Ultra-Low Aspect Drive Axle Tyres From Bridgestone/Firestone

In November, Bridgestone/Firestone Europe (BFE) launched its latest product for the truck and bus market, the Greatec Mega Drive (GMD) super single for drive axles. The launch took place at BFE’s Technical Centre in Rome and began with an overview of Bridgestone/Firestone’s corporate activities, presented by General Manager for Truck and Bus Tyre Sales, Gerard Van Der Veen. Three quarters of Bridgestone/Firestone’s turnover comes from tyres, with the remaining 25% accounted for by diversified products, such as conveyors, pipelines and shock absorbing materials.

Tyres are produced in 46 factories across the globe and there are three technical centres (Akron, Tokyo and Rome), adapting products to suit local operating conditions. The company is the world’s largest tyre and rubber manufacturer, but being number one is not important as an end in itself, said Mr. Van Der Veen.

However, being a global player is important as it gives Bridgestone/Firestone the resources and finance needed to develop new products and technologies. When it comes to truck and bus tyre plants, Bridgestone/Firestone has 13 worldwide and the importance of this sector is shown in the figure, which gives market shares in various areas. These percentages include both OE and replacement market sales and are for the Bridgestone/Firestone group, rather than a single brand.

In Europe, BFE has six tyre factories, including two commercial tyre factories in Spain, and 16 sales companies. The company claims second place in Europe overall, with an 18.2% share of the truck and bus tyre replacement market.

Among some of the best-performing individual countries are Ireland, Spain and the UK, for which BFE claims (respectively) replacement market shares of 43%, 24.5% and 23.3%.

Again, these are figures for the group as a whole. Real Answers To Real Questions The development philosophy behind the Greatec Mega Drive can be summed up by “asking real questions and providing real answers”. To put it even more simply; find out what the customer needs and supply a product which gives him value and benefits.

The areas looked at are Environment, Service, Handling/Comfort and Economy, all of which are related to safety. Take the environment. One of the questions Bridgestone/Firestone asked was ‘Is there a way to get rid of studs in tyres, without losing grip on snow and ice?’ – hauliers cannot afford to stop working when the weather is bad.

The company’s answer was its (patented) Multi-Cell compound, which contains small cells that act like a sponge and grip the ice. Service and back-up is becoming increasingly important to fleet operators and, as fleets are becoming increasingly pan-European, they require a service that is pan-European too, and one which operates 24 hours a day. BFE’s Truck Point network has been set up with these aims in mind and currently contains 1,207 outlets across Europe.

As traffic increases on Europe’s roads, the need for safe, heavy road transport increases. Bridgestone asked whether it was possible to improve grip without lessening other aspects of performance? The answer was the R227, which BFE says was the first uni-directional front axle pattern tyre. Margins on transport are diminishing as competition increases, so the question which BFE asked itself, and which led to the development of the GMD, was: ‘Is there a new tyre concept to enhance transport economy, safety and environmental awareness?’ Technical Background Technical information about the Greatec Mega Drive was given by Enrico Artoni, Section Manager, Truck and Bus Tyre Development, who described GMD as “a big revolution”.

Global concerns cover such factors as increasing fuel costs, vehicle emissions and scrap disposal, but what contribution can a tyre manufacturer make? BFE’s answer is GMD. Replacing two tyres with one means that the vehicle operator can either make more efficient use of the available space or, as was the case with BFE’s French development partner Heuliez (a member of the Iris Bus group), a narrower bus could be designed. Using Greatec tyres, Heuliez has reduced the external width of its city buses by 20 cm, without contravening aisle width legislation.

Another advantage: as the GMD tyre/rim combination gives a weight saving of 80kg on the drive axle, the load carrying capacity is increased by the equivalent of one extra passenger. GMD also offers less rolling resistance and, at the end of its life, less material to be disposed of. GMD development was not all plain sailing; twin tyres share the load and share the torque, but with a single low profile tyre to shoulder the entire burden, how can the level of durability be maintained? CAD and computer simulation identified the greatest areas of strain as being in the bead area and the belts.

The belt problem was solved using existing Bridgestone technology; 60 series truck tyres already incorporated waved reinforcement belts in addition to conventional belts and these were used in the construction of the GMD. In total, six belts were used – four waved and two standard – giving very low strain levels. Stress in the bead area was overcome by wrapping the ply end around the bead core, rather than the usual turn up ply.

Although the new tyre looks impressive – especially in size – it is more a case of evolution rather than revolution. True, the turn-in ply bead is different, but there are no radical technological innovations – the compound used is an existing Bridgestone compound and the tread pattern, certainly for the heavy truck size GMD at least, is reminiscent of that of the M729 truck tyre. BFE has taken the best of its existing, admittedly already advanced, technology and made slight improvements in a number of fields in order to produce the Greatec Mega Drive.

The new tyre will be produced, initially at least, in two sizes. The first, designed for city buses, was designed in conjunction with the Heuliez Bus Co. It is size 435/45 R22.

5 and replaces 275/70 R22.5 twin fitments. As mentioned earlier, there is a weight saving of 80 kg per axle (tyre and rim), rolling resistance is 10% better and there is 20% less material to dispose of.

Wear, durability and performance (both wet and dry) are at least equal to the tyres being replaced. The city bus tyre will be available from February next year. For heavy trucks, there is the Greatec Mega Drive 495/45 R22.

5, which replaces 315/70 R22.5 twin fitments. Weight saved varies between 80-110 kg/axle, rolling resistance is improved by up to 10%, and 25% is saved on disposal material.

It will be on the market in mid-2002. BFE hopes, indeed expects, that entry into the market for the truck version of GMD will be through the replacement sector, then, as more users realise the advantages associated with the tyre, this will filter back to truck designers. For the bus version, Heuliez is already fitting the tyres as OE.

In addition to the advantages outlined above, BFE point out that GMD can be fitted with standard equipment, plus the fact – and this could be attractive to OEMs – more space is available for brakes, or even electronic or run-flat systems. When it comes to the price of the tyre, BFE’s target is a figure some 10% higher than that of the existing twin fitment. However, the company believes that this will be more than offset by the savings made in better fuel economy and the benefits of extra payload.