Are we talking "cowl shimmy" or actual steering wheel shake?

Shimmy, Rattle, and Roll
 

Hormonics? Anyone who has worked as a collision technition will tell you that most cars have hormonic off-set weights possitioned on the chassis somewhere. I am certain that most Nissan Pathfinders have a 4 or so lb. weight bolted hanging off the frame just under the pasenger side "B" center pillar post. This is to counter-act the hormonics generated by the engine chassis/suspension. I believe we are all dealing with some hormonics in all makes of our cars. Shaving and truing tires and all the other remedies mentioned and you may still have a slight shaking due to the hormonics. Live with it and enjoy your ride, a small price to pay for our enjoyment of a real performance car.

Hey Jim:
Believe me I read your link. I've put a lot of thought and effort into trying to eliminate this problem. While I understand that it may go away for some owners when they balance the tires or get the wheels aligned, for some of us it just goes on.

I would love to put my tires on one of these Hunter machines your link recommended but I have not been able to find one. I am convinced that 90% the vibration comes from the tires with maybe 10% coming from the wheels. I understand that tires that are dimensionally round may not be round dynamically. When they roll under load they go up and down. When I worked for Armstrong Rubber (as a tire engineer for 12 years) we had a machine that could identify these out of (dynamically) round tires and correct them. It was only used for OE tires!

There is a good chance that little cars with big (heavy) tires are more prone to this condition than are heavy cars with little tires. One the harmonic sets up (60 to 80MPH) there is really no way to stop it. I think the shake comes and goes because the tires do not roll at the same rate and cancel and reinforce the vibration as the car progresses down the road.

I have been driving now for 40 years. When I started driving in 1962 there were no such thing as dynamic balancing or computerize alignment. In spite of lacking the new high tech gizmos cars of 40 years ago did not have steering wheel shake! I driven a number of rust buckets over the years and none of them had steering wheel shake!

Could it be that radial tires and Cobras do not get along well? Could it be that Trigo wheels are not round?

Bob

I didn't set up my Unique, but I can happily report that the steering (and car for that matter) are rock steady at all speeds. I'm running the standard setup i.e. MGB steering assembly and Compomotive 16" wheels and Goodyear rubber.

My Unique also has not had steering wheel shimmy, but it did have a cowl shake at around 60 mph. I got the wheels balanced
and it went away.
My friend's Classic roadsters has a harmonic type of body shudder at 60 to about65 mph. ( feels like it starts at the rear then
passes through the middle of the car and goes out the front, does this over and over) An inspection revealed that the rt rear tire
is out of round radially by about 1/8 " We suspect that is the cause. Does anyone know where to get a tire shaved in the Houston
area?
Steven:)
PS do they use shaving cream when doing so?:JEKYLHYDE

My Unique used to have a very noticeable shimmy at around 50 - 60 mph - I have to guess because the speedo didn't work back then. During the rebuild I swapped out the old MGB front suspension for Unique's newer coilover setup with the adjustable shocks, new rack, etc. At that time, I also installed 15 X 7.5 & 9.5 PS Eng. bolt ons with BFG 245 and 275's. Now there is no shimmy at any speed and I'm very pleasantly surprised at the quality of ride and handling. There is a bit of twitchiness at high speeds, though, due to a slight toe out up front which I will correct as soon as my tire shop finishes setting up their new alignment machine.

BOB IN CT:

THE LINK TO HUNTER'S SITE IN JIM C'S POST TAKES YOU TO HUNTER'S "SITE". AT THE TOP RIGHT CORNER OF THE PAGE CLICK ON "LOCATE A GSP9700".

I LIVE IN ASHBURN, VA (2.3 MILES FROM NOWHERE) AND THE SITE IMMEDIATELY PRODUCED 41 SHOPS WITHIN 25 MILES USING THE GSP9700. THE PAGE LETS YOU SEARCH A RADIUS OF 10, 25 OR 50 MILES. FIVE OF THE SHOPS ARE WITHIN SIX MILES.

GOOD HUNTING AND - - - - Y'ALL HAVE A REALLY GREAT DAY,

BLACKJACK

My older Unique was rock solid when I first got it with the 16" wheels and Z-rated Potenzas. When I replaced those with used 15" Compomotives and new BFG's it started shaking wildly at various speeds. After 3 trips to the wheel balancer only the front shakes slightly between 60 & 70. I met a guy with his own brand new mounting & balancing set-up and as soon as I get time I'll run them through the mill again.

Rich

Rich, question please
 

What year is your car? Or chassis number. What size tires have you run and have any of them rubbed.
Thanks
Rick

Rick,

It's a 1990, chassis #9063. The tires are 235/60's & 295/50's. And yes, if I hit a large dip in the road they rub. I think that's due more to the worn out rear springs than the tire size.

Rich

Thanks Rich
 

So they only rub on the rear? I am planning on going with the new Kumhos that are 255 and 275/60 and trying to get a feel for if someone has run that size. Currently I have 225/60 and 275/50 and they never rub.

Chassis 9063! I have chassis 9007. We should compare notes. Are you still running the MG front end? Jag brakes? What have you done to your chassis and brakes? I am anxious to compare notes with someone else.

Rick,

If I had it to do over again I'd go with the 255 & 275's.

As far as chassis & brakes, I haven't done a whole lot. The car still has the MGB front suspension, and other than some tired bushings, it handles great. The few things I have done, such as a 50% larger front sway bar and new steering couplers, have made a huge difference. Polyurethane bushings and new front Konis are on the schedule for this winter.

I want to see some pictures of your front suspension set up.

Rich

Rich,

Out or curiousity, why did you change your wheels? Sounds like you were better off before (ridewise). Did they look bad?

Tony

Tony,

I was better off ride-wise and the handling was much more crisp (crisper?). The old wheels were a black mesh, BBS style right out of the 80's. I wanted a more classic look and, at the same time, something different than all the other Cobras.

These have just the look I was after:

http://www.clubcobra.com/cgi-bin/pho...=2105&size=big

Rich

Rich,

Nice car, real nice wheels. If that's your house in the background, you must be related to Bill Gates!

Tony,

Thanks!

That's the summer place. Any resemblance to the Sun Valley Lodge in Sun Valley, Idaho is purely coincidental.

Rich

Unique chassis #9047
 

Hi guys - Good to see your posts! I'd be interested in comparing notes also. I running 245/60 and 295/50 BFG's on Americans. I have a slight steering shake around 60 that I have been trying to remedy. I think I'll try finding a shop to balance the tire assembly on the car. That seemed to worked for a couple of the other guys on this forum. I would be happy to hear what has worked on your cars also. Len

To you front end gurus:
Do you think adding a little more caster would help eliminate some of the shake reported here?

How Unique
 

Well this certainly has turned out to be a Unique thread!!

Rich... of course you post the coolest picture of your car ever, in front of my place... show off. :p

I sure hope some "shimmy remedy" comes from all of this. I Hope I hope I hope......

Zderf :3DSMILE: