Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Front end shake - Malvern Dance?

I was driving from our MOG autocross event back to the hotel which was 20 miles away(I'll post photos later). I was going about 55 mph and down hill when I had to start to slow down for an intersection. As I was slowly, but firmly pressing the brakes the front end starting to shake violently so I had to let off the brakes and give a little gas. It seemed like there was a harmonic point in which the vibration would occur and perpetuate it. It occurred for what felt like 8 seconds, but was probably more like 4. Does anyone have any suggestions for what could fix this? Very scary.
I have a pretty original 1967 +4 four seater. Here is my drive home after the weekend at MOG43 for the DC Morgan Club.
http://www.youtube.com/watch?v=M6vipxMA0h4&feature=youtu.be

I've not had it, but it sounds very much like it. The logical cure is a steering damper, see details on the Gomog website.
http://www.gomog.com/allmorgan2.html

Also a kit from Mulberry Fabrications:
http://www.mulfab.co.uk/our-products/8/steering-suspension/steering-damper

I'm sure others more knowledgeable re this problem will be along soon!

Nigel

Time to thoroughly check the front suspension, chassis etc.

While it feels scary, a harder press on the brake pedal to reduce speed will usually stop the wobble.

Spent over 18 months trying to cure mine (the kingpins / bushes etc. had all been replaced over a year earlier). Turned out there was a crack in a front chassis leg and there was rust forcing the triangulation plates away from the chassis (so losing support). Plates changed for neweer, much longer versions, crack(s) welded. Also fitted negative camber plates. With positive camber there isn't the natural damping effect, so a bump induced wobble can get worse, rather than reduce. All sorted by New Elms in the end.

Swap the front wheels with the rears and check at the same time if you've thrown a balance weight. If you've not had it before the chances are it's something simple.

For those who fiddle with camber: just what camber seems to suit the Morgan best for road use?

Hi Vitruvius, I'm new to Morgan but not to cars - including old cars. My first impression is that the braking has induced the shaking and that it could be the 'Malvern dance' but not for sure. I have learned that Morgans are prone to shake/shimmy and that it appears at a certain speed. All components included in the steering & hub construction has it's built-in natural 'shake' frequency and it will result in 'shake' if there is any disturbance at a certain speed. Usually the whole front end construction can 'handle' the disturbances; correct castor angle and steering dampers are vital but also the absence of play in all joints. In your case I get the feeling that your brakes were affected some way - water or oil/grease - causing uneven breaking forces, thus inducing the shake. Since it became violent there could be some play in any of all the relevant parts as king pins, steering box, joints etc.

Hi Vitruvius,Certainly sounds like the Morgan shuffle.Had this on my car when I bought it, used to occur around 45 MPH .Have since fitted new kingpins and bushes which has completely cured the problem.Check for movement in each wheel by jacking up the car one wheel at a time . Check by lifting the wheel from the bottom upwards and outwards,the ideal would not to feel any free play here.
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Regards Barry 78 4/4 4 Seater

Besides checking the system for wear and play, the friction damper on the hub is there to calm the shimmy you have experienced. The friction damping is between the bronze/brass plate and the top surfaces of the hub. If these bearing surfaces are well lubricated then this reduces the friction that you actually need. You will get more friction from that damper by running it with just a smear of light oil, that might be enough to control the shimmy.
https://sites.google.com/site/morganatica/70-modifications/vw-hydraulic-steering-damper
Regards PJB.

When this happened to our car, there were 2 loose bolts at the base of one King Pin - I had been too idle to do a spanner check after 2 long journeys. Lesson learnt.

This is proper Morgan Shimmy Vitruvius, as opposed to St.Malvern's dance (totally different thing!). Yes it's horrible! My old 4/4 I had in the early 80's suffered badly from it, in desperation I took it to the factory. The then chief test driver took it out then on return said it was the worse case he had ever seen outside the factory, he spent 30 mins or so adjusting the damper blades and shims then Perfect!
I had done this myself many a time to no avail. I think he may have checked the wheel balance etc.also but the damper blades appeared to be the main cause. It cost me £15 cash then, probably 2/3 days wages at the time !
It did return now and again after time but I was able to control it. 'Hope you get it sorted,do the above plus the usual checks, keep us informed!