Sudden wobble? Ease off and stop
A shake that starts suddenly or a wobble that grows can mean a loose wheel, a damaged tyre or tread coming away. Ease off the accelerator, don't brake hard, hold the wheel steady and pull over somewhere safe. If the engine light is flashing with the shaking, stop as well. Don't drive on to see if it settles. Get everyone clear of the traffic, call roadside assistance if you have it, and if anyone is hurt or in danger, call 000.
When does the car shake?
| Where to look first | How soon | |
|---|---|---|
| At idle, stopped at the lights | The engine: a misfire, or worn engine mounts, the rubber blocks that hold it in place. | Soon. Now if the engine light flashes. |
| Steering wheel, at higher speeds | Wheel balance, usually at the front. RAC WA names this as a sign a balance is due. | This week. |
| Through the seat, at higher speeds | Rear wheels and tyres, or a driveshaft on a rear-drive car or 4WD. | This week. |
| Only under braking | The discs and pads. See car shaking when braking. | Have it checked promptly. |
| When accelerating | CV joints (the flexible joints in the front axles), or driveshafts and engine mounts. | Soon. |
| Wiggling at low speed, like driving on a corrugated road | A tyre with a bulge or separating tread, a bent rim, or loose wheel nuts. | Stop and check now. |
Why does the steering wheel shake at high speed?
High speed steering wheel shake is usually an out-of-balance wheel. RAC WA says even the slightest difference in weight around a wheel can cause vibration. The faster the wheel spins, the stronger the shake, and it tends to show up in a band of speed, then ease above it. That's the suspension resonating with the wheel.
The small weights clipped or stuck to the rim can fall off, often after a pothole or kerb. Mud or clay packed inside the rim does the same thing, and RAC WA lists mud after off-road driving as a cause, so if you've just been on a dirt track, have a look. If balance doesn't cure it, the next suspects are a bent rim, a tyre with internal damage, worn steering joints or suspension. RACQ lists wheel imbalance, alignment, suspension and internal tyre damage as the usual causes.
One thing that's commonly confused: wheel alignment and wheel balance are different jobs. Balance deals with weight around the wheel and stops vibration. Alignment sets the wheel angles, and a car out of alignment tends to pull or wear tyres unevenly, not shake.
Why is my car shaking at idle?
A car shaking at idle that smooths out on the move usually means one cylinder isn't firing properly, from a spark plug, an ignition coil or a fuel injector. It feels like a rhythmic stumble. Worn engine mounts feel different: the engine runs evenly, but you feel every bit of it through the floor, and it's often worse in Drive at the lights than in Neutral.
That Drive and Neutral check is a useful clue you can do yourself with your foot firmly on the brake. A change between the two points toward the mounts. No change points toward the engine itself.
What to check when you've stopped
Walk around the car
Parked, look at each tyre for a bulge, a cut, a flat spot or uneven wear, and see whether the rims look bent.
Think back on the wheels
If any wheel has been off recently, for tyres, brakes or a puncture, ask for the nuts to be checked. Loose nuts are on RAC WA's list and shouldn't wait.
Check tyre pressures
On cold tyres, against the placard in the driver's door frame or the owner's manual. A low tyre can make a car feel unsettled.
Note the speed
Tell the mechanic the speed the shake starts and stops at, and whether you feel it in the wheel or the seat. It's the most useful thing you can give them.
What the mechanic will check
They'll usually road test it first, then put the wheels on a balancing machine, inspect the tyres inside and out, and check for play in the steering, suspension and wheel bearings. For an idle shake they'll read the engine computer for misfire codes and look at the mounts. Some vibrations take a bit of finding, so ask them to explain what they ruled out and how.
Keep the estimate to what's been found. If new tyres or a full suspension job are suggested for a simple shake, ask what test led them there. A good mechanic for this is one who does tyres, steering and suspension regularly.
What you can do, and what's the mechanic's job
You can
- Look over the tyres and rims, parked.
- Check tyre pressures when they're cold.
- Note the speed the shake starts and stops.
Leave to the mechanic
- Balancing the wheels, and checking tyres inside and out.
- Checking wheel nuts, bearings, steering and suspension.
- Reading misfire codes and testing the engine mounts.
Where we'd start
A mild shake at one speed, on a car that otherwise drives fine: we'd get the wheels balanced first, since it's the most likely answer. A shake at idle: we'd have the codes read. A sudden wobble or anything that's growing: we'd stop, and have someone come to the car rather than risk the drive.