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Tire and Wheel Balancing - GSP9700 Road Force Measurement™
GSP9700 Balancer and Vibration Control System
Hunter Engineering supplied photo.
Balance is Only Part of the Solution
Today's cars and light trucks are designed to ride smoothly and handle
safely. Unchecked, excessive wheel vibration can result in:
 | Excessive tire wear |
| Damage to suspension and steering parts |
| Unsafe steering and handling |
| Unsafe driving conditions |
What Causes Excessive Wheel Vibration?
At 60 miles per hour an average sized tire rotates 850 times per minute.
[Rotation for smaller tires is slightly faster, for larger tires it is slightly
slower.] At this speed slight variations in balance, sidewall stiffness or
roundness can cause the wheel to literally slam into the pavement 14 times
a second.
Wheels Out of Balance
Static Balancing - uses a single weight plane and only address
"up-and-down" imbalance. This is simply not adequate for today's vibration
sensitive vehicles.
Dynamic Balancing - uses two weight planes. This eliminates
"up-and-down" and "side-to-side" imbalance. Dynamic, two plane balancing should
always be requested, even on custom wheels when hidden weights are required.
Wheel Force Variation
A perfectly balanced tire can still vibrate due for Force Variation...
Wheel Force Variation - is most frequently caused by wheel runout or
uneven tread or sidewall stiffness. Runout means a tire or rim is out of round
when rolling, frequently caused by a bent rim or uneven tire wear.
Uneven tread or sidewall stiffness - can be found in new or worn
tires. Tires, by design, are never uniformly flexible throughout nor are they
perfectly round. And no two tires are exactly alike.
How Wheel Force Variation is Corrected
| Matching the high point or stiff spot in the tire with the lowest spot in
the rim can make the wheel "round when rolling". This procedure is called
ForceMatching™ and solves most vibration problems. |
| Tires or rims with extreme runout or force variation often cannot be
matched and must be replaced to solve vibration problems. |
Tire Pressure and Wheel Alignment
Improper tire pressure and/or misalignment causes irregular tire wear which
creates and amplifies imbalance, resulting in wheel vibration. Alignment can be
adjusted and wheels serviced to reduce or stop the vibration. See
Alignment for details.
Steering and Suspension Components
Steering and suspension components need periodic inspection. They can
eventually wear out resulting in wheel vibration. Excessive wheel vibration from
other causes can also shorten steering and suspension component life.
Other Hidden Causes of Wheel Vibration
| Wheel to axle mounting error |
| Brake component wear or failure |
| Drive train or engine component wear or failure |
| Vehicle component characteristics |
A knowledgeable technician with proper training and equipment can diagnose
these problems. But the only way to rule out all wheel related vibration
is a computer simulated road test.
Stop Wheel Vibration
Q. What's the difference between
Wheel Balance and Force Vibration?
A. An unbalanced wheel causes vibration when spinning
because of a heavy spot in the wheel. Force Variation causes vibration
because of uneven stiffness in the tire sidewall or tread, or because the
wheel is out of round when rolling. Balance and Force Variation can affect
one another. Balance is measured by spinning the tire. Force Variation is
measured by placing it under load to simulate actual road force. This can
only be done using a computer simulated road test. Ask your technician to do
this test during tire service. |
Q. How often should I have my wheels
checked for excessive vibration?
A. Follow the vehicle manufacturer's recommendation
noted in your owner's manual. But, whenever you notice excessive vibration
you should have a qualified technician inspect for any of the possible
causes mentioned here. Gradual worsening of wheel vibration can be difficult
to notice, so as a general rule have your tires checked every 10,000 miles
or at least once a year. |
Eliminate Tire and Wheel Vibration
Hunter's GSP9700 is both a balancer and a vibration control system. It is
also a Road Force Measurement analyzer for passenger car and light truck
tire/wheel assemblies.
Each tire/wheel assembly is tested for the amount of dynamic/static imbalance
and Road Force.
The GSP9700 simulates a "road test", with a unique "load roller" which
applies up to 1400 lbs of force against the rotating assembly. The roller
measures the loaded runout of the assembly (deflection while under load) and
automatically recommends corrections when needed. The GSP9700's technology
eliminates many of the time consuming, subjective and often non-productive
manual measurements previously used to diagnose and repair ride disturbance
concerns.
GSP9700 diagnostic screen.
While driving a vehicle, consider all the wheel-related items that can cause
vibration
- Wheel Imbalance
- Runout of the:
- Rim
- Tire
- Rim and tire as an assembly
- Force Variation of the Tire
- Mounting Error While Balancing
- Issues Related To The Vehicle:
- Bent hubs
- Mounting of the wheel to the vehicle hub off center
- Excessive radial runout of the studs
- Out of balance rotors and drums
Up until now the wheel service industry could just balance wheels. The
GSP9700 fills the gap doing 75% more than wheel balancing.
