AT THE HEART OF THE ROAD TRANSPORT INDUSTRY.

Call our Sales Team on 0208 912 2120

SW AN

24th March 1994, Page 42
24th March 1994
Page 42
Page 43
Page 42, 24th March 1994 — SW AN
Close
Noticed an error?
If you've noticed an error in this article please click here to report it so we can fix it.

Which of the following most accurately describes the problem?

1.011If?

Low-profile tyres reduce overall and loading height and can improve handling, but they don't last as long and may increase fuel consumption.

Low-profile users give us their views.

The distance between the tread surface and the rim on a conventional truck tyre is usually about 90% of its width. This percentage figure is known as the aspect ratio; if it is below 90% the tyre is classed as low-profile.

Some hauliers specify low-profile tyres because they are hoping for improved grip and handling. Others opt for them because they want to stay within the four-metre continental height limit without sacrificing cargo space, with the added benefit of lowering the loading height.

Many hauliers contemplating a switch to low-profiles fear that they won't last as long as normal casings and will be more prone to accidental damage. They also worry that they won't be able to recut or retread them as easily, and that availability of the right sizes may prove a problem when it comes to replacement in an emergency.

This becomes a particular concern where operators are thinking about fitting ultra-low 60% aspect ratio tyres, and some of their fears are justified. Cargo Care fleet control manager Hans van Maanen reckons that the low-profiles he fits to the drive-axles of 239269kW (320-360hp) tractive units have to be replaced at around 200,000km.

By comparison, conventional drive-axle tyres average 275,000km, he says, and are

WHEELS

EUPI

& TYRES

recut once. "We have recut a few low-profiles, but we have to be very careful about it.".

His company runs a mixture of 285/60R22.5 Continentals and 295/60R22.5 Michelins and Goodyears. It started using these sizes three or four years ago after spotting them by chance at a truck manufacturer's test track. "The tyres concerned were Continentals, and had been originally designed for fitment to a city bus," says van Maanen "The minute we saw them we said 'that's exactly what we want'," he recalls.

At one stage van Maanen was running low-profiles on 19.5in wheels on lowpowered tractors; he switched to 22.5in because he couldn't get hold of the wheels he wanted. He was also concerned about brake overheating problems with the smaller wheels. "Daf suggested we fit a retarder if we were going to use them," he says.

A high level of casual damage is not a problem in van Ma.anen's experience because the sidewalls are so stiff, and this stiffness has brought an unexpected benefit: "Conventional wisdom argues that the smaller the wheel the higher the rolling resistance, and in general this is so," van Maanen says. "But with low-profiles this is offset by the fact that, because of the stiffness of the sidewalls the tread doesn't move about so much when it is in contact with the road."As a result there is no fuel consumption penalty, he says.

Although they don't last as long, the 60% aspect ratio low-profiles he uses tend to be cheaper than the 315/80R22.5 tyres he has also fitted. "The quality has improved over the years too," he says.

In van Maanen's experience quality still varies considerably between manufacturers: "but I won't say which one is the best because we are a testbed for all of the companies I have mentioned, and we want to remain friends with them".

The additional cost is also outweighed by Cargo Care's reason for fitting them to so many of its 1,400 trucks and trailers in the first place: "They mean you can haul a mega trailer and stack three rows of goods on top of one another rather than two," he explains. "That extra productivity has to be worth having."

He has trailers fitted with 385/65R22.5 singles, and trailers shod with 245/70R22.5 twins. "The latter last longer-140,000km as opposed to 130,000km," he says.

Swift Transport Services' engineering director, Colin Miles, says that low-profiles are susceptible to damage "But if you have a keen driver awareness of the danger this need not be a problem," he adds.

He too has experience of running 285/60R22.5 tyres, on an ELIO 4x2 tractor hauling a Montracon triaxle semi-trailer (tested in CM 15-21 April 1993). The first tyres he fitted were Continental prototypes

"Initially we were having to run steer axle tyres on the drive axle and that whipped treads off like there was no tomorrow," he says. Things have improved since those early days but he still sees room for improvement: "We got 80,000km out of the second set of prototypes. That wasn't brilliant, and we're hoping to do better out of the set we're running on at present. "It should be remembered that we've been running with a 23-tonne payload at 38 tonnes gross on a fairly intensive operation, with lots of motorway and A-road work, and plenty of hills. We've found that the ride is harsher with low profiles."

Miles has specified 305/60R22.5s on a 6x2 FI112 which is about to go into service. "That's the tyre I am looking to go forward with," he says. "I can achieve 6.7 tonnes on the front axle with them as opposed to 6.3 tonnes on the 285/60R22.5s."

Scottish supermarket giant William Low has been running a number of its 62 tractor units on 295/80R22.5 low-profiles for the past 18 months. It has fitted Dunlop SP331s to the steer axle and SP431s to the drive axle.

Dundee-based transport section manager Peter Ramsey has eight Leyland Daf 95.330 4x2 tractors running on low-profiles and also fits them to some ERFs: "We've just taken one set off at 225,000km and we're about to have them recut," he reports. "This compares with the 250,000 to 260,000km we'd expect to get out of an ordinary set, so the mileage is a fair bit down."

The artics gross out at anywhere between 25 to 36 tonnes, depending on the work they are used on. These higher-aspect-ratio lowprofiles aren't at all prone to damage in Ramsey's experience: "We had one problem in the early stages when a driver ran over an iron bar and it went straight through one of them," he reports. "But it would have done the same to a conventional tyre."

He too reports that low-profiles affect the ride, but not dramatically. "Not all drivers notice it, to be honest," he says.

They don't seem to be hitting fuel consumption either: "I know that we're getting 8mpg out of the trucks concerned," says Ramsey, "and I don't think that's too bad."

Low-profile tyres are gaining in popularity, but it is not always as easy to get hold of ultra-low sizes as tyre manufacturers and operators might like hauliers to believe.

Renault truck dealership Arcade of Enfield recently spent six hours on the phone trying to locate enough 315/70R22.5 low-profiles for four Renault Magnums it was supplying to Purfleet, Essex, based Myers Group (CM 10-16 March). It ended up fitting a mix of Pirellis and Bridgestones because no single brand was available in sufficient numbers.

n by Steve Banner


comments powered by Disqus