Rover 3500 S

35.000 miles - long term report

In our 11 October 1973 issue, we reported on the first 16.000 miles with this Rover 3500 S and explained that the car has given extremely good service and remained trouble-free. Now continuing the story, we deal with the subsequent 14-month period, taking the car beyond the 35.000-mile point, and in general the excellent behaviour has continued.

In a recent run to familiarize ourselves with the Rover as it is now, it was feared that the engine was beginning to show its age. Smoke from the exhaust was noticed both on the overrun and when accelerating hard, and maximum speed tests were quite a long way down. Instead of 123 mph at 5.130 rpm, the car would not exceed 116 mph even in a long run with perfect weather conditions.

However, checks of the service records revealed that renewal of the sparking plugs had been overlooked at the last service, and nearly 15.000 miles had been covered on one set of plugs. This had resulted from earlier experimentation with sparking plugs to find a type which would eliminate misfiring; the service department were under the wrong impression that a plug change was not yet due. The type used, incidentally, is Champioen L92Y - the answer for any owners of the model who suffer misfiring during extensive traffic work.

Performance tests carried out after new plugs had been fitted proved fairly well up to standard obtained with the model when new. Unfortunately it was not possible, in the time available for this report, to repeat the maximum speed tests. Smoking from the exhaust still occurs, particularly on the overrun at speed.

Service history of the car since the last report has included two medium and two major routine maintenance attentions. New front disc brake pads have been fitted (at 21.000 miles), and the battery was renewed at 17.800 miles. At renewal, the battery was only just over a year old, but the earlier report explained there had been severe corrosion at one of the terminals. Although there is much to be said for locating the battery in the boot, away from the heat and dirt of the engine compartment, it inevitably comes in for less regular attention as a result.

Considerable hissing noise is now audible from the power steering when taking sharp corners, and it could be that trouble is on the way in this quarter. As the noise is high-pitched and not unlike the beeping of a car horn, it is sometimes disconcerting until the driver has become familiar with it.

Oil consumption is still negligible and fuel consumption, even on the old plugs, was still nearly 21 mpg on a long run. In London traffic, mpg falls to the region of 18, which is again moderate for the size of the car and its engine, It is a nuisance that 5-star fuel is necessary, and we notice that the number of garages stocking this top grade fuel is ever diminishing. The 15-gallon tank, with positive reserve controlled by a knob on the console, enables one to put almost 300 miles between fuelling points unless driving very hard.

Starting is always reliable although far from prompt when cold. The mixture control has to be pulled right out, and several turns on the starter are needed before it will fire; there is some tendency to snatch and hesitate in the first couple of minutes from cold. Once warmed up, starting is immediate, and the engine is as crisp and smooth as ever. Engine quietness at all speeds is still outstanding, and the lack of fuss or apparent stress in 100 mph cruising at just over 4.000 rpm is not equalled by many cars today. The level of wind noise is relatively high, against the mechanical refinement. Appreciably more engine noise is heard under hard acceleration particularly in third gear, and it is suspected that some of the slight roar heard is corning from the gearbox.

Clutch smoothness and the precision of the short-travel but rather notchy gearchange remain up to standard, and it speaks well for the transmission that it has stood up to a continued exposure to London traffic conditions, not to mention two sets of performancé tests at MIRA, without need for attention. When examining the underbody, it was noticed that there has been some loss of oil from the front seal of the fixed final drive unit. Reverse gear is always rather difficult to select without an undignified crunch of gears, which is rather irritating.

In all other respects, the condition of the car underneath, with its almost total lack of corrosion, is very reassuring and a credit to the effectiveness of Rover underbody protection. The original equipment exhaust system is still in use and looks very sound.

There has always been criticism of the Rover´s rather soft and floating suspension, and in an effort to improve this, new suspension dampers were fitted at 24.000 miles. These made little improvement, and were replaced again last month by Koni dampers front and rear. These have made a major contribution to taughtening the suspension and giving a better, more positive feel to the car. The tendency to roll on corners has been slightly reduced, and suspension "float" on undulations is much less than before, the drawback being that the suspension is now slightly "knobbly" and harsh on poor surfaces.

At 17.000 miles it was decided to try the car on the new Dunlop Denovo safety tyres, and the original tyres and wheels were put in storage. The Denovos are mounted on special wheels with a distinctive trim which, in our view, detracts from the look of the car; they also need special wheel nuts. The spare wheel is, of course, dispensed with, and an emergency repair kit is supplied, including a list of Dunlop repair centres at which a punctured tyre can be properly repaired.

