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MG TD TF 1500 - Shaking TD

On 4000 on the tacho my TD is starting to shake...
I remember a post on this phenomenon, I think it was several months ago. But unfortunately I do not remember the title...

Anybody with a better memory?

Thanks in advance!

Jasper
Jasper L Nederhoed

Jasper,
Is it at 4000, or at 50+ mph???? I have been batteling this "shimmey" for quite a while, and have not found a solution,,,it is a speed related shimmey in the steering wheel,,,

SPW
STEVE WINCZE

It was at 4000 with a speed of 80 kmh (50 mph). The whole car began to shake, not only the steering wheel.

Jasper

Jasper L Nederhoed

Bring the car up to the speed that it starts to shake,,, then depress the clutch,,, when the RPM's slow down, I believe that you will find that the shaking is speed related, and not RPM related,,,

SPW
STEVE WINCZE

I guess you're right.

In the future I must try to be more specific when something strange occurs...

Tomorrow I'll follow your suggestion and after that let you know what I find.

Jasper
Jasper L Nederhoed

Two wild guesses!

a) Rear wheels need balancing
b) Prop shaft out of balance. I read somewhere it's important to put the shaft back on in the same position it came off. I remember marking mine carefully with a file but I'm at a loss to figure out what happened to the marks!

AJ
A R Jones

Maybe you were thinking of my "4000 rpm" post? At that rpm the engine started to cut out and would not rev any faster. The resolution was a set of points that would not hold their setting. Resetting the gap solved the problem immediatly. (Since then I've replaced the points with new.)
Ed
efh Haskell

Ed,

That's the one! However, another issue than mine.

Thanks!

Jasper
Jasper L Nederhoed

Err so if it is speed related rather than RPM related does this help with the diagnosis ?
I have a similar problem at the same speed/RPM range- but I know my wheels are balanced but have buckles and run out of true.
Frankly I am suprised that the problem only occurs in such a narrow range give the expression on the face of the last guy who tried to balance them...

:-)

Dave 1955 TF
Dave Moore

"Rocky", my '52, does it between 55 and 57MPH....Really weird. Once I get the speed up to 60, it smooths out...
Prior to that , no real problem...
I am chalking mine up to stiff springs, and low fluid in one of the rear shocks...but I don't know...
I am going to look for a tire balancer that will do it either on the car, or with a lug-centered machine.
If that doesn't fix it, then I will look for other reasons.
Edward
E.B. Wesson

I have it also but between 54 and 57 mph.
Bruce Cunha

The bane of my TF driving enjoyment, the shake at about 53 to about 57 mph. Isn't it interesting how many of us have the same issue. Was it designed in?
I have done several things that have helped a little bit: I had the drive shaft balanced, rebuilt a bad front shock, the pertronix and good timing with an advance timing light helped a little. I had one wire wheel out of true. Had that trued up this summer. THAT helped quite a bit. I am comfident that the shake is a wheel balance issue. You guys who have access to "on the car" balance work should feel lucky. I'll bet most of us don't. I did have the other wheel/tires balanced in August by a local tire shop that just bought a new Hunter spin machine. I wonder if it is the machine Steve W mentioned in his nearby thread. Better balancing helped.
I guess I am 90% better off than I was a year ago, for all these interventions.
Our cars are old! That is true.

Tom
'54 TF
Tom Norby

Steve,

I've checked the shaking behavior today. And yes, it's related to speed. To be more precise the shaking occurs between 55 and 57 mph. Above that range the shaking disappears.

