Wheel Alignment
Definition : The wheel alignment means correct adjustment of the front wheels with respect to pivot axis and controlling steering movement to the wheel giving the directional stability to vehicle, promotes case of steering and reduces the wear to a minimum.
● The directional stability of vehicle means the condition that it possess if it can run straight down on road, enter and leaves the circular path easily and resist road shock.
Purpose (Necessity) of Wheel Alignment
● Due to running of vehicle over a period of time on various road conditions leads to change in the setting of all the above mentioned parameters.
● In wheel alignment all these parameters are set to their design values. Otherwise directional stability of vehicle gets hampered. Uneven tyre wear, damage to various links of steering system may result.
● The front wheel alignment depends upon wheel geometry i.e. caster, camber, kingpin inclination, toe in-toe-out, as explained earlier in wheel geometry.
● The following factors affects the wheel alignment:
1. Factors pertaining to wheel:
(a) Balance of wheel
(b) Inflation of tyre
(c) Steering geometry
2. Steering geometry:
(a) Camber
(b) Caster(c) Kingpin inclination
(d) Toe-in and Toe-out3. Steering linkage.
4. Suspension system.
Procedure (Checking) of Wheel Alignment:
● The first step of wheel alignment, is to inspect the king pin inclination, camber and caster angles and toe-in.
● For rigid axle suspension system camber angle and kingpin indention is fixed and caster angle can be adjusted by caster plate.
● Whereas for vehicles having independent suspension system, the above mention angles are adjusted by a shim between the lower and upper arm brackets or by eccentric clamping bolts of the arm.
● For inspection of camber, caster and king pin inclination, a specific type of standard gauges are used. This gauge consists of two part
(i) Level and angle gauge,
(ii) Turn table
● One of them gauge is optical gauge of Dunlop Tyre Co. gives very accurate and precious reading used to measure toe-in. Telescopic gauge is commonly used in workshops.
● This gauge consists of two pipes, of which one can be slide on another to adjust the width. A vertical rod is mounted on each pipe and can be adjusted at any position on the pipe according to requirement of wheel. The vertical rod is provided with adjustable pointer which moves up and down on rod.
● To inspect the toc-in the pointers of the gauge touches with the front wheels, measure and note the reading on the pipe.
● Similarly, when the pointers of the gauge touches with the rear portion of the front wheels and note the reading and calculate the difference between the two readings gives the value of toe-in.
Wheel Balancing
Definition: It is a process that ensures wheel spins truely as they are fitted on a vehicle. In case wheel are not spinning properly then there are problems like uneven tyre wear, a vehicle pulling on one side, excessive bouncing of a vehicle, wheel shimmy at which we face. To avoid them this is done.
● The method, of addition of small weight to the wheel rim to avoid wheel wobble and vibration and easy to steer for the it should be statically and dynamically balance.
● Wheel balancing is the process of correcting the lateral run, radial run out and addition of weight to avoid uneven distribution of the weight about the rotational axis of wheel.
Purpose of Wheel Balancing (Necessity)
● During the running of vehicle the tyres gets won out and wheel rim gets bend or damaged.
● There may be lateral run out of wheels, Radial run out may be created due to tyre or rim out of conditions. This leads to uneven distribution of weight around axis of rotation of wheel assembly. Because of this there is an unbalance created in the wheel assembly.
● If this unbalance is not removed, then this may lead to wobbling of front wheels, vibrations, tyre wear, and may adversely affect steering system assembly parts. This can be avoided by balancing.
● The balancing of a tyres wheel is most essential to avoid the front wheel wobble. Which affects steering and increase tyre wear rate. The factors affecting the wheel balance are as follows:
1. Lateral run out of the wheel.
2. Radial run out or run of round the wheel, caused by tyre or rim out.
3. Uneven distribution of the weight around the axis of rotation.
● Therefore it must be necessary to inspect the wheel centering, before checking the wheel for balancing lateral run out which result of a wraped rim from bumps and can be corrected by arbor press.
● The tyre must be removed to straighten the wheel rim. Tum the wheel about its axis and check the wheel inside flanges retaining the tyre bead and the rim well from run out in excess of 1.5 mm.
General Procedure of Wheel Balancing:
Fill tyre with recommended tyre pressure, check for tyre / wheel damage don't use damaged rim for balancing.
1. Mount wheel on balancing Machine and lock it. Remove old balance weights.
2. Set balance for size of tyre and start the machine.
3. Read values of imbalance on right and left side of wheel on display. marks.
4. Put respective weights on both sides on marks.
5. Start balancer again and check that reading is zero on both sides then the wheel is balanced.
6. If reading on both sides is not zero then repeat the procedure.
Methods of wheel Balancing:
Static Balance of Front Wheels:
This can be done with the wheels installed on the vehicle by using electronic balance. This gives remarkable advantage of balancing the wheel along with the other rotating masses. The procedure is as follows:
(a) Lift the front wheels on hydraulic jack such that the wheel is freely rotated.
b) Arrange the spinner, which carries the balancer equipment, with its pulley in touch with the tyre tread, the wheel should be in straight ahead position.
(c) Move the balancer into position to point to strobe light at the wheel.
(d) Position the pickup magnet in contact with a clean flat surface on the front suspension as closed to the wheel possible.
(e) Apply the reference mark on the wheel cap on the tyre, consisting of a radial line, Use chalk or a length of tape.
(f) Shift the balancer switch to position 1 and wait some minutes to allow the warm up of tubes if the pick up magnet is in proper contact, the strobe light will flash when the top of the tyre is tapped.
(g) Start the wheel by hand, snap on the switch of the spinner motor and hold the spinner pulley against the tyre tread to revup' the wheel.
While spinning the following conditions are experienced:
1. The flashing of the strobe light will make the reference mark on the wheel appear to be fixed in the same position.
2 Watch the meter of electronic balance. The needle will move on from zero position. When it reaches its highest reading and starts moving back, pull the spinner away.
3. Inertia causes the wheel to keep turning, and the needle will rise again. When meter needle shows its higher reading, note the position of the reference mark. Consider the reference mark as the hour hand of a clock. The"time" the reference mark indicates the position to remember.
(h) Repeat the above inspection procedure and note maximum needle reading on meter dial. If the needle still moves beyond green area of meter dial, proceed as follows:
1. Stop the wheel.
2. Move the wheel on same reference mark position or time recorded at g.
3. Change or shift the balance weight applied, to wheel.
(i) Repeat the check as directed previously. If the wheel is still out of balance, proceed with the balance procedure, till the meter needle remains in the green area of dial meter.
Dynamic Balance of Front Wheels :
(a) Turn the wheel out approximately one half of their steering angle.
(b) Position the pickup magnet in contact with the external front end of the brake housing flange at the wheel rotation axis.
(c) Spin the wheel and record the highest meter reading as well as corresponding position of reference mark as per static balancing procedure.
(d) If the mater moves out of the green area on the dial meter, the wheel is out of balance, in this case follow the procedure as:
1. Move the wheel by hand to the same reference mark position as noted at 3.
2. Divide the total indicated weight in half and apply.
One half at the inside front end of the wheel, in line with horizontal wheel axis.
The other half at the outside rear end of the wheel, in opposite position to the first half.
(e) Check the dynamic balance of the wheel as done for the static balances.
(f) If still out of balance, stop the wheel and bring the reference mark recorded in f.
(g) Repeat the inspection as previously directed. If wheel is out of balancing, repeat the above procedure till the meter needle remains in the green area of the dial meter.
