Identifying Mechanical Mounting Repeatability Errors

 

Chasing weights, changing weight angles, changing weight amounts, and changes in runout and force variation may all be produced by incorrect mounting or worn/damaged adaptors. Balancers cannot identify mechanical mounting errors caused by incorrect mounting methods or worn/damaged mounting adaptors. Correct mounting must be verified by the technician, including identifying the on-vehicle mounting method. Adaptors must be inspected for excessive wear and should be cleaned regularly to prevent dirt from affecting the balancer results.

Before checking for mechanical mounting errors, perform a Quick Cal Check to verify accurate balancer calibration. Look at the calibration readings to verify weight angle position and view the non-rounded weight readings. The weight should be approximately 4.31 oz. for one plane and 0 oz. for the opposite plane with the default “A” width and diameter dimensions (224 mm, 4.9 inch, 14 inch).

To test electronic and hardware repeatability:

  Mount an assembly on the spindle shaft.
  Input the weight location dimensions using standard clip-on weight locations.
  Measure and record the non-rounded amount of imbalance on each weight plane.
  Repeat this procedure four times without removing the wheel to verify the balancer can repeat measurements within 0.05 ounce (per plane). If it does not repeat the measurements, check the wheel for debris or water in the tire.

To test mechanical mounting repeatability:

  With the assembly mounted on the spindle shaft, perform a balance spin (with the load roller enabled for GSP9700).
  Record the non-rounded weight amounts for the inner and outer planes. (Do not apply weights.)
  When the data is recorded, loosen the wing nut and using the foot pedal to lock the spindle in position, rotate the wheel 90 degrees clockwise. Perform another balance spin with the load roller enabled. Record the non-rounded weight amounts for the inner and outer planes.
  Repeat the above steps twice more so measurements are taken at 0, 90, 180, and 270 degrees. The weight amount from the highest to lowest recorded number should not vary by more than 0.15 ounce for smaller passenger car wheels (per plane), 0.30 ounce for SUV wheels (per plane), and 0.75 ounce for larger light truck wheels (per plane). If recorded readings change by more than this, repeat the measurements at 0, 90, 180, and 270 degrees again.

Data Analysis:

NOTE: Larger rim/tire assemblies may experience more variation in data than smaller assemblies. This should be considered when comparing data.

Do not check repeatability using ALU mode because it's “hyper-sensitive” in comparison to clip-on weight placement. In ALU mode the diameters are smaller and the planes are closer together compared to standard clip weight balance, therefore any change in re-centering will be amplified compared to when clip-on weight planes are dialed-in.

For example, a wheel that needs 0.25 or 0.50 oz. weights in ALU mode may show zero's in clip-on weight mode. You can also get cases where dynamic imbalance on standard is small, such as 1 oz., and it jumps to 4 or more ounces in ALU if the planes are close enough together. All balancers will do this… and that's why most balancers have such a hard time hitting zero on the first spin.

If the imbalance amounts change and the readings from the first sample data and the second sample data are NOT the same for 0, 90, 180, and 270 degrees, the assembly is not being mounted correctly. Refer to “Mounting the Wheel on the Spindle Shaft” for proper mounting techniques.

If ALL readings change, BUT the readings from the first sample data and the second sample data are the same for 0, 90, 180, and 270 degrees, the hub/shaft assembly is out of position. Use a dial indicator to check for runout on the hub face and on the shaft. Runout on the hub face should not exceed 0.0015 inch. Runout on the shaft should not exceed 0.0015 inch. If runout exceeds these limits, remove the threaded hub/shaft assembly and inspect for any debris or nicks on the tapered mounting surfaces (DSP & GSP9702 only, spindle and hub assembly must be replaced on GSP9712). Remove any nicks using a fine grit stone. Remove only the raised portion of the metal around the nick. Do NOT use sandpaper! Clean parts and lightly oil before reassembling and re-measuring runout.

