passed through the tyre to detect any penetrations to the casing.

Michelin’s multi-life process
Truck and bus tyre retreading offers a great deal of savings potential, as a retreaded tyre reduces the total operating costs for both goods and passenger transport fleets, being around 30 per cent cheaper than an equivalent new tyre.

Michelin manufactures a wide variety of truck and bus tyres, for every type of use from long-distance to regional operation, urban to on/off road, and a new MICHELIN tyre is usually purchased with a specific use in mind.

From new, this tyre may cover hundreds of thousands of kilometres during its first life in service. When the tread depth has worn to around 3-4mm, the tyre can be removed from the wheel and regrooved by a qualified technician for a second life in service, following an approved regroove pattern. The process of regrooving a tyre increases the potential life of the tyre by around 25 per cent in its most fuel-efficient state – meaning it’s around five per cent more fuel efficient than a new tyre – whilst also extending its grip potential.

A regrooved tyre is finally considered worn out when its tread reaches the legal wear limit of 1 mm. It is then removed and sent to Michelin for retreading, via the dealer.

Once it has been retread as a MICHELIN Remix tyre – a process carried out exclusively on Michelin casings which have not previously been retread – it is ready for its third life in service. When the tread depth has worn to around 3-4 mm again, the MICHELIN Remix tyre can also be regrooved. In this way, a MICHELIN Remix tyre offers the same mileage performance as a new tyre, with the regrooved Remix tyre delivering a fourth life in service – again, extending the tyre’s life in its most fuel-efficient state.

Encore
Also housed within Michelin’s retread facility in Stoke is an equally modern retreading operation called Encore, which follows a similar process to Remix, but which allows the potential to extract additional lives from a worn MICHELIN Remix casing. However, the Encore process is also able to reuse tyre casings originating from a selection of other manufacturers.

One of the key benefits of Encore is that it allows an operator to undertake a smooth switch over to a Michelin policy from a competitor tyre brand. This is achieved by taking old tyres which pass Michelin’s quality standards and processing them as Encore, whilst at the same time introducing MICHELIN new and Remix tyres onto the vehicles.

Michelin is very open about the origin of its Encore tyres. Sidewall markings reveal whether it has been manufactured from a MICHELIN Remix casing (a Grade M), one of several other major brands (Grade 2), or a good condition casing sourced from a lesser but still reputable manufacturer (Grade 3).

French explains: “The Encore range is central to our circular economy solution, reducing raw material usage and ensuring we extract the maximum performance out of every possible tyre casing. The fact we can even retread a worn Remix casing for an additional life in service is testament to the quality of our verification and manufacturing processes in Stoke-on-Trent.”

A skilled workforce
As Michelin has established advanced retreading facilities across Europe, it has had to develop a skilled workforce capable of meeting its demand for premium quality.

In Stoke-on-Trent, the retread factory operates with a workforce of 180 people, spread across 3 shifts per day, 5 days per week, 24 hours a day. The team is highly professional, highly qualified, and thoroughly trained, with some factory roles requiring up to 6 months on-the-job training in order to master the skills and level of precision required by Michelin.

Vincent Gridel, Factory Manager, says: “You don’t achieve the consistent levels of quality we deliver with our MICHELIN Remix and Encore product without an extraordinary effort. Yes, we rely on some highly complex and often bespoke machinery as part of the retreading operation – but we also need a team which knows the process intricately and can maintain our high standards with every single retread tyre they produce.”

“We have people in the factory who’ve been doing the job for decades, some since they first joined Michelin as an apprentice. Plus, we have colleagues whose parents and grandparents have worked here before them. Michelin has been synonymous with Stoke for generations, and we’ve built up a fantastic loyalty and skills base which we believe is unmatched in our industry.”

Michelin estimates that the European tyre retreading sector is responsible for around 32,000 skilled jobs, often concentrated in industrial areas which are reliant on the tyre industry for employment opportunities.

Gridel adds: “Compared with the importation of non retreadable single-life truck and bus tyres, we generate a number of job opportunities. It’s not something that’s often considered, but a fleet retreading its tyres with us is supporting UK manufacturing, UK employment, and doing their bit for the planet.”

Where can you fit a retread tyre?
The only difference between using a new and a retread tyre is that, in line with long standing recommendations from the British Rubber Manufacturers Association (BRMA), Michelin advises against the use of retread tyres on the steer axle.

Indeed, when Michelin defines a new tyre policy for a customer, it will typically prescribe new tyres for the steer axle, as they wear the fastest, and also for the rearmost trailer axle, as they endure the most lateral scrub.

“It’s a strategy which works well for most businesses,” explains French. “With retread tyres you need a flow of product to feed your casing bank, so by fitting new tyres on the steer and rear trailer axle, you should always have a supply of retreads for your drive axles and first and second trailer axles.”

A life after the tyre
In Europe, all old tyres must be recycled. So what happens to a tyre that is no longer suitable for retreading? These tyres are recycled in plants into rubber granulate and steel.

The rubber granulate recovered in this way is primarily used in sports surfaces and road construction, as well as in door seals on vehicles. The steel from within the casing is also recycled and further processed into quality steel.

Around one billion tyres worldwide reach the end of their service life every year. Michelin is therefore constantly researching the opportunities for recycling old tyres for an even more efficient and innovative recycling process.

In this context, Michelin is cooperating with the Swedish start-up Enviro. On the basis of a technology developed by Enviro, various raw materials such as soot, oil or steel can be recovered from old tyres instead of rubber granules, and recycled even more flexibly. According to current plans, 90 per cent of the recycled materials are intended to be used for the manufacture of rubber-based products. Enviro uses a new, patented process to recover the raw materials. Thanks to this technology, tyres are recycled into high-quality raw materials.

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