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lq02 WIDE-SINGLE TYRES

Suddenly everyone wants to fit widesingle tyres on the front of their artics. * For many operators they signal the end to uneven tyre wear; others cite their enhanced flexibility. But when it comes to fuel economy there's a price to be paid for having big rubber boots up front. Is it a price worth paying? CM's exclusive test comes up with some figures.

hoever first fitted wide-single tyres on the front of a truck has a lot to answer for. Not so long ago they were seen as a continental oddity; but they've spread across the Channel like a windblown virus to the point where it seems every other UK tractor buyer is speccing new wagons with 385/65 R22.5s on their steer axles.

Times have certainly changed since a handful of brave hauliers experimented with widesingle trailer tyres up front. Following an initial reluctance to have anything to do with the phenomenon, the tyre manufacturers have been dragged to the party—all the major suppliers now offer purpose-made steer-axle pattern 385/65 R22.5s, The wheel manufacturers have also responded to this demand by developing offset models to suit the wider tyres in both steel and aluminium.

• HARD-HEADED So what's all the fuss about, and why are so many hard-headed hauliers queuing up to fit bigger, more expensive tyres on the front of their tailors?

It seems that many were simply fed up with t the uneven shoulder wear they had experienced with conventional 295/80 R22.5 steer

1 axle tyres. One large tyre fitting company recently told CM that it recommends wide-singles unreservedly: "On a normal tyre the cam

ber pushes all of the weight towards the outer edge, which leads to a dropped shoulder. Fitting wide-singles results in increasing road contact, from 220mm to over 330rnm, which reduces the transfer problem."

Converts also report vastly improved mileages on steer tyres (see operator experience, page 51). Then there's the chance to have those wide-singles remoulded for a second lease of life on your trailers -that has to make strong economic sense.

Wide-singles also have the potential to run with higher front-axle weights, up to the legal nine-tonne limit. With the exception of a handful of reefer operators carrying diminishing loads, ifs hard to see who'd want more than the usual 7.5 tonnes, but next year the (.1{ will finally move to 40-tonne artics and 18-tonne rigids, and wide-singles will then offer much greater front-axle loading tolerance.

So far so good, but you can't simply bang on a wide-single tyre on the front axle. Your truck must be capable of accepting a wider tyre within the legal 2.55m width limit. Scania's latest 4-Series has been designed to take a 385/65 front tyre: not so the old 3-Series. Several operators running wide-singles on 3Series tractors seem to have overlooked that. Whether the police or VI will overlook it in a check or at annual test remains to be seen.

Wide-singles may do wonders for tread life but we've yet to hear what effect they're having on steering gear: a 385/65 R22.5's wider footprint must generate higher forces through wheel bearings, king pins, track rods 10.

WIDEESINGLES: FITTING FACTS 41 and steering linkages Then there's the matter

of adhesion.

Continental warns that operators considering wide-singles should consider "the potential deterioration in wet grip performance". The German tyre giant adds: "Wide-single performance may not match that of a standard tyre. The wider tread profile, particularly when running unladen, may mean that the pressures placed on the road are insufficient to maintain traction and lead to the tendency of aqua-planing."

That concern would certainly be exaggerated if an operator fitted a standard trailer tyre to a steer axle, and Conti recommends that "specific steer axle patterns are used".

And what about increased rolling resistance? It's no good saving on tyre wear if you're going to lose it all through increased fuel consumption. But just how much extra juice are we talking about?

During our recent roadtest of the Daf 95XF480 (CM 23-29 Oct 1997) Leyland Daf's roadtest supremo Richard Kingston poured scorn on the use of wide-singles on front axles. As someone who's loath to fit anything to a wagon that will hit fuel economy, Kingston wants a cast-iron guarantee before he'll spec anything out of the ordinary on a Daf demonstrator.

So when he asked: 1 wonder how much wide-singles affect fuel consumption?" we replied: "You supply the truck and tyres, we'll provide the drivers and venue and find out."

A quick call to Continental showed them to be up for it. Pausing only to grab a stopwatch and clipboard, we headed for the test track...

• TYRE TRIAL: TEST METHOD Millbrook's two-mile banked oval track nestling in the heart of the Bedfordshire countryside is the ideal site for specific fuel con

sumption tests. That's why CM uses it whenever we want to examine the wilder claims of some manufacturers, not least on aerodynamic equipment.

