Ride control complaints are one of the most common types of concerns expressed by customers. Quite often, the customer’s description is vague or misleading. Attempt to gather as much information from them as possible prior to performing an inspection. For example, do you only hear a “funny” noise when driving n bumpy roads or on smooth roads as well? If you suspect that the vehicle is heavily loaded with cargo at times, ask if the “wandering” they experience only occurs when heavily loaded, etc. The customer’s descriptions of an issue should be considered merely as a starting point. It’s up to you to inspect and road test to determine the actual cause of the complaint.
EXAMPLES OF COMPLAINTS
My car seems to pull to the left (or right) when I’m driving.
My car vibrates when I hit my brakes.
I hear funny noises going down the road that seem to be coming from underneath the car.
When I get my car to about 55 MPH, my steering wheel starts to shake. Or I feel a vibration in the seat.
The car is harder to keep in a straight line than it used to be.
DON’T JUMP THE GUN
Rule #1 when discussing this type of customer concern: NEVER diagnose anything at the counter. Inform the customer that your technicians will perform a thorough inspection to address the specific complaint. Make it clear that once the problem has been properly diagnosed, the customer will be informed regarding the cause of the problem and the parts and labor that will be required to fix the issue. Resist the temptation of jumping to a conclusion before the vehicle can be inspected.
Always check initial tire inflation at all wheel locations as one of the first steps. Improper inflation can easily result in not only accelerated outer tire shoulder wear, but may be the culprit for directional pull and/or a wandering complaint.
ISSUE #1: PULLING IN ONE DIRECTION
Always check the basics at the start of any ride control diagnosis by checking tire size and inflation, as well as ride height. This initial check can provide a verification starting point, or can help to lead you in your diagnosis.
A directional pull while driving can involve any of a number of issues. Begin by checking tire size, verifying that both tires on the same axle are the same size. If a previous tire replacement resulted in only one tire being replaced of a different diameter, the smaller diameter tire will cause the vehicle to pull in the direction of the errant side. For instance, if the left front tire features a smaller diameter as compared to the right front tire, the vehicle would tend to pull to the left. All tires should ideally be the same make and model, and overall tire diameter should be the same at both sides of each front and/or rear axle.
Improper inflation pressure is one of the leading causes for a directional pull. Depending on the sensitivity of the suspension design, as little as a 3 psi change per axle side can account for a pull. The pull will occur at the side that features the lower inflation pressure. The severity of the pull will depend on the comparative difference in the same axle’s tires. Tire inflation differential isn’t limited to the front steering axle only. Uneven rear tire inflation can cause a pull as well.
Worn or improperly installed upper strut bearing assemblies can lead to unusual grinding or rattling noises, in addition to compromising steering stability.
Even if tire inflation pressures are correct and the vehicle still pulls, consider swapping left and right side tires (if the tires are directional, this will require dismounting, re-mounting and balancing). Internal tire construction may be different enough to result in a slight difference in belt reaction to road forces.
Checking vehicle ride height (and comparing your findings to factory specs) can help to quickly identify a potential spring fatigue/failure condition.
Wheel alignment angles can have a profound effect on the vehicle’s tendency to pull in one direction. This includes toe, camber and caster. Excessive toe-out on one side can cause the vehicle to pull in the direction of side with more toe-out. If camber angles differ (beyond specification), the vehicle will tend to pull in the direction of the wheel that features more negative (or less positive) camber angle. For instance, if the left front wheel has negative 1 degree of camber while the right front wheel has 1.5 degree positive camber, the vehicle will pull to the left. While the caster angle on many common vehicles may not be readily adjustable, uneven left/right caster angle that is beyond specification can easily cause a pull, with the pull taking place at the side with less caster angle. As an exaggerated example, if the left front wheel has a caster angle of 0.5 degree positive and the right front wheel has a caster angle of 2 degrees, the vehicle will pull towards the left.
