Gentlemen,
With how new most of your cars are, I highly doubt it is anything other then the tires or wheels. Like I posted earlier, I had to have my front tires BALANCED ON THE CAR. I had zero vibration till I put new tires on my car. And they weren't cheap ones. I put Michelin Pilots on it. Then the vibration started. I took them off three times to have them balanced, road force balanced, check tires and wheels for roundness, etc. Every person said the last guy did them wrong. And every time they still vibrated. After they were done on the car, they are next to perfect.:3DSMILE:
Scott

Hopefully you have already resolved your problem. I also have SPO 2028 and had the same problem. I had the wheels computer balenced and got the same shimmy at 60 and up. I then had them Hunter balanced. That's where they put a motor that turns the wheel on the car and then they make the appropriate weight add/removal.

Problem resolved. It has not shimmied since. The Hunter balancing system is really a step back in time. It used to be big in the 60's and 70's until computer balancing came in. However, since our cars are so light, this is really the only way to go.

Good luck.

That being said, there may be some of you that have some imbalance in the brake rotor assembly.

That's the beauty
 

Of having the tires balanced on the car...that looks like the first and best option to me, but unfortunately I have not been able (as yet) to find anyone in the Northwest that does it...but if I do, I will have it done even though my problem is acceptable now...

Didn't know it was called hunter balanced.:confused: I did see the machine they used to get the tire up to speed. It looked like it was from the 1940's!
If you are patient, you could buy the stick on weights and do it your self. I balance rotors on our 1000 hp high speed wood grinders basically the same way. Get it up to speed, see how bad it vibrates. Add weight in a random location and see if it gets better or worse. Make a note and add weight or subtract weight. You could probably get it done with about a tank full of gas!!
On my car, it ended up being only the drivers side front. They ended up with weights to the far inside, and a couple of ounces in between the webs only in one spot.
Like Rick said, it can be any part of the rotating parts. I new it was the tire, since mine was fine before the new set.
Scott

PS: I'm sure you won't find a regular tire shop to do this. The place I took my car was a place for high performance cars and race track set ups.

If you are patient, you could buy the stick on weights and do it your self.,

And you wonder why I drink so much alchol, jeeeezzzzz.

Steering Vibe
 

Put Another Set(the Original 15 '') Back On The Car And Took Off The 17"" And The Pilots. The Steering Wheel Still Vibrates, I Think It Is Worse With The 15'' And Eagle Gt II. It Happens At The Speed That Is Common , In This Thread (65-70 Mph). Then Stops.
I Will Have To Re Torque The Pins And See If I Get As Lucky As BartRuff1 Did. Tightened The Steering Rack And It Made No Difference Either. I Will Post Any Findings When It IS Fixed.

Shaky Blue 427

A lot of balance problems come from pretty wide wheels ( pretty wheels that are pretty wide) where there is a resistance to put weights (ughly) on the out side of the rim and all the weights are on the inside where they aren't visable. This compounds the shake problem because adding all the denser mass lead to one spot causes a cross talk coupled vibration to the outter side---it will be in static balance but gets an wobble at a set higher rotational speed--probably about the rotation rpms of 65-70 mph

Another vibration area can come from the driveshaft as it is very short ( creates higher angle from mis alignment) and the critical speed could be as low as 2000-3000 rpms

Jerry

Scott,
Where did you get your wheels on car balanced here in the Bay Area?

Thanks,
Dan

Dan,
You can check with Top of The Hill Performance Center in Livermore and they should be able to point you in the right direction.
www.topofthehillpc.com

I just purchased a New in the box set of Superformance 15" rims and brought them to Roger Kraus Racing to have them install a new set of GT BB's.

After reading all these "vibrations" posts I sort of made a big deal that I wanted the best possible balance on my new wheels. Especially on the GY BB's.

After a few hours Roger Kraus gave a me a call to tell me that they tested the balance on the bare rims first and that each of the the front rims (without tires) require 4 to 6 ounces of weights just to get the rims balanced. That is a lot of weight...
Let me add that tires, alignment, balancing, and racing with what Roger Kraus specializes in for the past 20 to 25 year. They are good.

He then mentioned that most people blame the tires without checking the rims. this makes sense, but I have not read that on any of the posts on cc yet.

I called the SPF dealer where I purchased the rims from and he said that either the rims are damaged or all the SPF rims would have the same problem as they are all made from the same mold. This does make sense so I'm not sure I'm going to exchange them.

Is that common for New OEM Superformance rims to be so out of balance?

Thanks,
Dan

I believe SPF uses Vintage Wheels for its Cobras these days. Many happy customers here.

Custom Alignment in Mountain View.http://www.customalignment.com/

Scott

interesting , i had a little vibration on the freeway but it went away in 10 mins.

still have to go see the guys in mtn view.

4 to 6 oz of weight imbalance on the rim is alot. I am sure no rim or tire is perfect nor is the stiffness in the tiresidewall consistent. I would attempt to find a manufactures spec on rim imbalance. Here is a calculation I did for discount tire when they pissed me off one time.

