METROLOGY REPORT

GROUP MEMBERS

Saikumaran.A

Saktivel.K

Shameena Ayesha.N

Vasantha kumar.V

Vijayalakshmi.M

Wheel Runout:

The amount wheel moves in and out away from its true center as it is rotated. If runout is excessive the wheel can be seen to wobble as it rotates.A car exhibits bad characteristics when the wheels are bent --- it will shake at highway speeds, the steering wheel may shimmy or the car may "buck," like a bucking bronco. How far off-center the wheel is bent is called runout. All these symptoms point to one of two types of runout, or a combination of both. By understanding both types of runout for wheels, you will understand the specifications as well.

Types of wheel runout:

Lateral runout Radial runout

Lateral runout:If you hit a curb sideways violently, the wheel more than likely will become bent.

According to professional technicians at AA 1 Car, the side bending is called lateral runout. The chief symptom of lateral runout is that the car shimmies or shakes. The shaking becomes more violent as the car goes faster.

Radial runout:If you hit a pothole, more than likely radial runout will occur. Instead of the wheel

being perfectly round, it acquires an oval shape. The chief symptom of radial runout is the car "bucks," like a horse bucking. This is because the wheel has low and high spots. The bucking becomes more violent the faster the car goes.

Measuring the Wheel's Runout

Theory and Information Information

Setup Procedure Preparing to measure runout

Measurements Off-Vehicle Radial Runout Measurement Off-Vehicle Lateral Runout Measurement

Specifications Runout Specifications

Diagnostics Diagnostic Action to Take

Theory and Information

Excessive tyre and wheel runout can cause a noticeable vibration.  As the vehicle is driven, the wheels and tyres are exposed to great stresses and abuse.  Wheels can bend and tyres can separate, the result is a vibration.  This test will determine if the wheel, is responsible for the vibration.

Setup Procedure

Mount the wheel on a tyre balancer as shown below to allow runout measurements to be performed.

Measurements

Measure the radial runout of the wheel's inside tyre bead lock contact area as shown below.  Be sure to measure both sides of the wheel.  Mark the high and low runout points on the outside of the wheel.

Measure the lateral runout of the wheel's inside tyre bead contact area as shown below.  Be sure to measure both sides of the wheel.  Mark the high and low runout points on the outside of the wheel.

Specifications

Specifications Steel Wheels Aluminum WheelsRadial Runout 0.040 inch

(1.016mm)0.030 inch (0.762mm)

Lateral Runout 0.045 inch (1.143mm)

0.030 inch (0.762mm)

Diagnostics

If the runout is excessive, replace the wheel and check the new wheel's runout to insure it is within specifications.

Tyre & Wheel BalancingThe technical definition of balance is the uniform distribution of mass about an axis of rotation, where the center of gravity is in the same location as the center of rotation. A balanced tyre is one where mass of the tyre-when mounted on its wheel and the car's axle-is uniformly distributed around the axle (its center of rotation). Balanced tyres can spell the difference between a positive and negative driving experience. Drivers of high performance vehicles will be more sensitive to imbalance problems, but no driver is happy with an annoying vibration.

An out-of-balance tyre and wheel assembly:

Degrades ride quality and driver comfort. Shortens the life of tyres, bearings, shock absorbers, and other suspension

components. Vibration is the most noticeable effect of imbalance. It is dependent on vehicle speed. It often first becomes apparent between 40 and 45 mph and increases in magnitude

with greater speeds.

Sources of ImbalanceTwo sources of imbalance occur in tyres: heavy or light spots in the tyre and radial or lateral run-out. Imbalance also can be caused by:

Variations within the wheel, such as thickness and welds. Rotor and axle imbalances.

Heavy or Light Spot ImbalanceThere are two types of imbalance caused by heavy or light spots: static and dynamic.

Static imbalance: Occurs when there is a heavy or light spot in the tyre so that the tyre won't roll evenly and the tyre/wheel assembly undergoes an up-and-down movement.

Dynamic imbalance: Occurs when there is unequal weight on both sides of the tyre/wheel assembly's circumferential centerline. The tyre/wheel assembly has a side-to-side

Heavy or Light Spot BalancingAchieved either statically or dynamically, depending on the type of imbalance that has occurred.

Static balance: Achieved with a bubble balancer but does not correct for dynamic imbalance.

Dynamic balance: Achieved with a spin balancer where the tyre/wheel assembly is balanced both statically and dynamically.

Radial or Lateral Run-out ImbalanceThis results from poor bead seating on the rim or the placement of components. Poor bead seating is usually the result of improper mounting or the use of improperly made wheels. A small degree of this imbalance is acceptable, but too great a run-out causes vibration and excessive tyre wear.

Radial Run-out: An "out-of-round" situation where vibrations are produced as the wheel spindle moves up and down.

Lateral Run-out: A side-to-side or wobbling movement of the tyre and wheel. It is less common than radial run-out. Sensitivity of a vehicle to vibration from radial run-out is four to eight times that of wobble from lateral run-out.

Run-out BalancingDepends on whether it is radial or lateral run-out.

