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Wheel Shimmy

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Judge Jeffs Avatar
Judge Jeffs Gold Member Bill Jeffries
Chichester, West Sussex, UK   GBR
1959 MG MGA "Maggie"
In reply to # 3807747 by JimNH the spec for alignment is zero degrees toe in - both wheels straight ahead. I find that a very small bit of toe in is desirable, however - and makes the car handle better (less "skittish"winking smiley at speed.

Other than that, and assuming it's not the wheel balancing or the tires themselves, I would guess something has been mis-assembled during the rebuild.

Do you have anohter MGA close by that you can do a side-by-side comparison with?

HOw about borrowing the other guys' wheels and tires to see if that solves it? Do your wheels on his car create a shimmy?

JIM in NH

Hi Jim,
The tracking has been checked and the car handles very well and I’m confident over the alignment of the suspension. However, I will recheck everything.
I’ve got a mate with a spare set of wheels which we will try if all else fails thanks.
Bill.

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Judge Jeffs Avatar
Judge Jeffs Gold Member Bill Jeffries
Chichester, West Sussex, UK   GBR
1959 MG MGA "Maggie"
In reply to # 3807865 by Redhawk1689 Do you know anyone else that has wire wheels near you? If so, (I know this would be asking a lot) you might try swapping all wheels and see if that solves the problem. At least then you would know it is the wheels or that it isn't! With knock-offs, this little experiment shouldn't take more than an hour or two at most.

Steven,
Sorry I didn’t make it clear, they’re original steel wheels.
Thanks.

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Judge Jeffs Avatar
Judge Jeffs Gold Member Bill Jeffries
Chichester, West Sussex, UK   GBR
1959 MG MGA "Maggie"
To add to the thread, suggestions from an old friend that worked for MG Abingdon in BL days.
Bill,



Below (a) is a simple check that may be the cause of the problem, particularly that you say one wheel is not true!!

Are all 4 wheels running in parallel, it could be that the rear axle is misaligned, so checking the wheel base on each side may a good check, or have it 4wheel aligned?



(a)Support the car so the wheel is free to turn. Place a reference pointer physically near the tyre, and give the wheel a spin. Check lateral run out of the edge of the wheel rim first. If the wheel runs true within 1/8 inch all the way around on both sides, this is probably not a problem. If the wheel rim runs more that 1/8 inch out of plane, then you should repair or replace the wheel before you worry too much about the tire(s). Lateral run out as much as 1/4 inch at the edge of the wheel rim will definitely cause this sort of shaking problem at road speed.

Assuming the wheel itself runs true within 1/8 inch, then place the pointer near the tyre tread, spin the wheel again, and check for lateral run out of the tyre. Apparently, this tracking problem can cause a steering system wobble with each rotation of the wheel that can induce a chassis shake very similar to a wheel out of balance. The shake caused by this tread tracking error may be felt more at the steering wheel. The only real cure for a crooked tyre problem is to replace the tyre.



dc





From: Bill Jeffries [mailto:billnjeffries@gmail.com]
Sent: 10 September 2018 18:50
To: Dave Cato; Ray Hadaway
Subject: Wheel Balance.

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3066james Avatar
3066james Gold Member Jim Cheatham
Amelia, VA, USA   USA
Don’t drive faster than 64 mph! smiling smiley

Sounds like others have made all of the suggestions I can think of. Have you had an alignment done?

Jim

In reply to # 3807291 by Judge Jeffs Ongoing issue on the A with wheel shimmy, which starts at 65, progressively worsens as speed increases and transmits up through the steering wheel.

Bill.
www.mgarestoration.com

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Judge Jeffs Avatar
Judge Jeffs Gold Member Bill Jeffries
Chichester, West Sussex, UK   GBR
1959 MG MGA "Maggie"
Jim,
Yes, alignment done and all ok when first back on the road, but I’m going to check it all again.
I do try to keep at sensible speeds, but I’m not always sensible! It just loves to be driven hard.
Bill.

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Judge Jeffs Avatar
Judge Jeffs Gold Member Bill Jeffries
Chichester, West Sussex, UK   GBR
1959 MG MGA "Maggie"
Spent the morning going through all the possible causes of the wheel shimmy.
I checked sidewall and tread runout - zero at sidewalls, but both fronts have about 1/8th” runout at the tread.
I then checked front wheel bearings and then all suspension and steering mountings, shock absorbers etc.
The only thing I found was that one of the front shocks was dry, which I think I might have failed to check when I fitted the new pair.
The front and rear wheels are parallel.
On testing, the refilled shock made a difference to general handling, but unfortunately the shimmy still comes in at 70 and is unpleasant.
I think the next step is to try another set of wheels and tyres.
Bill.


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ghnl Avatar
ghnl Silver Member Eric Russell
Mebane, NC, USA   USA
1961 MG MGA "Calvin"
Nice looking pointer! Did you also try it along the tread - not just the sidewall?

