Guys... quit the sniping.
Please.
Keep this on topic.

Ron
ClubCobra Moderator

Sorry, Ron;)

a-arm bushes
 

I spoke to my buddy in chassis engineering in 1999 when I had the same problem with my Miata.

It appears that a lot of manufacturers battle with this.
He mentioned using a different kind of a-arm bush to reduce the effect.

I can't remember the details and also lost contact since I moved.

What type of suspension bushes do you run? Did anybody try a different version?

Isn't vibration also related to diameter (in addition to speed)?
So smaller tires or bigger should vibrate at different speeds.

This will not really help to find out, but would be intersting to know anyway.
Pity that the US speed limit falls in that range...

Dominik, Cape Town

Shimmy
 

My Lonestar shimmys from 60-70 (not as bad during acceleration)
I just had the car aligned and found both caster and camber to be way off... so its possible that the Goodyear Eagle GT II's on Centerline rims could have worn enough to be a problem.. I'll have the run out and balancing checked and then spring for new tires.

FWIW some of the FFR guy's have this problem also. The BFG TA's have been the culprit and others badly balanced rims from the manufactuer. Some have installed Jeep steering stabilizers to both sides to eliminate this problem. Mounting brackets are needed to be fabbed and welded to the frame. You can see it at the FFcobra website under the FAQ's section. Click on steering vibration. G.

For what it's worth... A new set of Goodyears solved my problem..
However.. I blew the engine while testing them out. New 350 Chev. "Fastburn" crate motor has been installed ... life is good.

Hub or Lug Centric Wheels?
 

I know this may sound simple but shimming has caused me problems in the past. Rim manufactures make rims either hub centric (the big circle in the middle it the dead center but the lugs can be off) or lug centric where the dead center of the lugs is the center of the tire and is totally independent of the hub (look at my picture, I used 4 lugs cus I can't draw!). The problem is when you have the wheel balanced on a machine that is hub centric but have a lug centric wheel or vice-versa. The wheel will repeatedly be balanced on the machine but when you put it on the car it shimmies. This has been a problem for many Toyota truck owners (that use a stock lug centric wheel) when they go to a standard tire seller and have their wheel balanced on the standard hub centric machines that MOST of the tire seller’s use. The fix is to know how you wheel is manufactured and make sure you go to a tire place that can balance the type you have, probably a lug centric. He will need to use a lug centric adapter when balancing your wheels. I went to a few places that said “no problem, we can do that” to have the car shimmy as drive away. I have learned to take my truck to a Toyota dealer that charger $2.00 more and does it right the first time. When putting a lug centric wheel on you need to make sure to snug ALL the lugs in a "skip a lug" pattern before making them tight. This will center the wheel properly

Rwillia4:
Your post may be the on money for many cars. Keep in mind however, that many Cobra owners with non-lug wheels have the problem. I reduced the vibration in my SPF by having the tires "trued". www.amermac.com
Bob

I actually checked my wheels before mounting by "rolling" them on my lathe bed and put a dial indicator in the spindle chuck.

The centers were about .002 out. I can not turn the wheels ( saddle size ), so I live with it. But, I do not get a shake.

:3DSMILE:

Bob, I have never experienced the shake problem. The Classic Roadster Cobra was built by Don Scott and has a GM tilt steering column.

The tires are TA radial with 245 X 60 X 15 in front, Compomotive HB 8" , 4" backspace , and 275 X 60 X 15 in rear, Compomotive HB 9", 4.6 " backspace.

The tires were rebalanced when I moved the mounting of the tire's white print to the inside, no reason other than personal preference. The alignment is the same as when Don built the Cobra.

HAPPY HOLIDAYS

Regards

Don

Don:
Can I assume your steering column has a "rag joint"? If so, the vibration is eliminated before it gets to the steering wheel.

Bob

Bob,

Where in CT did you find the Chevy dealer with the tire machine you spoke of ? Did you have your tires trued up at Major Tire in Bridgeport ? For the record 1993 Unique, MG front end , Compomotive HB wheels and B.F. Goodrich tires. It starts to dance around 60mph.

Pete Wolff

Major Tire, dealt with Dave for truing. Hunter machine at Chevy dealer in Milford on Route 1. Hunter machine is overrated (in my opinion).

Bob

Bob, am I correct in assuming that the tire "truing" didn't correct your steering wheel shake ? I am planning on having mine done in the spring......worth it or not?

Don:
I stand corrected! I took my tires and wheels to Major Racing Traction in Bridgeport. They're at 20 Union Avenue, 203-367-7223, talk to Dave.

Pete:
It did not eliminate the shake but it significantly reduced it. Others I know say it all but eliminated it. A rag joint in the steering column would help a lot.

Bob

Bob:

Don Scott built my CR, no rag joint, his reply:

Don, I don't use a rag joint. I use a solid shaft with u-joints at each end to connect to the GM column and rack. The rag joint is usually a leather or rubber cushion between the rack and the steering shaft. It does help eliminate vibrations and steering wheel shake. Flaming river sells a joint with a vibration dampner built in. I have found that most of the time the problem is in the wheel balance and the alignment.
Don

As a new Cobra owner I had noticed the steering wheel shake, buit it did not feel like an out of balance thing. I was running Bridgestone Potenza 245/45/17 front and 275/40/17 rears. I wanted to get a little more rubber on the rear so changed the Bridgestone to the Goodyear IIs 245/45/17 front and 315/35/17 rear. Discount Tire did what they called a performance tune on the tires/wheels for an additional $10/tire and it is now smooth as glass with no wheel shake. I am running solid steering u joint. I don't know if the old tires were out, but they did not have to do anything with the alignment. If they are in your area you might give them a try.