CARGO GOES FURTHER
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• There have been many milestones in the six-year career of Iveco Ford Truck's highly-successful Cargo range — but none with such far-reaching implications as the fitting of Lucas Girling's disc brake system to both axles of its 6.0 and 7.5-tonne GVW models.
In an exclusive roadtest round our dis tribution and Welsh routes with a fullyladen all-disc-braked Cargo 0813 we have been able to evaluate the effectiveness of the new system, and catch up on an important model that has long eluded us.
Under normal road and weather conditions the 0813 gave a very good all-round performance. More importantly, apart from one or two misgivings, the brakes proved to be something of a revelation.
Over the past decade both Ford and Lucas Girfing engineers have accumulated considerable expertise in the use of disc brakes on CVs at this weight, first in Brazil then with Concept Cargo.
In Europe, however, Volvo was the first to fit them on both axles to its 11-tonne FL6, an example of which first appeared at the last Frankfurt show (CM September 21, 1985). That system has, of course, now appeared on the British market on the FL4, but not the FL6.
Other manufacturers also have experience of using them on front axles, including Daimler-Benz, Iveco Ford, on its Italian-built 'Z' range, and Leyland Daf with its latest Roadrunners, but as far as the UK market is concerned Iveco Ford has taken a carefully calculated step to become the first company to offer discs on both axles.
With Mintex Don having made the break-through on non-asbestos pad material and Lucas Girling's proven twocylinder caliper system becoming available, Iveco Ford avoided the expense of re-engineering its own axles, adopting instead two new Rockwell components that are designed to accept the new brakes. At the same time it took the opportunity of fitting lighter, parabolic springs on the rear.
The 0813's new brakes are of the reaction beam caliper type. Two hydraulic pistons mounted in the inboard beam pressurise the pads onto the disc; the inboard pad directly and the outboard one by reaction through the clamping frame.
For simplicity and ease of maintenance Iveco Ford has carried out several important changes to brake actuation. It has changed from an 'L' split to a vertically split air-over-hydraulic system, at the same time reducing the air storage pressure from 11 to 9.5 bar.
With the new settings comes a new foot control valve which, according to Iveco Ford, gives a more progressive feel to the brakes.
Our track tests highlighted the fact that the resulting system is very different in behaviour from traditional drum brake setups. The pedal "feel" is firmer, and is heavier to push than the typically light Ford clutch. The different characteristics mean that smooth braking is best achieved with a firm initial push followed by a gentle relaxation in pressure.
On the rolling road tester provided by a helpful Dip testing station the brakes showed a superb level of efficiency, with very high figures (above 80%g) and only slight differences across the axles. Subsequent testing at MIRA bore out most of the promise shown on the rollers.
Full-pressure stops from 32, 48 and 64krn/h on a clear, dry track and using a Motometer recorder showed very high peaks of deceleration rather than the usual lower but flatter recording traces. The ultimate stopping times were short: for example, the stop from 64km/h was accomplished in 2.8 seconds – that is a full 0.3 seconds faster than the already impressive figures achieved by the Leyland Roadrunner 813 with disc front brakes which we tested recently.
On the track, the Cargo achieved indicated decelerations of just over 80%g, where the Roadrunner peaked at a creditable 73%g. As we expected, the pedal presures needed to reach these figures on the Cargo were higher than on the Roadrunner, at some 37kg compared with 25kg.
The slight cross-axle imbalance – which seems to be the price paid for the convenience of a self-adjusting system – leads to single-wheel lock-up and consequent slewing of the vehicle at maximum decelerations from speeds of over 501m/h.
Fortunately the 0813's brakes behaved extremely well under normal traffic conditions.
One aspect that intrigued us was how the discs would perform in wet weather.
To find out, the vehicle was driven several times through MIRA's hub-deep wading trough until the discs had had a good soaking. Immediately afterwards more full pressure applications from 321cm/h stopped the 0813 as well as if it were dry. On the test hills the new park brake really excelled, holding firmly on a 33% (1-in-3) grade facing up or down.
Instead of the previous duo-servo arrangement with a single actuator, the 0813's self-adjusting park brake operates on the rear calipers using only the lower cylinder and is actuated by normal spring brake chambers.
Parabolic springs are now standard on these disc-braked models, with a single leaf at the front and twin-leafed with a slipper-ended helper leaf at the rear.