Brake drag can cause both an accelerated brake pad and rotor wear issue and a directional pull. If the caliper pistons on one caliper do not retract fully (during non-braking or after a braking), the pads can retain enough rotor contact to reduce the free-wheeling operation of the rotor, in which case the pull will result towards the side with the sticking caliper. Sticking/stubborn caliper pistons can be caused by corrosion in the piston bore as the result of moisture contamination, or following a brake pad replacement after the brake pads have been allowed to severely wear. If the vehicle was operated with thin pads for an extended period, the caliper piston travel distance within its bore has been limited, with possible rust/contamination building up in the un-used area of the piston bore. Once the new pads have been installed, this causes the piston(s) to be further retracted, now travelling win a non-smooth area of the bore, potentially resulting in the piston being slowed down or stuck in the contaminated bore area.
If everything seems to check out and you don’t find any obvious causes for the directional pull, consider how the vehicle’s cargo is distributed. If one side of the vehicle is excessively loaded as compared to the other side, this can affect the front wheel alignment angles with changes to toe and camber angles. Granted, the uneven loading would have to be rather severe, but it’s worth considering during the diagnosis.
While the use of an impact wrench can speed up wheel installation, the only correct method requires the use of a calibrated torque wrench. Improper wheel fastener tightening can easily lead to hub/rotor warpage, which results in a lateral vibration. This is especially critical when dealing with alloy wheels and many of today’s lighter, thin-hat brake rotors.
ISSUE #2: VIBRATION DURING BRAKING
If a vibrational complaint involves the problem occurring during braking, the most likely cause is a warped brake rotor, causing the pads to bounce on/away from the uneven rotor surface. Brake rotor warpage can result from various causes, including brake rotor overheating, lateral or radial runout, sticking caliper pistons and even improper wheel fastener torqueing. Many passenger cars today feature thin-hat rotors that are easily distorted if the wheel fasteners are unevenly or excessively tightened. This is another reminder that a calibrated torque wrench should always be used, especially when installing alloy wheels. Avoid the use of impact wrenches during wheel installations, and always tighten to factory specifications, following the correct tightening sequence.
Some aftermarket alloy wheels may require the use of hubcentric adapters in order to properly center the wheel to the hub. This is due to some wheels being manufactured to fit a range of vehicle fitments in terms of rim diameter, rim width, back space and offset, where the vehicle hub s may differ in diameter. In these cases, the wheel’s center hole may feature a larger diameter for some vehicle applications. The extra space is compensated for with the use of a hubcentric adapter ring that is inserted into a counter bore in the rear of the wheel’s center hole, with the inside diameter of the adapter sized to snugly fit the vehicle’s hub. If the center hub hole of the wheel is too large relative to the hub, the wheel may be installed creating a radial runout condition, which would account for the customer’s “vibration” complaint.
Check brake rotors for lateral runout’ Lateral runout causes the rotor to “wobble” as it rotates, kicking the brake pads in and out during braking, resulting in pedal bounce. When checking lateral runout, the rotor must be secured to the hub with all wheel fasteners (not only two or three wheel nuts or bolts), with fasteners torqued to specification. Mount a dial indicator base to a solid and non-moving surface and lace the indicator plunger perpendicular to the rotor disc surface. Preload the plunger by about 0.050” and then zero the indicator gauge. Slowly rotate the rotor a full 360 degrees and observe the movement of the gauge needle. Compare your reading to factory specifications. Generally speaking, lateral runout exceeding 0.0025” is too much and may require rotor replacement. However, before replacing an otherwise acceptable rotor, mark the orientation of the rotor to the hub (matchmark one wheel stud and its adjacent location relative to the rotor). Remove the rotor and re-position it to the hub in the next clock position and re-check for runout. You may have a stack-up of runout tolerance between the rotor and the hub. If you start to see an improvement, re-position the rotor to the next clock position and re-check. It may be possible to find that “sweet spot” where hub runout and rotor runout cancel each other out.
An example of a hubcenteric adapter ring installed to an aftermarket alloy wheel. This allows the wheel to be properly centered to the hub. Not all aftermarket wheels require these adapters. If adapter rings are needed, it’s simply because the specific wheel may fit a number of different vehicle makes/models, with the exception of the wheel center hole. The manufacturer may design the center hole to fit the largest vehicle hub diameter, then require adapters to fit other hubs that are smaller in diameter.
