Disc Rotor Refurb?

thirty-six wrote:
On 16 Jan, 20:53, z wrote:
thirty-six wrote:
On 16 Jan, 16:13, Nate Nagel wrote:
Peter Cole wrote:
DougC wrote:
On 1/15/2010 4:27 PM, (PeteCresswell) wrote:
A new 6" rotor is only about twenty bucks, but I've accumulated a
few rotors that *look* ok, but pulse badly.
Tried boiling in water for awhile on the latest one, but no
change.
I thought sand blasting for a moment, and then it seemed like
that would be asking for irregularities in thickness.
Anybody got a tried-and-true method of refurbishing a rotor that
doesn't require a machine shop?
For $50 each plus shipping, I can make them work like new.
--------
Seriously, it would be interesting to see exactly what the problem is.
To make sure they're not warped, you would need....... a machine shop.
You coat one side with dye (or just draw a grid on it with a permanent
marker) and then scoot it around gently on a granite flat, and any
"high" spots will have the marking ink rubbed off before everywhere else.
~
The classic way to get a cheap flat surface (i.e. for lapping) is to use
some plate glass. I've checked auto heads/blocks for flatness with a
ground (e.g. Starrett) straightedge (~$10).
yup, I have trued up oil pump covers using a piece of thick plate glass
and some wet/dry sandpaper (not having a milling machine in my garage.)
Ought to work for rotors as well, I'd be a little worried about the
thinness of the metal however, the rotor might actually flex while
you're sanding it, so I can't guarantee you'll get perfect results.
On the car I've used a file applied to the disc with the engine
running to remove the overhang at the edge. For a disc still fitted a
similar method could be employed on a bicycle say using a drill chuck
applied to the tyre to turn the wheel and an abrasive pad against the
disc.
What do you gain by filing the overhang?

Absence of annoying scraping noise. This was still while the disc was
within manafuacturers limit of servicable thickness but only just. If
the disc has been re-fitted (bike) then it is possible that the pads
will run on and off an old wear track so creating unwanted braking
modulation. Although the real answer is to ensure the disc is fitted
concentrically with the wheel I cant see a little abrasion to even
things up doing any harm.

I've had my pads wear down quite close to the rivets and never had an
annoying scraping sound. Of course I also have the rotors turned every
time I replace the pads. At $10/rotor and only needing it every other
year or so, there is no reason not to do it.

z wrote:
thirty-six wrote:
On 16 Jan, 20:53, z wrote:
thirty-six wrote:
On 16 Jan, 16:13, Nate Nagel wrote:
Peter Cole wrote:
DougC wrote:
On 1/15/2010 4:27 PM, (PeteCresswell) wrote:
A new 6" rotor is only about twenty bucks, but I've accumulated a
few rotors that *look* ok, but pulse badly.
Tried boiling in water for awhile on the latest one, but no
change.
I thought sand blasting for a moment, and then it seemed like
that would be asking for irregularities in thickness.
Anybody got a tried-and-true method of refurbishing a rotor that
doesn't require a machine shop?
For $50 each plus shipping, I can make them work like new.
--------
Seriously, it would be interesting to see exactly what the
problem is.
To make sure they're not warped, you would need....... a machine
shop.
You coat one side with dye (or just draw a grid on it with a
permanent
marker) and then scoot it around gently on a granite flat, and any
"high" spots will have the marking ink rubbed off before
everywhere else.
~
The classic way to get a cheap flat surface (i.e. for lapping) is
to use
some plate glass. I've checked auto heads/blocks for flatness with a
ground (e.g. Starrett) straightedge (~$10).
yup, I have trued up oil pump covers using a piece of thick plate
glass
and some wet/dry sandpaper (not having a milling machine in my
garage.)
Ought to work for rotors as well, I'd be a little worried about the
thinness of the metal however, the rotor might actually flex while
you're sanding it, so I can't guarantee you'll get perfect results.
On the car I've used a file applied to the disc with the engine
running to remove the overhang at the edge. For a disc still fitted a
similar method could be employed on a bicycle say using a drill chuck
applied to the tyre to turn the wheel and an abrasive pad against the
disc.
What do you gain by filing the overhang?

Absence of annoying scraping noise. This was still while the disc was
within manafuacturers limit of servicable thickness but only just. If
the disc has been re-fitted (bike) then it is possible that the pads
will run on and off an old wear track so creating unwanted braking
modulation. Although the real answer is to ensure the disc is fitted
concentrically with the wheel I cant see a little abrasion to even
things up doing any harm.

