Ride quality complaints are much more common now than they were even just a few years ago, which can be tough for drivers to handle. But it’s great news for the technicians who know how to fix these problems.
In very general terms, drift, pull, wander and vibration concerns usually mean wheel, tire, alignment and drivetrain concerns and those ride quality complaints usually can be corrected by diagnosing and fixing problems in those systems. But it’s important to know what to look for and where to look to keep repairs profitable and keep diagnostic time to a minimum.
Here’s a guide to get you started.
Defining the Concern
When diagnosing ride quality complaints such as drift, pull, wander or vibration, it’s important to start with the basics before getting into deeper diagnosis. A good place to start is with the tires themselves. If you’ve spent much time with newer-model cars and trucks, you’ve probably noticed that many of those new vehicles are now coming right from the factories with larger rims and tires than they were a decade (or more) ago. And since larger tires have larger contact patches, big-wheeled cars and SUVs can be more susceptible to directional and handling issues when they encounter ruts left in the roads.
This mount looks OK, but the only way to know for sure is to test it under the conditions the complaint occurs.
Tire pressure
Adjusting tire pressures used to be a favorite trick for those “undercover test” cars. TV shows would send “bugged” vehicles to various garages to test how honest they were: one tire would be set much lower than the others and the “customer” would complain about a pull to one side. The “correct repair” was simply correcting the tire pressures, and usually a painfully high number of shops did not repair the problem correctly, instead selling alignments and complete sets of new tires as the hidden cameras rolled.
Checking and correctly setting tire pressures usually is pretty easy, and it’s very important because incorrect pressures can and do cause problems. If one tire pressure is incorrect, the vehicle can pull. If all tires are overinflated, the ride can be harsh (among other problems). Therefore, even on vehicles with tire pressure monitoring systems, it’s still important to check that tire pressure is correct and also that it’s checked correctly (usually on cold tires) with an accurate gauge before going any further in the diagnostic process.
And if indeed one tire is much lower than the rest, it’s important to find and repair the cause of the leak (possibly a leak or puncture) so that the customer doesn’t return with the same problem in a few days.
Tires, Rims, and Wheels
Even big tires can wear out surprisingly quickly and worn tires, uneven tread, feathered tread, shifted belts, or similar tire problems can cause very noticeable handling concerns. Unfortunately, sometimes the way to repair handling complaints is by replacing tires. But since tires are expensive it’s important to make sure that that is indeed the problem before recommending this costly step.
Start by visually inspecting the tires for problems (you can do this as you check tire pressures to save time). Look at the treads and run your hand across them. If the edges are rough or feathered, the vehicle’s alignment might have caused rough tire wear patterns and you might have found the cause of the problem. If so, be sure to correct the vehicle’s alignment when the new tires are installed to protect the customer’s rubber investment.
Along with noticeable signs of rough wear, also look for human-error things that can cause ride quality problems such as directional tires installed incorrectly, mismatched tires, aggressive treads that are used on smooth, dry roads and the like since those things can and do cause handling complaints, especially on vehicles that are seldom used (such as seasonal vehicles or pleasure crafts).
Note too that snow or mud build-up on the rim can cause ride quality complaints, as can wheel damage, or rims with the incorrect bolt pattern. I’m mentioning bolt pattern because one of our customers once bought rims on the Internet with the wrong bolt pattern, so he drilled his own holes and came to us hoping we could repair the resulting vibration. (We did not even try. New rims were the only fix.)
If the tires and wheels look OK but you still suspect a bad wheel, find out if the problem occurs everywhere the vehicle’s driven or only on a particular road. If the condition occurs everywhere, start the diagnosis by rotating the wheels front to rear (if possible). If the condition stops then, likely there was an issue with one of the tires and it’s time to closely inspect them for problems. In some cases it might even help to swap each wheel assembly, one at a time, with a known good one until the problematic assembly is identified. If the condition continues even with the wheels rotated, then a deeper alignment issue may be the cause.
However, if the problem only occurs on one particular road, find out more about the road – you may be trying to fix the unfixable if the road has a steep incline or is severely “crowned” to facilitate water run-off.
Alignment
One of the main causes of handling problems is incorrect alignment – whether it developed slowly over time or as the result of a sudden impact. Therefore, another good preliminary check is, while walking around the vehicle to check tire pressure and condition, also taking a look at how the vehicle is sitting. Incorrect ride height can indicate problems that affect vehicle alignment. Manufacturers’ directions for checking ride height varies from vehicle to vehicle, but the left and right sides of the vehicle should be the same height whether you’re measuring in inches, fingers, points on your knee, or whatever method you use to guestimate that ride height is the same from side to side. If it’s not, it’s important to find out why – usually broken or worn suspension components.
