The front brake rotors, almost every time. The rotor surface has become uneven, so the pads grab and let go dozens of times per wheel turn, and you feel that as a shudder in the steering wheel and a pulse in the pedal. New front rotors and pads cost $574 to $698 at an independent shop (RepairPal).
It's safe to keep driving gently for a week or two. Book it anyway. The shake gets worse, and a pulsing brake stops the car less well than a smooth one.
What the shake is telling you
A brake that works properly clamps a flat disc with even pressure. If the disc has high and low spots, the clamp force rises and falls with every rotation. At 60 mph that's many pulses a second, which is the vibration you feel.
Where you feel it says which end is bad. Shaking in the steering wheel points to the front brakes, because the front wheels are connected to your hands. A pulse mainly in the pedal and seat with a steady wheel points to the rear.
Most people call this "warped rotors." Rick's Free Auto Repair Advice makes the case that it's rarely true warping, because cast iron needs about 2,150°F to deform and hard street braking tops out at around 700°F to 1,200°F. What's really going on is disc thickness variation: the pads have deposited friction material unevenly, or the rotor has worn unevenly because it wobbles slightly on the hub. The fix is the same either way, so the name doesn't matter much. The cause does, because if you don't fix it the new rotors go bad again in 2,000 to 3,000 miles (same source).
Most likely causes, in order
Rotors first, then the things that make rotors go bad, then the stuff that only feels like brakes.
Cause | How it feels | Shop cost (RepairPal unless noted) |
|---|---|---|
Uneven front rotors (thickness variation or runout) | Steering wheel shakes, pedal pulses, worse from highway speed | $574–$698 for rotors, plus pads |
Rust between rotor and hub, or wrong lug torque | Same shake, often soon after a brake job or tire rotation | Clean hub and retorque, a short labor charge |
Worn or glazed pads, debris in pad | Shudder on light braking, grinding when worn out | $335–$394 for pads |
Sticking caliper slide or piston | Shake plus pulling to one side, hot smell, one wheel dusty | $898–$968 per caliper |
Worn wheel bearing | Hum that changes when you steer, shake under braking | $346–$504 |
Out-of-round rear drums | Pedal pulse, little steering shake | Varies by car |
Tire imbalance, bent wheel, worn suspension | Shakes while driving too, not just braking | Varies |
RepairPal's ranges are national averages for parts and labor and don't include tax. Rotors on a heavy truck or a German car cost more; a Corolla costs less. Calipers are rarely the first thing to replace, but the price is there so you know what "stuck caliper" means on an estimate.
Rick's list puts rust on the wheel hub as the number one cause, followed by lug nuts tightened with an impact gun instead of a torque wrench. Both tilt the rotor a few thousandths of an inch. Some cars allow as little as 0.002 inches of runout. That tilt makes one pad touch the rotor on every revolution even with your foot off the pedal, which wears a thin spot. A few thousand miles later you have a shake.
Pep Boys adds a point that catches people out: tire imbalance and bent wheels get blamed on brakes all the time. The tell is that a tire problem shakes at a steady speed on the highway whether you're braking or not. A brake problem only shows up when you press the pedal.
Can you keep driving, and for how long
Yes, for a week or two, if the shake is mild and the car still stops straight. Brake pulsation is a wear problem, not a failure in progress.
Three things change that to "today." A grinding noise means the pads are gone and you're wearing metal on metal, which turns a $350 pad job into a rotor job. Pulling to one side under braking suggests a caliper is sticking, and a stuck caliper can overheat a wheel on a long drive. A burning smell or smoke from one wheel after driving is the same caliper problem, further along. RepairPal's own advice is an immediate inspection when anything about the brakes feels wrong.
If the shaking started right after a tire rotation or a brake job, go back to the shop that did it. It's almost certainly rust left on the hub or lug nuts torqued wrong, and that's a quick fix under warranty.
What it costs
Pads and rotors on one axle: about $574 to $698 for rotors and $335 to $394 for pads (RepairPal), though most shops quote the two together and the combined price is usually less than the sum. Ask for a quote for "front pads and rotors" as one job.
Resurfacing (machining the rotor flat) used to be the cheap option. Many shops now skip it because new rotors are thin to save weight and don't have enough metal to spare. If a shop offers it on an older car, it can save a couple hundred dollars, but the rotors go bad again sooner.
Two things to insist on. Ask the shop to clean the hub face with a wire wheel before fitting the rotor, and to torque the lug nuts with a torque wrench, not a gun. Rick's advice is that skipping these is why the problem comes back. Then bed the new pads in: a series of firm stops from about 40 mph without coming to a full halt, to lay down an even transfer layer.
What to do today
- Note where you feel it. Steering wheel means front, pedal and seat means rear. Tell the shop.
- Test on a quiet road: does it shake at 60 mph with your foot off the brake? If yes, it's likely a tire or wheel, so start at a tire shop.
- Feel each wheel after a normal drive. One wheel much hotter than the others means a sticking caliper. Get that one looked at this week.
- Book brakes. Ask for front pads and rotors as one quote, and ask them to clean the hubs and torque the wheels by hand.
- Check your lug nut torque after any wheel work. The figure is in your owner's manual, and most tire shops will retorque for free.
Sources
- RepairPal: What Is Causing My Brakes to Vibrate
- RepairPal: Brake Rotor Replacement Cost
- RepairPal: Brake Pad Replacement Cost
- RepairPal: Brake Caliper Replacement Cost
- RepairPal: Wheel Bearing Replacement Cost
- Rick's Free Auto Repair Advice: Brake Pulsation Caused by DTV
- Rick's Free Auto Repair Advice: Car Shakes When Braking, the Most Common Causes
- Pep Boys: Why Does My Car Shake When I Brake?
Featured image: A close-up view of a vehicle’s brake system, featuring a rusted brake disc and caliper. by Stephen Dumba (CC0). Source
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