Because the Millbrook oval removes all the variables you'd encounter on the open road (such as traffic congestion) we can come up with an objective, repeatable result. And, unlike ars Scottish artic test route, the Millbrook oval means we're less at the mercy of the weather and any headwinds are likely to be balanced out.

Our test method was simple enough. 10. • Having driven the 95XF and laden triaxle semi-trailer to Millbrook we swapped its normal 295/80 R22.5s for a brace of Speedline's latest alloy rims fitted with new Continental HS45 steer-pattern 385/65s. We then ran a warm-up lap to set the 95XF's EGAS cruise control to a steady 55mph before starting the stopwatch and completing 30 laps of the twomile circuit.

Using an extremely accurate JPS flow meter we measured the fuel consumed by the 95XF's 12-litre engine as we circumnavigated the banked oval track.

After 30 laps we stopped the clock and meter and returned to a holding area where Continental's Arthur Allen and Steve Howat were awaiting us with air gun, torque wrench and a new set of HS45 295/80 R22.5s mounted on Kingston's regular Speedline alloy wheels.

The wheel changes took long enough for everything to cool down before we returned to the test track for another warm-up circuit and 30 more measured laps. To ensure we ran at exactly the same speed we kept the previous cruise control setting in the 95XF's EGAS memory The difference in the time taken to complete both runs (all of 0.6sec) shows the uncanny accuracy of Oaf's electronic cruise control when it comes to maintaining a constant speed!

At the end of the second run we looked at the flow meter readings to compare fuel consumption with standard and wide-single tyres.

• TYRE TRIAL: RESULTS

When CM originally mooted this test, Conti faxed us its own calculation of what wide-singles would do to fuel economy. According to Howat you're looking at a 4.5% increase in rolling resistance which equates to a (theoretical) increase in fuel consumption of 1.4-1.8%. It seems that Conti (and Howat) know their onions as our test showed an average increase of 1.9% in fuel consumption between our

truck running with 295/80 tyres and with 385/65s.

Fuel consumption isn't the only thing we noticed about the wide-single run. At 55mph Kingston reckoned there was a slight, but definite, front-wheel shimmy which died away when we slowed down to 50mph at the end of the run. A 385/65's wider footprint might make it a touch more sensitive to uneven road surfaces, although to be fair we didn't have the wheels balanced. It would be interesting to see how wide-singles perform on a rutted motorway: operator feedback suggests they actually improve ride comfort.

• TYRE TRIAL: THE BOTTOM LINE Are you thinking of switching to wide singles? Then sharpen your pencil first. A 1.9% increase in fuel consumption might not sound much, but there's no point increasing your tyre life if you end up blowing any savings out the exhaust pipe.

Wide-singles offer potential savings in tyre wear, with gains in flexibility, reduced service costs and less downtime. Against that you've got to set slightly higher fuel bills and the relative costs of the tyres themselves. Each 385/65 HS45 Continental wide-single is likely to cost around £90 more than a regular 295/80 HS45, and you'll also be paying for new wider wheels to carry your wider tyres.

Howat reckons that a 1.4-1.8% increase in fuel consumption will have a significant effect on your operating costs. "Using current statistics, a 38-tonne artic costs £24,243 in fuel and oil and .C3,995 in tyres per annum," he says. "Using 385/65 R22.5 tyres on the steer axle may improve tyre mileage performance but this could be detrimental in the form of an increased fuel cost of £340-£436."

Based on the average mpg figure of 9.39mpg returned for CM's 295/80 R22.5-shod artic if you covered 100,000 miles a year you'd consume 10,649.6 gallons of diesel. At 9.22mpg (the figure we achieved with our wide-single arctic) your annual consumption would rise to 10,845.9 gallons, which is an extra 196.3 gallons to pay for. Using last week's average retail diesel pump price that would add £564 to your fuel bill for every truck running on wide-singles.

There's no doubt that wide-single steer tyres offer many benefits to hauliers. But remember the old Yorkshire saying: "You don't get owt for nowt." Judging by Cifs tests that's still the case—and we've a hunch that we won't be seeing them on Daf roadtest vehicles for a long time to come. right, Mr K?

C by Brian Weatherley _ Oft SWAPPING THE 11! FRONT TYRES on our

Daf 95XF brought same interesting fitting issues to light. At 29mm, the centre nave on the latest 120mm offset Speedline 511266 alloy wide single wheel is noticeably thicker than the 23mm nave on the conventional (146mm offset) 51905 wheel. A steel wheel nave is typically around 12mm.

