BUSHES AND
ALIGNMENT Issue 15/2017 SHOCK ABSORBER, SUSPENSION, BRAKES, TOWBARS AND WHEEL ALIGNMENT SPECIALISTS
Suspension Bushes and the Effects of Maintaining Suspension Bushes and the Effects of COMPRESSION BUSHES (RADIUS/STRUT CorrectCorrect Wheel Maintaining Wheel Alignment Alignment ROD BUSHES) The role played by suspension bushes in locating and
Compression bushes bear load in two directions on
role playedaligning by suspension bushes in locating and aligning other suspension other suspension components is very important. the same axis, e.g. caster rod bushes (backward and ponents is The veryfollowing important. The following information will assist selecting information will assist you in selecting theyou inforward load) and shock pin bushes (up and down load). most suitable bush to achieve the maximum effect for While these bushes are new they have equal amounts most suitable bush to achieve the maximum effect for the car. the car.
of rubber with equal pressures which centrally locate the component. es, in mostBushes, cases are a locating and as such, when deteriorate allows in most casesdevice are a locating device andthey as such, he control when arms and arms they to move. effects thearms alignment of the is a very resilient material and has a ‘memory’, theytrailing deteriorate allowThis for the control Rubber trailing arms toThis move. This effects alignment i .e. ension andand wheel alignment. is why Peddersthe stress the importance ofit will return to its original position when in good of properly the suspension and wheels.anThis is why steering Pedders and suspension condition, but after repeated cycles of compression king bushes when conducting undercar stress the importance of checking bushes properly during normal operation, they become work-hardened k. Bushes when absorbconducting road shocks accurately locate allowing anand undercar steering andcomponents, suspension whileand permanently deformed, losing the ability to return to to move in the directions they were designed to move. A bush must therefore be shape and position. check. Bushes absorb road shocks and accurately their original locate while allowing to to move in the position. If a bush is too hard, too soft, or to compress, but components, to a precise degree, and thenthem return its original A classic example of bushes which are over looked in directions they were designed to move. A bush must aged in any way, the ride, handling and steering geometry will be compromised, alsothe there may be an with Symptoms servicing, are strut/radius rodissue bushing. therefore be able to compress, to a certain degree, and cle safety. of bad strut rod bushing are often mistaken for brake then return to its original position. If a bush is too hard, trouble. This is because, when the car is under braking, too soft, or damaged in any way, the ride, handling and the having load placed on the bush isor extreme and it will way to understand the importance of a bush being in good condition and the right elasticity steering geometry will be compromised, also there may compress, allowing the wheel to move rearwards and if pressibility,beisan byissue considering the setting with vehicle safety.of the toe angle. As you know, most vehicles are given toe in, this is a the bush is in inferior condition, this can effect the wheel ic” setting for a “dynamic” situation. This is to allow for the change in alignment angles produced by the motion One way to understand the importance of a bush being base and cause the car to “pull” under brakes. e vehicle. When vehicle isand in motion, or right 'rolling', the front-end bushes compress, allowing the wheels to in gooda condition having the elasticity or Soft strut rod bushes can also cause steering pull during me exactlycompressibility, parallel , i .e. the angle changes the from toe inoftothe zero. is by considering setting toe normal driving as toe and caster angles are “loose”. If the angle. As you know, most vehicles are given toe in, this bushes allow the caster angles to decrease, the vehicle bush is tooissoft, or is damaged, correct rolling toe angle will a “static” setting forthe a “dynamic” situation. This is to not be achieved, resulting in steering miswill have vague steering. If the bush is distorted, the allow tyre for the change alignment angles produced ment and rapid wear. The in rear suspension bushes are justbyas important. a worn bush onagainst a controlFor armexample, can vibrate and thump the chassis. theaxle motion vehicle. When a vehicle is in motion,of the final drive housing, which in turn produces ng arm, live typeofofthe suspension will cause mis-alignment If the car still pulls under braking, inspect these bushes. or ‘rolling’, the front-end bushes compress, allowing wheel steering, causing the car to pull or drift and as a consequence, increase theway ratetoofspot tyrea wear. One easy bad strut bush is to look for a the wheels to become exactly parallel, i .e. the angle tell-tale shiny or polished area on the frame around the changes from toe in to zero. orrectly diagnose bush wear, we must first understand the different type of bushes: bush. Look also for cracks, distortion or gaps between If a bush is too soft, or is damaged, the correct rolling the bush and the frame. toe angle will not( be achieved, resulting in steering MPRESSION BUSHES RADIUS/STRUT ROD BUSHES ) mis-alignment and rapid tyre wear. The rear suspension bushes bear are just asin important. For example, wornaxis, bushe.g. caster rod pression bushes load two directions on theasame on a trailing arm, live axle type of suspension will cause es (backward and forward load) and shock pin bushes (up and down load). mis-alignment of the final drive housing, which in turn e these bushes are new they have equalcausing amounts produces rear wheel steering, theof carrubber to pullwith equal sures which centrally locate the component. or drift and as a consequence, increase the rate of tyre wear.
