Read the guide: Why your car vibrates at 60 mph
How to test your car
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Step 1: Find your tire size on the tire sidewall or on the sticker inside the driver's door frame, for example 225/65R17. Not sure? Choose Typical car.
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Step 2: Agree on the speed where the shake is worst, such as 60 mph. The driver's only job is to hold that speed on a straight, smooth road where it's legal and safe.
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Step 3: As the passenger, enter that speed and your tire size, then tick I'm a passenger.
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Step 4: Place the phone flat, screen up, on the center console, or hold it flat on your lap. Tap Start. On iPhone, tap Allow when Safari asks for motion access.
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Step 5: Keep the phone still for the 30-second measurement, which starts as soon as you tap Start. Avoid lane changes and rough patches.
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Step 6: Measure again about 10 mph slower, where the car feels calm, and compare the two results.
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Step 7: Tap Save image to show the result to your tire shop or mechanic.
What your result means
Your result lands on one of four levels. This page uses the machines and appliances scale, which is based on RMS velocity in millimeters per second (mm/s).
| Level | Range (RMS velocity) | What to do |
|---|---|---|
| Smooth | Under 0.71 mm/s under 0.028 in/s | Very little shake at this speed. If you still feel one, test again at the exact speed where it's worst. |
| Normal | 0.71 to 1.8 mm/s 0.028 to 0.071 in/s | Little shake at this speed. If it reads clearly higher than your calm-speed run, a wheel balance is still worth doing. |
| Rough, check it | 1.8 to 4.5 mm/s 0.071 to 0.177 in/s | A clear shake. Many cars read this high on ordinary roads, so compare with the calm-speed run: if this speed reads clearly higher and the frequency matches your wheels, get the tires balanced and inspected. |
| Too much vibration | 4.5 mm/s or more 0.177 in/s or more | Strong shake. If it's much higher than your calm-speed run, drive gently and get it checked before any long trip. If it started suddenly, pull over safely and look for a bulging tire or loose wheel nuts. |
Reading your car vibration test result
Start with the comparison from step 6. Every car carries some road shake, and on this scale, which was written for machines, ordinary driving can already read Rough or higher. What points to a problem is a clear difference: the speed where you feel the shake reads clearly higher than the calm speed, and its main frequency matches your wheels.
Your car vibration test result shows a main frequency in Hz. The tool compares it with how many times your wheels turn each second at the speed you entered: wheel frequency = speed ÷ (π × tire diameter). A 225/65R17 tire is about 724 mm tall, so at 60 mph it turns about 11.8 times a second (707 RPM).
- Within about 10% of the wheel frequency: likely a wheel or tire problem, such as balance, a bent rim or tire damage.
- About twice the wheel frequency: possibly a tire that’s out of round.
- No match: it could be the driveshaft, an axle or the engine. These often turn faster than a phone can measure.
Why does a car shake at highway speed, then calm down as you go faster? The wheels, tires and brakes bounce on the springs at their own rate, often around 10 to 15 Hz. When the wheels turn at that rate, often between 50 and 70 mph, a small imbalance becomes a big shake. The tire vibration frequency calculator shows the numbers for your tires.
Common causes and fixes
Shake that matches the wheels
- Wheel imbalance. The most common cause. A clean rectangle on the rim where a weight used to be is a clue. Fix: balance all four wheels.
- Mud, snow or ice inside the rim. Clean the inside of each wheel, then test again.
- Tire damage. A bulge in the sidewall or a wavy tread can mean a broken belt inside the tire. Replace that tire now.
- Bent rim or out-of-round tire. A normal balance won’t fix these. Ask for a road force balance, which presses a roller against the tire to find high spots.
- Flat spots. Tires that sat for weeks can shake for the first few miles, then smooth out.
Shake that doesn’t match the wheels
- Driveshaft or U-joints on rear-wheel and all-wheel drive cars. The driveshaft turns faster than the wheels by the axle ratio, often about 3 to 4 times, so at 60 mph it can be near 40 Hz. That’s too fast for a phone.
- CV axles on front-wheel drive cars. A worn inner joint often shudders when you accelerate and eases when you coast.
- Engine and mounts. If the shake follows engine speed rather than road speed, test the car parked with the car idle test.
Shake only when braking
This usually points to uneven brake rotors, often called warped rotors. Brake service fixes it. Balancing won’t.
See a mechanic soon if the shake came on suddenly, keeps getting worse, or comes with clunks, pulling or a burning smell. A loose wheel can feel like an imbalance at first.
Front or rear?
A shake in the steering wheel usually comes from the front wheels. A shake in the seat and floor usually comes from the rear. Run this test on the console, then the steering wheel test near the steering column, and compare. If a tire rotation moves the shake from the steering wheel to the seat, it moved with a tire or wheel.
What this tool can’t measure
- Anything faster than about 30 Hz, including most engine and driveshaft vibration at highway speed. You’ll then see “The main vibration may be faster than your phone can measure.”
- The shake at the wheel itself. The phone reads what reaches the cabin, after the springs and seats soften it.
- Which wheel is at fault. All four wheels turn at about the same rate.
- A certified rating. The bands come from machine vibration guidance (ISO 10816-1), so for a car they are a rough guide. Treat every reading as a good guide, not a certified measurement.
Frequently asked questions
Why does my car vibrate at 60 mph but not at 50?
Your wheels and tires bounce on the springs at their own natural rate. When the wheels turn at that same rate, a small imbalance gets amplified into a shake you can feel. Above and below that speed it fades, which is why the shake often lives in one speed band.
Can the driver run the test alone?
No. The driver's hands and eyes belong on the road, and that includes a phone in a mount. Ask a passenger to enter the numbers, tap Start and read the result.
Is a phone accurate enough for car vibration diagnosis?
It's a good guide, not a certified measurement. The frequency is the most useful part, because it tells you what turns at that rate. Shops use vibration analyzers, often called NVH tools, with sensors placed around the car.
What if the result says it's not matching the wheels?
First check that the speed and tire size you entered are right. If they are, the source likely turns at a different rate, such as the driveshaft, an axle or the engine. If your car lets you pick gears, try a lower gear at the same road speed: if the shake changes, it follows the engine.
Will balancing the tires fix it?
If the shake matches your wheel frequency, balancing is the cheapest first step and often fixes it. If it comes back or never goes away, ask for a road force balance and a check for bent rims. After that, look at worn suspension parts.
Last updated .