As we torqued up the wheelnuts there appeared to be less available length on the stud to tighten the nut. Even fully clamped, some 4-5 threads were still visible on the inside of the nut. Fortunately the nuts supplied with Speedline alloy wheels have a threaded collar that extends back from the nut flange through the wheel holes to ensure adequate thread contact. Speedline's visiting engineer and BPW, its UK distributor, proved that the engineering adage of having a contact area one and a half times the diameter of the bolt was well covered by the shafted nuts having 24mm of thread engaged when the minimum would have been 20mm. Fair enough, but it still didn't look quite right to the uninitiated, and we were left wondering what a Vehicle Examiner might make of it at the roadside. If you're going to specify alloy wheels for your wide-singles (and CM understands that both Alcoa and Speedline types have a similarly thicker nave than a normal steel wheel) and you want the stud to protrude beyond the outer face of the nut you can always spec longer studs on your 95XF tractor. They'd have to be retrofitted by

a dealer as Daf doesn't fit them on-line (and check that they don't take a vehicle over width with an alloy wheel).

• Speedline's smart SL1266 wide-single alloy wheel will available soon. It will add around £100 to the cost of a pair of standard 51905s, which retail at around £1,240. The SL I 266 wheel weighs about 27kg and has a loading capacity of 4,500kg. For details contact Nigel Stevens at BPW Suspension Systems.

Contact: 0116 2816100.

WIDE•SINGLES: OPERATOR EXPERIENCE

Whitney, Oxon-based international haulier Gavin

Macburnie is running nine tractors on wide-singles in his fleet of 13. "We've got them on three R143 Scanias, one FH1 2 Volvo and Five new Dal 95XFs," he says. "As the other trucks come up for replacement then well add more,"

Why switch to 385/65s? Macbumie explains: "The first thing we were noticing with 295 steer tyres was that when we got down to 8mm of tread they were starting to scallop out in all sorts of weird places like a threepenny bit. We tried everything—laser alignment, toe-in, toe-out but at around 140,000km that's no good when you've still got 8mm left."

Following up on comments from an operator in CM he bought a set of wide wheels and Bridgestone tyres and trialled them: "In terms of evenness and wear, at 200,000km they still had lOmm of tread and were perfectly fiat."

As a result Macburnie has been speccing Michelin FXA wide-singles on all his new vehicles, One set, on the FH Volvo, have already done 190,000 and he reports: 'There's still a good 7-8mm on them. I reckon I'll get 230,000 out of them easily."

Macbumie has also achieved greater utilisation from each casing as they're remixed for the trailer. So are wide-singles cost effective? "The way I see it," says Macbumie, "we keep a truck for around three years. Before wide-singles I was fitting one set of drive axle tyres and two, possibly three sets of tyres on the front. With wide-singles I'll probably only need to buy one set of steer tyres—and I've also got the casings. Normal steer-axle casings are no good to me.'

When it comes to fuel savings Macburnie acknowledges that 295s might offer a cheaper route, but right now his 95XFs are delivering over 9.5mpg and he's happy with that. He's less impressed by the wear rate of the Michelin energy tyres on the drive axle and plans to revert to conventional lyres.

• Within its 50-strong fleet, Framptons International at Shepton Mallet has fitted wide-singles to six FL! Volvos and one 6x2 Daf 95 Super Space Cab—some of them have been running for almost two years.

Transport manager Richard Fry says: "They definitely increase tyre life. It also allows us to use them on the trailer, and they certainly improve ride comfort."

However, he warns that tyre pressures must be monitored closely: "If you let them run soft then they tend to wear even quicker than a regular 295." Fry also recommends using a specific steer-axle pattern to maximise shoulder wear. On the subject of possible fuel consumption penalties Fry says: "It doesn't entirely surprise me but we've seen no difference in fuel consumption."

How cost-effective are wide singles compared to conventional 295s1 Fry says: "It's difficult to get a hard and fast percentage but we certainly don't change them as often as a 295, and with widesingles you're getting three uses of the tyre—that's new, recut, and then remoulded for the trailer."

• Mike Beer Transport of Dover has been running wide-singles on its steer axles for a couple of years, and managing director Mike Beer is enthusiastic about them: "We're gelling an extra 30% on tyre life, and it's much more comfortable for the driver." The wider steer tyres also suffer less from road ruts than conventional 295s: "Tramlining—that's quite a remarkable difference," says Beer.

