What can be wrong when your wheels just got balanced and aligned and the car still seems to shake?

Answer 1

Many factors can contribute to shaking in the front end of a vehicle; and, although an alignment coupled with balancing the tires diminishes the possibility that the components involved in these procedures may cause this problem, they are not altogether eliminated from suspicion. Let's take the tire/wheel combination. The tire/wheel combination can be balanced with something inside. If the valve stems were replaced, and the old stem was removed with the tire mounted to the wheel(but 'broken-down'), the possibility exists that a portion of this old valve stem fell into the tire when the stem was pulled out of its hole; and, the small portion inside will roll around until it reaches the same speed as the rotating tire. This is how the tire is then balanced. When the wheel is subsequently installed onto the car, with the balancing weights affixed to the rim, the small rubber stem-bottom is rolling around inside the tire. Now, when the tire rolls down the road, not only is it improperly balanced, but that little rubber gremlin adds to the problem by again moving all around until it begins to spin at the same speed as the tire--- at which time it is nowhere near any point which would balance the tire. The only cure for this is to break the tire back down, remove the rubber remnant of the valve stem, remove the balancing weights, air the tire back up, and re-balance the tire/wheel combination once more. Other possible causes have missed notice on many occasions: A separating tire, a bent wheel, an out-of-round tire, a badly seated tire, and a tire/wheel combination into which tire sealant(Fix-a-Flat?) has been introduced. Tire sealant is particularly notorious for leaving a pool of liquid inside the tire, causing much the same problem as the valve-stem scenario, but without the telltale noise of something rolling around inside when checked. This stuff has to be sopped-out of the tire with a towel. Only then can the tire be properly balanced with the rim. If the tires, wheels, and tire/wheel combinations are in good shape, an alignment can be performed--- if the suspension and steering are tight. This brings up a point: An alignment is an adjustment procedure. The purpose of an alignment is to restore the steering and suspension geometry to the specifications found by the engineers of that vehicle which provide the optimum compromise between handling, stability, control, and wear factors. This is achieved at a specific loading of the vehicle, at a specified ride-height, with a certain amount of gasoline in the tank. An alignment may also be performed on a vehicle which has suffered some types of damage which necessitate attention be given to the rear axle areas as well as the front. This introduces the four-wheel alignment and the thrust-alignment. While settings exist for effecting corrective measures where geometry can be adjusted back into line, no bent part is usable if found: It must be replaced. Much inspection, therefore, is given to parts when an alignment is performed; but, some things are not always clearly evident. When weak struts which cause a vehicle to bounce are found, the finding is usually presented to the customer, who makes the decision for or against replacement. These WILL cause tire wear; and, the cupping of the tires can cause the front end to shimmy. When tie-rod ends are inspected, they may not be loose; but, on rack-and-pinion steering, the inner tie-rod-ends often go undiagnosed as a culprit until a customer complains. At this point, a good technician can find the wear and know the customer will not feel harassed by the news. Lower ball-joints usually require a procedure to be used whereby the joint is 'unloaded' in order for wear to be determined; and, this takes time--- time many customers do not have. If there's nothing outwardly evident of joint failure, the joint is given a visual once-over and a cursory tug at the edge of the wheel. If no exotic movement is felt, all is okay--- until the customer complains. At this point, the customer has the time for the inspection; and, they are ready to make repairs. As far as control-arm bushings, much the same can be said. Ditto for sway-bar bushings. As far as connecting links for the sway-bar ends, these are visual; and, when a customer can be shown the wear, replacement is forthright. Literally, anything which is loose or worn to a certain degree that otherwise should be 'tight' in the suspension or steering can cause a shimmy. This may be observable by routine inspection or special inspection and testing. Some problems may be remedied through low-end replacements, while some may be costly. If CV-joints are coming apart, allowing the shafts to rotate in an orbit rather than concentrically, money is involved. If front wheel bearing assemblies are needed, money is involved. If a lower steering sector has a worn sector-shaft bushing, money is involved to replace the unit. If a couple of shocks are needed, the money expended is less. If the shimmy you feel is only at the times when you apply your brake, this should be conveyed to the detective(mechanic) charged with finding the problem; because, while YOU know this as a 'shimmy' in the front-end, HE knows this as 'pulsation' from warped BRAKE rotors being transmitted to the steering. In this case, a little extra in the way of communication can save a lot of time and inconvenience; and, your car will receive the proper attention sooner.