And, even though they have been balanced (keeping in mind a square tire can be balanced...), there is still the possibility of a 'road force imbalance'. Think of it as a stiff area in the tire's tread. As the tires goes around this stiff area doesn't flex the same as the rest of the tire causing it to move up & down mimicking an imbalance.



Eric Russell ~ Mebane, NC
1961 MGA #61, 1981 Alfa Romeo GTV6, 1984 Alfa Romeo Spider, 1991 Honda ST1100

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Judge Jeffs Avatar
Judge Jeffs Gold Member Bill Jeffries
Chichester, West Sussex, UK   GBR
1959 MG MGA "Maggie"
In reply to # 3808930 by ghnl Nice looking pointer! Did you also try it along the tread - not just the sidewall?

And, even though they have been balanced (keeping in mind a square tire can be balanced...), there is still the possibility of a 'road force imbalance'. Think of it as a stiff area in the tire's tread. As the tires goes around this stiff area doesn't flex the same as the rest of the tire causing it to move up & down mimicking an imbalance.

Yes, I tested the runout on the tread section and there was a variance of about 1/8th inch on one side. I’m not sure if that’s enough to make the level of imbalance that I’m experiencing.
But what you say makes sense.
Bill.

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Blueosprey90 Avatar
Blueosprey90 Jeff Sienkiewicz
New Milford, CT, USA   USA
Judge Jeffs Avatar
Judge Jeffs Gold Member Bill Jeffries
Chichester, West Sussex, UK   GBR
1959 MG MGA "Maggie"
Thanks Jeff, but that is aimed at touchy skittish steering at speeds, while mine is a classic wobble felt through the steering wheel.
All the checks mentioned in Barney’s piece have been carried out and all components were overhauled or new, including the tyres.
I’m going to fit a set of modern alloys from a friends 57 coupe, that had a similar problem on its original steel wheels.
Bill.

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mgaex189 Avatar
mgaex189 Gold Member Giovanni Delicio
Obrigheim, Rheinpfalz, Germany   DEU
1955 MG MGA 1500 "C2"
1955 MG MGA 1500 "4-seater"
1955 MG MGA 1500 "C1"
1960 MG MGA 1600 Coupe    & more
Hi Jeff,

did you use standard bushing on the lower control arm ?

If you use the bushing set of an MGB GT V8 (Moss UK parts# BHH1123) the car will act more stable.


Gio

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Judge Jeffs Avatar
Judge Jeffs Gold Member Bill Jeffries
Chichester, West Sussex, UK   GBR
1959 MG MGA "Maggie"
In reply to # 3809312 by mgaex189 Hi Jeff,

did you use standard bushing on the lower control arm ?

If you use the bushing set of an MGB GT V8 (Moss UK parts# BHH1123) the car will act more stable.


Gio

Thanks Gio
Yes, I used V8 bushes in the rebuild.
Bill.

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mgaex189 Avatar
mgaex189 Gold Member Giovanni Delicio
Obrigheim, Rheinpfalz, Germany   DEU
1955 MG MGA 1500 "C2"
1955 MG MGA 1500 "4-seater"
1955 MG MGA 1500 "C1"
1960 MG MGA 1600 Coupe    & more
The last solution would be to install a dashcam on the front wing and see what happens while driving faster than 70 miles !!

Gio

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Judge Jeffs Avatar
Judge Jeffs Gold Member Bill Jeffries
Chichester, West Sussex, UK   GBR
1959 MG MGA "Maggie"
Update on shimmy problem.
I took on board the suggestion that balancing the wheels off the car on a machine that mounts the wheel on a post, that uses the wheel centre (not the four wheel studs, could be the cause of my ongoing problem.
I recently found a shop that has an adaptor that enables the wheels to be mounted as they would be on the car.
The finding was that it did make a difference, but did not cure the problem.
I then decided to recheck the front wheel alignment as a last resort.
I’d had the tracking set by the shop that fitted the tyres and assumed it would be spot on. What do they say....never assume....!
Anyway, I used the old fashioned string method which I learnt in my apprentice days, which involves...yes, string, axle stands and a steel rule (see photos).
The result was that one side was toing-in half an inch, not just the odd degree!
Having reset it to a very slight toe-in on both sides, unsurprisingly the improvement is enormous, both in the shimmy, but also in the reduction in skittishness over drain covers, potholes and the like.
There is still a slight shimmy through the steering at 70+, but nothing I can’t live with. I guess it’s possibly 60 year old wheels.


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MGA1962 Avatar
MGA1962 DAVID JONES
Hop Bottom, PA, USA   USA
1962 MG MGA
I had the same frustration on my MGA with Vredesteins tires.

I found the solution here.

http://www.ktvintagecars.com/tiretruing.html



It did wonders for my car and and made driving much more enjoyable.

Dave

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