For a 99 Civic LX 4-door sedan, can someone please post the specs for --

-- rotor thickness
-- brake pad thickness
-- drum shoe thickness, if it uses drums in the rear

I have a friend with this car who gets vibrations in the steering wheel when
she brakes. Anything else you'd check right now?

"Elle" <elle_navorski (AT) nospam (DOT) earthlink.net> wrote in
news:GJvje.4074$Lc1.3696 (AT) newsread3 (DOT) news.pas.earthlink.net:


Other than rotor runout due to actual warpage...

http://www.babcox.com/editorial/bf/bf100326.htm

Make certain that
1) All glaze deposits have been sanded off the rotor
2) All rust has been sanded off the hub and rear of the rotor's "top hat".

http://www.tegger.com/hondafaq/misc/rotor_off.jpg
http://www.tegger.com/hondafaq/misc/glaze.jpg
http://www.tegger.com/hondafaq/misc/glaze-off.jpg

Glaze makes "hard spots" that differ in friction properties from the
unglazed portions of the disc. Glaze is simply pad material that has
embedded itself into the surface texture of the disc. The pads will
regularly grab more or less depending on what they are travelling on, and
this will be felt as vibration. A wire wheel or lots of work with 50-grit
emery cloth will fix that.

If there is any sort of rust, or any particles on the flange or the back of
the rotor, the rotor will sit crooked on the hub, and runout will be
excessive, and this will be felt as vibration.

Once you are past that, then you need to read the Babcox article **very**
carefully.

Don't let anyone tell you overtorqued wheel nuts have caused this. On
Hondas this is simply *not* true unless there are other factors at play,
such as flange rust.

Another factor is tires. When you brake, the front tires are pressed into
the pavement more firmly than if you are just cruising. If the tires are
cupped or otherwise unevenly worn, this can show up most when they are
pressed harder (or lighter!) into the pavement. Of course, odd tire wear
leads us directly to the possibility of suspension wear...

Check the brakes first.


--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

Thanks, Tegger. Update: My friend's car was due for an oil change and so she
decided to let the dealer do it today and also check out the brakes. She
said the rotors just needed an "adjustment."

Not sure what that means, or whether she had the wording right (though I
mentioned rotor warping to her as a possibility before all this, so she was
attuned to something possibly being wrong with them) but I gather it may
simply have consisted of cleaning off the rotors.

TeGGeR® wrote:
the babcox article /does/ mention torque as a factor in causing runout -
it's the 4th point after the first paragraph on that subject.

deficient in that is does not acknowledge the important fact that in a
runout situation, [ie. where the disk is wavering fron side to side]
there is a momentum effect. a single piston caliper has a significant
mass & therefore momentum differential between the piston side & the
caliper side. the piston is light & can follow the disk runout much
more easily than the heavier caliper, no matter how easily that caliper
may be able to slide. for low speed runout, the effect will be small or
indeed negligable, but at higher speed, the caliper will always be
playing "catch up" to the piston because of its higher mass and will
therefore create a pressure differential in the hydraulics, which will
in turn be felt at the pedal.

in a fixed caliper, with opposing pistons, provided both pistons are
equally free to float, the there will be no pulsing under runout because
the momentum of both pistons is the same. maybe carryng this
assumption from fixed calipers to single piston calipers is the cause of
this omission.

jim beam <nospam (AT) example (DOT) net> wrote in
news:wfednQk-G--qig3fRVn-qA (AT) speakeasy (DOT) net:




Since the caliper cannot move more quickly than the piston, the piston is
eventually kicked back into the caliper as the rotor strikes the pad on the
piston. The caliper/pad assembly therefore eventually floats free of the
rotor anyway, same as the fixed caliper type.

If the caliper or pads are frozen in place and cannot slide correctly, then
the effects are a bit different.



--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

TeGGeR® wrote:
right, momentum.

yes, but there's a time delay, and that's where the hydraulics
experience a pressure pulse.

for single piston, if the caliper's not free to slide, the effects are
more pronounced & happen at lower speeds, but the net effect is the
same, the piston being forced in & out of the caliper causing the pulsing.

jim beam <nospam (AT) example (DOT) net> wrote in
news:YoWdndVEho9hFA3fRVn-2A (AT) speakeasy (DOT) net:


I see your point. I suppose Babcox could have emphasized that more, but
then how many other things could they have emphasized?

Regardless of that, the Babcox article deals with the causes of pulsation
complaints, not specifically with the effects of those causes.

The main premise of the Babcox article (as I gather it) is that it is too
common for pulsation complaints to be incorrectly identified as "warped
rotors", and for the "warpage" to be wrongly identifed as actual distortion
of the friction faces. They are saying that you need to investigate several
other significant causes of pulsation before pinning the blame on distorted
friction surfaces.

--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

TeGGeR® wrote:
indeed!

yep. i've seen disks be worse after being skimmed than they were
before, so the babcox article is great in that it encourages people to
not assume it's the disk every time.

piston caliper theory a bit, that's all.