4/16/2012
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 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 offcenter 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 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 wheel runout can cause cause a noticeable 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 result is a vibration. This test will determine if the wheel, is responsible responsible for the vibration.
Setup Procedure
Mount the wheel wheel on a tyre balancer balancer as shown below to allow runout measuremen measurements ts 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 sides of the wheel. wheel. Mark the high and low runout points points on the outside of the wheel.
Measure the lateral runout of the wheel's inside tyre tyre bead contact area area as shown below. Be sure to measure both both sides of the wheel. Mark the high and low runout points points on the outside of the wheel.
Specifications Specifications Radial Runout
Steel Wheels 0.040 inch (1.016mm)
Aluminum Wheels 0.030 inch (0.762mm)
Lateral Runout
0.045 inch (1.143mm)
0.030 inch (0.762mm)
Diagnostics
If the runout is excessive, excessive, replace replace the wheel wheel and check the the new wheel's runout runout to insure it is within specifications.
Tyre & Wheel Balancing The 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 wheel assembly:
Degrades ride quality and driver driver comfort. Shortens the life of tyres, bearings, shock absorbers, and other suspension components. components. Vibration is the most noticeable effect of imbalance. It is dependent dependent on vehicle speed. speed. It often first becomes becomes apparent between between 40 and 45 mph and increases increases in magnitude magnitude with greater speeds.
Sources of Imbalance Two sources of imbalance occur occur in tyres: heavy or light spots in i n 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 Light Spot Imbalance There are two types of imbalance i mbalance 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 undergoes an up-and-down movement. Dynamic imbalance: imbalance: Occurs when when there is unequal unequal weight on both sides of the tyre/wheel assembly's circumferential circumferential centerline. The tyre/wheel assembly has a sideto-side
Heavy or Light Light Spot Balancing Achieved either either statically or dynamically, dynamically, depending depending on the type of imbalance that has has occurred.
Static balance: Achieved with a bubble balancer but does not correct for dynamic imbalance. Dynamic balance: balance: Achieved with with a spin balancer where the tyre/wheel tyre/wheel assembly is balanced both statically and dynamically.
Radial or Lateral Run-out Run-out Imbalance Imbalance This 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 i mbalance is acceptable, but too great a run-out causes vibration and excessive tyre wear.
Radial Run-out: An "out-of-round" "out-of-round" situation where where vibrations are produced produced as the wheel spindle moves up and down. Lateral Run-out: A side-to-side side-to-side or wobbling wobbling movement of of the tyre and wheel. 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 Balancing Depends on whether it is radial or or lateral run-out.
Radial run-out balancing: balancing: Achieved by rotating the wheel and tyre assembly two stud positions on the hub, hub, or by rotating the tyre 180° 180° on the wheel. 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 assembly run-out with the wheel 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. 2. 3. 4. 5.
Wheel is securely seated on the hub face. f ace. All lugs have proper proper torque. torque. There is no buildup of dirt between the hub and wheel. The wheel is not bent. Both tyre beads beads are securely securely seated on on the rim.
Custom or Alloy Wheels Custom or alloy wheels require an increased level of care over steel wheels. There are several key points to note when mounting tyres. t yres. Avoid scratching scratching or bending alloy alloy wheels during 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 f rom scratches and damage. During the mounting mounting process, proper lubrication lubrication is a must. Both top and bottom beads must be lubricated with an approved tyre tyre lubricant. If the beads beads do not seat at 40 psi, the installer must break the entire assembly down and re-lubricate re-lubricate the bead areas.
Observe match-mounting procedures. procedures. Proper tyre and wheel assembly balancing is important from a vehicle safety standpoint. In high-speed driving, improperly balanced 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 the vehicle and support support it with floor stands. stands. 2. Measure wheel wheel runout with a dial dial indicator as illustrated. illustrated.
3. Replace the wheel if wheel runout runout exceeds the limit.
MEASUREMENT SPECIFICATION Steel 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 wheel (radial)
0.3 mm ( 0.012 in )
Aluminum type wheel wheel (axial)
0.3 mm ( 0.012 in )
WHEEL NUT TIGHTENING 1. Steel and aluminum alloy wheel tightening torque. TORQUE SPECIFICATION
Specified 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 doublecheck each nut for tightness.
WHEEL BEARING END PLAY INSPECTION 1. Inspect the play play of the bearing while the vehicle is jacked up and and resting on floor jack. jack. 2. If there is any play, remove the hub cap and then release 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 SPECIFICATION Service limit 0.005-0.025 mm ( 0.0002-0.001 in ) or less 4. If the end play exceeds exceeds the limit, the rear wheel bearing bearing nut should be tightened to the specified torque and check the end play again. 5. Replace the rear hub bearing bearing unit if an adjustment adjustment cannot be made made to within the limit.
WHEEL ROTATION 1. Rotate the tyres tyres in the patterns illustrated. illustrated.
CAUTION The temporary spare tyre should not used in the t he wheel rotation.
Checking for pull and wander If the steering pulls pulls to one side, use use the following wheel wheel rotation by following procedure. procedure. 1. Interchange the front right and front front left tyres, and perform perform the road road test in order to confirm the vehicle stability.
2. If the steering wheel wheel pulls to opposite opposite side, interchange interchange the front and and rear tyres, and and again perform the road test.
3. If the steering wheel wheel continues to pull pull to one side. Interchange Interchange the front right and left tyres again, and again perform the road test.
4. If the steering wheel wheel continues to pull pull to the opposite side, replace the front wheels with new ones.
Wheel: Testing and Inspection Wheel Runout
HOW TO MEASURE MEASURE WHEEL RUNOUT To 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 (0.055 inch)