GSP9700 CenteringCheck™ Feature (Software Version 2.1 and higher)

CenteringCheck™ may be used with either a “bare rim” or a “rim with tire assembly.” On-screen prompts lead you through the procedure.

The GSP9700 can be used to inspect each mounting to identify possible centering errors, preventing improper measurements from occurring. Using the inner Dataset arm, the GSP9700 will automatically measure wheel runout at 0 degrees and 180 degrees. The CenteringCheck™ feature will confirm if the wheel is centered for the operator and display one of the following screens.

Select “Perform CenteringCheck™” from the menu.

Place the inner dataset arm against the rim at a location that will maintain unobstructed contact for a complete revolution.

Press the outer dataset arm button or “Start” when ready to take readings.

Position the valve stem at 12 o'clock, and then press “Enter Valve Stem.”

After measuring rim runout, you will be prompted to loosen the wheel and reclamp at one half turn (approximately 180 degrees) from the current position.

Position the valve stem at 12 o'clock, and then press “Enter Valve Stem.”

Place the inner arm against the rim as shown.

Press the outer arm button or “Start” when ready to take readings.

Once more, position the valve stem at 12 o'clock, and then press “Enter Valve Stem.”

If the rim is centered properly, the following screen will appear briefly.

The GSP9700 will then proceed to the “Balance” screen.

If a centering problem is detected, the following screen will appear.

Loosen and relocate the wheel and adaptor from the present location.

Place the inner arm against the rim.

Press the outer arm button or “Start” when ready to take readings.

The procedure will repeat the re-centering check four times and always compare the previous measurement to the next check. If centering is not achieved after four attempts, the following screen will appear.

Check for:

  Correct mounting cone/adaptor for this wheel design.
  Wheel defect such as a metal burr interfering with the cone/adaptor.
  Dirt or debris interfering with the cone/adaptor.

Follow the on-screen prompts, and then press “Restart Procedure.”

GSP9700 Mounting Error Detection (During Wheel Measurement)

Mechanical Mounting Error Detection is an available feature in GSP9700 Software Version 1.2 and higher. While taking rim runout measurements, the GSP9700 will warn that a mounting error has occurred. If the software detects similar radial/lateral runout motion (parallel dial indicator gauge deflection) in the rim, it will warn the user that there is a possible mounting error. This does not compensate for all mechanical mounting errors or for worn/damaged adaptors, but it does identify gross mounting errors.

To address a non-repeatability complaint, ask the technician to measure rim runout on the assembly. The GSP9700 may be able to detect the mounting error. If a mounting error is detected, refer the technician to “Mounting the Wheel on the Spindle Shaft” for proper mounting techniques.

Balancer Mounting Methods

Mounting the Wheel on the Vehicle

Since today's vehicles are more sensitive to road feel, it is critical to be aware of how the wheel mounts on the vehicle. Acceptable ride quality depends on accurately mounting the wheel on the vehicle hub. Step torquing lug nuts in a star pattern should be followed on every installation.

If the wheel is not placed on the vehicle using the same centerline that was used on the balancer, the wheel balance, runout, and force variation will not be duplicated.

Improper wheel centering is a huge problem when the hub bore of the wheel does not “slip fit” onto the hub of the vehicle. Extra caution should be used when mounting these types of wheels after servicing on the balancer. This is especially prevalent on lower cost aftermarket wheels. In many cases, a tire and/or wheel is blamed for creating unacceptable vibration when in fact it was merely mounted on the vehicle improperly.

Mounting the Wheel on the Spindle Shaft

Since today's vehicle designs are lighter and more sensitive to road feel, it is critical to achieve the best balance. Proper balance requires that the tire/wheel assembly be centered on the balancer. Most balancers will balance the tire/wheel assembly to zero, even with the tire/wheel assembly mounted off center. The main objective of the balancer operator is to center the wheel on the balancer using the best available method. Mounting the wheel off-center on the balancer creates incorrect measurements of imbalance and runout conditions.

