I recently bought a used Toyota Camry and it already seems to have a problem. When I step on the brake the steering wheel will violently shake back and forth. I checked the pressure in the tires and it seems to be fine and the tires themselves seem fine…what is happening?
I think you are ok, not a major problem anyway. What you are describing is called “warped brake rotors” and its very common. The brake rotors on the front of the vehicle are not smooth anymore, due to heat and friction they are now “out of round”. The brake rotor is the round metal part that the brake pads grab onto and stop the vehicle.
I like to describe the brake rotor as the white part of an Oreo cookie, take a look at my picture below
I also like to describe the brake pads like the two darker outer pieces of the that same Oreo cookie (does this make you hungry), and since we are showing pictures, the brake caliper is the part that holds the brake pads, one brake pad on either side of the brake rotor..remember the caliper holds the brake pads.
So I said all that to say this…when you step on the brake pedal, it sends brake fluid into to the brake calipers which produce hydraulic pressure to push in the brake pads and squeeze the brake rotor.
So I said all that to answer your question. So what is the cause of brake rotor warp? Well, brake rotors become “warped” which is basically having an uneven or high spots on the rotor surface which is due to normal wear and tear caused by friction.
But it can also become warped due to expansion and contraction of the metal material in the disc rotor. This happens a lot due when driving through a large puddle of water on the freeway exit ramp after a long trip on the freeway then the driver smashes on the brakes at the stop light. I’m sure that has never happened to you.
So what do you do if you have warped brakes? It’s pretty simple really and it should be part of a routine brake job. You need to get the brake rotors “trued”, and that is where the mechanic uses a lathe to shave off a thin layer of the rotor surface which will make the surface smooth and “true” again.
Here is an picture of the truing process . There is a problem though, the rotor has a limit to how much material can be removed, this “minimum thickness” specification is stamped on the side of the rotor for the mechanic to follow. If the rotor has been trued before, or needs to be trued down more than the minimum specs will allow it will have to be replaced.
So know I bet you want to know how in the heck does this rotor warp cause that vibration in the steering wheel you are experiencing? When you step on the brakes, the brake caliper and the brake pads start to squeeze the brake rotor which stops the vehicle. The brake rotor is turning at the same speed as the tire and wheel is spinning.
When the brake the rotor surface is warped, it will cause the brake pads to pulsate back and forth inside the brake caliper as they come in contact with a high spot on the rotor. This pulsation causes the tire and wheel to shimmy or vibrate from side to side, and that vibration can telescope and be felt in the steering wheel.
But, a shimmy in the steering wheel is only caused by warped FRONT rotors since the rear wheels are not connected to the steering components. The shimmy usually gets worse at freeway speeds because the rotors are spinning faster and the high spots on the rotors will be more pronounced at higher speed.
Can having warped rotors cause damage to my brake pads or anything else? You did not ask that but just so you know, yes is can cause premature brake pad wear, but more importantly it can be dangerous in a panic stop situation….it can be hard to steer with the steering wheel shaking back and forth.
Like I started this reply with, truing the brake rotors is usually part of a routine brake job…so I would bet you are in need of one now.
Hope this helps.
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