Join Date: Mar 2017
Location: Surrey , England
Many thanks for the comments and advice - I confess to have run the car for a trip to Avignon and back last year without the sub-frame dampers on at all, as the old ones were useless. The vibration issues were probably present but I was struggling with more serious vibration which had been present for a year and for which Phantom Motors and Royce Service had given various diagnoses.
It was wheel to steering wheel vibration which kicked in at 60mph and became pretty dreadful the faster I travelled, so it was never tested beyond 85mph. Upon the various pieces of advice from the experts, I rebuilt the entire front suspension and steering , including rack and pinion box and ball-joints and steering column UJ coupling etc. Having removed and replaced the eccentric bolts, I then took the car to various specialists who claimed to be able to set up the geometry properly - I only felt this had been achieved after Royce did the work ( 3rd attempt ), although I am told that this is a very difficult exercise and not even convincing . However, the vibration continued and so I was advised to have the prop-shaft out and rebalanced amidst ghastly stories of how Crewe struggled to produce properly balanced prop-shafts etc. whether true or not I do not know ? I did not embark on this as it was a bridge too far for me while not being a convincing diagnosis.
The solution was brilliant to stumble across - I took the wheels to be balanced for the umpteenth time, being convinced that this was still the most likely cause, notwithstanding all the advice from others. This time I insisted that the chap balancing the wheels should take a reading before removing the weights - then balance the wheels and then de-mount and re-mount each wheel at least 90 degrees different from the first attempt - each time the wheel was massively out of balance on the second attempt. Upon very close examination it transpired that the cone being used on the wheel, to mount it on the balancing machine, very slightly impinged on the lug which houses the thread for the wheel centre covers. This was almost imperceptible until we discovered that we could slide a feeler gauge through the gap. I then ground off a chamfer from each lug so that the cone sat properly against the wheel and to my delight we found that we could obtain a 0 - 0 reading on each wheel even after turning the wheel on the machine.
Vibration has 99% disappeared and maybe the final contribution to achieve a smooth ride is to replace the sub-frame dampers, although I am told that the Conti R never aspired to be as silky smooth as previous models ??
Maybe this experience will assist anyone else who cannot get the wheels to stay in balance - I hope so, because any vibration ruins the joy of driving the car - maybe it should be the topic of a different thread. Anyway , I appreciate all the sincere advice given by others and will now speak to FS on Monday to negotiate a price to purchase their little dampers.