The much thicker tyre wall of the Denovo gives a very firm hold of the tread and makes a big improvement in roadholding, especially in the wet. This aspect of Denovo, we feel, has not so far been sufficiently emphasized in earlier tests of the tyre. There is also a small gain in steering response and directional stability. The penalty of Denovo, particularly marked on this car, was severe tyre whine and roar, particularly in the 30-40 mph speed range. Dunlop engineers say that this problem, accentuated by the Rover´s suspension design in which front wheel loads are fed back to the scuttle, varies in the 3500 S from one particular car to another. It was not until the tyre design had been finalized that it was realized that the two cars being used for research were less prone to this noise problem. At that stage it was too late to alter the tyre tread pattern, but it is emphasized that the noise is caused by the particular coarse tread pattern chosen, and is not from the Denovo safety feature.

Because of the whine, which was proving tiresome at traffic speeds, the decision was taken to forego the advantages of Denovo, particularly the major advantage of not having to carry a spare, and revert to the original wheels which had been fitted with new tyres (conventional Dunlop Sports) shortly before the change to Denovos. When removed, the Denovos had covered 18.000 miles, and the tread had worn approximately 4mm at the front and 3mm at the rear. This wear rate was more rapid than on conventional tyres, perhaps as a result of the rather low pressure which had been recommended initially. Dunlop now advise normal tyre pressures for Denovos, which gives a very harsh ride.

Before the Denovos were taken off, it was decided to carry out a deliberate burst at very high speed.. Endless tests have been made of course, at speeds in the 60-70 mph region, but the real safety factor of Denovo is the more valuable the higher the speed. Dunlop kindly co-operated in the tests and although we had wanted to carry them out on our own car, this proved impracticable because of the elaborate electrical equipment required to set off an explosive change on the sidewall. This detonation blows a hole in the tyre about an inch in diameter, causing immediate and complete deflation - a much more severe test than the partial deflation one is more likely to experience on the road.

In the event, we had some trouble with the equipment, the charge first tending to fly out, deflating the tyre without any explosion, and then exploding without bursting the wall. But the experience of complete deflation of a front offside tyre with the speedometer reading 105 mph was finally achieved.

I had not feared at all for the stability of the car with a tyre burst at such high speed, since the reputation of the Denovo has long since dispelled any doubts about it. But I did need some reassurance about stopping, as ever with air in the tyres the straight used at MIRA left little spare distance in which to bring the car to rest from 100 mph, and I did not fancy an ignominious sortie into the emergency sand bank.

The crack of the explosion, and a momentary pall of smoke past the driving window, left one in no doubt that the charge had gone off, but there was no pull at all on the steering. It was not until the brakes are applied that a slight movement to the right had be checked, but there was still no question of having to fight the wheel or anything of that kind. On one run I tried "hands off" braking after the deflation and the car certainly wandered to the right, but it was still only a deviation, not a violent pull.

There need have been no worries about arresting the car with a flat, the stopping distance was the same as with all tyres inflated. The only difference was that the deflated tyre, under firm braking, left a pencil thin black line on the road. If one has any doubts as to whether one could have a Denovo burst, remain unaware of it, and continue driving at speed, the answer is that the 2in. drop of the car´s attitude on the side which has deflated is remarkably noticeable. One would have to be very insensitive as a driver not to notice this and realize that something was wrong.

After these experiences one might have had second thoughts about the wisdom of ending our Denovo tests and reverting to conventional tyres, but it should be borne in mind that much of this car´s mileage is covered in traffic, with no opportunity for very high speeds. If it were in use for long Continental journeys the relative importance of Denovo safety would be much greater.

The car itself is now well into the third year, and the question of its replacement has naturally been considered. As far as the driver, our managing director Tim Gold Blyth, is concerned, replacement would only be with another 3500 S, as the model suits him ideally in almost every way. The condition of the car is excellent, and it seems rather doubtful whether the cost and extra depreciation involved in replacing the Rover at this stage would be justified. So, particularly bearing in mind, Autocar´s interest in the life and durability of the model, the decision has been taken to retain it for at least another year. We will be reporting again sime time after passing the 50.000-mile mark.

Autocar / UK January 1975

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