He's specifying purpose-designed Pirelli 365/65s as standard on his new tractors (mostly Leyland Dor 95XFs) which are Fitted with the appropriate offset alloy wheels, but he's been using trailer-pattern tyres as replacements. The tyre manufacturers do not recommend this, particularly in wet weather, but Beer is adamant: "Between a proper 295 steer tyre and a wide-single trailer-pattern tyre our drivers can't tell the difference." What's more, 365-section trailer tyres are cheaper than 295 steer tyres, and are more widely available.

• Kenny Rayment is one of the first operators in the UK to match a disc-braked Mercedes Actros tractor with a disc-braked trailer, and he decided that his tyres should match too. The front wheels of his two Actros 1848 Mega Space tractors have been replaced by the same offset Alcoa alloys used on his Schmitz reefers, and they're fitted with Toyo trailer-pattern 385s.

"I may as well have the same spare wheel as on the trailer," says Rayment. "With these I'm getting no problems; they're running cooler than normal." The wide-singles are only about half worn after 90,000km.

Rayment echoes Mike Beer's observation that the wide-singles handle tramlines better than standard 295s, but he's moved over to Pirelli for most of his tyres and will be buying purpose-designed Pirelli steer-axle 385s when it come to replacement time.

FITTING WIDIESINOLES: POINTS TO PONDER

• Since the advent of the 2.55m overall width limit the dimensional problems of using wide-singles on a steer axle have been eased a little—but they still exist.

Many new trucks have been designed to accept wide-singles, either as an on-line or dealer fitment, but any operator considering speccing or retrofitting wide-singles should check with the manufacturer to ensure that they would not put a vehicle overwidth, and that they will fit inside the existing muclwings.

* Operators should also ensure that wide-singles will not foul the chassis on full lock.

,t If you are considering using wide-single steer tyres you should check that the front axle, brakes, springs and steering box and linkage are capable of handling the extra forces generated by the tyre's wider footprint.

=e Operators should spec wide-single wheels carefully, bearing in mind that they will have a different offset to a conventional steer-axle wheelrim. As alloy wheels generally have thicker naves that will have implications for nuts and studs.

* Birmingham-based Spatz produces a range of "Super Fruntz Kitz" steer-axle wheelarch extensions to help overcome problems of wide-single sidewall protrusion on older or narrow tractors. Contact: 01527 68168.

TYRE WEAR AND FUEL ECONOMY

FOR THE SAKE OF COMPARABILITY both of our runs were carried out using brand new tyres: even the smallest difference in tread wear would have affected the figures. To get a feel for the likely scale of such variations we consulted Stewart Nancollis, external technical manager at ERF and a man who's spent a lot of time looking at fuel consumption, especially through his involvement with ERF's "Fuel Duel" fleet.

Tyre wear can certainly influence fuel figures, he reports, especially if you're using your tacho readings for calculating distance covered. But those figures may not tell the whole story. "If you take a new 295/80 rear tyre with a full tread depth you'd be getting around 305 revolutions per kilometre," he explains. "On one where you've worn down to around 20mm of tread you'd be looking at 315 revs per kilometre."

The effect of that, says Nancollis, is to fool the tacho into thinking the truck has actually covered more ground across the same distance—so when an operator divides his fuel return into that increased tacho mileage the figure will be distorted. A worn tyre can result in a 3% error on the distance calculated by a tacho—and the higher the mileage reading the better the average consumption will look.

That's why CM calculates fuel economy on our roadtests by using a fixed, known distance rather than relying on the distance recorded by the test vehicle's tacho. As Nancollis says: "I've had operators ring up and complain about a drop in economy only to find out they've recently changed tyres on the truck without realising the effect it can have on tacho mileage."

The higher rolling resistance of a new tyre will also affect fuel economy. "When a tyre wears you're expending less energy through the tread because there's less movement in the blocks," he says. "That's why__you'll always get better economy off a port-worn tyre. A red gut feel would be between 1-2%. Improvement, but to get a definitive figure you'd need to do a really scientific test." Maybe that's something for a future CM test...

Continental's prediction of the effect of front wide-singles on a typical five-axle 38-tonneris fuel economy 385/65R21.5 tyre vs 295/80R22.5 tyre

The front axle accounts for 15% of a five•axle rolling resistance.

The 30% increase In rolling resistance with the wider tyre equates to a 4.5% increase in the artists overall rolling resistance.

This equates to a total fuel increase of 1.4.11%.