I put new pads on my 99 Suburban K1500 4x4 about a month ago. I then
noticed that there was a slight pulsation in the pedal and decided to
replace the rotors because the last time they were turned they said it would
be the last time and they would have to be replaced. About a month went by
before I got around to replacing the rotors, now that they are replaced the
pulsation and shaking is worse. Is it because I waited so long before
replacing the rotors and the pads have worn uneven and now it is shaking?
A couple of things may have happened. First problem, you don't
say what kind of rotor you purchased. Were they original factory
rotors, or did you go with cheaper aftermarket ones? Often, you
get what you pay for. Sometimes the aftermarket rotors can be
a bit "green" and will warp quite rapidly.
The other thing that might cause this is not cleaning the hub area
well enough when you install the new rotor. If you just throw the
new rotor on and don't clean the hub area (if it has rust/corrosion
built up), then the rotor can have a certain amount of runout (ie: it
will not run true). Now at first, you won't notice anything, because
while the rotor has excessive runout, it is still parallel....so you don't
feel a pulsation. But eventually the runout will cause the pads to
touch the rotor every revolution, cause a hot spot or wear at that
location, and the rotor will develop what is called "thickness
variation". At this point, you will feel a pulsation. Usually...this
doesn't occur for about 10-12K kilometres....so I'd guess that
you may just have cheap rotors.
I bought the $80 Ray Bestos made in the USA brand. They appear to be turned
ones and not composite ones. They were immediately worse than the ones I
took off. Didn't take a few miles. I noticed by the time I got to the end
of the driveway. Guess I will pull the wheels off and make sure the hubs
are cleaned up good. Didn't appear to be bad at all though.
I don't really recommend anything...but you might want to
get a hold of a dial indicator, and/or the proper size micrometer
and measure up the rotors. Then you will have some ammo
when you go to try to return the rotors.
cheap rotors are cheap for a reason.
the cheap ones are just made of mild steel.
they heat fast take long to cool are thinner and warp easy.
and the more they are turned the worse braking you will get and the above
problems happen much faster!!
if your going to change them do yourself a favor and get the drilled and
slotted ones. they are a much higher grade of steel, take longer to heat up
cool off much faster and i've never been able to warp them. (yes i try to
warp them everytime i have sold a car)(because the factory ones always need
i have used 3 different brands..
the brand names don't really matter.
just look for the ones with a gold sheen to them.
if they have the gold sheen they are made from a much higher quality of
steel. around 80,000 -90,000 p.s.i. tensile strength
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