Tire Shake and Road Force Variation - Pontiac G6 Forum
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post #1 of 2 (permalink) Old 08-14-2005, 10:50 AM Thread Starter
Join Date: Aug 2005
Posts: 5
Tire Shake and Road Force Variation

I have been doing some research on causes of tire shake and imbalance.
The Hunter 9700 wheel balancer can detect RFV through a roller that is placed against the tire to measure resistance of the tire to a givin amount of pressure or weight to simulate the wieght of the vehicle at each tire.

The machine is only as good as its calibrated and its operator. Also, a vehicle should be driven 10 miles to warm up tires to operating temp before checking for RFV.

The dealer said our car is within the GM spec. It still shakes. The GM spec may be to liberal. A tighter spec may be needed for this car and tire combo.

Here are some notes from many different sources I have come across.

Only a 0.25-oz. of imbalance can produce a noticeable vibration in some vehicles. It depends on the sensitivity of the steering and suspension, the type of wheels (alloy wheels tend to be more sensitive to imbalance than steel wheels because of their rigidity and lighter weight), vehicle weight and speed.

Not all wheel assemblies indicate the point of minimum radial run-out, rendering uniformity match-mounting sometimes impossible.

Another problem that can cause unwanted vibrations is radial force variation - a point of strong argument across the industry today. A tire can be perfectly balanced and round as a cue ball, but still shake due to force variation. In a nutshell, force variation - both radial and lateral - can be caused by inconsistencies in the tire, the wheel and even the brake rotor or drum.

With regard to the tire, these inconsistencies are caused by variations in materials assembly, heavy or weak splices, ply arrangements, weight imbalances and variations in spring rates around the tire.

Force variation has long been understood by the tire industry, and has become more prevalent as passenger vehicles have gotten smaller, lighter and more finely tuned.

One alternative here is a balancing product that goes inside the tire to provide long-lasting benefits. For many years, fleet owners have used powder-based balancing products inside their over-the-road medium truck tires.

The dynamics of rotation cause the weighted powder to cling to the inside of the tire in such a way that it equalizes balance. Extensive testing and real-world use shows that not only does this help maintain balance for the life of the tire, it also results in a smoother riding tire. Other similar products that use glass beads or liquids also claim to provide similar benefits.

Last edited by snosport; 08-14-2005 at 10:56 AM.
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post #2 of 2 (permalink) Old 08-26-2005, 01:21 AM
Join Date: Aug 2005
Posts: 22
as i mentioned in the other post...dirt or an imperfection on a brake rotor can keep the rotor from sitting flush against the hub and is a very common cause of vibration...especially on older vehicles where rust has formed and a sloppy mechanic didnt take the time to clean up the mating surfaces after a brake job...since the car is new i'd be pulling the rotors to check them on the inside and the hub. Its hard to believe you still have a vibration after 4 sets of tires...kinda makes me think its not the tires.
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