Jim Grant's Tech Tips
'97 Chevy Silverado, Brake Pulsation
Q:
I own
a '97 Chevy Silverado that has been totally rebuilt by national franchise.
New pads, resurfaced disc in front and new drums and all in rear. After
all of this, the brakes still pulsate, not as bad as it was. The shop
even resurfaced the front rotors a second time. It was a little better
but not perfect. Sometimes it stops smooth. The brake shop is saying it
could be a bent rim or out of round. As nice as this truck is, it should
stop smoothly. I have 64k miles and under ext warranty- gm protection
plan. The salesman from the dealer is giving me the run-around with advice
in this matter.
A:
Because
brakes are a wear item it's difficult to place them as a warranty issue.
Asking a salesman for advice on braking problems puts a grin on the face
of about any tech reading this article. I'm not sold on the bent rim as
being the cause. Why? The problem is during braking only. A bent rim will
cause a shake or vibration as the vehicle is being driving and will not
change if brake work is done. You're going to want a tech to get serious
about pining down the cause for your brake shake and that might take an
hour or more. My approach would be to isolate the front brakes from the
rear and test drive the vehicle. This allows one to determine if the offending
brake is at the front or rear of the vehicle. Once the problem area has
been determined it is time to take measurements. Not just of the brake
rotor or drum, but of the surface that they are bolted to. A brake rotor
or drum can be machined just perfectly, but if what they're bolted to
is not then a brake shake will occur. It isn't a matter of looking in
or outside of the box, it's making sure the box is built right.
|
