BIG TEST

This is one clever CatCrikey!

Story Wayne Munro Photos Gerald Shacklock

The setback second steer axle made the CT630 look pretty ugly as a cab/chassis, but now this first of a new breed has its Transport & General tipping body and its RMD paint job, it looks like it was meant to be

potential traction problems when offroad unloaded.

A design was completed. A second Meritor MFS 14-143A wide-track axle was specced to match the first steerer, which is on three-leaf parabolic springs. And, on Wilkinsons’ recommendation, Neway air suspension was settled-on for the second steer – “because Wilkinsons had used it before in quite rugged applications,” says Kernohan.

On paper the whole concept was a dream. “Really, the last part was getting somebody brave enough to front up and try it,” he sums up.

So then he was chatting to Tauranga operators Mark and Scott Sherson about a new truck for their RMD bulk cartage fleet – “and they were talking about going to twin-steers, but said the problem is the traction…as soon as you’ve tipped your load off. ‘Specially if you’re dragging a five-axle trailer around.”

Bingo! “So we said have a look at this concept. We turned up with a line drawing and an explanation of how good it was going to be.” For sure, there was no concrete evidence that it would work as promised…but

the Shersons “were quite happy with the concept…and placed an order for two!”

Adds Kernohan: “Some people grasp the concept really well…..they just see all of the advantages straight away: ‘Crikey, that’d be good in this situation….hey can you do it for a tractor unit…..’ ”

In fact, Mark Sherson reveals that RMD had already been considering something different for some HPMV units – encouraged by talk in the leadup to the 50MAX regs being introduced, that “nine axles of any configuration” would be allowed.

“Our problem has always been with the big trailers, tipping into sheds. So we wanted a longer truck – we were looking at a five-axle truck (a twin-steer 10x4)…and a

Main pic: Tipping off the trailer load of stock feed at a Waharoa dairy farmAbove: Solar-powered night safety lights and grated step up onto the drawbar are nice touches

T’S A STORY OF GOOD OLD KIWI NUMBER EIGHT WIRE ingenuity….applied to new-age technology.

It all started a year or so ago, with three blokes sitting in an engineering shop in Cambridge – looking at a 6x4 Cat CT630 in for conversion into a twin-steer….and shaking their heads.

They were reflecting on the amount of work involved in relocating stuff to make room for the second steerer, as Gough Cat national truck manager Murray Kernohan explains: “We’re going ‘crikey, to put the axle there, all the fuel tanks have gotta come back, the exhaust system’s gotta be modified, we’ve got to make up a new step, we’ve got to put a battery box on….’

“It's incredibly expensive every time you put a spanner on them and change anything. The dollars just start racking up. The reality is you’re looking at not quite 50 grand.

“And we’re thinking, ‘crikey, it’d be so much easier (and a lot cheaper), from a conversion point of view, if we could just position the axle further back – because there’s a big chunk of clear chassis there.”

TSV Consultants senior engineer Marin Vujcich – one of the trio, along with Peter Wilkinson, boss of Wilkinson Engineering (which does the Cat conversions work) – said that, in fact, the regs on the two-metre maximum wheelbase for twin-steer axles had just been relaxed.

It was a bit of a “Eureka!” moment. It meant that, theoretically at least, the second steer axle could fit into the relatively empty space on the chassis – pushing the steer axles’ wheelbase out to three metres rather than the 2m of the seven or eight 8x4s built previously.

And so it began. As Kernohan recounts: “So then we started thinking ‘well, alright, how can we physically get it to work.’ ”

A steel-sprung suspension was

immediately discarded as impractical – “because, as soon as you went over undulating ground, it would start to take the full weight of the truck.

“So then we thought: ‘Could we run an airbag and spring?’ And again, it was ‘yeah, nothing in the regulations stopping us doing that.’

“We thought ‘crikey that’d be great.’ Because straight away we realised that if we’ve got an airbag we’ll be able to dump the air (for added traction).

“So then we were talking to one of the bodybuilders about the concept and he said ‘crikey, if you put ECAS on it that would be fantastic.’ ”

Now, Kernohan concedes that he honestly didn’t know much about electronically controlled air suspension – figured pretty much that it was just a trailer technology. It is, in fact, pretty common these days on European, even Japanese, air-suspended trucks, according to WABCO Australia application engineering manager Tony Cheyne.

