Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Calming the front suspension.....

Science is science and seat of the pants is very subjective. I am convinced that Peter Ballard has it exactly correct when he says that there should be no force exerted by the upper and lower spring pushing against each other. Contrary to what one would think the two spring rates become cumalative 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.

Increasing the rate of the upper spring may simply mask the problem because the the accumulated spring rate will hold for so long that the lower spring seldom become free. This means that if you have an upper spring with 140 pounds per inch and a lower spring of say 200 pounds per inch the actual initial spring rate is 340 pounds per inch. Very rigid ride and a lot of initial roll resistance, but the moment the lower spring becomes free, say with a hard bump mid corner, the car will make a lurch to that side. Sure it can also be controlled with high damper settings but whilst it may be effective on good roads it would hardly be comfortable, and may be a bit disconcerting, on bad roads.

Peter Ballard has opted for more comfort with his spring rates and strongly specifies that the much higher rated rebound spring should be only just kissing the bottom of the sliding hub at static ride height. This strong rebound spring limits the rise of the outside wheel in cornering and reduces body roll. For those that require a more sporting suspension the Ballard designed race kit is available or, alternatively springs from the race kit could be ordered with the standard set up.

Which ever way you go I believe that the springs should be set so that you have a short high rate lower spring that is set, with spacers if necessary, to match the ride height required when it is at full extension, that is to say not under load. The upper spring should be set to support the car at that height.

The SSL (Suplex) kit makes this easy because it has adjusting ring nuts above the spring. It also has the advantage of having an inner rising rate spring that comes into effect in severe bumps and/or really hard cornering.

Having said all that the current range of trad Morgans have much improved springing and the SSL kit, I believe, is actually specified as standard for some markets so it could even be installed from new by the factory.

If you want to read Peter's more complete (and more correct) explanation of this topic it can be found at https://sites.google.com/site/morganatica/suspension/springs-progressive-rising-rate

I see nothing in Heinz's discussion of Mulfab 140 in/lb setup related to rebound springs. However I have removed My Suplex Kit and re-installed the Mulfab setup. I measured the gap and cut the rebound spring to fit the gap. There is no pressure at static. The rebound springs turn freely. I must say I prefer the Mulfab setup. But the difference in road handling is dramatic. The ride is more compliant with the Suplex kit installed and subjective. I think the Mulfab kit vs Suplex is apples vs oranges.

All,

Many thanks for your responses. Clearly a complicated and very subjective topic; it's currently well beyond my comprehension!

I must admit the Mulfab set up with 140lb springs initially appeals, and possibly a little cheaper than the Suplex kit?

Would this be a relatively easy DIY option? If not then I'll probably wait until replacing the kingpins (my cars on 16k miles so I guess that jobs probably not to far away).

Thanks again,

Andy

Really? Bit like Ferrari clutches then - just a few k cheaper.

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.

Sorry Howard,

I thought I'd read kingpins had a life span of around 20k miles, subject to the level of ongoing maintenance. Is that not the case?

I bought my car secondhand so I don't really know how well it had be looked after prior to my ownership.

Wouldn't know about Ferrari clutches, but standard king pins don't have a great life. Hence the hard chrome aftrermarket versions which should run to 50k plus provided regular lubrication and shrouds to keep out road crud.

Andy, I let it make together with a change of the king pins. You could PM Spanner Juggler as he has good experiences with changing to Mulfab 140 pound springs together with AVOs and some satisfied customers as well.

Button, is it possible you are referring to Peters' (Gambalunga) post?

Morgan front suspension is like asking how do you like your tea?

I like mine just weaker than average with no sugar. With milk.

The Rutherford/Mulfab set up with steering bearings is just right for me.

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.