I (after doing some alignment and tire work) have noticed a subtle rhythmnic vibration. It can be felt in the steering, but also under foot. The vibration eases in, increases to a max and then eases out...then the whole cycle repeats...all at highway speed.

Any ideas?

 

ttt ......I'm curious too??????????? :U

 

Did your tire work include computer wheel balancing ?

 

check for flat spots.

 

Yes, tires were balanced on the Hunter GSP? 9700...the king of all balancers.

Just to clarify, this is actually a fine tuning issue to me. The wheel alignment was so far off that I cooked my new rears inside of 6000 miles. I had an extreme toe in condition on the rears. The rear camber adj bolt was not real tight and both rear shocks were loose, plus I had play in the main wheel bearing nut that allowed the wheels to rock in both axis..

So what I have now is amazing compared to what it was. I am just curious as to what could contribute to a "rhythmnic vs constant" vibration.




[Modified by redvette1986, 9:52 PM 8/11/2003]

 

That sounds like a" harmonic" vibration, and it sounds like the tires. :flag [IMG]Flat spots are measured using two criteria; peak to peak changes and harmonics.

No tire is perfectly round and the peak to peak changes ( P/P ) reflect how much pressure must be applied to the tire in downforce to make the tire perfectly round. That is, you apply pressure at the axle while the tire is rotating until the tire is perfectly round. A flat spotted tire will increase this value by a minimum of about 4 psi. In our testing, we have seen this value more than double from the original value! Our actual test showed a change from 16.0 to 32.2 psi.



Harmonics are measured from 1 to 10 with ten being the least case scenario. A first harmonic flat spot ( 1 ) means that for every rotation of the tire, at any speed, the flat spot is felt. As such, you would feel this going 22 mph or 122 mph. A high harmonic flat spot, 6 or above, is often not recognized as a flat spot but is often confused with a mechanical problem. This is best explained as a particular speed where the problem manifest itself. An example would be a car that has a shimmy or vibration from 66 to 70 mph but none above or below that speed range. This is almost always a high harmonic permanent flat spot.

We know of cases where torque converters, clutch assemblies and half shafts have been replaced trying to fix the problem; it is almost always tire flat spotting. For the car owner this is very time consuming and frustrating, expensive too if the car is out of warranty.

Your tires are designed to operate in a wide variety of temperatures. Most performance tires are designed to function best at triple digit temperatures. While the rubber compounds offer the best performance at these temperatures, flatspotting is also accelerated. What makes your tires work also helps them to flatspot. Parking a hot, soft tire on a cool concrete surface accelerates flatspotting because the contact patch is stressed by the temperature and density differences. Basically the tire must "give" because it is softer and hotter than a concrete floor.

[/IMG]


[Modified by offershore, 3:27 AM 8/12/2003]

 

Well, that is great news to me cuz I just put new ones on the rear but the fronts are gonna wait until I replace my front spring...this weekend. The fronts are safe, but tired and probably not worn evenly.

Thanks

 

I had a wierd vibration for a while with my old set of tires they had 1000 miles on them. I changed to diffrent tires and we found out the tire store forgot the hubcentirc rings for my aftermarket rims. Did you check to see if you needed them for your wheels.We put new rings and tires and no vibration after 3k on new tires.

 

harmonic vibration will ruin your wheel brgs.
It would be a good idea to check the cups for chatter.


[Modified by offershore, 4:50 AM 8/12/2003]

 

" the tire store forgot the hubcentirc rings for my aftermarket rims"????

Huh? What the heck are these? I am using "American Racing Torq Thruster II" wheels 17X9.5