You'd have to run alongside the car to feel the wheels. The only choices to feel a vibration are the brake pedal, steering wheel, or seat, (entire car).
If the brake pedal pulses up and down, that is due to "thickness variation" in a brake rotor. That is probably the less common way a rotor can warp. You may feel that in the steering wheel too but the brake pedal will get your attention. Thickness variation is diagnosed by the symptom, and it is verified by using a micrometer to measure the rotor's thickness at a half dozen different points around it.
Most commonly when a rotor warps, the center mounting plate is not parallel to the braking surface. That causes the caliper to slide back and forth once per wheel revolution. Moving that mass quickly, as in higher vehicle speeds, can tug on the steering linkage. That's why you would feel that in the steering wheel. Unless that warpage is real bad, you won't normally feel it in the brake pedal. This is also diagnosed by observing the symptoms, but in this case a dial indicator is used to measure the amount of "lateral runout". The same symptoms can occur if rust or scale falls between the hub and rotor during some other service. That would still show up with a dial indicator, but the mechanic will check for that debris when he takes the rotor off, and he will double-check the rotor on the brake lathe to be sure it really is warped.
Both types of warpage can be corrected by machining the rotor on a brake lathe, as long as it ends up still being thicker than the published legal minimum thickness. There's a limit to how much material can be cut off to true up a rotor, but it's becoming more common to just replace them at every brake job. In the '80s it was common for a rotor for a small car to cost over $100.00. Machining one used to cost around ten bucks, so doing so made sense. For a number of years now new rotors can cost less than 20 dollars. With the cost of cutting bits that wear out very quickly, and the mechanic's time, it is often less expensive to just install a new rotor and throw the old one away.
Be aware that new rotors made in China will usually warp after about three months. A simple machining on the brake lathe will solve that. It has nothing to do with the quality of the part. When we make parts from cast iron, we let them "age" for 90 days before we do the final machining. Chinese rotors are cast just like ours are, but they ship them right away and let them age on your car. They work perfectly fine after that light machining, but that means you have make a return trip to the shop that installed them.
Monday, November 18th, 2013 AT 1:17 AM