Contrary to what one would think the two spring rates become cumulative when the springs are acting one against the other. This gives a very high initial spring rate but when the lower spring is freed, either in bump or due to cornering forces, the rate suddenly falls. This is what gives rise to the nodding dog syndrome.
I think that is part of SteveH & Harry's car's problem. When I had a look (admittedly passenger side while Harry was sitting in the car) there was no freedom on the rebound spring. I suspect more miles and resetting the suspension again may sort the nodding dog that is sometimes experienced.
Graham. You have just confirmed my suspicion. The springs are very high quality and will not settle for many, many miles. If incorrectly adjusted the problem should, and could, be resolved now.
The problem is that it is not easy to set the suspension because the suspension camber has the effect of locking the position of the hubs on the king pins. As the front of the car goes up and down the wheels have sideways forces exerted on them. While the car is rolling you would not even notice it but while the car is stationary just try bouncing the front end and you will see how rigid it is. If there were plates under the wheels that allowed them to slide sideways you would be able to bounce the front end quite easily.
The preload adjuster ring nuts should be set correctly by the installer (who, in my opinion, should rectify the adjustment if it is found to be incorrect) however with the C spanner supplied with the kit it is possible to make an adjustment even with the wheels on.
Firstly you need an absolutely level piece of pavement. As I drive in with the wheels absolutely straight ahead I bump the brakes lightly a couple of times to get the suspension to settle. Then lying down (on a piece of old carpet) at the front of the car I can then see and feel if the lower rebound springs are just touching the hub and are just free to turn. Note that in some cases the bottom of the rebound spring may be blocked from rotation in the lower camber adjustment plate, so a degree of judgement may be required.
With the wheels on the ring nuts can be adjusted, all be it with difficulty, by turning the wheels to the opposite side and accessing the adjuster from behind the wheel. If it is a matter of closing up a gap between the bottom of the hub and rebound spring the measurements can be taken and the ring nuts lowered by that amount. If, however, it is a matter of releasing pressure a bit of trial and error may be required. Raise the ring nuts by a few turns then, without locking them, swing the wheels straight ahead again, rock the car backwards and forwards an inch or two a couple of times to get the suspension to settle, then check the rebound spring. When all is satisfactory lock the upper ring nut down against the lower. Take the car for a drive and then check again.
Additional notes.
In theory the springs could be different one side from the other but in my case I have both sides adjusted with exactly the same thread exposed above the adjusters. My feeling is that for optimum results the adjusters should be set for the correct static ride height when at least the driver, or perhaps driver and passenger, are in the car but given that the passengers are almost over the rear wheel I don't think that they add very much load to the front so in practice it probably makes little difference.
There is a 20mm spacer provided with the kit which
must be used. For maximum ride height it is placed above the sliding hub and for minimum ride height it is placed below. Shim washers or different spacers could be used but they must add up to 20mm. At the moment I am running 10mm above and 10 mm below which effectively lowers the car by 10mm to compensate for the fact that I am using 195/65 R15 tyres which are 10mm taller than the standard tyres.
People speak very well of the Rutherford kit and without a doubt it works well but it does not offer adjustability or a rising rate system. I would certainly want to set it so that the lower rebound spring was not under load for the reasons I previously mentioned.
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