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MG TD TF 1500 - Vibration again

I have a vibration that starts around 50 MPH. The wheels appear to be running true. I checked the drive shaft to make sure the U-joint are in phase with each other. I did notice however that the I can wiggle the drive shaft around .020 at the spline connection. Would that be enough to cause my problem?
Thanks for your impute
Bill TD-24570
Bill Brown

To me that vibration would be caused by the wheels. Check tires for true roundness and then double check for wheel balance.
Sandy
Sanders

Yup , the drive shaft is rotating very fast at 50 mph,, so it wouldn't give you the vinratoon,, its the dreaded 50 mph shimmey caused by the wheels being out of true !!

Steve
SPW Wincze

I've had the same problem with my 54 TF. I got the wheels (wire wheels) balanced (several times). I did not shave the wheels. I don't think it's the drive shaft.
I changed the Moss standard A arm bushings to urethane and that helped.
There is some discussion in the archives about "scuttle" shake or vibration. I have heard that you can "drive through" it and it will smooth out. I doubt that and I can't bring myself to go that fast with that vibration.
I did a little vibration analysis. At 50 MPH the vibration is around 13 to 15 Hz. That relates roughly to the wheel size and rotation. That would excite the out-board hanging wings.
They are not supported that well. I think both the TF and TD.
The engineers were probably thinking about this when they added a connecting bar from wing to wing on the TF.
I think that the architecture lends itself to vibration issues. Everything has to be tightened down and secured. A-arm assembly, damper mounts, body to frame. Make things stiffer best you can.
I do drive mine daily summer and winter. Under 50 mph.
That's my history and I hope your vibration is not too bad.
Peter Dahlquist

Thanks Peter,
That is a thorough analysis. I've already ordered a new yoke an u-joint so I'll install that an also play around with tire pressures and see what happens.
Bill TD 24570
Bill Brown

There was a discussion some time ago that the TD wheels (pierced steel) ate not centered on the middle (big) hole such that routine balancing may introduce an imbalance. The discussion implied that the centering was through the lug holes and that most balancing doesn't use them. My new tires and wheels were balanced on the big center hole (before I heard of this issue) and I have a vibration (shimmy) at about 53mph. since I rarely exceed that speed, I've lived with it.

Perhaps more knowledgeable folk will chime in and confirm or correct me.

Jud
J. K. Chapin

It will not be enough to simply change the yoke and joint. You will need to have it ready balanced as well.
W A Chasser

Bill,

I had a similar vibration around 50mph in my TF with disk wheels caused by two problems:
1) My tires were out-of-round.
2) The left front brake drum is way out of balance. Can't be corrected by an off-car balancing system.

Mark at Doug's Alignment in Sanford Florida cured both problems.

First, he shaved the tires while on the car to make them round.
Second, he spin balanced the whole wheel assembly - tires/wheels/hubs/drums -- while on the car. The rear wheels must be mounted onto the front to shave and spin. (He didn't mount a rear wheel onto the left front because of the out-of-balance drum.)

Few shops still exist that can shave and balance on-the-car.

Jud is correct, the disk wheels on our T-cars are "Lug-Centric." The center of the wheel is determined by the center of the circumference of the lugs. Notice how the cone of the lug nuts moves the wheels as they are tightened to center the lug in the wheel. The gap between the hub and the center of the wheel confirms that the wheels are lug-centric.

If a shop balances your disk wheels off of the car, then ask for them to be mounted on the machine "lug-centrically", usually requires a separate attachment. This link explains:
https://www.gregsmithequipment.com/Hub-Centric-Vs-Lug-Centric

Here is a video of Doug's Alignment shaving and balancing the tires and wheels on my TF:
https://www.youtube.com/watch?v=CFvHeVzhepI

