It would be hard to find anything more boring than these three
Items and yet they crop up every time the cars are discussed. Ad nauseam!
In order to help you decide what to use on your car I have outlined all the information below.
Tyres
When they were new MKVI’s and R’s were sold with 6.50” X 16” cross ply tyres. These are still available from specialist suppliers and are expensive, short lived, have far less grip in the dry and are dangerous in the wet unless you travel so slowly that you are a nuisance to other road users. They also “tramline” so that the car is steered by overbanding, white lines and road surface irregularities.
Tyres have improved dramatically since the early fifties!
As a result of the problems listed above and because exactly the same size is available as a radial truck tyre, most owners now fit 6.50” X 16” Michelin XCA’s and they are a dramatic improvement over the original cross plies. The only disadvantage is that they are heavier than the originals so that it pays to overhaul the front shock absorbers as per the instructions also on this site.
In the nineteen sixties Radials gradually replaced Crossplies as original equipment on new cars and sizes were introduced to fit existing cars. In the case of ours these were 185 – 16 and they too, are still available from Specialist suppliers. They are wider than the originals and improve grip but they reduce the diameter of the wheel by about 1” on an already under geared car. Otherwise they are better than the Michelin XCA’s.
Some people have used Range Rover 205 X 16 because they are the same diameter but 8” instead of 6.50” wide and this may cause problems.
More recently van tyres have come on the market that are 195/75 X 16 and these are roughly the same size as the 185 X 16 supplied by the specialists but about half the price!
Van tyres and Michelin truck tyres tend to have a maximum speed rating of 95-105 mph so should not be used on the Continental model.
Michelin recommend 36 psi. front and 38 psi. rear for their tyres and all radials require much higher pressures than crossplies. You may need to experiment to get the best results.
Petrol
Rolls-Royce has said that all their cars are suitable for use with unleaded petrol and so most owners run on Premium unleaded without apparent problem. However on a number of engines I’ve seen in bits lately, the exhaust valves are quite low in the block so I feel that if you are having the engine rebuilt, it would be a good idea to have hardened seats fitted at the same time.
All the research that was done on unleaded petrol in old engines suggests that provided engine speeds are kept below 3,000 rpm, valve seat recession was minimal. On all but the last R Types and the Continental this equates to 66 mph. Cars fitted with Norman Geeson’s axles and some of those exported to Australia have a slightly higher final drive ratio so that 74 mph is 3,000 rpm.
Oil
Some time ago an article appeared in the RREC bulletin in which it was stated that R-R are now supplying all new cars will Esso Ultron 5-50 fully synthetic oil and that they now recommend for all their cars after an engine rebuild. If your engine has not been rebuilt then 15-40 semi-synthetic is recommended. They are worried that detergent in fully synthetic oil might loosen detritus in the engine and block an oil way. This seems illogical to me because there is detergent in semi synthetic oil too.
Some time later in Spares Corner it was suggested that modern oils were too thin and that Castrol Classic oils should be used because they were thicker!
Company recommendations make sense in that modern oils are far better than what was available when the car was new and synthetic oils are a major advance that cannot be ignored. R-R actually stated that you might never need to rebuild your engine again if you used it.
The stated advantages of fully synthetic oils are:
1. That is thinner when cold and reaches everywhere in an engine more quickly on start up than old oils.
2. That it maintains its viscosity at far higher temperatures than conventional oil and will mean better oil pressure.
3. That it sticks to surfaces for longer than conventional oil so increases protection of infrequently used engines.
4. That it is more reluctant to dissolve in petrol than conventional oil and therefore protects the engine better from excessive flooding or when the choke is out.
5. That it withstands greater temperatures and pressures than conventional oils. This is important in our engines because cam profiles are not as wear resistant as modern ones and the tops of the bores wear more on long stroke engines. Both should be better protected.
I’ve used fully synthetic oil in very worn engines and rebuilt ones and, as you might expect, can detect no difference between it and the cheapest oil you can buy. What has convinced me to continue to using it is that oil experts confirm that it is major advance and there is anecdotal information from major manufacturers to support these claims. BMW for instance, tested it for 1,000,000 miles in a 3.25i and found the engine was still in spec when dismantled.
Its introduction has caused near hysteria in some traditionalists and all sorts of stories are in circulation about oil leaking from everywhere, engines seizing up, you name it and someone has a barmy story about it. None are logical or born out by the facts.