Anyway, Kernohan didn’t have to go far to find out more – just to Transpecs, a sister company in the Gough Group and a WABCO agent: “And they came back straight away and said ECAS would be bloody perfect for this.”

Perfect because, as Kernohan enthuses, not only did it appear to make the ideal positioning of the second steer possible….it also promised great traction offroad.

And that would lend itself to the likes of an 8x4 HPMV doing tipper work – because the ECAS system would theoretically overcome a standard, steel-sprung 8x4’s

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Mud....but not greasy enough to trigger the ECAS and the traction control system

or three times – because it was almost too good to be true! Yeah, it was spot-on. I was prepared to spend some hours doing that final tuning and as it worked out it was very, very simple.”

Cheyne isn’t aware of any other manufacturer doing exactly the same thing with ECAS: “We do various configurations in Europe, but that one there – with the spring on the first steer and air on the second steer…..yeah, that took a little bit of thinking.

“We’ve got a few oddballs over here (in Australia) that are sort of similar – but not with that big wide spread on the front axles. Not completely the same – but enough that I was confident we could make it work.

“There was really no reason why it wouldn’t work.”Essentially, the ECAS system works to maintain an

accurate levelling of the chassis by way of an electronic control unit (ECU) that uses information from a sensor – adjusting it, if necessary, by actuating a solenoid valve to control the pressure in the airbags.

But, as it’s turned out, the solution to making the setback second steerer possible, has come with another big bonus: “The beauty of it,” adds Kernohan, is that the ECAS system “ties into” the automatic traction control system with the Bendix ABS that’s standard on the CT630s….

So that it automatically dumps air out of the airbags on the second steerer if there’s any wheelspin on the air-suspended drivers, below a set speed.

According to Cheyne, the system can be programmed to any speed or weight on the air-suspended axles. It can even be programmed to allow an axle to be overloaded….but “only under a given speed, for a given number of seconds.” In this case it’s been programmed to ensure that the steerers are not overloaded.

“Because normally you run into traction issues when

you’re running light.…so what we’ve done is said okay, when it’s running light and it goes into wheelspin, we’ll dump the air out of that tag…which will load up the drive enough to keep it moving.”

Career truck driver Ken Wilson, who’s taken over the new RMD CT630, has already encountered a couple of muddy farm tracks on deliveries – giving him a taste of the ECAS system’s capabilities: “There was a boggy place I went into and you could feel it bite……and bite…and away we go! It’s awesome.” There is a switch that allows the driver to manually dump the air in the second steerer as well and he’s also tried that. The result was just the same: “All it is, is you’re a couple of seconds quicker.”

We meet up with Ken and the (so far) rare Cat at Gough’s Wiri base, where it’s just had its 5000km service.

In terms of the mechanical package in this RMD truck, nothing’s changed: The only engine option is, of course, a Cat C15 ACERT – with 550-horsepower/410kW at 1800rpm and 1850 lb ft/2508Nm of peak torque at 1000 to 1500rpm.

It's an engine that has a remarkable history – of being pulled from production by Caterpillar because its technology couldn't economically meet the US EPA 2010 exhaust emissions standard...

Only to later famously make the Australian ADR80/03 standard – when engineers went back a generation, to the US 2002 ACERT engine, made a software change and added an engine breather and twin diesel particulate filters.

The C15 has a three-stage engine compression brake that produces 550hp/410kW at 2100rpm.

RMD has gone for the standard Eaton Roadranger RTLO-20918B 18-speed manual transmission, rather than the optional UltraShift Plus AMT, and an Eaton Fuller Easy-Pedal clutch.

An above & below view of the new second steer axle – positioned back, behind the cab. It's a much simpler installation

"We’re just trying to put it in places we used togo and see how it goes, you know"

four-axle trailer. That would have solved the problem…. It would have added a lot more versatility, working on rural properties and what-have-you. But we couldn’t get away with it because of legislation.”

With RMD’s work, though still largely rural, tending towards more linehaul, the Shersons were keen to add some 50MAX units to their fleet of 30-odd trucks – but had been put off 8x4s by other operators, who told them that it was hard to get them to weigh-up without overloading the steer axles.

