front end vibration

[thunder1]

at around 60 mph I get front end viberation, Ihave both tires balanced on car still it shake and not just a little. I use my dial indicator and the run out was .0025 to .0035 on the face and i.d of rim is this within specs I don,t know I don't think it,s the drive shaft had it replace and it had the same problem any ideas? Backdraft #84

[Tony Aprile]

Thunder1

Check out these other threads

Steering Wheel Shake, a Poll

Steering Wheel Shake, A solution!

They both deal with the problem

Tony

[Bob In Ct]

Ed:
It's the tires. they are not dimensionally or dynamically round. The fact that most Cobras do not have rubber flex couplings (rag joints) in their steering systems to dampen the vibration is the other side of the problem.

Although many Cobra owners feel this is a balance problem, it is not.

Bob

[JayBar]

Thunder1,
Had the same problem, called Reg, who suggusted the following.
Jack up the front, loosen all the lug nuts. Then go around the pattern turning one or two turns each, this centers the wheel.
In my case it worked great.
Jay B

[Snak Iyz]

#127 has the 'big' shake as well at 60-68mph, in addition to a little tire/wheel shimmy I am trying to figure out.

All I know is that I called my dealer (CA Cobra) and he sent a note back saying he gave Reg a heads up on my problem and asked me to call him. He called it a manufacturers issue...(????) All I know is I have a shake.... Also, my car feel very scattered going over rough road, etc. Don't know if you other guys are feeling this as well.

Hopefully I will speak with Reg soon and get it figured.

jaybar - thanks for the suggestion. I will give this a try for the shimmy.

If anyone receives more feedback, please post as soon as you can. I will do the same.

