Buick – Tire Wear, Alignment & Vibration (1988)

hello my name is dick Bratz I’m a tire wheel service engineer with the General Motors proving ground in Milford Michigan here in the tire lab we study tire wear alignment and vibration conditions our objective is to provide cars and trucks for our customers that offer the best possible tire and wheel performance since 1984 almost all Buick models have come equipped with all season radial tires as standard equipment because of their design all season tires provide exceptional traction in wet dry and snowy conditions while still providing quiet operation low rolling resistance and excellent wear characteristics in fact most all-season radials can be expected to last at least as long as the highway tread designs they replaced but if an all-season radials subjected to abuse it may wear in patterns unlike those normally associated with highway treads to better understand why this happens it’s important to understand a little about tire tread design in general on a tire with a typical highway tread design the tread pattern is laid out in five obvious rows some of the rows are separated by only small shallow cross grooves while other rows are separated by larger cross grooves when the tread row is separated by large cross grooves the row is actually divided into sections of rubber commonly referred to as tread blocks it’s the combination of randomly placing tread blocks between the numerous cross grooves that separates all season tires from highway tires you see with the tread blocks divided by numerous random cross grooves the all-season tires gain superior all-weather traction it’s also because of these random cross Groo that all season tires are more likely to wear differently than tires with highway treads since the numerous random cross grooves divided the tread into numerous individual blocks of rubber the blocks have less structural support when compared with a highway tread under normal circumstances this isn’t a problem as the tire rotates the tread blocks remain relatively stationary but when a car corners frequently or the toe is incorrect the tire tread is subjected to a great deal of lateral force which causes the tread blocks to twist and squirm in an unusual manner it’s the twisting squirming action of the tread blocks that causes all season tires to wear and patterns commonly referred to as irregular an added characteristic of irregular wear is that it’s usually isolated to the non driven tires of both front and rear wheel drive models you normally don’t find your regular we’re on the driven tires because they have a tendency to wear in more uniform patterns but the non driven wheels are often subjected to the exact lateral forces which contribute to the three different irregular wear patterns the first of these is characterized by the stepped wear pattern it leaves in the individual tread blocks of the tire this wear is referred to as heel and toe wear and often causes increased tire noise the easiest way to identify this pattern is to rub your hand from the front of the tire towards the rear of the tire if you feel a sawtooth roughness or step pattern in the tread the tire has heel and toe wear it’s normal for all-season radials to experience minor heel and toe wear near the outside shoulders of the tire this is particularly true when the tires are on the front wheels of a rear-wheel drive model or the tires are new and the tread depth is deepest and most likely to squirm to eliminate this wear check that the tire pressure is equal to the specifications listed on the driver’s door edge placard and simply rotate the tires all of our tire suppliers recommend the MA idec’s method of tire rotation which calls for the tires from one side of the car to BX to the other side of the car this method eventually puts each tire on all four corners of the car this allows each tire to rotate in both directions and to operate on both the drive axle and the non drive axle this combination