“So when we talked to Murray (Kernohan) about the idea of the second axle distributing air from the rear, we thought well, that makes sense. Why not? It solves a ride issue too – they ride a hell of a lot better than a twin-steer steel-sprung.”

RMD has had 8x4s on its fleet before but this currently is the only twin-steer. The Shersons have a strong liking for Caterpillar engines, with the yellow engines powering about half of the company’s trucks….which are a mix of Western Star, Freightliner, Kenworth and Cat (with four Cat CT630 6x4s already in the company’s colours before this twin-steer version).

Getting the Cat also made sense in another way, Mark Sherson explains – a decision made at the time they bought the first four Cats to stick with Gough Group companies Transpecs and TWL for “all our running gear – as a one-stop-shop.”

So when Kernohan laid out the concept of the setback axle 8x4 it also fitted that policy, and “we thought well, there’s no reason not to give it a go.”

Sure, the axle and suspension setup is a bit different, but Sherson reckons that essentially it’s “just another

truck eh. Should do the job pretty well.” And besides, he adds, “we’ve got the backup if there are issues.

“And if you look at the basics of it, it’s so simple. Where’s the issue going to be? “Basically, they were built on the great run we’ve had with Cat motors.” And with Murray Kernohan: “He’ll do anything to make sure it works. It’s the people you deal with isn’t it.”

The subject of our Goodyear Big Test this month is the first of the two RMD Cat 8x4s – so far with just 10 days and 5000-kilometres of work behind it….and living up to all expectations.

In fact, Kernohan reckons, that started as soon as the thing was built – when it was progressively loaded up and made a series of weighbridge visits while WABCO’s Cheyne programmed the ECAS system and the truck and trailer unit was set up weight-wise.

Kernohan was delighted to find that the unit “actually weighs up better” than its 8x4 predecessors: “By moving that second steer axle back under the body it actually starts taking more of the load. So the real nice part for an operator is you can get it to weigh-up extremely well.”

The RMD unit, which has a 50-tonne H permit, was loaded up to 57t in the weighbridge trials, without overloading the front axles (the allowable maximum is 5.4t each, 10.8t for the axle group).

Cheyne, who managed the Cat 8x4 project for Transpecs and WABCO, regarded it as essential that he fly over from Melbourne to “spend a bit of time to get the parameters (on the ECAS system) set right on that first one.”

He too was delighted with the outcome: “It weighed-up well enough that I ran it over the weighbridge two

The main dash display is standard Cat fare....but elsewhere in the cab are nice touches carried out by RMD inhouse, including the cutback engine intrusion. It makes for more footroom...and an appreciated footrest

next three hours trying to get out.“It is 23m long. Yeah, after the 19m Western Star, you

know it’s out there.”And yes, he adds: “Oh well, I think there will be some

places it won’t be able to get into. But if you work in with the dispatcher and say ‘well, that was a hard one,’ we’ll know next time.”

You get the feeling that Ken wouldn’t be one to give up easily on jobs, just because they’re challenging. After all, that is, he reckons, one of the big pluses of the job: “I like to get off the old beaten track a bit…places you’d never go to otherwise.”

Like carting fert to an airstrip “out the back of Kawhia: We thought ‘is this the right road?’ There was actually grass growing in the middle of it!

“And some of those jobs are a real challenge. You know – like, can you get that gear in there – without dragging out a post?”

Working in the twin-steer Cat’s favour is that it is “very manoeuvrable. I thought it’d be too long, you know – you’d have to do three-point turns or nine-point turns and that…but there’s been a couple of places where I’ve just turned around and like ‘holy! That did alright!’ ”

With less than two weeks behind the wheel, Wilson says he’s still very much getting to know the Cat. But it’s all positive so far: “I’ve been impressed with it, to be honest. I’m pleased with it, you know.”

It’s a mix of many positive things. There is, for instance, the offroad traction: “Oh it’s there. It’s up there.”

The work over the first 10 days of its life has been typical: The Cat’s been in and out of Auckland a couple of times, to Tauranga/Mount Maunganui regularly, all around the Waikato on farm deliveries, to and from Taranaki….and has done a couple of runs through the central North Island, to the Manawatu.