The overall effect of this change is quite noticeable, but the fitting of an optional anti-roll bar at the rear certainly improved the ride. With the load biased more towards the front the ride seemed very firin with just a trade of body roll al the rear.
On the ride and handling circuit it gave an outstanding performance, showing off the clear benefits of its revised suspension. The only untoward effect was the shock felt in the cab at speeds of around 56km/h over the sunken potholes.
It was a real revelation when being thrown into bends with adverse camber and coped quite well with the worst of the A road section east of Cheltenham, some of which bears scars from the appalling winter.
While a particular driveline has a certain level of performance, one of its most critical points lies in the choice of final drive. Our 0813 test vehicle has Ford's 94kW (net) naturally-aspirated 6.2 litre diesel with the ZF S5-35/2 five-speed synchromesh gearbox.
Both of the new single reduction hypoid axles — the C411, which is used on 06 and 07 prefixed Cargos with the 62kW four-cylinder engine, and the D120E fitted in the 0811 and 0813's — are rated at 5.5 tonnes.
With the direct top gear, the tallest 3.73:1 of the four final drives assigned to the D120E, and 9.5R 17.5 tyres, the 0813 has a geared top speed of 109km/h (68mph) at 2,6()0rpm.
For a 7.5-tonner this theoretical figure fells short of its maximum motorway limit but in practice, being governed at 2,900rpm it will achieve and hold 1121(m/h (70mph) quite easily. On the test track it reached 119km/h (74mph).
The choice of 17.5in wheels over the 16in models used previously is something of a compromise to ensure an adequate flow of cooling air around the discs. This has also raised the chassis slightly, but where this is critical the use of optional low profile tyres will bring it close to its original height.
Its overall average speed was much higher than that of the 0811 with the 81kW Dover engine, but its 18.81it/1001cm (15mpg) overall fuel consumption was, predictably, worse than the 0811's 16.51it/ 100km (17.1mpg).
It certainly could not hope to emulate the superb 14.51it/100km (19.4mpg) of the diminutive 6.0-tonne Cargo 0609.
Appropriately enough, on economy it ranks alongside Iveco's equally powerful 79.14 which returned 18.71it/100km (15.1mpg) but a few points below the MAN 8.136F's 17.9fit/1001un (15.8mpg) at a much slower 70. 91crn/h (44.1mph).
For some of the journey the 0813 smoked rather heavily, particularly on Wantage Hill where the steepening 14% (1-in-7) gradient exposed some longish gaps between 3rd and 4th, then 2nd and 3rd gears.
Another annoying factor was the engine's low tickover (just below 500rpm). When manoeuvring through the 90° turn out of Ledbury's high street, it cut out at a critical moment as the power-assisted steering imposed extra engine load, and this was repeated on several similar occasions.
• CAB COMFORT
Our test vehicle was originally intended to have a boxvan body, hence the cab's blanked-off rear wall. The omission of rear windows highlighted the importance of broad rearview mirrors. The Cargo had these but they were over-convex and distorted the view so that in a narrow road with parallel kerbs the view via each mirror gave the impression that the truck was on a part lock, which took a while to get used to. These mirrors do, however, seem much more robust than those fitted to earlier Cargos.
This Cargo cab has lost its dark cloth seat-covers with colourful piping, in ex
change for a lighter but plain woven plain cloth that looks durable but drab.
Disc brakes are not new in themselves but fitted front and rear, along with new axles and rear suspension, they give Iveco Ford's lighter Cargo models a significant boost.
In general terms, there is litle doubt about the stopping power of the Iveco Ford/Lucas Girling brakes using Mintex Don 7250 non-asbestos pads. Their feel and characteristics under hard braking could, however, need getting used to.
Iveco Ford also predicts reductions in maintenance costs that will not go unnoticed by the long-distance boys.
Compared with conventional linings these pads are expected to have twice the life (a pad life of 60,000km is forecast) and can be changed quicker and more cheaply. Brake relining costs are expected to reduce by 60% over three years or 120,000Ian, says Iveco Ford.
At 215,690 the 0813 is not cheap, but represents good value for money, with a good payload and an excellent all-round performance in terms of economy, fast journey time and superb handling.
The cab is as comfortable and easily accessible as you might expect from a light truck range that dominates the 7.5tonne sector with a massive 43% share in the first quarter and one that looks set to continue in the same vein.