will best minimize irregular tire wear if heel and toe wear continues unchecked it can eventually wear into a more advanced and extreme pattern known as diagonal wear this wear is characterized by the diagonal patterns that actually wear across the tire tread when tires reach this state they can’t be salvaged by rotation and must be replaced a third type of irregular tire wear is similar to diagonal wear and is commonly called cupping cupping appears as a somewhat diagonal pattern towards the edge of the tread the big difference between cupping and diagonal where is the width of the wear pattern diagonal wear patterns run across the entire width of the tread while cupping patterns remain on one side usually cuffing is found on rear-wheel drive cars that corner frequently if a car has a chronic case of a regular tire wear it’s a good idea to check the rotation history of the tires if they haven’t been properly rotated at the scheduled intervals there’s a good possibility that’s the cause if they have been rotated chances are the toe angles on the non driven wheels are incorrect excessive toe angles on non driven wheels cause irregular tire where excessive toe angles on driven wheels cause regular but premature tire wear one common misconception about irregular tire wear is that it’s caused by wheel imbalance will run out or faulty shock absorbers that’s just not true besides road conditions and driving conditions the three service areas that can cause irregular wear our improper inflation pressure lack of rotation using the modified X method and misalignment specifically told because proper alignments are such an important part of keeping irregular tire wear to a minimum it’s vital that four wheel alignments are done properly to assure good alignments the proper pre alignment checks must be performed to begin with the alignment equipment itself must be in good working order check alignment rack turn plates and slider plates at least on a monthly basis they should travel freely without binding or sticking some alignment rack manufacturers suggest frequent turn plate lubrication while others discourage it check the manufacturers recommendations for your particular rack some equipment maintenance procedures such as rack levelness and alignment head calibration are normally performed by alignment equipment professionals these checks should be performed twice a year or more frequently if needed remember the accuracy of your alignment depends on the accuracy of the equipment you use equally important to equipment checks is getting the car ready for the alignment begin by making sure the trunk is free of heavy objects aligning a car with excess weight in the trunk can result in false alignment readings next slide the seat or seats to the full rear position give the inside of the car a quick once-over to make sure there’s nothing heavy in the interior and look at the fuel gauge buick alignment specifications assume the fuel tank is full if the tank isn’t full either fill the tank or simulate a full tank by adding six pounds of weight for each estimated gallon that’s missing now that the car has the front seat properly positioned excess weight removed and the equivalent of a full tank of fuel the suspension is ready for in affection loose suspension parts can alter an alignment every time the car hits a bump by inspecting suspension components before the alignment worn parts can be spotted before a needless alignment is performed section 3 of the service manual highlights checks for many important front and rear suspension components the final pre alignment inspection is for proper vehicle trim height buick alignment specifications are designed with the car resting above a minimum trim height specification the know-how reference manual explains exactly how to check the trim height and includes the latest trim height specifications once the preliminary checks are complete attach the alignment heads and perform the four wheel alignment remember always align the rear

wheels first so that they can be used as an accurate reference when aligning the front wheels if you don’t the cars thrust line may be incorrect the cars thrust line is an imaginary line established by the toe angles of the two rear wheels ideally the rear wheels should track directly behind the front wheels when the car is moving straight forward when this happens the thrust line points in the same direction as the vehicle centerline if the rear wheels don’t follow directly behind the front wheels the thrust line points in a different direction than the center line of the car this can happen if only one of the wheels is towed inward or outward or if the entire rear axle is offset in either case the thrust line deviates from the vehicle centerline and the front wheels must compensate for the car to travel in a straight path this is commonly recognized as dog tracking and results in several problems first the steering wheel does not rest in a centered position the car understeers when turning in one direction over steers when turning in the opposite direction and since the toe is off promotes irregular tire wear similar to a misaligned thrust angle is a aligned cradle on a front-wheel drive car this typically happens if the car has a minor collision or hits a big pothole the first clue to a misaligned cradle is a caster difference from side to side of more than one degree if you suspect the cradle is out of alignment place a set of guide pins in the gauge holes of the cradle if both guide pins fit in the gauge holes the cradle is aligned properly and should not be adjusted if one or both of the guide pins doesn’t go into the gauge holes loosen the cradle bolts just enough to allow cradle movement and maneuver the cradle back into its proper position if the cradle still doesn’t align it’s possible the cradle or body may be misaligned due to damage once it’s positioned it’s very important to torque the cradle bolts in the proper sequence this secures the cradle with even loads and reduces the possibility of future misalignment one area that seen a lot of improvement in the last few years is the rolling smoothness of our tire wheel assemblies with the development of radial tires improvements in tire and wheel manufacturing techniques and better balancing equipment vibration complaints are down nonetheless a lot of older cars are still on the road and even some of the new ones may still experience a tire wheel vibration complaint most vibration complaints result from imbalances in the tire wheel or wheel cover the most common imbalance is a single plain static imbalance this imbalance results from a heavy spot which affects the tire along a single plane because of the heavy spot the tire attempts to move in an unwanted up-and-down direction this up-and-down motion creates vibrations that are eventually felt by the driver and passengers the other type of tire and wheel imbalance is called two plane dynamic imbalance this imbalance is called two plane because the tire has a heavy spot that sits along one plane tries to move to another plane when the tire spins since the weight can’t go where inertia is forcing it the wheel and tire vibrate the most common method of solving both single plane and two plane imbalance is with a computer balancer an important part of accurate computer balancing is the way the wheel is mounted on the machine in almost all cases the appropriate mounting cone is placed against the back of the wheel and the wheel is mounted so that the front side of the wheel faces outward most computer balancers have three adjustable settings wheel width wheel diameter and wheel distance from the balancer typically these adjustments are very easy to make and don’t take much time but it’s important to remember that inaccurate or careless measurements affect the accuracy of the balancer and as you probably know balancing a tire and wheel assembly with the wrong settings can actually create an imbalance condition the know-how reference manual explains the instance when back coning is not recommended one final note on computer balancers relates to calibration as with the alignment rack computer balancers must be calibrated to provide accurate readings the simplest way of checking a balancer is to balance to tire and wheel assemblies this should be done at a time