If, during initial inspection, you observe a discolored rotor, this is a sign of an overheat condition, which could be caused by several factors, the most likely of which is poor braking habits by the driver. The driver may have a habit of abusing the brakes by nailing the brake pedal at the last moment during stops instead of applying moderate pressure prior to final stopping. Or, the brake pads may be the wrong choice for the application, requiring excessive brake pedal pressure. Upgrading the pads to a more robust pad material may solve the issue. Of course, if the rotor is glazed and/or heat checked, the rotor(s) must be replaced as well. If the application involves an emergency vehicle, such as an ambulance or police vehicle, only heavy-duty, high performance pads that are designed for fade-free panic stopping should always be installed.
Worn control arm bushings can result in a number of issues, including erratic ally –changing front wheel angles, a wandering complaint, undercar noises and accelerated tire wear
ISSUE #3: NOISES
A “noise” complaint has the potential for covering quite a lot of ground. Try to obtain more detailed information from the customer. What type of noise do you hear? (clicking, groaning, grinding, popping, whirring, whistling, chirping, banging, etc.). When do you hear the noise? (while starting the engine, while cruising, during braking or turning, or when braking).
Loose lower strut mount fasteners can also contribute to a wandering complaint and can affect uneven tire wear. Whenever replacing struts, even if the vehicle design does not theoretically permit camber adjustment, any tolerance space between the bolts and holes can result in improper camber angles. Always perform a front wheel alignment when struts are replaced.
One of the inspections that may be performed when diagnosing a brake pulsation, shimmy or directional control issue involves checking for lateral runout. When checking a rotor for lateral runout, set up a dial indicator and slowly rotate the rotor a full 360 degrees, noting changes in runout. Note: in order to simulate the stress of an installed wheel and to obtain correct readings, all wheel fasteners must be installed and torqued to specification.
Worn front wheel bearings will typically produce a grinding or clicking sound. Worn or damaged upper strut bearings will typically produce grinding, squeaking or popping noises best heard during slow turns. Worn or dry CV joints will cause a clicking noise, usually experienced during a slow turn (into a driveway or parking spot). Worn shock absorbers may produce a squeaking sound when the driver enters the vehicle or during operation over uneven road surfaces.
A whirring, groaning or squealing noise may be heard due to a dry or worn power steering pump, or engine belt idler pulley. Squealing or chirping noises heard during engine startup, idling or upon initial acceleration may be indicative of loose, out of alignment or worn engine drive belts.
Loose, damaged or badly rusted exhaust system components can cause rattling or banging noises. This includes pipes, hangers, heat shields, etc.
Some front-wheel-drive vehicle rear suspensions may feature left and right lateral links that attach to a center-mounted “watts link”. This serves to reduce body side-to-side movement in relation to the chassis/tire road contact. If the center bushing of watts link wears out, this can create a very noticeable banging/thumping noise that can easily be mistaken for a failed rear strut mount.
Worn suspension components. If the vehicle features front-wheel drive and the rear suspension features a Watts link (also called a bell crank), it’s not uncommon for a worn Watts link center bushing to be worn out, which will result in a banging noise as the vehicle is driven over bumps or uneven road surfaces. This is often mis-diagnosed as involving loose or worn-out rear shocks/struts. A worn-out Watts link won’t really cause any major drivability issues, but the resulting banging noise can be quite nerve-wracking, making the vehicle owner concerned about a major problem.
Naturally, a loud booming or unusually loud exhaust note is likely due to a leak in the exhaust system (rusted-out or muffler, pipe, etc.).
A ticking or clacking noise during engine startup and during warm-up may be caused by piston skirt clatter until the pistons expand at normal operating temperature. A dreaded deep knocking noise during engine operation is a sign of worn/damaged connecting rod bearings (out of your shop’s realm unless you happen to offer engine rebuilding or replacement). A clattering noise during engine startup and idle that seems to be coming from the top of the engine is indicative of loose rocker arms, which, depending on engine design, may involve insufficient oil delivery to the top end (clogged oil passage due to sludge/infrequent oil changes), worn cm followers, etc. We won’t delve further into engine noises, since we’re trying to concentrate on ride-related concerns in this article).