ber is a very resilient material and has a 'memory', i .e. it will return to its To correctly diagnose bush wear, we must first nal position when in the good condition, butbushes: after repeated cycles of compression understand different type of ng normal operation, they become work-hardened and permanently deformed, g the ability to return to their original shape and position.
assic example of bushes which are over looked in servicing, are the strut/radius rod bushing. Symptoms of bad rod bushing are often mistaken for brake trouble. This is because, when the car is under braking, the load placed e bush is extreme and it will compress, allowing the wheel to move rearwards and if the bush is in inferior ition, this can effect the wheel base and cause the car to “pull” under brakes.
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rsional bushes are the type that allow a component to ist or move through an arc. Not only are they a pivot the suspension,. they are also an insulator which sorbs vibration, noise and shocks. When the bush is w, the 'ferrule' or centre tube is in the centre of the sh with equal pressure from the rubber in all ections. This maintains the central location of the rule. As the bush wears and is subjected to load, the rule can be forced off-centre. When this happens the rubber 'flows' around the ferrule creating unequal pressures. is allows the bush to move moreIssue easily 15/2017 in the direction that is carrying the most load, causing changes in 'rolling' gnment and tyre wear.
BUSHES AND
ALIGNMENT
SHOCK ABSORBER, SUSPENSION, BRAKES, TOWBARS AND WHEEL ALIGNMENT SPECIALISTS
me torsional bushes have the rubber bonded to the metal surfaces. This allows the rubber to 'torque' or twist with rmal suspension movement. As the bush wears and is subjected to load, this are bonding can break or and the rubber There exceptions to this for thatitself matter, the bush TORSIONAL BUSHES may incorrectly timed its by natural a previous fitter. If in doubt n split open between the two cases. This causes excessive movement of thebe bush and prevents 'torqueing' Torsional bushes are the type that allow a component contact your nearest Pedders store or vehicle dealer for ion. The bush must replaced. to twist or be move through an arc. Not only are they a
information. pivot for the suspension, they are also an insulator OIDED BUSHES which absorbs vibration, noise and shocks. When the bush is new, the ‘ferrule’ or centre tube is in the centre oided , or Noise-Vibration-Harshness (N.V.H.) they are of the bush with equal pressure from thebushes, rubber as in all herwise known, are usually of the torsional are designed with directions. This maintains the centralvariety, locationbut of the ferrule.inAs the bush wears is subjected load, noise, the ids or air holes the rubber. They and are designed to to absorb vibration ferrule can be forced off-centre. When this happens d harshness, to prevent it being transmitted to the vehicle body. The the rubber ‘flows’ around the ferrule creating unequal portant thing to remember when fitting most voided bushes is that they pressures. This allows the bush to move more easily ed to be 'timed i.e. to have voids correctly aligned. Normal ll during normal driving as toethe caster angles "loose". If the in the ',direction that isand carrying the mostare load, causing inbush ‘rolling’ alignment and wear. ocedurewill ischanges tohave fit the with the voids in tyre line with thethe arm, to absorb vehicle vague steering. If the bush is distorted, control
V.H. as it Some travelstorsional up the arm. There to this bushes haveare theexceptions rubber bonded to and the for that atter, the bush be incorrectly timed by a previous fitter. If in doubt metalmay surfaces. This allows the rubber to ‘torque’ or twist bushes. One easy way to spot a bad strut bush is to look for a tell-tale with normal suspension movement. As the bush wears ntact your nearest Pedders store or vehicle dealer for information. subjected load, thisorbonding can break or theand the bush. Lookand alsois for cracks, to distortion gaps between the bush INSPECTING BUSHES rubber itself can split open between the two cases. This nspecting Bushes: ,
causes excessive movement of the bush and prevents Whenever inspecting or repairing suspension and its natural or ‘torqueing’ The bush be replaced. henever inspecting repairingaction. suspension andmust steering, and also when diagnosing noises, rattles or noises, steering, and also related when diagnosing related mps , you should always conduct a comprehensive inspection of all bushes. rattles or bumps, you should always conduct a onent to comprehensive inspection of all bushes.