I've had my pads wear down quite close to the rivets and never had an
annoying scraping sound. Of course I also have the rotors turned every
time I replace the pads. At $10/rotor and only needing it every other
year or so, there is no reason not to do it.

I'm assuming he's referring to a pad replacement and NOT having the
rotors turned. If you have them turned the lathe operator ought to cut
the rotors well past the edge of the pad, so, no problem.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

On 16 Jan, 21:23, Nate Nagel wrote:
z wrote:
thirty-six wrote:
On 16 Jan, 20:53, z wrote:
thirty-six wrote:
On 16 Jan, 16:13, Nate Nagel wrote:
Peter Cole wrote:
DougC wrote:
On 1/15/2010 4:27 PM, (PeteCresswell) wrote:
A new 6" rotor is only about twenty bucks, but I've accumulated a
few rotors that *look* ok, but pulse badly.
Tried boiling in water for awhile on the latest one, but no
change.
I thought sand blasting for a moment, and then it seemed like
that would be asking for irregularities in thickness.
Anybody got a tried-and-true method of refurbishing a rotor that
doesn't require a machine shop?
For $50 each plus shipping, I can make them work like new.
*--------
Seriously, it would be interesting to see exactly what the
problem is.
To make sure they're not warped, you would need....... a machine
shop.
You coat one side with dye (or just draw a grid on it with a
permanent
marker) and then scoot it around gently on a granite flat, and any
"high" spots will have the marking ink rubbed off before
everywhere else.
~
The classic way to get a cheap flat surface (i.e. for lapping) is
to use
some plate glass. I've checked auto heads/blocks for flatness with a
ground (e.g. Starrett) straightedge (~$10).
yup, I have trued up oil pump covers using a piece of thick plate
glass
and some wet/dry sandpaper (not having a milling machine in my
garage.)
* Ought to work for rotors as well, I'd be a little worried about the
thinness of the metal however, the rotor might actually flex while
you're sanding it, so I can't guarantee you'll get perfect results.
On the car I've used a file applied to the disc with the engine
running to remove the overhang at the edge. *For a disc still fitted a
similar method could be employed on a bicycle say using a drill chuck
applied to the tyre to turn the wheel and an abrasive pad against the
disc.
What do you gain by filing the overhang?

Absence of annoying scraping noise. *This was still while the disc was
within manafuacturers limit of servicable thickness but only just. *If
the disc has been re-fitted (bike) then it is possible that the pads
will run on and off an old wear track so creating unwanted braking
modulation. *Although the real answer is to ensure the disc is fitted
concentrically with the wheel I cant see a little abrasion to even
things up doing any harm.

I've had my pads wear down quite close to the rivets and never had an
annoying scraping sound. Of course I also have the rotors turned every
time I replace the pads. At $10/rotor and only needing it every other
year or so, there is no reason not to do it.

I'm assuming he's referring to a pad replacement and NOT having the
rotors turned. *If you have them turned the lathe operator ought to cut
the rotors well past the edge of the pad, so, no problem.

Yes, using this skimming method I have found it quick and easy to
replace brake pads. It's only done once, the discs usually require
replacing after the second set of pads on a small car and this is
probably the most economical setup. There can be no error in re-
assembly and time spent is minimal it taking about three minutes.
Brakes work perfect following this procedure. I should add this was
with multiple thickness checks between the edge and inwards to
establish a low level of variability.

On Jan 16, 9:13*am, Nate Nagel wrote:
yup, I have trued up oil pump covers using a piece of thick plate glass
and some wet/dry sandpaper (not having a milling machine in my garage.)
* Ought to work for rotors as well, I'd be a little worried about the
thinness of the metal however, the rotor might actually flex while
you're sanding it, so I can't guarantee you'll get perfect results.

A plate glass "sandwich" comes to mind.
DR

DirtRoadie wrote:
On Jan 16, 9:13 am, Nate Nagel wrote:
yup, I have trued up oil pump covers using a piece of thick plate glass
and some wet/dry sandpaper (not having a milling machine in my garage.)
Ought to work for rotors as well, I'd be a little worried about the
thinness of the metal however, the rotor might actually flex while
you're sanding it, so I can't guarantee you'll get perfect results.

A plate glass "sandwich" comes to mind.
DR

I like it, that might actually just work.

Damn, I just threw out a busted mirror, sucker was super thick glass,
maybe I should have saved the biggest piece to cut up for this purpose?

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel