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Leroy #744428 13/06/22 06:24 AM
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Leroy, I`m NO expert. I have read of shimmy or St Malvern`s dance over the years which could rise to almost uncontrollable levels in the days when tyres were thinner and had less of a footprint on the road surface thus less able to reduce shimmy, at which time the damper played a part in reducing the shimmy effect. With modifications made to reduce the amount of steering effort, if there was a tendency to shimmy, what are the chances that such modifications might exacerbate the effect..?

As to the actual causes of shimmy there have been many theories and possibilities starting out with wheel balance through play in the steering gear, and ending up around rake or trail.. adjusting cross heads etc. etc. etc.. Morgan foibles were ever accepted as part of their endearing nature, and it seems many a Mog was somewhat spoiled by the attempts of their owners to modify the foibles away..?

I think Trad Morgans can indeed run well, but within the limitations of their initial design. My old +8 has zero shimmy, the suspension is close to standard spec other than stainless king pins.

Good luck in resolving your issues, it can all be part of the fun...

Leroy #744432 13/06/22 06:38 AM
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Scruffy Oik
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Originally Posted by Leroy
After installing some bearings under the main spring and removing the damper blades I expected the shimmy to go, but it's still there.


Put your damper blades back on. The steering bearings decouple the main springs from the stub axle, but they won't stop shimmy caused by the steering angle being too steep.


Tim H.
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Hamwich #744436 13/06/22 07:20 AM
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Originally Posted by Hamwich
Originally Posted by Leroy
After installing some bearings under the main spring and removing the damper blades I expected the shimmy to go, but it's still there.


Put your damper blades back on. The steering bearings decouple the main springs from the stub axle, but they won't stop shimmy caused by the steering angle being too steep.

So that would suggest Tim that all post damper blade models with R & P steering will suffer from shimmy, which is clearly not the case. I can't see anything in later Morgan front suspension/steering evolution that would allow shimmy unless rack/kingpin/bush/bearing wear, tyre problem or some adjustable, including ride height not optimised.

As Simon suggests having track rods horizontal at static ride height is best compromise.


Richard

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RichardV6 #744446 13/06/22 08:29 AM
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Originally Posted by RichardV6


As Simon suggests having track rods horizontal at static ride height is best compromise.


Not horizontal at ride height- perpendicular to the kingpins....


Simon @ Sifab.co.uk

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SimonH #744454 13/06/22 09:46 AM
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Originally Posted by SimonH
Originally Posted by RichardV6


As Simon suggests having track rods horizontal at static ride height is best compromise.


Not horizontal at ride height- perpendicular to the kingpins....

Thanks, yes that makes sense thumbs


Richard

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Leroy #744460 13/06/22 11:47 AM
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I was thinking of checking the toe in, but I recall when the new tires were put on last year that the 50 year old wire wheels are not perfect. There is a definite wobble side to side when they are spun. I don't notice it when driving, But if toe in should only be 1/8", well the wobble is a little more than that I suspect. How do you measure the toe in accurately?


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Leroy #744461 13/06/22 11:59 AM
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PaulyG, I suspect you would be waisting time trying to determine the tracking of your Morgan with wheels that do not run true. The track measurement (toe in) it usually ascertained by measuring the distance between the the two front wheels at their rims, and a variety of means have been used over the years to measure this.

Leroy #744482 13/06/22 03:17 PM
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My thought as well. The only way I think I could possibly do it is off the brake rotor. Though it would have to more like 1/16"


Paul

73 4/4 "Henry A"
53 +4 Flat Rad "Pug"
84 Citoen 2CV Spec "BeBe"
60 MGA
https://morgan34.org/
PaulyG #744485 13/06/22 03:29 PM
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Originally Posted by PaulyG
My thought as well. The only way I think I could possibly do it is off the brake rotor. Though it would have to more like 1/16"


Or get the wheels straightened?


Simon @ Sifab.co.uk

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Leroy #744487 13/06/22 04:09 PM
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I get the feeling that would be an expensive preposition, but maybe not. Something to look into. Not way out, and I don't feel it when driving, but for measuring Toe In it wouldn't work.

If I get them straightened once every 50 years I won't have to do it again until I'm 110!


Paul

73 4/4 "Henry A"
53 +4 Flat Rad "Pug"
84 Citoen 2CV Spec "BeBe"
60 MGA
https://morgan34.org/
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