Ken has always liked Cat engines, so there’s been nothing unexpected there – nothing to phase the C15 at

(or close to) 50t in the northbound climb out of Taranaki, for instance: “Yeah, she just slips over Mt Messenger – not a problem mate. Nah it’s good as gold…you don’t go into the low box there.”

The comfort of the Cat’s been noteworthy. Ken reckons he’s at an age “where you try and get the roughness out of life. You don’t want any more bouncing around and carrying on. No more noisy exhaust pipes.”

And the Cat, he says fits well with that: “You drive from the Mount to Taranaki or down to Shannon and you hop out and you’re pretty refreshed, you know.”

Mark Sherson too reckons that’s a Cat strength: “Actually the six-wheelers ride bloody good too. It’s sort of an American driveline with a European ride. They’ve got the ride right – they do handle very well.”

More specifically, says Ken, “you can feel that (second steer) air suspension. Nothing through the steering though: I was waiting for that old eight-wheeler kickback.

“It’s like a six-wheeler (the way it rides). I reckon the airbag is taking the jolt out of it.” Even running empty “you get bugger-all” kick through the twin-steer.”

And by his judgment, “it’s relatively quiet too – and the pipes are right there.” The twin high-rise exhaust stacks, he means – right behind the cab.

He’s even changed his mind about the way the thing looks! “When they first came out…..aw, they looked a plain-Jane truck. When you first look at them, you think, ‘no, that’s not me!’ You look at a Western Star and it looks like a working man’s truck, you know. Like a Mack and a Kenworth.”

Seeing this truck as a bare cab/chassis didn’t help: “I thought ‘ohh, I don’t know about that!’ ”

But then, even Kernohan concedes that the new 8x4 “does look quite ugly as a cab/chassis. One guy reckoned ‘that’s a face only a mother could love.’ But now the RMD truck has gone on the road…you’d drive past that truck on the road and you’d never notice (that it has a setback axle).”

“I’ve been impressed with it, to be honest"

It has Arvin Meritor RT46-160 rear axles, with inter-axle and diff crosslocks, on Hendrickson Primaax EX severe-duty air suspension.

What the RMD truck does have that’s new is an Ali Arc bumper that rounds out the formerly bevelled angles and has a bigger, improved central towing eye.

RMD has added to that a polished stainless steel sunvisor and a bug guard. The crowning glory with the shiny silver stuff is the Transport & General alloy bulk tipper body and the matching five-axle trailer.

The Alcoa alloy wheels on the truck are fitted with Goodyear G182 RSD 11/R-22.5 drive tyres and Goodyear Marathon LHS II 295/80R 22.5 steerers. The Alcoa alloys on the trailer wear Hankook TH10 265/70R 19.5 tyres.

The Transport & General bulk bins have auto-locking taildoors, with roll-tarps and nice touches including a driver-friendly checkerplate step up onto the drawbar.

The cab access steps are, of course, as per the 6x4s – two grated steps mounted on the fuel tanks each side, with a skinny bottom one and a deeper one above – both supplemented by decent grabhandles each side.

Mark Sherson says the company’s trucks have a high percentage of fully-loaded running, and this Auckland trip – even though a service has been fitted into it – is no different: From Gough Cat we head for the Lion brewery in East Tamaki, to pick up a load of grains recycled from the beer brewing process for stock feed.

It’s a regular backload out of Auckland, down to the Waikato – and the loading’s pretty typical too: As we head south, there’s 16.5t payload on the trailer and 10.5t on the truck – so, given the unit’s 19.2t tare weight, we’re around 3.8t shy of its regulated 50t maximum.

The LoadSense onboard scales are still being calibrated and aren’t yet quite right – indicating that we’re a couple of hundred kilos heavier than the weighbridge weight. It’s close…but not close enough, says Ken: “You want it right on the money.”

The truck runs close to fully loaded constantly, he explains: “Since day one, we’ve been running at that. Yeah, that’s the whole idea.” The whole point of 50MAX, he means.

Ken has been driving trucks for 30-odd years, since starting out at 19 in a little Bedford, doing general freight around Whangarei for Child Freighters.