Radial run-out balancing: Achieved by rotating the wheel and tyre assembly two stud positions on the hub, or by rotating the tyre 180° on the wheel. If run-out is still over specification, check wheel run-out and mark the low point. Rotate to match the high point of the assembly run-out with the wheel low point. If the assembly run-out is still too high and the wheel is within specification, replace the tyre.

Lateral run-out: Achieved by using a run-out gauge to check both the tyre and wheel. Chalk-mark the highest point of run-out on both the wheel and tyre. Replace whichever (wheel, tyre, or both) is out of specification.

1. Wheel is securely seated on the hub face.2. All lugs have proper torque.3. There is no buildup of dirt between the hub and wheel.4. The wheel is not bent.5. Both tyre beads are securely seated on the rim.

Custom or Alloy WheelsCustom or alloy wheels require an increased level of care over steel wheels. There are several key points to note when mounting tyres.

Avoid scratching or bending alloy wheels during installation. These wheels are manufactured with extremely soft metals with a greater sensitivity to scratching and distortion under pressure. Modern tyre machines apply equal pressure to both top and bottom beads with no pressure on the wheel itself. A pad on the base of the mounting machine protects chrome-plated, painted or machined wheels from scratches and damage.

During the mounting process, proper lubrication is a must. Both top and bottom beads must be lubricated with an approved tyre lubricant. If the beads do not seat at 40 psi, the installer must break the entire assembly down and re-lubricate the bead areas.

Observe match-mounting procedures.Proper tyre and wheel assembly balancing is important from a vehicle safety standpoint. In high-speed driving, improperly balanced tyre/wheel assemblies will cause a vehicle to lose stability and not operate in a safe and comfortable manner. Improperly balanced tyre/wheel assemblies also cause abnormal treadwear patterns.

To facilitate proper balancing, Most tyre manufacturers place red and yellow marks on the sidewalls of its tyres to enable the best possible match-mounting of the tyre/wheel assembly. There are two methods of match-mounting tyres to wheel assemblies using these red or yellow marks

WHEEL RUNOUT 

1. Jack up the vehicle and support it with floor stands.

2. Measure wheel runout with a dial indicator as illustrated.

3. Replace the wheel if wheel runout exceeds the limit.

MEASUREMENT SPECIFICATIONSteel type wheel (radial) (average of LH & RH) 0.6 mm ( 0.024 in ) Steel type wheel (axial) 1.0 mm ( 0.039 in ) Aluminum type wheel (radial) 0.3 mm ( 0.012 in ) Aluminum type wheel (axial) 0.3 mm ( 0.012 in )

WHEEL NUT TIGHTENING

1. Steel and aluminum alloy wheel tightening torque.

TORQUE SPECIFICATIONSpecified torque 90-110 Nm ( 900-1,100 kg·cm, 66-81 lb·ft )

2. CAUTION:

When using impact-wrench, final tightening torque should be checked using a hand torque wrench.

2. Tightening order.

Go around the wheel tightening every other nut until they are all tight.Then double-check each nut for tightness.

WHEEL BEARING END PLAY INSPECTION

1. Inspect the play of the bearing while the vehicle is jacked up and resting on floor jack.

2. If there is any play, remove the hub cap and then release the parking brake.

3. Check the bearing end play. Place a dial gauge against the hub surface, then move the hub in the axial direction and check whether or not there is end play.

MEASUREMENT SPECIFICATIONService limit 0.005-0.025 mm ( 0.0002-0.001 in )

or less

4. If the end play exceeds the limit, the rear wheel bearing nut should be tightened to the specified torque and check the end play again.

5. Replace the rear hub bearing unit if an adjustment cannot be made to within the limit.

WHEEL ROTATION 

1. Rotate the tyres in the patterns illustrated.

CAUTION

The temporary spare tyre should not used in the wheel rotation.

Checking for pull and wanderIf the steering pulls to one side, use the following wheel rotation by following procedure.

1. Interchange the front right and front left tyres, and perform the road test in order to confirm the vehicle stability.

2. If the steering wheel pulls to opposite side, interchange the front and rear tyres, and again perform the road test.

3. If the steering wheel continues to pull to one side. Interchange the front right and left tyres again, and again perform the road test.

4. If the steering wheel continues to pull to the opposite side, replace the front wheels with new ones.

Wheel: Testing and InspectionWheel RunoutHOW TO MEASURE WHEEL RUNOUTTo measure the wheel runout, it is necessary to use an accurate dial indicator. The tyre may be on or off the wheel. The wheelshould be installed to the wheel balancer of the like for proper measurement.Take measurements of both lateral runout and radial runout at both inside and outside of the rim flange. With the dial indicatorset in place securely, turn the wheel one full revolution slowly and record every reading of the indicator.When the measured runout exceeds the specification and correction by the balancer adjustment is impossible, replace the wheel. If the reading is affected by welding, paint or scratch, it should be ignored.Steel wheel Radial runout limit: 1.14 mm (0.045 inch) Lateral runout limit: 1.40 mm (0.055 inch)