Also determine if the vehicle has been in any type of impact or accident, if it hit a curb or parking stone, or had some other alignment-altering interaction.
Any such impact could have tweaked the alignment enough to cause the condition, but still leave the angles within the manufacturer’s specified range. If so, even if the suspension components might be functionally okay, the alignment might need to be set up to correct the results of the impact.
It’s also important to remember that a vehicle’s alignment angles can be within specification and still cause a vehicle to pull or wander. Manufacturers leave a range of tolerances for alignment angles, but even within that range there’s enough room to make a vehicle drive abnormally if the adjustments are at the extremes rather than closer to the middle of the range. Just because everything’s within specification does not mean the vehicle won’t pull or wander.
Incorrect toe angles not only can cause handling problems, they can cause a vehicle to ruin its tires quickly. Improper toe adjustment on the rear of the vehicle could cause directional stability issues for the vehicle. Unless the manufacturer says otherwise, all toe adjustments should be equal from side to side on the axle.
Offsetting camber by 0.5 degree from side to side can cause slight pulls, drifts or wandering. Offsetting by a full degree can cause more extreme pulls and concerns. Fortunately camber usually is adjustable and usually can be corrected without replacing components.
Caster, however, usually is not adjustable, and it easily can cause a drift, pull or wander when out of specifications from left to right. But correcting this usually involves replacing suspension components.
Look at the total effect the values have on handling and proceed from there. Always remember to take into account tire wear and the manufacturers’ recommended range of alignment angles for the particular adjustment.
One important note: If the customer regularly carries heavy loads (such as tool boxes) on one side of the vehicle (or is heavy himself), that can affect handling characteristics and the solution may well be performing the alignment with the load (or even the customer) in the vehicle to correct for the weight imbalance.
Vibrations
Vibrations can be tricky to diagnose since they can be caused by so many things. Determining if the vibration is related to either speed or load can be really helpful.
If a vibration occurs at a particular speed, regardless of the gear range selected, chances are the vehicle has a wheel-rim-driveline issue that can be positively located by closely inspecting the components or with a roadforce-type wheel balancer. A bent rim or belt shifted tire will show up on the road force machine’s measurements, even if not obvious to the naked eye. Driveline issues can be caused by wheel bearings, driveshafts, leaking (not “sweating”) shocks or struts, broken springs or worn or damaged suspension components.
If the vibration occurs at a particular rpm range, regardless of vehicle speed, then chances are it’s a powertrain issue. These issues can be a little tougher to diagnose, because they can be caused by anything from a faulty mount, poor running engine or even a transmission with internal problems. I’ve found it’s usually best to begin by visually inspecting of all engine and transmission mounts, while the engine is at that rpm if possible, to check for excess play or contact with the body. Then repair, replace or retorque the mounts as necessary and verify the repair by road testing again.
If the mounts are OK, an intensive diagnostic road test might be required. This might mean an overnight road test if your shop is located in a congested urban area. One of my very wise colleagues performs these diagnostic road test by driving the vehicle until the condition is happening and then, when it’s safe to do so, shifting the transmission manually into another gear range (third to fourth or third to second; you want to change rpm, not blow up the engine) to change the engine rpm. In his experience, if the condition occurs with the rpm in a different range while still maintaining the same speed, then the problem likely is transmission-related. If the condition stops when the engine’s in a different rpm range, then the problem likely has to do with the engine and he rechecks the mounts and the engine’s actual running condition for things such as intermittent misfires.
As an example, one vehicle came into my colleague’s bay with a vibration through the body on acceleration from a stop. He road-tested it extensively and figured out that the vehicle drove perfectly fine under all conditions except for a vibration on acceleration from a stop. He watched the mounts while an assistant loaded up the engine. The problem was indeed an engine mount, even though it had looked just fine. The front engine mount on the passenger-side frame rail was traveling too far and transferring engine vibration through the body because the rubber insulator was weak and allowed excessive movement. Replacing the mount fixed the problem.
Another vehicle had a slight vibration at highway speeds and the vehicle had been to other shops for various unsuccessful repairs. The problem was fixed by replacing a faulty spark plug that was causing an intermittent misfire under load.
Conclusion
One of the nice things about diagnosing handling complaints is that they usually are constantly present. Intermittent handling concerns really are rare which makes diagnosing these complaints much easier. Even if you’re convinced that it is indeed a pattern, confirm your suspicions so you don’t look waste time and money. With a bit of practice you’ll learn to quickly identify the common causes of handling complaints and you’ll be able to repair them quickly and profitably to keep both you and your customers happy.
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