A red dot on a tire indicates the tire’s point of maximum radial force variation (RFV). In order to match-mount the wheel and tire, some wheels (usually OE) feature a dot or mark on the wheel to indicate the wheel’s point of minimum radial runout. By aligning these two marks, RFV is minimized by cancelling out the radial runout of the tire and wheel assembly. Some wheels are marked for minimum RFV, in which case a weight balancing method is required to minimize/cancel RFV.
ISSUE #4: SHAKE AT SPEED
A “shake” complaint by the customer in somewhat ambiguous, since the issue may involve a vibration or a “shake.” Potential wheel imbalance is an obvious starting point. A road test will help to confirm this. If you suspect a wheel imbalance, and you check the wheels on a balancing machine and find no issues, consider a road force variation issue, where the construction of the tire(s) features isolated hard spots. This may be verified and remedied by using a balancing machine that features a road force simulator.
Other potential factors might include a driveshaft imbalance. Inspect the driveshaft for a missing balance weight and check for worn front and rear universal joints. Also inspect for a bent or dented driveshaft. If the vehicle features rear-drive and a solid axle housing, check the pinion angle. If the axle assembly pinion angle has been moving vertically, this changes the driveshaft angle, which could explain a shaking or vibrating issue. If the rear suspension features leaf springs, inspect the spring mounts and spring pad U-bolts for wear and looseness.
A yellow dot on a tire indicates the tire’s point of least weight. When mounting, align the yellow dot with the valve stem, which should reduce/minimize a balance issue, finalizing with a weight balancing operation.
If by chance the vehicle is equipped with a manual transmission, ask the customer if a clutch job was recently performed, and if so, did the “shake” issue begin to occur after the clutch service. It is possible that the wrong clutch assembly was installed, or that the flywheel was replaced. If a zero-balanced flywheel was installed to an externally balanced crankshaft (or a flywheel with an offset balance was installed on an internally balanced crankshaft), an engine and driveline vibration is more than likely.
This may seem like a stretch, but also check for any body/chassis issues involving a component that is affected by oncoming air at highway speed, such as a front lower air diverter or rear airfoil/spoiler. If a component that experiences forces inflicted by air pressure, and if that part is loose or damaged, this can cause the vehicle to experience a “flutter” as air speed increases.
ISSUE #5: VEHICLE WANDER AND SHOCKS
Severely worn shock absorbers (independent shocks or strut dampers) prevent controlled vertical wheel travel, reducing correct tire-to-road surface contact pressure, resulting in a “floating” sensation at highway speed. In combination with speed-related vehicle air resistance, this can give the driver a feeling of a light, “wandering” condition. Worn shocks/dampers will allow over-travel of the suspension, allowing excessive body lean in both lateral (side to side) and longitudinal (front/rear) planes. The reduction of damping and spring harmonic control leads to not only directional wander and body lean during cornering but nose-dive during deceleration and braking, as well as noticeable wheel hop, since a failed shock is not able to control suspension spring oscillation. While signs of hydraulic oil leakage are indications of wear, internal pistons and seals may be worn with no observed fluid leaks.
Worn lower ball joints cause clunking noises, vibrations felt through the steering wheel and wandering left/right.
Worn shocks/struts create a number of issues, including allowing the vehicle to be more susceptible to the force of wind gusts and crosswinds, requiring the driver to constantly correct the steering. Poor suspension dampening due to work shocks/struts contribute to uneven, often “cupping” tire tread wear as the tires are compressed and released repeatedly against the road surface. Braking distances are reduced because even though the brakes are trying to do their job, the reduction of suspension control allows body inertia to permit the body to keep moving forward. This places excessive stress and wear on front brakes, and diminishes the effectiveness of the rear brakes due to body weight distribution as the rear of the body tries to lift upwards, reducing rear tire grip. This results in longer stopping distances and premature brake wear.
Since poorly performing or worn-out shocks/struts don’t control the suspension properly, this creates a domino effect by placing greater loads and stress on other suspension parts such as control arm bushings, springs, anti-roll bar bushings, lateral links, etc.