Thanks,
- Snak Iyz

~~~~~~~~~~~
Paul

[Ron61]

ED,

I am sure this was in one of the posts threads listed earlier, but my biggest problem was that they just put balance weights on the inside of the wheels. Since I run all four tires the same size I had switched the fronts to the rear and I still had the same shake around 60+. After having them balanced with the weights on both the inside and outside of the wheel most of that went away but there is still some vibration at higher speeds.

Ron

[FrankysCobra]

IMHO, it may be your rotors out of balance. I have heard that a few guys have banged their heads against the wall balancing after wheel balancing to eventually find out that the wheels are fine, but the rotors are not balanced. It's at least worth checking out. It wouldn't be a bad ideal to have the wheels berings checked while you're at it. I hope that helps.

[jhaynie]

Tire pressure the same in all wheels?? (probably too simple).

John

[Bob In Ct]

I'll say it again, it's the tires and the lack of a rag-joint. Try getting the tires trued or adding a rag joint or both. It's more than coincidence that so many Cobras have this problem and street cars don't.

Bob

[C-man610]

I agree with Bob in CT, its the tires and rag unit.

I had same problem with vibration around 60MPH. A Cobra owner suggested a dynamic and dimensional balance of the front tires.

I followed the suggestion and the steering vibe, front end vibe and ride vibe all disappeared.

I would suggest going to a tire or alignment house that uses Hunter Engineering GSP 9700 Road Force Balancing equipment. Accept no substitute!!!!!!!!!!!

Happy days

[JohnB]

How do we go about getting rag joints (and actually what are they). I too have the shake, rattle and shimmy at about 60mph. It is very anoying for a performance car like this to not feel like my BMW.

[Bob In Ct]

A "rag joint" is a damper put into the steering mechanism, Look at any 60s Corvette (or many other cars) at a show and you can't miss it. Basically the wheels keep shaking but the vibration is intercepted before it gets to the steering wheel.

The other approach is to get the tires ( which are not dimensionally round) shaved so that they are round. Very little rubber is removed if the job is done correctly.

Bob

[Rogers]

snak iyz....I have BDR #91 and have the same problem....It is really bad on a 2 lane black top...you can feel every bump in the road either thru the steering or thru the entire car. When I get on a dual lane I can go 100+ and the car feels better. I do agree...at this point its the tires. I jacked up one side..front...to just above the floor...say 3/8". I notice an irregularity as the tire spins. I've been told you should not see this. We need to get with Flaming River and get a package deal on rag joints....aside from new tires....I don't have any tire shavers around here...I'll try the lug nut thing first.

[Snak Iyz]

Thanks for the feedback...... Mine is the same at 100+...smooth as glass. Unfortunately, the rest of the time, the only word I can use that seems to describe it properly is 'scattered' over little bumps etc. that should not be shaking it.

I am all for shaving the tires as I have noticed my fronts are slightly out of round. Also, despite some of the lack of handling rag joints may provide, these would be a great option as well. Anything to get me back to no steering wheel shake. Shouldn't we push on Reg to offer the rag joints?? Or can any rag joints fit our cars??

At this point I have done dimensional and dynamic balancing of all four tires. This did improve things significantly, but there is still the overall shake.

One thing to mention, and this may be a 'Duh!' comment, but if I am leaning into it, I don't feel the shake or at least notice it hardly at all (maybe I am hanging on for dear life). It is primarily under 'normal' acceleration that I feel it. Anyone have insight as to why or is this just normal....??

Thanks for the continued dialogue on this topic....

-Snak Iyz

[Bob In Ct]

Snak Iyz:
When you're accelerating there is less weight on the front tires. This may aggravate or lessen the problem depending on your springs and shocks.

I'll bet the problem comes and goes as you drive down the road! Do different temperatures and inflation pressure have an effect?

Bob

[John Poling]

Originally posted by C-man610




I would suggest going to a tire or alignment house that uses Hunter Engineering GSP 9700 Road Force Balancing equipment. Accept no substitute!!!!!!!!!!!

Happy days

I found a local shop that had the Hunter as described above and it was amazing to see the results. One of my front wheel/tires checked out to be balanced correctly on this machine but when they performed the "Road Course" test on the machine it found that the tire had a "harder" spot in one area that when driving on the road would be similar to a 25 pound weight on one area of the wheel. Keep in mind that it was balanced a was okay in a normal spin-up. My major vibration used to start at around 35-40 mph and didn't stop to at least 95 (that's all the higher I felt like going with the extreme vibration.

After the rework with the Hunter 9700 machine the major vibes were gone and now I am experiencing the minor vibes in the 58-70 mph range and they are mostly gone at 105-110 mph. I performed a runout test on the surface of the rotor that my wheel bolts to and found between .004" and .007" on all four front rotors that I have. I think the next step is taking two of them to a machine shop and have these faces trued to the C/L axis of the rotor and see what that does. The next step is to install a "rag" joint if the machining doesn't fix it. I have a real problem shaving a set of Michelin Pilots. That would be a last resort.

John

[Snak Iyz]

BOB: The acceleration point you made, makes sense.

As for temp and air pressure tests, I have not made them. Not much flux in temperature in So Cal. Since I have owned the car (2 months), I have been running out in temps around 70-85.

My tires are the BF Goodrich 15/50's. Fronts are at 28 and the rears are at 24.

John/C-man610: It sound like the Hunter's are a definte high end machine. I will try to find someone down here who may have them and give that a shot first.

Question for the group: Would you go the rag joint route or try to get the 'shakes' figured out without them....??

thanks!

[Bob In Ct]

When I say I had my tires sheved, I am talking about taking just enough rubber off to make them dimensionally round. If you saw my BFGs you would not even know I had them done.

Bob

[rdorman]

Tons of stuff can cause this. The tire issues shows up most at around 60. BFG's seem to be the worst offenders. Out of round, force variations and of course balance all can contribute. Top it off and there is no isolator between the steering wheel and the tire.

Find a Hunter GSP9700 http://128.242.141.111/pub/search/findgsp9700.cfm

It can check tire uniformity, tire and rim runout, wheel to balancer mounting errors (human), improper bead seating, etc and yes of course, it balances.

For more fun, fleet vehicle often don't use wheel weights. There is a powder that goes inside the tire to balance. No more wheel weights. As the people with the Hunter about it.

Rick

[rdorman]

Oh, by the way, if you need/want to shave the tires, look up a retreader. They have the equipement.
Rick