Since then he’s done a bit of everything, including linehaul (for NZ Direct and Regans), 10 years in Aussie on interstate B-doubles, triple roadtrain fuel tankers and goldmine quad roadtrains, then loggers and rural carrying in Taranaki, before recently joining RMD.

And still, in his 55 years, he’s also had time to squeeze in stints as a repo man, go crayfishing in the Chatham Islands, run a chauffeur business in Perth and work as an operating theatre technician in an Aussie hospital. Hilariously, he reckons that he told the nun who hired him: “I just want to meet people.”

Even for someone who’s driven roadtrains that stretch out to 57m or longer, this 23m rig immediately made its length felt, particularly since the unit’s often “in and out of cockeys’ driveways”….delivering palm kernel, sand, gravel, fertiliser or other bulk loads.

This is still very much a learning phase – for him and the RMD dispatcher: “It’s all new. We’re just trying to put it in places we used to go and see how it goes, you know. I haven’t turned down a job yet with it.

“Farm deliveries are a big part of the job.” And they can be the worst conditions encountered – in spite of what the farmers reckon, “because the farmer, he’s got this thing: ‘Oh I take me tractor down there. AND a little trailer….’ That’s how it works.”

So, as Ken adds, “you DO have to hop out and check things out. You’ve gotta walk up the guy’s tanker track and figure it out – you’ve got to. Until you get to know what you can do with it. Another 10 minutes is better than having it all dented. Why go in there and spend the

Wilson agrees: “When it was all together and painted, you know, it completely changed. And then you get in one and you go, ‘wow!’ ”

Sherson has reached the same conclusion…for different reasons: “People look at it and think, ‘that looks strange.’ But it’s what’s on the bottom line that counts.”

Going up the Bombay Hills Ken reckons he’ll need to drop the Roadranger to a full gear off top, maybe a split on top of that.

We start out just under 90k, a split off top and the C15 hangs in pretty well and sits at 1300rpm for a long time at around 75k. When the revs drop to 1100 he downshifts to 7th High. He’s prepared for another split near the summit: “It might just squeeze over the top eh….yep, it’s away now.”

Ken, who hopped out of an RMD Western Star with a three-pedal Eaton AutoShift to take over the new Cat, reckons he doesn’t mind whether it’s a manual or an AMT: “I’m just getting used to this 18-speed. It seems to hop in there alright.” He has an easygoing driving style – usually only letting it lug down to around 1200 before downshifting on hills and upshifting around 1700.

We start down the southern side of the Bombays in 7th High at 60k – the C15’s engine brake on its third and strongest setting. Another full gear down and we settle

Above, both pix: The C15 copes well with the 50MAX loadings

The Cat's high-tech – just like the Lion brewery behind it....but there's room still for some No. 8 wire ingenuity

only time will tell.”He shrugs off any talk about the choice of the Cats with

their setback second steers being a risk: “No. No risk at all. The main telling point will be tyre wear. The indications now are that they’re fine, but they haven’t done a lot of miles yet.”

It’s the same thing with their fuel economy – “it’s too soon to tell” how they’ll compare with the fleet average, which Sherson says is “around the 1.8, but we have a high percentage of loading. And, you know, when you run east-west over the Kaimais every day and Napier-Taupo, what-have-you, loaded both ways, your fuel does come back.”

Murray Kernohan says that, “as simple as it is,” the 8x4 with its setback second steerer is a project that “has taken a huge amount of time.

“But, we need it. This suits our truck and our applications and our market exceptionally well.”

And now that there are two trucks out working, the marketing push will kick in – and consideration will be given to extending the same concept to 8x4 tractor units.

“To be honest, we’ve kept really quiet about it until this truck went on the road: If it did half of the things that we thought it would, it’d be a very good solution. And honestly, to date it’s doing everything that we thought it would do.

“I just cannot see a negative at all. It’s just come together incredibly well.

“It all started off as a bit of as 'crikey!' moment…we didn’t set out to re-invent the wheel or anything: We had a problem and we set out to solve it. And that sent us down a path – and it’s one of those very few times when you come up with a solution that’s so right. It makes such good sense it’s a no-brainer.” T&D

at 60k and 1600rpm, with just an occasional dab on the footbrake pedal. Wilson rates it “alright.”

