Vehicle noises go bump in the night

Jan. 1, 2020
Customers seem to want their little sedan to ride like a big luxury car, even if it has a few hundred thousand miles on the clock. But diagnosing ride quality issues isn't always easy, especially because most components on higher-mileage vehicles jus

Determining what is making your customers' cars bounce, bang and shake is not a scary process.

undercar ride quality vehicle bumps vehicle shakes struts shocks vehicle diagnostics diagnosing vehicles repair shop training technician training A/C training automotive aftermarket Customers seem to want their little sedan to ride like a big luxury car, even if it has a few hundred thousand miles on the clock. (Perhaps that's why taxi drivers are often so grumpy.)

Whether the problem is a slight shake in the steering wheel at highway speeds or banging from the rear end on the highway, ride quality concerns can be anything from slightly annoying to actually dangerous, because poor ride quality not only affects a vehicle's safety and stability, it also increases driver fatigue.

On the bright side, even though vehicles with high mileage are more challenging to diagnose and repair than brand new ones, making an old, timeworn vehicle ride like it did when it was new makes you look like a genius and can earn you a customer for life.

But diagnosing ride quality issues isn't always easy, especially because most components on a higher-mileage vehicle justifiably could use replacement.

Even though it might be tempting to order every part in the catalogue, it's usually not the best way to repair a customer's vehicle. The trick on these high-mileage vehicles is identifying the components causing the biggest problems and replacing the components that make the most difference in ride quality for the amount of money the customer is willing to pay, even though every component on the vehicle is wearing out.

And here's a tip to make it just a bit easier: The diagnostic process for successfully identifying ride quality issue is actually quite similar to the diagnostic process used for other issues, such as electrical problems or drivabilty problems.

As with so many other vehicle systems, the key to diagnosing ride quality concerns is verifying the problem, identifying the main concern, testing the components to prove your suspicions are correct and then repairing the problem (if authorised).

And, of course, using as many quick and dirty diagnostic tricks as possible to make sure you're right.

Plus, that makes you look like a genius in the process.

Speeding up the Diagnostic Process

Fortunately, most ride quality issues are caused by problems with a vehicle's wheels or suspension components and mounts. With some practice and a few tips, you can quickly and accurately diagnose each of these problem areas and keep your customers happy.

Just as you would when diagnosing concerns in any other system, the first step in diagnosing ride quality concerns is a good visual inspection.

Start by walking around the vehicle and notice the way it sits. If something is sagging or uneven, that's a sign that something in the suspension system needs attention. (Remember, springs, not shocks, control ride height).

As you walk around the vehicle, push down firmly on each corner, not only to check that it returns smoothly to its rest position, but also for unusual noises. Creaks, groans, banging or the like indicate a potential problem area that should be inspected more closely when the vehicle is in the service bay. If there are obvious unusual noise concerns, one trick to help diagnose the offensive noises is to use a drive-on hoist and listen to the components while an assistant bounces the vehicle up and down above you. It's not the most high-tech test, but it does work.

As you continue to walk around the vehicle, look at each tire, checking that the brands and sizes match one another and also are worn at about the same rate (so that they're all about the same diameter). Look to make sure the tires are suitable for the vehicle. Hugely oversized wheels or mud-and-snow tires might look nice, but they negatively affect ride quality.

Check the wheels for signs of impact, and check that the rims are free from obvious signs of damage or abuse and of mud and snow, depending on where you live. A rim full of mud will vibrate the vehicle enough to shake the teeth right out of your head at highway speeds even though it will drive just fine in the city.

Finally, make sure both sides of the vehicle are sitting at the same height. Just quickly checking for clearance between the wheel and body opening can indicate problems that need addressing.

If you're lucky, this preliminary walk-around inspection will provide clues as to which system is causing the most problems and what to check out more closely on the road test.

If not, then the road test is your next step in finding the problem.

Diagnostic Road Testing for Ride Quality

Just as you would when diagnosing concerns in any vehicle system, when road testing the vehicle take special note of when the problem (or problems) start to appear. This step is critical to a successful diagnosis, because this information can provide a huge clue about where the problem area lies (wheels or suspension components) if you know what to look for.

Wheel problems, balance for example, usually appear at about 50 mph. A shake in the wheel at this speed usually indicates a wheel (or wheels) out of balance. It's a common problem and often a simple repair (simply balancing the wheels).

However, if the problem appears right at start-off, almost ripping the steering wheel from your hands, that can indicate a problematic wheel. In this situation, look closely at the tires and wheels, because there might be a tire with a shifted belt or a misshapen wheel (or tire) on the vehicle. This condition is fixed by replacing the problematic tire or wheel.

If you do indeed suspect a wheel is causing the ride quality concern, one diagnostic trick to help prove your theory is to swap the front and rear wheels to see if the problem goes away. But be careful of upsetting any tire pressure transponders that might not like the change in location.

Ride quality problems that occur at city speeds, however, or are not wheel-speed dependent usually are caused by suspension components, as opposed to wheel and tire components. The trick is identifying which ones.