Jasper

Jasper L Nederhoed

Same...drives me crazy. Sometimes it doesn't shimmy...then it will come back again (while keeping the same speed...58ish)
gblawson(gordon- TD27667)

Gordon,

Yours too? Could it be the color? ;-)

Jasper
Jasper L Nederhoed

Just to further annoy me, if the car is going "fast" , on a smooth road, with expansion strips, it is just plain uncomfortable....The stiff suspension seems to transmit about every imperfection of the road....
I remember , many years ago, that British Car afficianados, would say the cars rode "like a three-legged camel!"...But, then, that's why they call them "Sports Cars". It's not your father's Oldsmobile, for sure!
Edward
E.B. Wesson

I'M AMAZED AT HOW MANY HAVE THIS SYMPTOM!!!!!!! I'M SURE THERE ARE MORE OUT THERE,,,what do the race cars do???
STEVE WINCZE

I think my speedo did drugs with the previous owner and I disconnected it. Now I know approx. how fast I'm driving
Peter Dahlquist

I think this is "cowl shake". Remember the T-series chassis and tub are pretty flexible. The scuttle hoop was added very early in production to help cure this. Any slight imbalance, out of round,etc. just sets up this shaking. The drag coefficient had to be something like a brick, so I think aerodynamic buffeting contributes. I have really round Michelins, balanced brake drums, and still some shake high 50mph range. It comes and goes, like Gordon describes. Before restoration it was vastly worse, as most of the upper right tub wood was vaporized, so everything just flopped and rattled around. George
George Butz

Mine is just like the above with a mind of its own between 55-60. I think that is right, can't really tell with the way the speedo needle bounces around.
I have learned to drive outside of that area on the speedo and just slow down. One item of note, my knuckles are not nearly as white at slower speeds.

Tim
tw hager

FYI, the first gen Miatas have this same issue around 65. You will see a lot of people make this claim.

the secret for Miatas is balancing with a road force balancer and keeping tire pressure down to 26 psi or so.

I do the same with my TD and only notice a shimmy slightly now at 60mph
L Rutt

George, you are right. It is the Scuttle Shake. Most cars have it to some degree or another. I dont know at what speed my car does it but it is between 3300-3500 rpm's. goes away above that and below but it is there. I have balanced the engine, driveshaft, clutch wheels and all and it still happens. It does not happen in the lower gears, only in 4th. There has been a lot of discussion on this board and at various club functions I have been at and most agree it is the scuttle shake caused by most likely some sort of harmonics.
Tom Maine (TD8105)

Jasper,
One more area to check is the front wheel alignment. Specifications call for zero toe-in.

Run the car with wheels straight, onto a flat surface, and stop, so you can measure them. The distance between the wheels ought to be identical. A little bit of toe-in won't hurt, but if the front is wider than the rear, toe-out, the front wheels can "hunt" sideways or shimmy.

Obviously tire pressures, roundness, balance, bent/crooked wheels, are factors that you can examine.

Good Luck!
JIM

Jim Northrup

Jasper,
Jim is correct that the WSM calls for 0 toe-in, but in my seemingly endless search to find a cure for this syndrome, I have found that adjusting the car to have more toe-in helps to lessen the wheel shimmey,, experiment with more toe-in on your car and see if this helps,
.
.
SPW
STEVE WINCZE

All of you, thanks very much for the response. Important to know that many cars face this shaking behaviour. Well, as a first step I set the tire pressure to 2,0 ato in stead of 1,8 and that alone helped to minimize the shaking! Thanks again!

Jasper
Jasper L Nederhoed

I agree with George Butz about the aerodynamics. If you look at the profile of the wings on the car they areformed like an aircraft wing and are produsing lift.
With a little crosswing you will get lift on the side against te wind and turbulence over theopposit wing.The front starts to chake.
Just a wild asumption from my knowlege of
aerodynamics after 8 years of working with
aircrafts in the Air Force and 40 years with
modelaircrafts.

Thoralf, Norway TD 4490."Themosquito the wooden wonder.
Thoralf Sorensen (TD4490)

Maybe we should add a front "spoiler", like NASCAR does!
After all , our motto is "Safety Fast"!
Edward
E.B. Wesson

This thread was discussed between 13/10/2011 and 23/10/2011

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