The EBS on the trailer gets a bigger rap: “If you go into a corner a bit quick, it just pulls down your speed.”

A rough old stretch of State Highway 2 around Maramarua rocks the Cat around a bit, but there’s no jarring, no pitching. Says Ken: “Oh you’d be holding on in an 8x4 on springs! It kicks you.”

Credit to Cat for that….but a key part of the comfort inside is all down to RMD – and the extra detail work it typically does (a lot of it inhouse) before putting a truck on the road.

In the Cat’s case that includes cutting back the firewall intrusion – adding a polished stainless steel floor panel, a comfy footrest, more space around the footwell and extra insulation under a padded and pintucked vinyl finish. Other touches include RMD embroidery on the back wall – completing a nice interior that’s a mix of charcoal and light grey vinyl hard and soft surfaces.

Mark Sherson explains the logic behind the extra prep work: “Well, you’ve got to compete with what else we’re running – and most of the guys are driving Stars and Kenworths and that’s the interior that they like. It also cuts the noise – well, they’re a quiet truck anyway.”

In driver-friendliness terms, Ken Wilson also rates the easy functionality of the cab, where “everything’s within reach – you know, your diff locks and all that.”

He’s pleased with the vision too – although, he reckons: “A mirror off the door looking down to the side of the truck would be good – just to see where that old strainer post is.”

A dairy farm just outside Waharoa is the destination for the feed in the trailer and it’s a straightforward delivery: The track and the turnaround area by the feed bins is muddy, but with a solid base…and plenty of room. Fifteen minutes and the job’s done.

It’s here we notice a clever innovation on the rear corners of the truck and trailer bins – little SolarBright night safety lights. They’re solar-powered rear reflectors that, for instance, allow a trailer to be safely lit while parked-up overnight.

The lights, purposebuilt for use on trucks, trailers, earthmoving and agricultural machinery and the like, are reckoned to provide three days of continual lighting between solar charges.

They’re part of a lighting package that’s “very good,” says Ken. The LED headlights are “clear eh and very white.” Fog lights would be a good addition, he says.

Next stop is a dairy goat farm near Walton, where Ken unhooks the trailer and drives down a muddy track behind the big stables to tip off the truckload of feed. Again, there’s no wheelspin, so the ECAS system isn’t called into action.

A checkin with the RMD dispatcher sends us off to Horotiu, to a quarry for 11.5t of sand. From here, Ken will fill the trailer with pumice and head for home, in Taranaki. Another day done in this (so far) unique truck.

Since our test, RMD’s second 8x4 has also gone to work and Mark Sherson says that so far, “we’re very pleased with them.”

There are critical issues that it’s too soon to judge them on: “We’ve got to give it some time, because there’s things like tyre wear on that second axle. And

Above: The new 8x4 (left) has the second steer axle set back another 1m compared to its predecessors

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F YOU’RE GOING TO TEST THE UNUSUAL SUSPENSION SETUP ON Cat’s new 8x4, there’s only a couple of ways to do it.

The first is to get lucky enough, in the course of a randomly-selected day’s work, that the truck is sent on a job that demands delivering a load to a really nasty site, traction-wise.

That way we could see just how good this Cat’s combination of electronically-controlled air suspension, a spring-mounted front axle and airbags on the setback second steerer and the drivers is.

That one doesn’t happen: We do get some muddy farm tracks – but not bad enough to trigger wheelspin. So scratch that test. We’ll have to take driver Ken Wilson’s word for it, that the ECAS system – linked-into the truck’s traction control system – works brilliantly.

Second-best then is to find some gnarly, rough-as-guts stretches of main road to drive the twin-steer over and see how it copes.

Hence I get behind the wheel of this unusual-looking 8x4 near Maramarua, with a pretty average piece of State Highway 2 just ahead….and that leading directly onto the wavy, slumpy stretch of SH27

as it starts south across the peat-heavy, swampy Hauraki Plains.

That road, across the swamplands, is bloody terrible. So if this suspension/steering system is going to be found out anywhere onroad, this is the kind of place it’ll happen.

And….what a pleasure it is: There’s no kick-steer at all, even on the worst of the bumps. So you’d have to say that the ECAS is pretty good at doing its job, keeping us level.

