Wheels and Tires: Testing and Inspection
Wheels and Tires, Causes and Solutions for Vibration
=> [ Wheels and Tires, Causes for Vibration ]
=> [ Balancing ]
=> [ Road Test, Performing before Balancing ]
=> [ Stationary Balancing Machine ]
=> [ Vibration Control Tire Balancer ]
=> [ ]
=> [ Wheels and Tires, Radial Lateral Run Out ]
=> [ Wheel and Tire Radial and Lateral Run Out, Checking with Tire Dial Gauge ]
=> [ Disc Wheel, Checking Radial and Lateral Run Out ]
=> [ Matched Mounting ]
=> [ Flat Spots in Tires from Standing ]
Wheels and Tires, Causes for Vibration
There are many causes for vibration. Vibration can also be caused by tire wear, among other things. Tire wear caused by driving does not always develop evenly over the entire tread. Due to this, a slight imbalance develops which disturbs the smoothness of the formerly accurately balanced wheel.
This slight imbalance cannot yet be felt in the steering wheel, but it is present. It increases the tire wear and consequently reduces the service life of the tire.
Recommendation
In order to guarantee over the entire service life of a tire a
• Optimal safety,
• Optimal smoothness and
• Uniform wear
It is recommended that wheels/tires be balanced at least two times within the tire's service life.
Balancing
Before beginning balancing, the following requirements must be fulfilled.
• Tire inflation pressure must be OK.
• The tire tread must not be worn down on one side and should be at least 4 mm deep.
• The tires must not have any damage such as cuts, holes, foreign bodies, etc.
• The suspension, steering, tie rods and damper must be in proper working order.
• A road test has been performed.
Road Test, Performing before Balancing
If a vehicle comes to the workshop with the complaint vibration, a road test must be performed before balancing the wheels.
• That way, information about the type of vibration can be obtained.
• Observe at which speed range the disturbance takes place.
- Raise the vehicle on the platform immediately after the road test.
- Mark the installation position on the tire.
- Remove wheels from vehicle.
- Balance the wheels.
Stationary Balancing Machine
• Test drive performed. Refer to => [ Road Test, Performing before Balancing ].
Tension wheel on balancing machine
• Please keep in mind that cleanliness is the most important when balancing as well, just as for any other repairs you perform. Only then can a proper result be obtained!
Dirt and rust in the area of the contact surfaces and centering of the wheel distort the result.
- Clean contact surfaces, centering seat and wheel disc before tensioning wheel on balancing machine!
- Tension wheel with tire on balancing machine.
• To mount wheel on wheel balancer, use for example centering system for wheel balancing machines (VAS 5271).
• This way a 100% centering of the wheel and gentle mounting is possible!
• It is not possible to center it 100% on balancing machine with conical tensioners.
• With a deviation of 0.1 mm outside the center, there is an imbalance of 10 grams on the wheel/tire.
Wheel/tire balancing procedure
- Let the wheel and tire rotate on the wheel balancer.
- Check the run of the characteristic lines on the sidewall of the tire in the area of the rim flange.
- Check the tire wear pattern while the wheel and tire are rotating.
• In the event of one-sided wear, flat spots from braking or severe wear spots, smooth running cannot be achieved by balancing. In this case, the tire must be replaced.
- Check the run-out of the wheel and tire. If the wheel with tire runs untrue although there are no flat spots, a radial or lateral run-out may be the cause.
- Check wheel with tire for radial- and lateral run-out. Refer to => [ Wheel and Tire Radial and Lateral Run Out, Checking with Tire Dial Gauge ].
- If the radial and lateral run-out are within the specified tolerance, balance the wheel and tire.
• Do not use more than 60 grams of weight per wheel.
• If more weight is necessary, a smoother running can achieved by matched mounting of the tire. Matched mounting of tire. Refer to => [ Matched Mounting ].
• The display in the balancing machine should show 0 grams.
• Vibration control tire balancer (VAS 6230) can be inserted as an alternative to matching, refer to => [ Vibration Control Tire Balancer ].
- Bolt the wheel to the vehicle.
- First, tighten the lowest wheel bolt by hand to approximately 30 Nm.