"I visited Bay Area Blvd Discount Tire today (9/11/03). I noticed when the Tech balanced one of my tires, the balance machine indicated the tire to be .25 oz out of balance after he felt he was done balancing the tire. I notified the salesperson about the unbalance, the salesperson felt .25 oz was not enough to worry about. Being an engineer, I performed calculations on the force generated on the wheel assembly by the .25 oz of unbalance. As you can see by the calculations below at 65 mph, the .25 oz unbalance causes a force equal to 4.075 lbs. to act on the wheel/car 14 times per second!! This is what causes vibration issues and customer dissatisfaction. The other three tires were balanced to zero, how much longer would have it taken to balance the one wheel correctly, 30 seconds. Imagine being hit in the face by 4.075 lbs, 14 times per second, do you think you would feel it? Please share with your Techs so they can understand the importance of balancing a tire properly. As usual the customer pays the price with time and money. One thing I did gain from this experience is a story I can tell everyone I know about the ability of Bay Area Blvd Discount Tire.

Tire Imbalance Calculation

Tire Size P215/65R15
Rim Size 15”
Section Height of Tire = .65*215mm=139.75mm = 5.50 inches
Overall Diameter of Tire / Wheel assembly = 26 inches
Circumference of Tire = 3.14 (26) = 81.64 inches = 6.80 feet
RPM @ 65 MPH = 6600 ft/min * 1 rev / 6.80 ft = 970 RPM = 16.17 RPS
Force of unbalance in lbs = 1.77*W*R*(RPM/1000)^2
W= Weight in ounces
R= Radius in inches
Force of unbalance in lbs due to .25 oz unbalance at 65 MPH
F(lbs) = 1.77*.25oz*13*(970/1000)^2 = 4.075 lbs
According to the calculation at 75 MPH, 14 time per second 4.075lbs is acting on the tire!! The force goes up exponentially with speed, at 75 mph the force is 5.41 lbs, 16.17 times a second.

P.S.
I did contact the assistance service manager, James, he was very polite and agreed the service should have been performed differently. He suggested I bring the car back to have the issue resolved. Since my hourly rate is $75/hour, the better alternative for me is to take it elsewhere, where it can be done right the first time and minimize my time loss." [/i]

I had my bfg and 15" SPF rims checked with no weights and the whole assemlby was only out .75oz, had no vibration before the balance or after. Have them document what they found and spend some more of your valuable time trying to straighten out an incompenetent manufacuter.

madmaxx,

Your 15" SPF rims were dynamically balanced tested and they were only off .75oz?
That tells me that my SPF rims must be out of spec. If I can find one for the rims.

When I called the SPF dealer and informed him of the unbalance findings on the rims alone, they said that the SPF rims are made in a mold in the Africa factory and it is not possible to be different from the rest of all the rims that they mfr unless the rims are damaged or bent. There is no visible signs of damage from shipment.

It's going to be difficult to exchange these rims without a spec form SPF. Any ideas on how to get one?

Thanks,
Dan

Yes mine were .75oz out of balance for the assemlby. This could mean the tire was out of balance 1.0 oz and the wheel 1.75oz and they complimented each other to reduce total out of balance to .75oz. I had some old GM shop manuals the real ones (Helm) and they always had a spec for rim imbalance, run out etc. The specs exist you just have to find the manual and then convince the manufacturer if GM feels they are necessary what is your justification why they are not.

I do not care if the rims were made on the moon, their mold may be bad, how they poured the mold was wrong, who knows, tell the idiot on the phone to let you talk to the qualilty control over the molding process.

I would instruct the shop to give you details of the imbalance on each wheel. If they are all out the exact same then it is a poor manufacturing process, if one is out more than the others, greater than 25% than it is defective.

There are no spots on the wheel to grind off to get it balanced so they have to add weights. I would have them mount the tires, road force balance and then dynamic balance and if they can get zero, take it for a ride and see if you get any vibration. You can balance a spinning stick but that does not make it round, I would be more concerend with rim runout, radially and axially, if the wheel is shaped like an egg and wobbles then you will always have vibration regardless of what the balance is.

I would doubt that they only have one mold.

Gents,

Some of this could have been already covered but I wanted to share my experience/remedy with this issue.

My car is old - 186. I have the original goodyear gt yellow letter tires.

Had the same vibration that sets up in the 60s and settles down. Before the remedy it did it all the time and it was an announcance.

What I did was:

Had the tires tested for runout. They are very bad but I didn't want to give up the vintage yellow letters.
Instead of 18.5 lbs I have running 28.5.
Had the car 4 wheel aligned. Twice. Having a pro shop very experienced in 4 wheel alingment made a huge difference.
Tighthened the adjustment on the streeing box to the max.

The results:

I get it the vibration sometimes...not all the time now.
It is not nearly has bad as before. I suspect if I had round tires it would be fine
When I get it now it is a very percise speed and leaves versus hanging around from 60-70.

That's my report.

Best,

JEff