jim beam wrote:

that's doesn't in the least explain how i go to a shop for tire
replacement, and driving home, my disks are "warped". i take the wheels
off, clean up the hub, torque with a three-stage sequence, and then my
disks are unwarped again.

Just to be clear, I never said the disks actually warped.

Anyone who says that rotors commonly warp is clearly heading back
to the village missing its idiot.

However, to be 'fair', a lot of what people call warp is simply
runout, which is what I think you're referring to (since you could
never correct true warp short of machining the rotors).

A lot of other times, what people call warp is merely uneven pad
deposition, which, oftentimes, a rebedding run (especially one
with very harsh pads) will scrape clean & eliminate the judder.

Whatever they 'call' it, it's not warp because you can MEASURE
warp and they never ever measure it! Those who do, find out that
it's not warp. It's really that simple. Those who insist it's
warp seem to have no resistance with the q-tips in the ears.

This thread seems to be going in the right direction which is
to find the true cause of judder.

I will also try to read those scientific papers that were posted.

http://www.researchgate.net/publicat...7d38711887.pdf
http://sem-proceedings.com/20i/sem.o...-Roughness.pdf
http://sem-proceedings.com/14i/sem.o...Prevention.pdf
http://www.mecheng.osu.edu/adl/files/adl/C12-1.pdf
http://www.ehu.es/compmech/welcome/d...mputations.pdf
http://researchbank.rmit.edu.au/eser.../Rodriguez.pdf
http://eprints.hud.ac.uk/3878/1/2008-01-0818.pdf
http://cdn.intechweb.org/pdfs/5380.pdf
http://www.acoustics.asn.au/conferen...papers/p46.pdf
http://www.hitachi.com/ICSFiles/afie...009_07_107.pdf
http://ejum.fsktm.um.edu.my/article/1146.pdf
http://eprints.hud.ac.uk/3797/1/10_P...l_D_Bryant.pdf
http://www.mecheng.osu.edu/adl/files/adl/J187.pdf
http://pid.sagepub.com/content/217/6/419.full.pdf

On Sat, 16 Feb 2013 19:55:59 -0600, Vic Smith wrote:

This pad deposition is new to me.

The "theory" (as I understand it) for the uneven pad deposition
based brake judder is that a little "hill" of as little as
15 microns (according to one of the papers we listed) will cause
low frequency (around 100 Hz) brake judder.

I'm still trying to figure this out, but apparently two things
happen at the same time when the pads hit the deposition "hill".

1. The pads "push back" causing the vibration to be felt in the
brake pedal.
2. The force varies, causing the entire suspension to shudder.

At least that's how I understand it after reading the (complex)
papers a few times. I'm still reading them though, so consider
this a preliminary explanation.

On Sat, 16 Feb 2013 19:55:59 -0600, Vic Smith wrote:

I have very little experience with rotors that cause
pulsation. Only times it happened with me was with old worn rotors
that needed replacing anyway because they were grooved and eating
pads.

An interesting aside is that we all have seen grooved rotors,
and we all know the "fingernail test" (i.e., if it catches your
fingernail, it's too deep) - but - if you LOOK UP the specs for
grooves, they have to be absolutely huuuuuuge (like the thickness
of a dime!) to fail a rotor.

At least in my experience.

If anyone actually has a bona-fide "groove" specification for their
rotor - please share!

On Sat, 16 Feb 2013 19:55:59 -0600, Vic Smith wrote:

But here's what makes me believe that rotors CAN warp.
And I'm not NOT saying that it the cause of most brake pulsation.

I should clearly state that I too believe rotors CAN warp!

However, what MOST people "call" warp, isn't warp at all.
It's merely brake judder.
Which, as we've seen from the dozen papers, can be caused by a LOT
of things. And, as shown by the industry advertising anyway, most
of the time it's NOT warp.

Plus, how would anyone know it's warp if they didn't measure the
rotors on the bench, as that's the ONLY way to tell a warped rotor
(as far as I can tell).

On Feb 16, 9:18*pm, Joe Mastroianni wrote:
On Sat, 16 Feb 2013 19:55:59 -0600, Vic Smith wrote:
But here's what makes me believe that rotors CAN warp.
And I'm not NOT saying that it the cause of most brake pulsation.

I should clearly state that I too believe rotors CAN warp!

However, what MOST people "call" warp, isn't warp at all.
It's merely brake judder.
Which, as we've seen from the dozen papers, can be caused by a LOT
of things. And, as shown by the industry advertising anyway, most
of the time it's NOT warp.

Plus, how would anyone know it's warp if they didn't measure the
rotors on the bench, as that's the ONLY way to tell a warped rotor
(as far as I can tell).

my caravan carries a lot of weight, and the pads wear out
fast.........

Used to be garages demanded we turn the rotors, in my application they
would warp fast.

so now i just buy new rotors any time the pads get replaced.

my neighbor a highly skilled guy does lots of my vehicle repairs,
sadly i must find someone new.

he is a smoker and has lung cancer stage 4......

he is a good hard working guy i will miss him

On 02/17/2013 12:39 AM, bob haller wrote:
On Feb 16, 9:18�pm, Joe Mastroianni wrote:
On Sat, 16 Feb 2013 19:55:59 -0600, Vic Smith wrote:
But here's what makes me believe that rotors CAN warp.
And I'm not NOT saying that it the cause of most brake pulsation.