- Now tighten the remaining wheel bolts diagonally also to about 30 Nm. This process centers the wheel on the wheel hub.
- Put the vehicle on its wheels.
- Now use a torque wrench to tighten the wheel bolts diagonally to the specified tightening specification.
Road Test, Performing
- Perform a road test after balancing wheel/tire.
If a vibration is still detected during the road test, the cause may be due to tolerance in the wheel centering.
The component tolerances of wheels and wheel hubs can be additive in unfavorable cases. Vibration can result from this. This can be eliminated using a finish balancer. Refer to => [ ].
Vibration Control Tire Balancer
Expanded functions can be performed using vibration control tire balancer (VAS 6230) in addition to the previously known balancers.
A special characteristic of this system is testing the radial force of wheel/tire during rolling.
For this purpose, a roller presses a force of approximately 635 kg against the wheel. This simulates the tire contact force against the street surface while driving.
Tire contact forces fluctuate due to radial- and lateral run-out and differing rigidity in the tires.
The (VAS 6230) detects and stores the position of the maximum measured radial force in the tires. After that, the position of smallest dimension between rim flange and disc wheel center is measured.
Finish Balancer
• Working with a finish balancer requires instruction from the manufacturer of the balancer.
• For the balancing, the wheels of the tractive axle are set upon the turntable sensors, for example front wheels for Front Wheel Drive (FWD) and all 4 wheels for All Wheel Drive (AWD).
If it is determined when balancing on the vehicle the remaining imbalance is more than 20 grams, the wheel should be rotated on the wheel hub.
- Mark the point at which the imbalance is indicated.
- Afterwards, unbolt the wheel and rotate its position on the wheel hub so that the marking points downward.
• The wheel hub must not turn during this procedure.
- First, tighten the lowest wheel bolt by hand to approximately 30 Nm.
- Now tighten the remaining wheel bolts diagonally also to about 30 Nm. This process centers the wheel properly on the wheel hub.
- - Check again whether the imbalance is less than 20 grams using the finish balancer.
• The imbalance should not be smaller than 20 grams under any circumstances before changing balance weight.
- Remove the wheel bolts again if necessary.
- Rotate the wheel relative to the wheel hub once more by one or two wheel bolt holes.
- Tighten the wheels using the method described above.
• The imbalance should only be reduced by changing balance weight if the imbalance is less than 20 grams.
- Balance the wheels until the imbalance is below 5 grams.
- Tighten the wheel bolts to the specified tightening specification if you have not already done so.
CAUTION!
Always tighten the wheel bolts to the specified tightening specification with a torque wrench.
Wheels and Tires, Radial Lateral Run Out
Radial and lateral run-out occur when the wheel and tire are not running precisely true.
For technical reasons, 100% true running is not possible.
Therefore the manufacturers of these components allow a precisely specified tolerance.
Mounting the tire in a unfavorable position on the wheel can be the cause for exceeding the maximum allowed tolerance for wheel with tire.
The table shows the maximum permissible tolerance values for the wheel with mounted tire.
Tolerances for Radial and Lateral Run-Out of Disc Wheel with Tire
Wheel and Tire Radial and Lateral Run Out, Checking with Tire Dial Gauge
Checking lateral run-out
- Load the tire dial gauge approximately 2 mm.
- Set up tire dial gauge on the side wall of the tire.
- Slowly rotate the wheel.
- Note the smallest and the largest dial readings.
• If the difference is greater than 1.3 mm, the lateral run-out is too great.
In this case, lateral run-out can be reduced by matched mounting of the tire. Refer to => [ Matched Mounting ].
Peak values on the tire dial gauge due to small irregularities in the rubber may be disregarded.
Checking radial run-out
- Load the tire dial gauge approximately 2 mm.
- Set up tire dial gauge on the tire tread.
- Slowly rotate the wheel.
- Note the smallest and the largest dial readings.
• If the difference is greater than 1 mm, the radial run-out is too great.
In this case, radial run-out can be reduced by matched mounting of the tire. Refer to => [ Matched Mounting ].
Disc Wheel, Checking Radial and Lateral Run Out
- Mount the disc wheel on the wheel balancer.