If this is the case, continue the diagnostic road test and confirm this by including maneuvers such as stopping firmly (to check for dive), swerving (to check that the tires maintain contact with the road) and checking for body roll, bottoming out and any noises that indicate problems. Check if certain maneuvers make the problem worse or better or if one side of the vehicle is worse than the other.

Intermittent noise and ride quality complaints, ones that come and go especially over rough roads, usually indicate broken (rather than worn) components. Bringing the vehicle into the shop to check closely for any broken, missing or damaged components usually is the best way to find out the exact cause of the problem you're chasing.

Confirming Your Suspicions

Just like with any other kind of automotive diagnosis, successful ride quality diagnosis involves performing diagnostic tests, coming up with a theory, then proving or disproving that theory.

Hopefully after the initial inspection and road test you have an idea as to what's causing the problem or the area to inspect more closely. Then it's time to test your suspicions.

Suspension Concerns

In the old days, a vehicle's suspension systems were made up of large, heavy components that easily absorbed any vibrations or motions from the road and isolated them from the driver and the vehicle's other passengers.

One repair manual from the 1960s, recently discovered while cleaning out the parts room, recommended repairing vibration-related ride quality concerns by putting sheets of weight along the bottom of the passenger compartment!

Obviously, that's not the reality anymore. Cars are lighter and smaller than ever before, and adding sheets of weight will drastically increase fuel consumption. Plus weights are quite expensive.

The little sedans on the road today have little suspension components, so there's not much to absorb road movement once the components start to wear. That means as the mileage piles up, the ride gets harsher and the vehicle's ability to steer, stop and corner all deteriorate, too.

If you suspect that suspension components are causing the poor ride quality, consider that shock absorbers and struts are a very common cause of ride control problems. Shocks and struts can wear out without any external leaks or breaks, and replacing them can make an unbelievable difference in the way a vehicle rides, steers, corners and stops. Because they wear out slowly, over time customers might not even realize how much the ride has deteriorated.

However, if you do not suspect the shocks or struts, you need to perform a thorough visual inspection paying careful attention to the rubber mounts and bushings in the suspension system. Torn, squished, ripped or missing bushings and mounts also are some common causes of poor ride quality.

One trick is to watch for worn or separated control arm bushings, often noticeable only when the wheel is "hanging" and tugging on the rubber component. If the vehicle is inspected on a drive-on hoist where the wheels don't hang down, these can be easily missed.

If you do find a distorted rubber mount, consider what caused the problem in the first place rather than just replacing the part. Rubber mounts in proximity to an oil leak often swell up and lose effectiveness. In such a case, make sure that the oil won't ruin the new component as well.

Tires and Wheels

If you're convinced that the problems are from tire, rim and wheel concerns, there are a few ways to prove that suspicion before ordering expensive new parts.

By now you've already checked to see if the tire brands and sizes match (and are suitable), so now check the tread wear pattern for indications of problems. Run your hand across the tread to check for saw-tooth wear patterns or other indications of problems. Rough tire wear patterns will cause vibration problems similar to wheel balance concerns.

If that is the case after all, be sure to recommend a wheel alignment along with the new tires. Also check for the presence of wheel weights. If they flew off, the unbalanced wheel could be causing a problem.

If the problem is in the tires and you're replacing them to correct the problem, remember one important thing during replacement — that paint dot on the sidewall that you think should line up with the tire valve? It may not be intended to line up with the valve stem at all, and lining it up could actually cause a problem.

The paint mark on the sidewall might — depending on the tire manufacturer — indicate either the high side or low side of force variation. Radial Force Variation, or RFV, is a real problem that can cause vibrations from wheels that balance perfectly on conventional wheel balancers.

If that's the case and RFV is causing a problem, a special Road Force Variation balance — where the tire and rim position are matched together by removing the tire and repositioning it on the rim — is the best (and usually only) way to correct the problem. And it works really well.

One additional tip to eliminate vibrations from the wheel is to match the wheel to the hub by marking its position on the hub. If there's a high spot on the rotor or hub, rotating the wheel one bolt hole over might ease the problem.

Tires and wheels do indeed cause quite a few ride quality issues, and fortunately bad tires and wheels are usually easy to spot. Just keep in mind that things have changed that may affect the installation process and that the "regular" way of doing things may suddenly cause problems.

As Easy as That

Diagnosing ride quality issues on high mileage vehicles may seem intimidating, but it doesn't need to be.

Like diagnosing any other issues, it can be challenging at first but it does get easier — especially if you have a plan and a few diagnostic tricks up your sleeve.

Most ride quality issues do indeed come down to suspension components or tire/wheel issues and with practice it's easy to identify which problem is the main culprit.

Look for obvious signs of wear or damage on components and watch for distinctive identifying clues to point you towards one system or the other, and that alone will help keep diagnostic time down and keep headaches to a minimum.

Vanessa Attwell is a Master Technician for two major manufacturers and has also worked on the bench of an independent shop. She has developed and delivered training for both vehicle manufacturers and independents, and helped develop government training and regulation standards.

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