mmence off-centre ferrules, oil soaked bushes, and a pivot with a visual inspection, looking for splits, tears, cracks, Commence with a visual inspection, looking for splits, neral decay, if a bush looks bad, it is. which tears, cracks, off-centre ferrules, oil soaked bushes, and general If a bush looks bad, bush here is bushes appear worn or damaged or misaligned, follow the visual withdecay. a manual inspection. Useit ais.suitable ver to flex the bush or component to expose the bush surface for further inspection and or feel for of the Wherevisual bushes appear worn damaged or misaligned, cessive looseness or play. follow the visual with a manual inspection. Use a suitable
to flex the bush or component to expose the f the there are three basic tests which should expose any weaknesslever nally, in bushings. bush surface for further visual inspection and feel for ad, the excessive looseness or play. pens the rubber 'flows' around the ferrule creating unequal pressures. VOIDED BUSHES direction that is carrying the most load, causing changes in 'rolling' Finally, there are three basic tests which should expose
any weakness in bushings. Voided, or Noise-Vibration-Harshness (N.V.H.) bushes, as they are otherwise known, are usually of the torsional 1. Dry Park Check variety, but are designed with voids or air holes in the to the metal surfaces. theto rubber to noise, 'torque'vibration or twist with The Dry Park Check is the most effective way to check rubber. TheyThis are allows designed absorb and rs and is subjected to to load, this bonding can break ortothe itself steering components for wear. It is carried out while the harshness, prevent it being transmitted therubber vehicle body. The important thing and to remember when fitting'torqueing' most vehicle is at its static ride height, simply by rocking the es excessive movement of the bush prevents its natural voided bushes is that they need to be ‘timed’, i.e. to have steering wheel from left to right. This loads the steering the voids correctly aligned. Normal procedure is to fit the gear in the same way as motion of the vehicle, while keeping all components in their normal ride height bush with the voids in line with the arm, to absorb N.V.H. position. as it travels up the arm.
H.) bushes, as they are variety, but are designed with gned to absorb noise, vibration to the vehicle body. The st voided bushes is that they ectly aligned. Normal ine with the arm, to absorb
Straight advice, specialists you understand and...
BUSHES AND
ALIGNMENT Issue 15/2017 SHOCK ABSORBER, SUSPENSION, BRAKES, TOWBARS AND WHEEL ALIGNMENT SPECIALISTS
WARNING : When doing a dry park check on vehicles with power steering, it is advisable to have the ignition “on” for Electric Power Steering or the engine running for Hydraulic power steering assistance, this will guard against possible damage to the steering gear. 2. Roll Back Check A roll back check is for rear wheel drive vehicles with live axle and trailing arm suspension. It is not suitable for front-wheeldrive vehicles or those with independent rear suspension. A roll back check is carried out simply by locking the tail shaft. This is done by placing the vehicle in PARK if automatic, or in first gear if manual. Leave the handbrake OFF and ensure the ignition is turned off, then use a rear wheel to rock the car back and forth while an assistant checks the suspension bushes. The roll back check loads the rear axle in the same way as acceleration or braking, causing it to push and pull on the trailing arm bushes and expose any weakness or failure in the bushings. 3. Brake Reaction Bush Check (Radius Arm Bush) This operation takes the involvement of two technicians, one undertaking the test and the other observing. Have the first technician drive the car at walking pace in the work shop, Apply the brakes in short sharp “Dabs”. While this is happening, the second technician observes for any major rearward movement of the wheel. If it’s significant, then there is a good chance the bushes have deteriorated to the extent that they are no longer survivable and need to be replaced.