- Use the centering system for wheel balancing machines (VAS 5271).
- Load the tire dial gauge approximately 2 mm.
- Slowly turn the disc wheel.
- Note the smallest and the largest dial readings.
S Lateral run-out
H Radial run-out
- Compare determined value with specifications in the table.
• Peak values on the tire dial gauge due to small irregularities may be disregarded.
Specifications for radial and lateral run-out on disc wheel
• If the measured value exceeds the specified value, no acceptable smooth running can be attained.
Matched Mounting
General Information
If radial or lateral run-out from wheel or tire meet each other, the untrue running of the wheel and tire is increased.
For technical reasons, 100% true running is not possible. Refer to => [ Wheels and Tires, Radial Lateral Run Out ].
Before matching wheels which have been mounted and driven on a vehicle, they must be driven until warm. This eliminates flat spots from standing which may exist. Refer to => [ Flat Spots in Tires from Standing ].
Work procedure for match-mounting
- Let the air out of the tire.
- Press the tire beads off the rim flanges.
- Coat the tire beads all around with tire mounting paste.
- Rotate the tire 180° relative to the disc wheel.
- Inflate the tire to approximately 4 bar.
- Tension wheel with tire on balancing machine.
- Check the run-out or the radial and lateral run-out, as necessary.
• If the radial and lateral run-out value is not exceeded, the wheel can be balanced to 0 grams. Specifications are found on.
• If the radial and lateral run-out lies outside the specified values, the tire must be turned again.
- Let the air out of the tire and press the tire beads off the rim flanges.
- Rotate the tire 90° (one quarter turn) relative to the disc wheel.
- Inflate the tire to 4 bar and check for true running.
• If the radial and lateral run-out value is not exceeded, the wheel can be balanced to 0 grams.
• If the radial and lateral run-out is still outside the specified values, the wheel must be turned again.
- Press the tire beads off the rim flanges.
- Rotate the tire 180° (one half turn) relative to the disc wheel.
If the values for radial or lateral run-out are still outside the specified values, check the wheel for radial and lateral run-out. Refer to => [ Disc Wheel, Checking Radial and Lateral Run Out ].
If the measured values for radial and lateral run-out of the wheel disc are within the specified values, then the tire has excessive radial or lateral run-out. In this case, the tire must be replaced.
• Assembly paste from mounting tires is located between tires and rim flanges.
• Avoid strong braking or acceleration maneuvers during the first 100 to 200 km. Otherwise, the tires can rotate on the rims and the work done would then be undone!
Flat Spots in Tires from Standing
What is a flat spot from standing?
Terms like flat portion, flattening, are also used as a term for flat spots from standing.
Flat spots from standing cause vibration, like an incorrectly balanced wheel. It is important to recognize a flat spot in the tread from standing as such!
Flat spots from standing cannot be corrected by balancing, and can occur again at any time under various circumstances. Flat spots from standing can be corrected without complicated special tools. Providing that the flat spot was not caused by wheel lock during hard braking.
• Wear spots due to wheel lock are irreparable! Tires with such damage must be replaced.
Causes of flat spots from standing:
• The vehicle stands for several weeks in a location without being moved.
• Tire pressure is too low.
• The vehicle was placed in a paint system drying cabinet after painting.
• The vehicle was parked with warm tires in a cold garage or similar for a long time. In this case, a flat spot can develop overnight.
Flat spots, correcting
• Flat spots cannot be removed from tires with workshop equipment.
• Such flat spots can be driven out only by driving the car until the tires are warm.
• We do not recommend the following method during cold or winter weather.
Requirements/Conditions
- Check and correct the tire pressure as necessary.
- Drive the vehicle on the highway, if possible.
- If the traffic and road conditions permit, drive at a speed of 120 km/h to 150 km/h for a distance of 20 to 30 km.
CAUTION!
• Do not endanger yourself or other persons during this road test.
• Observe valid traffic laws and speed limits during the road test!
- Raise the vehicle immediately after the drive.
- Remove wheels from vehicle.
- Balance the wheels on the stationary balancing machine. Refer to => [ Stationary Balancing Machine ].