Modern Tire Dealer

JUN 2019

Magazine for the professional tire industry

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39 w w w . M o d e r n T i r e D e a l e r . c o m which shows the car owner the vibration caused by his unbal- anced wheels. With this device it is not necessary to remove the wheel from the car. The car is jacked up so that the knees are free and a small wheel, turned by an electric motor, is held against the wheel, revving it up to 100 m.p.h. If there is an unbalanced condition the customer can see the bumper, front end, doors, head lamps, and fenders shake and shimmy. After the wheels are balanced a glassful of water can be set on the fender and not a drop will be spilled due to vibration. Wheels roll improperly, causing erratic and difficult steer- ing and uneven tire wear, when any of the following are out of alignment: Camber, or wheel slant, Caster, or backward tilt of king pin, King pin inclination, or inward tilt of king pin, Turning radius, or proper relations of wheels on a curve. Toe-in, or wheel gather, Tracking, or relation of front and rear wheels to frame. Any of these faults might be caused by traffic accidents, hard bumping of curbs, unequalized tires, or the general carelessness of the driver. The cause, however, is not so important to the service man as the correction. Several manufacturers offer various machines for check- ing and correcting wheel balance and alignment, and the manufacturers' instructions for using this equipment should be followed. Complete static and dynamic wheel balancing machines can be bought on convenient purchase plans and they will quickly pay for themselves, not only in service sales they make directly, but added dividends in sales of recaps, wheel balancing weights, king pins and bushings, axle wedges, wheel bearings, shock absorbers, brake lining, etc. Wheel aligning equipment requires only 150 to 200 square feet of floor space and a dynamic balancer requires 20 square feet or less. The Bear Mfg. Co. has developed a balancer which will static-dynamic balance the wheel all in one operation and is applicable for use on truck wheels as well as passenger car type. Corrections required in most front wheel aligning work may be classed broadly as follows: Camber Corrections, due to curb bumping, road shocks, etc. Caster Correction, due to spring sag, worn shackle bolts and bushings, etc. Toe-in Correction, due to loosening of steering mecha- nism, tie rods, wheel bearings, drag link connections, etc. Steering Geometry Correction, due to bent spindles, and changes in camber and caster. In testing wheel alignment, it is necessary to first inflate the tires to the recommended pressure and then check for run-out of wheels and tires. Check adjustments of front wheel bearings and correct any excessive looseness of king pin. And, most important, make sure that wheels and tires are correctly balanced. There are two types of balance to consider: static and dynamic. Static balance is performed while the wheel is stationary. The wheel is rotated on a special balancing support and it reveals its heavy spot by stopping with that point at the bot- tom. Dynamic balancing is obtained by ascertaining where the heavy point of the assembly exists while it is rotating under actual road conditions. A wheel that is unbalanced statically tends to hit the road harder on certain spots of its circumference. This causes road tramp, producing a bumpy, uncomfortable ride. Static balance is a simple and inexpensive service and can be done profitably with any good equipment. Balance is achieved by attaching balancing weights to the tire rim flange to offset an opposite heavy point. When static balancing a wheel on the balancer it is recom- mended that the heavy section be permitted to settle at the bottom. Then, by taking two equal size weights and placing them equal distance from the center of the light portion of the wheel, a quick static balance can be obtained. e reason for using two weights rather than one is that in some instances 3 ounces might be too heavy, while 2½ ounces is too light. By using two 1½-ounce weights and parting them approximately five to six inches from the exact opposite point of counterbalance the difference is distributed over a wider area. Balance weights for passenger cars are made in ½-, 1-, 1½-, 2-, 2½-, 3-, 3½-, 4-, 5-, and 6-ounce sizes. Truck weights are made in various sizes from 4 ounces up to and including 20 ounces. It has been found in many instances when a wheel is off in dynamic balance after it has been balanced statically, the only correction necessary is to transfer the static weight to the opposite side of the wheel, or in some instances it is necessary to transfer only a part of the weight. The wheel should be in correct static balance before dynamic balance is attempted. Most modern dynamic balances reveal at a glance the smallest amount of run-out or vibration. When the wheel is in actual service revolving around the center line of the shaft, the centrifugal forces of the two halves act in opposite directions and along different lines, producing a couple action, or wobble. The dynamic balancer shows up this wobble, and reveals the exact point of overweight, inside or out, which produces the wobble. It is then a simple matter to adjust the weights as automatically indicated by the balancer. Operation of wheel alignment and wheel balancing equip- ment is really a none-too-difficult job for the experienced service mechanic. Some manufacturers of wheel balancing and alignment equipment provide schools for training operators on the principles and methods of wheel correction. In most cases these schools are free; the only cost to the student being his room and board. Many tire dealers have found wheel correction service the answer to the problem of helping their customers get the most possible mileage out of their tires and at the same time make up for profits lost on new tire sales. Many other dealers are going to recognize the value of wheel balancing and alignment and add these services to their activities in the interest of greater shop profit at this time when earning power must increase in the face of rising business costs and falling sales volume. ■

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