I had wondered if having that second steer axle so far back might have a bad effect on a bumpy road – even sending the truck into a porpoising motion. But there’s none of that. No jolts either.

In fact, you can’t feel anything specifically from that second steer axle. Not in corners either – it just feels like a well-set-up, standard steering system.

It’s pretty easy to quickly settle-in

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SPECIFICATIONS

CAT CT630 8X4

Engine: Cat C15 ACERT,

ADR80/03 compliant

Capacity: 15.2-litres

Maximum power:

550hp (410kW) at 1800rpm

Maximum torque: 1850 lb ft

(2508Nm) @ 1100-1500rpm

Revs: 1350rpm @ 90km/h

Fuel capacity: 625-litres

Transmission: 18-speed Eaton

Fuller Roadranger RTLO-20918B

manual

Ratios:

Low Low – 14.40 Low High – 12.29

1st L – 8.56 1st H – 7.30

2nd L – 6.05 2nd H – 5.16

3rd L – 4.38 3rd H – 3.74

4th L – 3.20 4th H – 2.73

5th L – 2.29 5th H – 1.95

6th L – 1.62 6th H – 1.38

7th L – 1.17 7th H – 1.00

8th L – 0.86 8th H – 0.73

Front axles: Meritor MFS-14-

143A, wide-track RHD, rated at

13,000kg

Rear axles: Meritor RT46-160,

rated at 20,900kg

Auxiliary brakes: Engine

compression brake

Front suspension: 1st axle –

parabolic springs; 2nd axle –

Neway air suspension

Rear suspension: Hendrickson

Primaax EX air suspension

GVW: 31,000kg

GCW: 90,000kg

behind the wheel: It’s a comfy truck – with a nice leather-trimmed Gramag air seat, a great feel through the gearstick straight through the floor from the Roadranger and a particularly good driving position.

An important part of that is a really nice footrest for your left foot – and plenty of room in the footwell. I can’t remember that from other Cat CT630s we’ve tested….and later we find out why: This is a nice bit of detail work carried out inhouse by RMD to improve the standard interior – cutting back the intrusion of the firewall into the floor space, opening-up the footroom and adding the footrest.

Cat take note: This is a very worthwhile alteration. The other thing I’d be looking at upgrading are the wide but shallow bottom steps, mounted on the fuel tanks each side. While they are grated and provide reasonable grip, they only just give you enough of a foot-hold. The top step and the grabhandles are fine.

It’s a nice cab actually – and one with a reasonable amount of storage, thanks mostly to a deep bin set on the floor against the back wall, between the seats.

The turnout brings the likes of the controls for the aircon, the stereo/radio, PTO, beacon light, R/T and the diff locks within easy reach.

There’s good visibility of the dash – and out through the windscreen and down the sides

of the truck and trailer unit via good rear vision mirrors. The sloping

bonnet minimises the blind

spot directly under the front of the Cat.The C15’s 550hp feels adequate, I guess, for the

50MAX work that’s this unit’s daily bread-and-butter. You can definitely feel that it’s running at a bit more than the standard 44t (although it is actually only another couple of tonnes).

In saying that though it copes with the short, sharp challenge of the Kaihere Hills beautifully. We’re a split off top in the Roadranger as we drop down to the foot of the hill and start our climb at 80km/h.

I drop it to 7th Low as we get into the best part of the climb and that gets us up to the 35k right-hander at around 60k and 1400rpm.

For the corner I downshift to 6th Low and we wind on up the hill at 50-60k, the C15 revving at 1600-1700. I’m probably a split lower than I need to be.

The handling through the tight bends on the hill is impeccable. There’s no tendency to understeer, no heaviness on the steering wheel. And the Transport & General five-axle trailer tracks lovely.

For the descent we start down in 6th High – and, with the engine brake on its third stage (the strongest), I don’t even need to dab the footbrakes.

My time behind the wheel amounts to a fairly brief taste of this 8x4, but it is also pretty convincing: I’m sure that the bumps and corners will at least hint at a handling problem…if there is one. And there’s nothing. It’s perfectly behaved.

Makes you believe that good old Kiwi ingenuity is still alive and kicking. T&D

Cat believes that its new axle/suspension setup is tailormade for the tipper work that's one of the CT630's favoured applications