[s-cars] Big Reds making Sandy red in the face...

[Sandy Sligh]

I think what happened over that week or two with the
NEW rotors is I got them hot and had the brakes on at
a stoplight or something.  Doing so left a high spot
of brake material on the rotors. And thats what Id
been feeling, the pads catching on the high spot. 

The vibes at high speed made me thing balance, so I
rotated the front wheels to the back.. No change.
Thats when I new it was with the rotors. Perhaps the
imbalance in pad material deposition is enough at
those speeds to make itself known withOUT braking..


I'm fairly certain i know whats making the new rotors
vibrate, its the vibrations with the old rotors which,
FYI, I just had reinstalled last night. So, today was
first full driving day with them. 50 miles or so, back
and forth to work.  Perhaps too soon to convict them
just yet. Perhaps the pads need to bed back into these
rotors after having been used on the brand new ones
for a couple weeks.

This is also what made me thing that, huh, perhaps I'm
missing something. 


S
--- Bruce Mendel <Brucem105 at comcast.net> wrote:
> S,
> 
> Thank you, thank you. :)
> 
> I don't know the answer, but the key seems to be
> that it happened after a
> week. All was OK until a week later?
> 
> That says something loosened, warped due to heat or
> improper torque, or pads
> were shot and keep leaving deposits on rotors, which
> were greasy and new.
> 
> Also, wobbling while cruising and NOT under braking
> also says something. And
> if I had an ounce of technical knowledge, I'd know
> exactly what that says.
> :(
> 
> Bruce
> ----- Original Message ----- 
> From: "Sandy Sligh" <sdslig at yahoo.com>
> To: <s-car-list at audifans.com>
> Sent: Wednesday, February 11, 2004 6:20 PM
> Subject: [s-cars] Big Reds making Sandy red in the
> face...
> 
> 
> > Ok, this email will be part Sandy's-an-idiot and
> > Sandy's-a-newb. Whichever is worse, who knows.
> >
> > SO. The S4 fails tech inspection due to worn-out
> front
> > rotors (993tt). No problem, I'll go pick up a new
> set
> > and put them on myself. How hard could it be
> really.
> >
> > I get the rotors in my hot little hands, pull off
> the
> > old rotors which are cracked inside edge to
> outside
> > (nice work, Bruce!! Thats some hard drivin!)  Pop
> the
> > rotor hats out and install said rotor hats onto
> brand
> > new rotors. WHee!!! Going pretty good.
> >
> > A week or so later I develop two vibrations. One
> felt
> > through the steering wheel (small amplitude) when
> > cruising at 120kph and higher, the second(medium
> > amplitude) when lightly braking from 100kph and
> down
> > to about 40kph. This second one I feel much more
> in
> > the steering wheel and also through the brake
> pedal.
> > With the hands off the wheel and braking, the
> steering
> > wheel noticably rocks back and forth rapidly,
> maybe
> > 3/4" to 1" in each direction.
> >
> > "There is no WAY I've warped these rotors!", Sandy
> > cries.
> >
> > I pull them off, pull out the hats and clean up
> the
> > mating surfaces considerably, mostly scraping off
> what
> > I assume was built up pad material.  Reinstall the
> > rotors.. same deal, vibrations are unchanged.
> (BTW,
> > I've been very methodically about torquing my
> wheels
> > correctly.  In a star pattern, first to 45ft-lbs
> and
> > then to 90. )
> >
> > Off they come again and I notice outlines of the
> brake
> > pads imprinted on the new rotors.. AH HA!
> Stoptech's
> > brake FAQ tells me what that is! I remove those
> rotors
> > and reserve them for later scrubbing with garnet
> paper
> > per Stoptech's suggestions (hopefully a new set is
> not
> > in order. $$$$)  In the meantime, I reinstall the
> old
> > rotors and plan on babying them until I either am
> > ready to try the new set again or break down and
> buy
> > another set.
> >
> > Well, low and behold, the old rotors are
> displaying
> > similar albeit slightly better symptoms.
> >
> > Questions:
> >
> > A) Do the sources of my vibrations reside
> elsewhere?
> >
> > B) Am I missing a crucial installation step, i.e.
> a
> > specific torque pattern on the rotor hat bolts? (I
> > devised a type of star pattern and just cranked
> them
> > down till they all felt equally tight)
> >
> > C) Do I need to go back over the mating surfaces
> again
> > and damn well make sure they are clean and flat?
> >
> > D) Maybe because I didnt' change the pads at the
> same
> > time? (why would this affect running the old
> rotors..
> > )
> >
> > E) Something else entirely?
> >
> > Please, anyone with BTDTs or suggestions unleash
> them
> > upon me.  I've spent more than a few nights in my
> > parking garage pulling wheels, pulling calipers,
> > pulling rotors, cleanings, tightening,
> reinstalling,
> > wash, rinse, repeat. Help make me smarter and the
> ride
> > out the the shop.
> >
> >
> > Thanks in advance
> >
> >
> > Sandy
> >
> > __________________________________
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> 


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