Jim Grant's Tech Tips
'02 Hyundai Sonata GLS, Brake Whirring
Q:
Upon
accepting delivery of our new '02 Hyundai Sonata, we noticed a whirring
noise like you hear when you drive onto a warning strip on the edge of
a highway, when braking from a speed of 40mph to a stop. No, I don't have
anti-lock-brakes. The demonstrator of same model and description doesn't
have that sound. The dealer started guessing and wanted to grind the brakes
down and turn the rotors and I told them no! This is a new vehicle and
I don't need guess work, that's why I traded my '99 vehicle in!
-
Jim G.
A:
I guess
you could say you have new brakes. If a customer were to come into our
shop and say that their new brakes were making a whirring when braking,
I would inspect the machined finish of the brake rotors. Why is that?
The contact area of the brake pads to the braking surface must be smooth
and non-directional. There are 2 common problems we see. 1. The brake
rotor has machine work that makes it look like an old vinyl record. There
will small groves that you can feel as you drag your finger nail across
the braking surface of the rotor. 2. A cross hatch pattern that has grooves
that you can feel similar to the grooves in problem number 1. The brake
pads on today's vehicles are of a high metal content. This type of brake
pad will not get along with brake rotors that have too rough of a machined
finish. The result of this disagreement is a whirring noise that can be
heard when the brakes are applied. Over time the machined surface of the
brake rotor will smooth and quiet down, but I cannot tell you how long
that will take. If you were my customer and the new brake rotor finish
was proven to be the cause of the noise, the brake rotors would be replaced.
|