So, you start your car, you drive off and you notice that something’s different. There’s a distinct vibration that only happens, perhaps at 40 to 60 km/hr or it just gets worse the faster you go. “Why is my car shaking?” you ask. It’s no fun driving a car with a vibration. It’s stressful, uncomfortable and makes any drive more difficult. A car shaking while driving can have all kinds of different causes, but what you shouldn’t do is automatically assume the worst. Read on to learn what are possible causes of car shaking and how to handle each of the reasons.
Why is my car shaking?
In short, it’s because something, somewhere, is out of whack. It all depends on the severity of the vibration, whether it happens at idle, where the vibration can be felt and a number of other factors. Shaking usually happens in one of three instances: while driving at certain speeds, while braking or while idling. The fix will depend on the root cause, but in any event the best advice is to avoid doing whatever makes the car shake (as much as possible) and get it to a workshop as soon as you can. Depending on the situation, the problem is likely one of the items set forth below.
Reasons for a car shaking while driving
If your car shakes at certain speeds, it may be an issue with the tyres and/or the suspension. Driving creates a lot of vibrations, and a working car does a good job of hiding them from its passengers. But if just a few components are worn or broken, certain speeds may create vibrating frequencies that manage to resonate throughout the whole car. Let’s look at some of the possible issues.
If a car shakes when driving, tyre problems are usually the No. 1 culprit. It’s usually due to a tyre or wheel that’s out of balance, which can result from a hard hit on railroad tracks, a curb or a pothole. A tyre can also start to go out-of-round due to an internal defect such as a belt that’s starting to shift, or a “bubble” developing under the tyre’s tread.
A tyre shop can easily check the balance on tires and correct an out-of-balance issue by adding wheel weights. A wheel that’s out of balance by as little as a gram or two can be enough for a car to vibrate at high speed, but maybe not at lower speeds or maybe only at certain speed ranges. Sometimes even a tire rotation can be enough to cure a mild vibration issue. When a car goes in for a tyre rotation, it’s routine practice to check balance on all the tyres. Simple wear can be enough to cause a wheel to go out of balance, since there’s less mass of rubber as the tyre wears down.
Suspension and steering problems
The front end of any vehicle is complicated, with bushings, shafts and linkages that help keep the vehicle pointed in a straight line or allow the vehicle to turn and then self-correct after making the turn. Things like worn bushings, idler arms, Pitman arms, drag links, control arm bushings or other problems (usually on a high-mileage vehicle) can be enough to contribute to a vibration, often with a generous amount of slop and play in the steering. Start with the tires; if the tires all check out as OK and properly balanced, have a look at the suspension and steering components. Bear in mind that if you let a severe vibration go for too long, that by itself can be enough to cause further problems with wheel bearings and other suspension or steering parts.
Vibration while braking
This is one that’s pretty common. You step on the brakes, the steering wheel shimmies, you feel a distinct pulsation through the brake pedal and the whole car starts to vibrate and possibly pull to one side. This usually indicates a problem with your brakes or, in rare cases, the car’s alignment.
Potential brake problems
This is often a sign of worn brake pads and/or rotors that have become warped. Disc brakes operate a lot like hand brakes on a bicycle; two pads of friction material are held in a calliper that encloses the rotor, which is a smooth metal disc. When you step on the brake pedal, hydraulic pressure forces the pads against the rotor, slowing the vehicle via friction.
When the pads are worn, they can start wearing grooves into the rotor itself. The rotor can also become warped out-of-spec from overheating or just lots of miles. Rotors can be machined as part of a regular brake job, bringing them back into spec again. Often, though, they’re worn enough that there’s not enough steel thickness left to do that, and the old ones just have to be trashed and replaced.
A car leaves the factory with the front wheels set to specific angles, designed that way by engineers for the best road manners, handling, ride quality and steering response. A hard hit on a pothole can be enough to skew a wheel out of those present angles, though, leading to alignment problems.
Signs of poor alignment can include:
- Persistent pull to one side or the other while driving in a straight line, as the wheel that’s skewed tries to continuously steer the vehicle in another direction
- Uneven wear along an inside or outside edge of a tyre’s tread
- Steering feels “heavy” and clumsy
- Steering doesn’t self-correct readily after rounding a corner
What usually isn’t a sign of poor alignment, though, is a vibration. In most cases, if you’re noticing a vibration and a pull to one side at the same time, they’re two separate issues that are happening at once. However, driving a car out of alignment for extended periods can lead to uneven tyre wear, which can absolutely cause vibrations.
Vibration at idle
So, you’re sitting in traffic with a foot on the brake and transmission in gear, and you notice a shake and rattle. Maybe it goes away when you put the transmission in “Park,” or maybe it doesn’t. Here are a few potential causes:
- Rough running condition, which you’ll probably also notice as a lack of power, roughness and poor fuel economy while driving
- Broken, worn, loose or failing motor mounts or transmission mounts
- Worn, loose or failing exhaust mounting hardware or hangers (possibly with an audible rattle as well)
A rough running condition can be due to worn spark plugs, worn plug wires (if so equipped), failing ignition coil or coil-on-plugs, failing oxygen sensor, vacuum leak, dirty air filter or failing emissions/fuel metering sensors (to name a few causes). If it’s any of these, you’ll also probably notice an illuminated “Check Engine Light” (CEL) as the failing component sends a trouble code to the engine’s computer, which then stores the code and sets off the CEL to alert you. Any of these problems are worth addressing as soon as you can because they won’t get better on their own.
Vibration through gas pedal or seat
Let’s say you only notice a vibration through the back of the seat, the acceleration pedal, the floorboard or maybe the seat’s bottom cushion itself. If that’s the case, there’s a good chance that it’s coming from the vehicle’s drivetrain. A vibration through the accelerator is common on a front-wheel-drive (FWD) vehicle that has CV joints that are starting to wear and fail; you might also notice a clicking or ratcheting sound while rounding a corner or feel a distinct “clunk” when you step on or let off of the accelerator. On a rear-wheel-drive (RWD) car, a vibration through the floorboard can mean a driveshaft that’s out of balance or a U-joint that’s starting to wear, allowing slop in the driveline and the same “clunk” you might notice on a FWD vehicle. Other causes for this kind of vibration can include exhaust system mounting problems, exhaust leaks or emission control issues.
Regardless of whether your vehicle is RWD or FWD, you’ll want to get any of these kinds of issues looked at promptly because, once again, they don’t just get better on their own.
How to keep your car from shaking
The best ways to try and prevent an issue with vibrations include:
- Regular tire rotations and wheel balance checks, which are required to keep your tire warranty valid
- Regular inspection and maintenance of your driveline
- Regular inspection of your suspension and steering gear
- Regular inspection of your tires for bulges, debris, excessive wear, other potential issues
Those inspections of the undercarriage should be done when it’s time for service or rotation, since the vehicle will already be on a lube rack, and the tech can get a good look at everything. Just like with your own health, it’s always better to address a problem and head it off at Stage 1 rather than wait until it’s at Stage 4. With the right maintenance, a car that vibrates won’t be an issue for you now or in the future.
Nelson Xavier Ssenyange
Germax Autos, Spares & Garage Ltd
Lukade Road, Naalya