Why Does My Car Shake When I’m Driving?

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So your car shakes while driving. Not good. Cars are supposed to drive smoothly. Shaking and vibration mean that something mechanical is wrong. But is it a minor issue, or is it something major that makes the car unsafe to drive? Let’s look at the most common causes that make your car shake.

Loose Lug Nuts

Did you just buy new tires? I have heard of cases where the lug nuts were only put on hand tight, and did not receive their final tightening. In just a few miles they can work loose enough to make a wheel wobble. That’s definitely not safe, because the wheel will eventually fall off.

If that seems likely, then take out your lug wrench and check every lug nut on the car. Perhaps you will find a loose lug nut clanging around inside a hub cap. Put it back on. If you find others loose, tighten them up, and return to the store immediately to have the issue documented and your car closely inspected for related damage. Or have the car towed back, if you feel it’s not safe to drive. Be safe, not sorry.

Did You Recently Buy Custom Wheels?

A good sales person will ask you to bring the car back after you’ve driven it 100 miles on your new custom wheels. Aluminum alloy is soft, and wheels made of it will lose a little lug torque with use, especially the first several hundred miles. Don’t ignore that request for a complimentary re-torque, as it also protects your new wheels.

A rare problem today, but quite common when radial tires first came on the market are defective tires. Tires would look perfectly round, but would change shape ever so slightly when under the weight of the car, and that would create a wobble. Like we said, that’s rare nowadays.

Where Is the Vibration, Wobble or Shaking Coming From?

Just like identifying where car noises are coming from, try to determine if you feel the vibration (or whatever you prefer to call it) in the steering wheel, or in the brake pedal, or if it seems like the entire car is shaking through the floorboards?

Steering Wheel Shaking

Does the steering wheel shake while you drive normally, or only when you step on the brakes? It matters greatly.

A steering wheel wobble (or oscillation side to side) without stepping on the brakes means you have a tire out of round, or a bent wheel on the front of your car. Maybe both front wheels are bent, but that’s rare.

If you ran over a pot hole driving fast, that could bend a wheel, or damage a tire. The car must be jacked up and both wheels turned by hand slowly and inspected for bends, flat spots or out-of-round. If found, rarely can it be repaired safely, especially if it’s badly damaged. If it’s a minor bend or flat spot, then maybe it can be fixed safely. Consult a wheel repair shop near you.

If both front wheels checkout OK, then you have a defective tire causing the wobble. Want to confirm your hypothesis? Rotate all four tires front to back, it’s a car fix you can do yourself. Then test drive your car. If the front wheel shimmy stopped, and especially if you can now feel the vibration coming through the floor of your car, one or both front tires is at fault. That’s a clever way to diagnosis a car, isn’t it? Congratulations, you just saved on some mechanical labor. Treat yourself to some new tools.

Front Brakes Make the Steering Wheel Shake

If the steering wheel only shakes when you step on the brakes, that means that the front brake rotors are out of true. They need to be machined or replaced.

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Sometimes the shaking will only happen when the brakes are extremely hot, like after a long, fast deceleration from freeway speeds. The rotors get hot and warp slightly, enough to wobble the disc pads slightly, which telegraphs back into the steering wheel. Do you know how to change brake pads? You need to fix your brakes.

The Brake Pedal Vibrates

The correct term for this is pulsates. If the brake pedal does that, but the steering wheel does not shake, then the problem is in the back brakes. Again, the rotors or drums are out of round. Fix the rear brakes. Sorry.

The Entire Car Seems to Vibrate

Very common. Your tires are simply out of balance. That happens with normal wear and use. Sometimes wheel balance weights will come off wheels, slinging free from centrifugal force, and cause an out of balance vibration. Same cure, have the tires balanced.

Working on an older car? Out-of-round tires were quite common decades ago, due to poor manufacturing processes. The fix was to have the tires shaved back into a round condition. Many shops that work on older vehicles still have tire shaving equipment. So, if you have tires that vibrate no matter how many times you’ve had them balanced, consider visiting a shop that can shave the treads back into round. They will roll better.

Less-Common Problems

Rear wheel drive vehicles have a heavy driveshaft, and that heavy part spins quite fast, about three or more times the speed of the tires. It’s supposed to be balanced at the factory, and probably was, until you had the universal joints replaced and the mechanic knocked the weights off the driveshaft.

Now you feel a vibration coming up through the floorboard, and the faster you drive the worse it gets. It’s cheap to fix, simply have the driveshaft balanced by a driveline shop. Google to find one near you. They mostly work on heavy trucks, but are usually happy to do automotive work as well.