Let's review some of these issues:
| Wheel Balance
Have you ever heard a customer say he is still receiving wheel vibration
complaints after he has balanced wheels? Many people do not realize that
balancing is only a small portion of wheel vibration. If the wheel never came
in contact with the road, then balancing would be sufficient. A square wheel
can be balanced, but a square wheel will not give a smooth ride.
|
| Runout
Not usually checked until there is a problem. Bent rims or defective tires
might be found "by an experienced eye," but we all know that most operators of
this type of equipment have little experience or training. Is it the runout in
the rim, tire or a combination? How much is too much? Is it affecting the ride
quality? These questions are tough to answer. Runout is usually considered
after the customer comes back complaining. This diagnostic time is usually
done at the expense of shop labor profits and can be time consuming. What
about the customers who have a problem and don't return going to another shop
looking for an answer?
Many rim manufacturers measure runout during the assembly of the rim . The
valve stem location is sometimes drilled to the request of the OEM at the low
or high side of runout or a paint dot or stamp is placed at the identified
location. Many rims on the market today are also purposely designed so
that the pilot hole is .002-.004" off-center to allow for adjustment
capabilities by the assembly lines when encountering force variation on the
tire. It gives the chance to adjust for tire force variation if runout is
induced into the rim. But up to this point ONLY BY THE OEM! Up until
now, anyone could measure rim runout at the bead seats with a dial indicator.
The drawbacks? It's too time consuming. The GSP9700 will automatically measure
the inner and outer bead seat and determine the effects on ride quality.
|
| Force Variation (Tire Uniformity)
Radial force variation is the amount of change in stiffness of the
sidewall and footprint when a load is placed against the tire. There are
specifications and acceptable limits from tire manufacturers. Up until now,
force variation has been measured only by OEM's in an industrial setting using
equipment in the range of half a million dollars. For example, a tire and rim
could be perfectly round when measured with a dial indicator (free runout) and
the wheel will still vibrate when driven due to excessive force variation.
Many tires on the market today have a "paint dot" or mark on the tire that
indicates either the high side or low side of force variation.
Many have attempted to solve vibration problems by blindly '"Lining up the
dot" with the valve stem. The operator assumes the "dot" is the high point of
radial force of the tire and the wheel valve stem hole is the low point of
runout of the rim. Unfortunately, this is not always true. Many tires are not
marked and many wheel manufacturers do not use the valve stem as the low
point. Other OEM's use the marks to indicate high points instead of low
points! The GSP9700 eliminates any guesswork. The locations of runout and tire
force are quickly located and measured. The GSP9700 also automatically
determines if they can be used to solve an existing non-balance related
vibration, before any extra work is performed.
|
| Mounting Error |
- The wheel, when balanced, must be mounted on the vehicle the same way it
came off the balancer. All too often, the technician improperly mounts the
wheel on the vehicle off center and the balance is compromised. Today's
vehicle designs are lighter and more sensitive to road feel. It has become
more critical to be aware of wheel mounting on vehicles to eliminate vibration
during balancing.
The GSP9700 will automatically alert the technician when a mounting error is
detected on the balancer, thus preventing improper centering on the balancer
from taking place.
In Conclusion:
| With the GSP9700, virtually all possible complaints due to Wheel Balance,
Tire Runout, Rim Runout, Tire Force Variation, and Mounting Error are all
eliminated before the tire and wheel assembly is placed on the vehicle. |
| 100% Seamless Quality Control of all wheels going out the door. It takes
no more effort by the operator, no more steps than doing an everyday type of
wheel balance. |
| If there is a vibration coming from the vehicle when it is driven after
the wheels are measured on the GSP9700...then the problem IS NOT WHEEL
RELATED! No more wasted diagnostic time. No more swapping of tires. No more
falsely blamed tires sent back to the manufacturer. No more loss of profits
tracking down blind vibration problems that cannot be traced. This is good for
the tire dealer, this is good for the tire manufacturer, this is good for the
consumer. There is no other piece of equipment available doing such a task.
|
| Now if there is a problem. What can we do to fix it?
1) Grinding the tire? Ugh...Who wants to have their brand new tire ground
away? There are numerous serious problems associated with this type of
technology.
2) Match the heavy spot of the tire with the light spot of the rim? No. For
years, traditional wheel balancers have offered this form of weight
optimization. The primary benefit here is reducing weight; however, this does
not take into consideration force variation. In some cases, weight
optimization can even increase force variation complaints. The vibration
becomes worse. |
Eliminating Tire and Wheel Vibration with the GSP9700
| Match the Tire to the Rim
This can be helpful if the first harmonic of the rim can be indexed to
cancel the force variation of the tire. As stated previously, this is not the
same as the relatively ineffective common practice of most balancers to match
imbalance of the tire to rim to minimize weight. |
| R & R Tire or Rim
Replace the defective rim or defective tire and also be able to locate and
quantify the problem. |
| Record the Value and Reuse the Tire on Another Rim!
If a rim and tire cannot be matched and the tire is not out of spec, the
actual value of the force variation can be written on the sidewall of the tire
and placed back on the shelf. At a given point in time the entire inventory in
that tire size can be "measured." Eventually a "measured" tire can be hand
picked to match a given rim. This would be analogous to picking an alignment
shim to fix the alignment condition and bring the wheel as a "tire and rim"
back into specification. The GSP9700 moves vibration solving in wheels to a
new level of professionalism. "Road Force Measurement" against the wheel
before the balance has been needed for years! |
For More Information
Most of the text on this page is copied from the Hunter Engineering web
site and pamphlets. For more Hunter Engineering information click
here.
Updated
2006/07/10
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