In addition to shock/strut damper issues, low tire pressure on one or both axles can easily cause a wandering effect., as the underinflated tire sidewalls are forced to flex excessively, resulting in a “loose” and sloppy steering control. Of course, under-inflation will also cause the tires to generate excessive heat, potentially leading to tire failure.
Worn steering system components, such as tie rod ends, drag links, steering gears, rack mount bushings, worn or loose pitman arms or idler arms, pitman arm or idler arm mountings are all suspects when inspecting for a wandering complaint.
Check the condition of the wheel bearings. Loose or worn wheel bearings will result in excessive lateral wheel play, easily contributing to a sometimes twitchy wander issue.
If one front hub that features a tone ring for ABS is replaced, the opposite side hub may have a different air gap at the sensor which can cause a MIL for ABS. From a ride standpoint, if one hub is worn, chances are the opposite hub bearing is due as well. Recommend replacing front hubs/bearings as axle pairs.
If the vehicle is equipped with a trailer hitch, ask the customer if the wandering issue only takes place when towing. If so, the wander may be caused by too much tongue weight which changes the weight distribution of the vehicle, placing too much weight at the rear axle and reducing weight at the front axle. This transfer of weight balance lightens the front end, reducing steering axle tire contact patches to the road surface, causing the driver to constantly correct for straight line direction.
In addition, the trailer may be unevenly loaded, with the majority of the trailer weight towards the rear of the trailer. This can result in the “tail wagging the dog” syndrome. In a severe condition, this can result in a very dangerous and difficult to control condition at freeway speeds.
If a vehicle is equipped with an air suspension, where air bladders aid in controlling both ride quality and ride height, if the system develops an air leak, the compressor begins to work harder, especially if the system’s air dryer is contaminated with moisture. Whenever you’re faced with an air leak in the system, during the repair or components replacement, always change the air dryer. This will prolong the life of the compressor and the air spring solenoids.
Common problems with an air suspension include:
Air leaks, which cause the compressor to run more or even constantly, which results in accelerated wear. Air leaks can be traced either to the air bag/bladder (most common) or leaks in air lines and/or line fittings.
Faulty air compressor. Again, compressor damage is most likely caused by an air leak that causes the compressor to over-work. In addition to noting that the compressor seems to run constantly, listen for telltale noises such as clicking, whining or grinding.
Moisture in the air system. The system features an air dryer to collect moisture and to prevent compressor damage. If excess moisture enters the compressor, this can result in internal corrosion. The air dryer should be changed anytime the air suspension system is serviced.
If an OEM air suspension system has been plagued with problems and the constant need for service, consider changing to a coil spring conversion kit. This will save the customer money in the long run, especially if they don’t need the load levelling capabilities that the factory system once offered.
Tip: If an air suspension-equipped vehicle suddenly illuminates the ABS/Stability Traction warning light, check the connection of the ABS sensor that is located near the top of the shock mount. It may have been accidentally disconnected or not seated fully.
Air struts heavily rely on the air bladder to absorb jolts and cushion the ride. All shocks and struts deteriorate over time as they cycle millions of times, compressing and rebounding over every bump, crack, and road imperfection. As vehicles and suspensions age, the viscosity of the shock’s oil changes, sensors can wear or be damaged, rubber air springs dry rot and other suspension components, such as bushings, eventually break down.
Instead of having the customer faced with an enormous bill due to OEM air strut costs, consider remanufactured system components such as those offered by Arnott as one example. A quality remanufactured OE strut will be steam-cleaned and media-blasted down to raw metal to remove corrosion and road grime. Arnott can recharge the damper with new high-performance shock oil. Worn internal components, such as the piston and rod guides, as well as the seal pack, are replaced before being repainted with corrosion-inhibiting paint. The shock and damping coil are dyno and functionally tested to assure OE performance. Remanufactured struts are then assembled with a rebuilt air spring assembly, which should include new components such as a polyurethane bump stop, heavy duty crimp rings, improved seals, check valve and airline fitting along with a multi-ply air bladder