I should clearly state that I too believe rotors CAN warp!

However, what MOST people "call" warp, isn't warp at all.
It's merely brake judder.
Which, as we've seen from the dozen papers, can be caused by a LOT
of things. And, as shown by the industry advertising anyway, most
of the time it's NOT warp.

Plus, how would anyone know it's warp if they didn't measure the
rotors on the bench, as that's the ONLY way to tell a warped rotor
(as far as I can tell).

my caravan carries a lot of weight, and the pads wear out
fast.........

Used to be garages demanded we turn the rotors, in my application they
would warp fast.

so now i just buy new rotors any time the pads get replaced.

which is what most people do. it "works" because the new disks are
clean and thus seat properly. if old disks were properly cleaned, they
would too, but since time is money for shops, and disks relatively
cheap, replacement is in fact an economic option.



my neighbor a highly skilled guy does lots of my vehicle repairs,
sadly i must find someone new.

he is a smoker and has lung cancer stage 4......

he is a good hard working guy i will miss him



--
fact check required

On Feb 17, 11:01*am, jim beam wrote:
On 02/17/2013 12:39 AM, bob haller wrote:





On Feb 16, 9:18 pm, Joe Mastroianni wrote:
On Sat, 16 Feb 2013 19:55:59 -0600, Vic Smith wrote:
But here's what makes me believe that rotors CAN warp.
And I'm not NOT saying that it the cause of most brake pulsation.

I should clearly state that I too believe rotors CAN warp!

However, what MOST people "call" warp, isn't warp at all.
It's merely brake judder.
Which, as we've seen from the dozen papers, can be caused by a LOT
of things. And, as shown by the industry advertising anyway, most
of the time it's NOT warp.

Plus, how would anyone know it's warp if they didn't measure the
rotors on the bench, as that's the ONLY way to tell a warped rotor
(as far as I can tell).

my caravan carries a lot of weight, and the pads wear out
fast.........

Used to be garages demanded we turn the rotors, in my application they
would warp *fast.

so now i just buy new rotors any time the pads get replaced.

which is what most people do. *it "works" because the new disks are
clean and thus seat properly. *if old disks were properly cleaned, they
would too, but since time is money for shops, and disks relatively
cheap, replacement is in fact an economic option.



my neighbor a highly skilled guy does lots of my vehicle repairs,
sadly i must find someone new.

he is a smoker and has lung cancer stage 4......

he is a good hard working guy i will miss him

--
fact check required

he has very little time according to his doctor.

its sad people get addicted to smoking then spend horrendous amounts
of money to get sick and die

On Mon, 18 Feb 2013 19:04:34 +0000, Tegger wrote:

None of the fairly-extensive Honda documentation I have gives any such
number. Neither does any of my other documentation specify a figure.

Thanks for checking.

Googling for random manufacturer's specifications, I find this GM spec:
http://www.procutinternational.com/supplier_gm.aspx
Which says:
Do not resurface rotors for light grooving. Resurface rotors only when
grooves of 1.5 mm (0.060 in) or deeper are present.

"A dime may be used to determine disc brake groove depth. Place a dime in
the groove, with Roosevelt's head toward the groove. If the dime goes
into the groove beyond the top of his head, the groove exceeds 1.5 mm
(0.060 in) and the rotor should be serviced. In Canada, if any portion of
the letters of "Canada" are covered, the rotor should be serviced. If the
groove is too narrow for the dime to be inserted, it is not a cause for
concern."

Conversely this spec:
http://www.raceshopper.com/tech.shtml
Says:
"Check disc for scoring or grooves over .012" depth. If either applies,
resurfacing or replacement is required."

But, the point is that grooves have to be "really big" to fail
a rotor.

PS: How did we get onto the side topic of rotor scoring anyway?

Since I have a parking lot instead of a drive way, and two of the stalls in that lot are just plain hard to get into, I use those stalls for myself rather than try to sucker a tenant into renting them. So, with a spare parking stall, I go to auto auctions whenever I down to just one car in case I get into an accident and need a car in a hurry.

One time I was putting a recent acquisition up on concrete blocks (for storing it) immediately after a rain storm. When I eventually put that car back on the road, I had the worst brake pedal pulsation you can imagine.

What happened is that the rain water between the rotors and the pads caused the rotors to rust really badly under the pads. I'm thinking the water that got between the rotors and the pads couldn't dry out and simply kept rusting the rotors. I tried to drive it off, but it wouldn't happen, so I just replaced the rotors. When I took the old rotors off I could see they were both badly rusted in one area on both sides.

I'm willing to bet dollars to donuts that a lot of cars with "warped rotors" on used car lots are cars that were last driven immediately after a rain. Since then, I've made a point to be aware of the weather before putting up a car for storage and that same problem hasn't happened again.