More information on my warped rotors.
In a GM Saturn Warranty Administration document, I quote the
following:
Lateral Run Out (LRO) can be induced when uneven torque is applied to
wheel nuts (lug nuts). Improper wheel tightening after tire rotation,
spare tire usage, brake inspection, etc. can be the cause of
pulsation. Again, it usually takes 4800-16000 km (3000-10000 mi)
AFTER an event for the condition to surface. The owner or driver does
not usually make the connection between the service event and the
awareness of the pulsation. The proper use of torque wrenches and/or
torque sticks (torque limiting sockets) will greatly reduce or
eliminate the pulsation conditions after wheel service events. The
improper use of impact wrenches on wheel nuts greatly increases the
likelihood of pulsation after wheel service.
End quote
In my case, all 4 rotors were machined July/06 to correct warpage.
After driving only 12429 km, I again experenced brake pulsation.
Dealer inspected brakes and found that rotors were again warped. At
this time, I didn't have the problem corrected. Since wheels had been
removed and replaced after brake examination, i decided to check the
wheel nuts tightness myself with a torque wrench. I discovered that
tightness ranged from a low of 75 pd-ft to a high of 180 pd-ft
(correct torque should have been 140 pd-ft). This was an indication
to me that a torque wrench had not been used. The miles I'd driven
since the last time rotors were machined is within the range mentioned
in the Saturn document. I maintain that if the dealer technicians
hadn't followed procedure this time, perhaps they hadn't back in July/
06 either. So my rotors may well have been warped the second time due
to improper wheel tightening.
I took this information to my dealer and he agreed to pick up the
labour costs for machining front rotors, servicing rear brakes and
replacing rear rotors. I had to pay for the cost of the rear rotors
themselves but the charge was less than retail. I didn't feel I
should have had to pay for the rotors but dealer maintained that there
was room for the possibility that hard braking may have been partly
responsible for the problem. I couldn't prove otherwise of course, so
partial compensation was better than none had I been stubborn about
this.
I hope this info helps some of you with similar problems. Check
tightness of wheel nuts after dealer does servicing.
Clark
On Jul 29, 2:14 pm, Clark wrote:
> Hello, I'm new here. I'm hoping someone can help with my problem.
>
> My vehicle is a 2000 GMC Sierra 1500, 2WD. Last July/06, I had both
> front and rear rotors machined due to brake pulsation - this corrected
> the problem. At that time the milage was 67338 miles. Since then
> I've put on an additional 7723 miles and am again experiencing brake
> pulsation. My GM dealer tells me the rear rotors must be replaced
> (not enough material left to machine them). And the front rotors need
> to be machined again.
>
> I asked why the rotors would be warped again after so few miles and
> was told it had nothing to do with the number of miles driven. I was
> told it could be caused by rust buildup or hard braking or 'panic'
> braking. There is no rust on the rotors and I don't see how hard
> braking would be the reason in my case. I'm not a fast driver and I
> consider most of my braking to be 'moderate'. That said, I would
> think that the rotors should be robust enough to withstand the
> occasional heavy braking. At the moment the pulsation is not severe
> and I've declined to have the work done.
>
> For what it's worth, here's the rest of the history on my brakes:
> - 03/2003 - rear rotors and pads replaced at 33555 miles.
> - 02/2005 - front rotors and pads replaced at 54060 miles.
> - 06/2005 - rear rotors and pads replaced at 55726 miles.
>
> I have heard or read somewhere on the internet that the brakes on this
> vehicle are not one of it's strong points. In addition I also read
> where GM decided to return to using drum brakes on the rear of these
> pickups. This suggests to me that rear disk brakes have been
> problematic on these vehicles.
>
> What I would like is for my GM dealer to replace or machine my rotors
> without charge since I think the damage should not have occurred with
> so few miles. GM won't give into my request easily of course if they
> can blame it on driver error.
>
> So what I'm looking for is written proof that these brakes just don't
> stand up well. Are there others who've had similar problems? Do you
> know if such problems have been written up somewhere - something I can
> take to GM to prove there is a problem?
>
> Thanks for any help you can provide.
>
> Clark >> Stay informed about: Brake Pulsation - 2000 GMC Sierra 
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