SELECTING THE CORRECT BUSH FOR THE APPLICATION You would be forgiven for thinking that there are just two options in bush material, rubber or Polyurethane. However, in catering for the needs of virtually all vehicles on the road in Australia, Pedders has identified the clear need for no less than three different types of bushing material. 1. Standard Rubber The most commonly used material in general applications where a soft, compliant bush action is required and where resistance to contaminants such as oil and grease is not a priority. Standard rubber is most effective in reducing noise and vibration, but less effective in providing component rigidity. 2. Heavy Duty Rubber Heavy Duty rubber is usually a synthetic rubber material which is more resistant to contaminants than standard rubber and is chosen for applications with higher loads and requiring more durability. 3. Polyurethane For precise mounting of components, where a hard and stable action is required at the expense of comfort, noise and vibration. Most suited for performance motoring, heavy duty load carrying and resistance to contaminants.
This test can also be replicated with the vehicle travelling backwards, applying the same procedure. It is worth noting, that observation of the rear suspension is worthwhile as well, because anywhere there are bushes, there is a possibility of movement.
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When Fitting Bushes, Remember: 1. Correctly 'time' voided bushes 2. Tighten mounting bolts at normal ride height 3. Check for tapered case type bushes,
BUSHES AND
ALIGNMENT
4. Ensure locating 'tits' on compression type bushes are facing the right way and are located in hole before tightening
Issue 15/2017
5. Do not apply grease or oil to rubber bushes (Mineral based lubricants are the enemy of rubber) SHOCK ABSORBER, SUSPENSION, BRAKES, TOWBARS 6. When lubricating Polyurethane bushes, using the correct lubricant, only lubricate the rotating, such AND WHEEL ALIGNMENT SPECIALISTS
as a ferrule or sleeve
When Fitting Bushes, Remember
7.1. Do not over tighten compression bushes Correctly ‘time’ voided bushes.
The Effect on the Wheel Alignment
When bushes experience wear, the arms they are a part of, are now allowed to move. This movement directly mounting height. 8.2. Tighten Do not tack weld bolts pressatfitnormal bushesride (Heat will destroy the bonding) relates to the position of the wheels, if they are not in 3. Check for tapered case type bushes. the same position as they were when the car had it’s last 9. Do not use spacers to increase compression on bush, too much compression will split the bush. wheel alignment, then it is a sure bet that the wheels are 4. Ensure locating ‘tits’ on compression type bushes are no longer set to the correct alignment. Thefacing Effectthe onright the way Wheel andAlignment: are located in the hole before tightening. This will allow for premature wear of the tyres. If any When bushes experience wear, the arms they are a part of,movement are now allowed move. This movement beyond to what is expected of a bushdirectly and any 5. Do not apply grease or oil to rubber bushes (Mineral movement is detected in a ball joint, it is recommended relates to the position theenemy wheels, they are not in the same position as they were when the car had it’s last based lubricants areofthe of if rubber). the offending be replaced A.S.A.P. wheel alignment, then it is a sure bet that the wheels are nothat longer set to thecomponent correct alignment. 6. When lubricating Polyurethane bushes, using the Movement in bushes can equate to massive Camber correct lubricant, only lubricate the rotating, such as a This will allow for premature wear of the tyres. If any movement beyond what2mm is expected a toe bushsetting and any and/or Toe changes, can alterof the by ferrule or sleeve. as the much as 10mm,component this is not good for steering stability movement is detected in a ball joint, it is recommended that offending be replaced A.S.A.P. 7. Do not over tighten compression bushes. or tyre wear. The same situation may occur in the rear suspension as well, when bushthe wears the arms it Movement in bushes can equate to massive Camber and /or Toe changes, 2mm canaalter toe insetting by as 8. Do not tack weld press fit bushes (heat will destroy will allow for a change of position of the wheel, whether theasbonding). much 10mm, this is not good for steering stability or tyre wear. The same situation may occur in the rear it be an I.R.S. or a live axle fitted with trailing arms. It is suspension as well, when a bush wears in the arms it will allow for a change position of“Rear the wheel, 9. Do not use spacers to increase compression on the very possible the carofwill develop Wheel”whether steer. it be an I.R.S. a live axle fitted will withsplit trailing arms. It is very possible the car will develop “Rear Wheel” steer. bush, tooor much compression the bush. One of the symptoms, for rear wheel steering, is that the steering wheel be aincentral a central position when One of the symptoms, for rear wheel steering, is that the steering wheel will will not not be in position when driving. driving.
So remember, check all the bushes front and rear so the car maintains good steering, handling and extended tire life.
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