Marketplace — Tyres
Tuesday, June 05, 2007
A big rise in van engine power and torque outputs over the past few years has presented tyre manufacturers with a major challenge.
As light commercials become more and more sophisticated the requirements placed on the tyres are ever changing. We take a look at the latest developments.
They've had to come up with products that can cope with greatly enhanced levels of performance while at the same meeting growing demands for car-like ride and handling and greater safety. In addition the tyres concerned have to remain capable of bearing hefty loads and withstanding the sort of battering that's dished out by drivers on city centre delivery work.
They invariably end up bouncing over kerbs in order to get as close as possible to the drop-off points for the items they're carrying. That can cause serious damage to the tyres on their vehicle if they're insufficiently reinforced.
At the same time as meeting all these expectations, van tyres have to make their contribution to keeping fuel consumption under control by offering low rolling resistance, they have to run more quietly and last as long as possible. “The more torque you have, the worse the wear on your tyres,” says Michelin product marketing manager, Steve Dolby; Michelin is best-known in the light commercial market for its Agilis range.
Continental Vanco 2
Tyre makers have responded by doing an enormous amount of detailed work on compounds, tread design and the tyre's internal structure. One product that's recently emerged as a consequence is Continental's Vanco 2.
Appearing at the British Commercial Vehicle Show, it is said to offer 20 per cent more mileage than the old model and be especially good at resisting aquaplaning.
“It's got a special reinforced band to protect it from kerbing damage and the way in which the shoulders are designed gives you a bit more traction if you have to venture on to, for example, a muddy building site,” says Continental product manager, Peter Robb.
“To help it last longer it's got quite a deep tread depth; 9.5mm to 10.5mm depending on the tyre size,” he continues. “A deep tread depth can make a tyre less stable, but the strength we've built into the shoulder ensures that stability isn't lost.”
Vanco 2 covers around 60 per cent of the market. That will increase to 85 per cent come December with the addition of another ten sizes.
“On top of that we've got our Vanco Contact range for car-derived vans, so we'll be offering 95 per cent coverage by the end of this year,” he says.
Wheel sizes have increased from 15in to 16in on many 3.5-tonners in recent times to accommodate the bigger brakes needed to cope with the aforementioned hikes in engine power. “There's now talk of 17in wheels,” says Robb.
The trouble with increasing wheel sizes is that you increase loading height and the vehicle's overall height at the same time, so van makers have increasingly specified low profile tyres. “There's a definite move towards low profiles as well as to higher speed limits,” says a Bridgestone spokesman.
That has thrown up its own set of problems for tyre producers because going low profile usually means a firmer ride and less air in the tyre to support the load. Again, tyre designers have been working overtime to deal with both these challenges.
The move to 16in at 3.5 tonnes has coincided with an end to the use of twin wheels — on vans, if not on chassis cabs — at each end of the back axle with an eye to reducing wheelbox intrusion into the cargo area. It's a change that's being seen higher up the weight range, with Mercedes-Benz's Sprinter now on offer with single rear wheels at 4.6 tonnes.
In response, Continental has come up with a 285/65 R16 C super single van tyre using a Vanco Four Seasons tread pattern. It's being fitted to the vehicle on the assembly line.
Switching to single rear wheels at 4.6 tonnes means that a 1,200mm Euro pallet can now be slid between Sprinter van's rear wheelboxes thanks to their reduced size. Previously clearance was limited to 1,142mm.
It also means reduced rolling resistance — four tyres offer more resistance than two — along with a slight improvement in payload. In addition it spells an end to the maintenance problems associated with inner rear wheels — checking pressures is invariably awkward — and two tyres are cheaper to replace than four.
The only drawback is that if one tyre out of four blows, then you've got a reasonable chance of keeping going until you can stop somewhere safe — a motorway service area, for instance — and get the problem sorted out. If one out of two goes bang, then you're liable to end up on the hard shoulder; not the safest place in the world to be.
Continental, Michelin and Bridgestone — it markets the Firestone Vanhawk range of tyres as well as the Bridgestone Duravis line-up — are by no means the only tyre companies developing their products with an eye to the needs of light commercial owners.
Goodyear, for example, is exporting some of the technology used in its Marathon truck tyres to its van tyre line-up under the Cargo Marathon banner. Up for grabs in 16in sizes, the new tyre is said to boast better traction in the wet than its predecessor and low noise levels.
A much less well known name in the UK than Michelin, Goodyear et al, Kumho has stolen a march on the competition by equipping Modec's Coventry-built electric van with its products as standard.
The Korean firm was involved in the Modec project at an early stage. Its KRS03 tyres were fitted to the prototypes.
“KRS03 features a wide, deep tread pattern and its newly developed casing minimises stress points and heat build-up,” says a company spokesman. “Stone ejectors improve casing durability.” Stones trapped in the tread can damage the tyre.
With some 5,500 employees, three plants in Korea and two in China — a third factory will have opened in the latter country by September — Kumho makes 44m tyres annually and has research facilities on three continents. Its Birmingham-based technical operation helps it develop tyres suitable for European road conditions.
Tyre designers constantly have to balance one set of demands against another. “For example, if you want to displace water rapidly at high speeds, then what you need are really wide tread grooves,” says Dolby.
“Unfortunately, going for really wide grooves means that there is not much rubber in contact with the road. They can also mean an increase in noise.”
Moving up the weight scale, at 7.5 tonnes operators often use different tyres for the steer and drive axles, and Goodyear has just introduced a new tyre for steer axle applications. It made its first appearance on this side of the Channel at the British CV Show.
“Until now many people running 7.5-tonners have had difficulties keeping the front axle weight legal,” says Jurgen Spielmann, tyre technology director at Goodyear Dunlop Tyres Europe. “This is particularly the case with refrigerated vehicles, which have the fridge unit mounted above the cab roof, and delivery vehicles with diminishing load problems.”
They can occur on 7.5-tonners on multi-drop work because the centre of gravity of the load may move forwards as deliveries progress. The driver should of course react by moving some of the load backwards, but it may not always be possible or practical to do so; either that or he may not realise what's happening to his wagon or not care much if he does.
“As a consequence we've developed our Regional RHS 225/70 R17.5 tyre, which increases front axle capacity by 200kg,” Spielmann says. “It also offers reduced wear and can be fitted to existing rims.”
No matter whose tyres you buy, or what size they are, don't forget to check pressures and tread depths regularly, and examine the exterior condition of the tyre periodically too. A big bulge in the sidewall may mean that serious internal damage has been sustained; so replace that tyre before you venture out on the road again.
As light commercials become more sophisticated, so does the technology of the tyres they use and it's good to see that serious money is being spent on research and development. After all, your life could depend on the performance of your vehicle's tyres.