when the balancer is known to be accurate balanced one assembly to zero the other to an imbalance state and then mount the assemblies on the balancer at least once every month to see if it agrees with the original balance if the balancer agrees with what’s written on the tires it’s still in calibration if it doesn’t agree you know the balancer needs calibration on car balancers are often successful in finished balancing problem tire and wheel assemblies the benefit of an on car balancer is its ability to recognize imbalances created by brake parts and in some cases wheel covers however this benefit is lost when tires and wheels are rotated with rebalancing when using the on car balancer on the front wheels of a front-wheel drive car it’s very important to support the suspension so the drive axles are kept at normal driving angles if the cv joints are driven at extreme angles they can be damaged also important is the speed at which self driven wheels are rotated when the car is off the ground the wheel spins at twice the speed of what the speedometer indicates this means that when the speedometer reads thirty miles per hour the wheel speed is actually 60 miles per hour which is ideal for balancing when you perform the on car balance after an off car balance it’s important to leave the weights from the off car balanced in place simply add more weights as needed for the on car balance occasionally a tire and wheel assembly produces vibrations even when it’s properly balanced when this happens it’s time to dig a little deeper and check the run out of the tire and wheel this wheel is set up for a lateral run-out check the check can be made with the tire on the wheel or off and the wheel either on the car or on a balancer like this to make this check mount the dial indicator so it contacts the side of the bead seat rotate the wheel to find the point of lowest needle deflection and zero the needle next rotate the wheel one complete revolution and watch the needle for maximum deflection disregard any momentary needle jumps caused by paint chips welds or dirt and compared the run-out measurement to specifications to ensure a thorough inspection measure both sides of the wheel if the wheels lateral run-out is out of specifications replace it but if it’s within specifications move on to the radial run-out check to make this check simply mount the dial indicator so it rests against the inside of the wheel again zero the indicator rotate the wheel one revolution and compare the reading to the specifications next repeat the measurement on the other side of the wheel if the radial run-out is out of specifications replace the wheel if the radial run-out is within specifications and there’s still a vibration check the tire and wheel for combined run out checking combined run-out helps determine if the tire itself has excessive radial run-out this is done essentially the same as checking radial run-out on the wheel alone only this time the dial indicator follows a strip of tape wrapped around the tread it’s important to understand though the combined radial run-out measurements are not as accurate as the wheel run out measurements alone it’s possible for a tire to measure within specifications and still cause a vibration condition the problem here is that the tire run-out can drastically change when the tire is loaded to get around this equipment is available that’s designed to measure the combined wheel and tire run out in a loaded state if the tire does have a high spot when it’s loaded the machine is capable of buffing away excess rubber so the tire rolls true when it’s loaded if this type of machine isn’t available at your dealership you can often match the highest spot of the tire with the lowest spot of the wheel to achieve a smooth rolling assembly this is called match mounting on most cars match mounting is done when the tires and wheels are first assembled the bright paint spot or sticker represents the tire high spot and the valve stem represents the wheel low spot you’ll notice that new Riegel’s don’t have the high point mark aligned with the valve stem in the wheel this is simply because more accurate tire and wheel manufacturing techniques have made match mounting unnecessary on the Regals eventually advancements in tire and wheel development will make factory

match mounting a thing of the past on all Buicks even as this program is being released continued testing is being done to provide even longer wearing better gripping smoother rolling tires in fact you should already be seeing some new tread designs on certain new models this coupled with what you’ve learned today in this program should provide your customers with tire performance that is the best in the industry