Mounting Wheels with Cones

The majority of wheels are mounted with a cone to center them on the balancer's shaft. Cones are manufactured with different tapers. The taper and the fit of the cone make a significant difference in accurate centering. Cones having a low taper fit the hub bore and guide the wheel for better centering during the mounting process.

Most wheels benefit with the cone mounted from the backside. This method is referred to as back cone mounting.

Some wheels do not center well using back cone mounting. These wheels must be centered by placing the cone from the front of the wheel, referred to as front cone mounting.

Back Cone Mounting Procedure

Select the proper wheel-mounting cone by placing it in the center bore of the wheel to be balanced.

Select the cone that contacts the wheel nearest the center of the cone.

Place the wheel-mounting cone on the spindle against the spring plate. Mount the wheel with the inner rim facing the balancer and centered on the cone.

Install the clamping cup and wing nut on the spindle shaft against the wheel and secure the entire assembly by firmly tightening the wing nut. Depress the foot pedal to hold the spindle in place (if available). Slowly roll the wheel toward you during the initial tightening of the wing nut. This helps the wheel to roll up the taper of the cone as opposed to forcing it to slide up the cone.

Back cone mounting (shown using scratch guard)

The scratch guard may be installed on the clamping cup to protect aluminum rims from being marred, but should not be used on steel wheels.

In cases where the mounting pad of the wheel is extremely wide, use the optional eight inch alloy wheel pressure cup.

Front Cone Mounting Procedure

This procedure utilizes a tapered cone inserted from the front side of the wheel instead of the backside as previously described.

Select the proper wheel-mounting cone by placing it in the center bore of the wheel to be balanced. Choose the cone that contacts the wheel nearest the center of the cone.

Mount the wheel with the inner rim facing the balancer. Place the wheel-mounting cone on the spindle with the small end of the cone facing the front of the wheel.

Install the wing nut and pressure ring assembly onto the spindle shaft against the wheel and secure the entire assembly by firmly tightening the wing nut.

Heavy wheel centering may benefit by pulling the tire away from the hub face at top dead center while tightening the wing nut. This helps the wheel to overcome gravity against the hub or spacer.

Wheels with center bore diameter over 3 9/16 inch may require the use of the light truck cones mounted from the outside of the wheel.

NOTE: Truck wheels are heavy and require care when using cones to center on the balancer's shaft. Always test the assembly for repeatability.

Mounting Wheels with Large Center Holes

A 3-jaw chuck is a relatively new concept in balancer adaptors available for mounting wheels with large center holes. The 3-jaw chuck self centers in the wheel's center hole as the jaws are tightened. Similar adaptors have proven very successful mounting hubless drums and rotors to off-car brake lathes.

An added feature is the ability to center a very heavy tire/wheel assembly on the balancer's shaft.

This is due to:

  No need to overcome gravity.
  Centering on the hub bore, and not the hub chamfer.
  Small slip fit clearance between the shaft and the adaptor.

Before mounting the 3-jaw chuck, inspect the wheel's mounting surface to insure the chuck will sit flat to the wheel. Mount the 3-jaw chuck from the inside of the wheel and expand the claws.

Pressure Ring

The pressure ring should be used to prevent the wing nut from directly contacting an adaptor or a cone.

It may also be used in place of a pressure cup if space is limited between the wheel and the end of the spindle.

Spacers

There are two types of spacers:

  Hub ring spacers
  Shaft spacers

Hub Ring Spacers

These light truck spacers are designed to build a larger pocket for front coning when using the extra large truck cone. It also provides a location for the centering pins found on some dual wheel configurations.

Shaft Spacers

The shaft spacer can be used to make the cone contact the hub bore more firmly.

For example, one cone size is too small because the captivated spring is not pressing the cone against the inner wheel opening, but the next larger cone size is too large and will not fit the opening. Use the smaller cone size, with the spacer, to extend the captivated spring and hold the smaller mounting cone against the wheel opening with greater pressure.

 

 
© Hunter Engineering Company Privacy Policy