Vibration

[frltsta11]

I HAVE POSTED THIS BEFORE BUT DIDN'T GET ANYWHERE. I HAVE A 97 THAT STARTS TO VIBRATE AT 55MPH. IT RIDES SMOOTH TO THAT POINT BUT ALMOST AT EXACTLY AT 55MPH IT STARTS TO VIBRATE. THE VIBRATION IS CYCLIC. THE CAR HAS BEEN ALIGNED, BALANCED(3 TIMES) AND A ROAD FORCE TEST. COULD IT BE SOMETHING WITH THE DRIVELINE, ITS COMPONENTS OR THE GEARS IN THE DIFFFERENTIAL? I HAVE AN AUTO. IT DOES IT IN DRIVE OR IF I THROW IT INTO NEUTRAL. ITS DRIVING ME NUTS.

 

[c4c5specialist]

Hi there,
I would suggest a bent rim possibly, or a lateral runout of the tire, which would NOT be found with a road force variation machine.
A sharp eye would spot this.
Please keep us posted, c4c5

 

[hcolon]

C4C5, what is lateral runout? Is that the condition that occurs when the wheel is incorectly torqued? Please explain what causes this and how to correct it....
Herbie

 

[c4c5specialist]

HI there, Herbie,
Sorry about that.
Lateral runout, is the side to side movement of an object, while spinning. Reference of lateral runout can be seen as you have stated, by a incorrectly torqued wheel causing runout of a brake rotor, which you would feel as a brake pulsation.
Sometimes, due to impact, or tires with a belt that has started to shift, the rim or the tire has lateral runout also. This will create all sorts of weird feelings, and vibration, if the runout is bad enough.
Of course, if you have this condition on any component, repair is different for any given part.
Machining a rotor, replacement of a tire, or rim, replacement of a wheel hub assembly, all repair a certain type of lateral runout.
I hope this helps, c4c5

 

[hcolon]

Thanks C4C5, I think I get what you mean. The reason why I asked is that I just bought new tires and when being installed the tire tech noticed a bend in the lip of the front right wheel(rim).
He said he can balance it, and in fact he did, but I still notice the vibration at higher speeds. He told me that was the rim and not the balancing and I should buy a new one. Since I just shelled out 1,500 bucks for four new Pilot Sports, and after your explanation, I see this would be the right thing to do. If I still have the vibration after installing a new wheel, would my next step be to look at the hub assembly? I just installed new cyrogenic/slotted rotors and Hawk pads, and I saw the tire tech with my own eyes torque the wheels to 100lbs per spec, so It shouldn't be brakes. I would like the tires to wear as evenly as possible since they are new....as always your expertise is appreciated...
Herbie

 

[c4c5specialist]

HI there,
Well, it sounds like you have a very competent person servicing your Corvette, which is reassuring.
Yes, if after your rim replacement, the vibration is not cured, then I would do a dial indicator check of the hub assembly.
Also, a tool that is used in GM dealerships, is an EVA2. Electronic Vibration analyzer, second design. This tool is the most comprehensive tool that is available to diagnose vibration concerns. I love the tool, and it works very well.
You can also use this tool, to help in your tracing down of the problem.
Let us know if we can assist further, c4c5