What's the clicking sound coming from my left wheel?

Dear Car Talk

Dear Car Talk | Oct 01, 1996

Dear Tom and Ray:

I am driving a 1985 Chevy Celebrity with approximately 39,000 miles. There
is a loud clicking sound emanating from the left front wheel. The click is
apparent at any speed, but it sounds faster at higher speeds. Three
different mechanics have checked this wheel for causes and came up with
nothing. Can you explain this? -- Tom

RAY: Sure, I can. What I can't explain is why these guys didn't at least
try to sell you something anyway. Not even a new pair of fuzzy dice! We're
going to have to drum these guys out of the Fraternal Order of Boat-Owning

TOM: My guess is that you have a warped disc rotor, Tom. The disc rotor --
which looks like an oversized audio CD -- spins along with the wheel. And
the brake pads sit on either side of the disc rotor, just a nose hair away
from it. That way, when you step on the brakes, the pads squeeze the rotor
immediately, and there's no delay in slowing the car.

RAY: And if that rotor is warped, even a little bit, every time the high
point in the rotor comes around, it pushes the brake pads back against the
caliper. And that's what makes the clicking sound.

TOM: Have your mechanic check the discs for "run out" with his dial
indicator, Tom. If they show signs of warping, I'd fix or replace them.
Aside from that annoying click, warped discs make the car brake less
effectively. And as they get worse, you may also notice that your brake
pedal pulses when you slow down from highway speeds -- although with only
39,000 miles in 11 years, I suspect highway driving isn't one of your big
pastimes. Good luck, Tom.

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