Lonnie
TF7211
LM Cook

Depends if it's a vibration or a shake
If it's tailshaft it could be tailshaft or engine/gearbox mountings
If it's a shake it's probably wheels
Just depends on the speed of the vibration
A tailshaft at that speed would be like a buzz/hum
Wheels more of a hop/shake
Best way is to jack the car up and support the rear axle on stands ,remove the rear wheels and run her up to 50mph and see if the vibration has gone -if it has it's wheel balance, if it's still there it's tailshaft

willy
William Revit

I just fitted a new set of tires on wire wheels. The rims were completely centered and balanced as well as the wheels. That made a dramatic improvement on the shake, so most of it was due to the wheels. I know that my front brake drums are not well balanced, which can be observed when they move freely. I am still looking for an idea to balance them individually (static balance would probably be sufficient).
There is still some vibration arount 3500rpm / 55 mph, but the difference vs the old wheels is significant.

Rgds Mike


Mike Fritsch

Willie, Lonnie and Jud et al, have made good points. To convert Jud's point to wire wheels, I have uploaded an image of an article (MGCC of South Australia) from 1988.

It points out that modern balance machines might not suit our wire wheels unless they have special FEMALE cones (to simulate the knockoff) to locate the outer end of the wheel centre.

There are two cures for this situation. 1: Make special cones to suit the modern computer balancer (locating on the same surface as the knockoff locates) or 2: Mount all wheels in a lathe/machine and "true-up" the surface where the modern balancer will locate with its male cone.

Cheers,
Bob Schapel


R L Schapel

The balancing cones are available, ordered a set from the U.K.

Shipping was not too bad really.

Peter
P G Gilvarry

Bob
Today was a lightbulb day
Your suggestion of trueing up the outer hole in the wheel to accept a boy taper is a fantastic idea----simple fix and no need for special balancer fittings afterwards
There's a shed down the road with a monster lathe, I reckon it will take a wheel, tyre and all
I know what I'm doing tomorrow----
willy
William Revit

For the wire wheels I took an old hub and had it bored large enough to fit on the shaft of the wheel balancer. Then mounted my wire wheels on that hub.
the result was a smooth running car.
Sanders

This has bothered me for years. And I think many T's will suffer this. Over the road vibration at 55 mph is about 13 Hz. Which is kind of low. Load path is thru the lower A arms/bushings directly to the frame. This is a forcing energy into the fenders and body panels. If there is any looseness this forcing energy can cause natural frequency. Much like the old days of worn ball joints going berserk and applying brakes shuts that down. My educated guess is the T's basic structure of the overhanging wings, attachment points etc. are prone to be excited at this natural frequency (13Hz) at 50-55 mph.
Dave Braun, and others, have commented on this vibration at speed and suggest you could accelerate thru this zone and calm down at 60 plus mph. This would make sense because the vibration before and after 13 Hz should not excite the car structure.
Peter Dahlquist

I believe I read sometime ago on this forum that some shake could be caused by excessive toe-in or toe-out. The TD should have about 1/4 in toe-in if I recall correctly. If one is spending time and $$ on a complete restoration then it should certainly be worthwhile to have the frame checked on a frame machine and the front end aligned to specs.

Jim
James Neel

No toe-in in a TD - 0.0 inches.
Lew Palmer

Best to have 1/8" or so if running radials.
Dave H
Dave Hill

I removed the bearings from a spare break drum,, Mounted it on a spin balance machine and balanced it,,The cones of the balance machine fit against the old bearing ridges..
Now, when I want to balance new tires, I first mount the brake drum, Then I mount the new tire and rim to that brake drum and balance it. This way, I am balancing the new tire and rim LUG CENTRIC, rather than using the old hole in the rim.
Hope this helps
Steve
SPW Wincze

Also I suffered from this nasty vibration. Of course, (steel) wheels properly balanced, drive shaft balanced, all wings fixings tight. Last year I had the front drums dynamically balanced but not satistying. Recently I took a friends suggestion and replaced my old metal fan by MOSS plastic 6 blades (sprayed black of course). And this made a tremendous difference: vibration is not completely gone but dramatically improved. And same on a friends TD
Huib Bruijstens

WOW, a lot to think about!
thanks all,
Bill TD-24570
Bill Brown

This thread was discussed between 21/08/2019 and 23/08/2019

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