Turning Rotors: a case study...
 

With all of the debate about turning rotors I thought I'd do a bit of
measuring and documenting while doing a brake job. Here is my results.


The car 1987(?) Honda accord; poor shape, 200,000K no brakes due to a
ruptured line. This soaked the pads and as per MAP standards required new
pads. Now disregarding the brake line (and the springs off in the right read
drum that he couldn't afford to repair) the car would appear as a prime
candidate for a DIY brake job in the front driveway. Both rotors had no
major grooves, very small ridge> I could picture this as a easy pad slap.

Now ASE standards have you measure several different angles to determine if
a re-cut is needed. We concentrate on the warpage factor. I don't feel like
buying a few hundred dollars more of measuring tools to tell me what one
pass on a lathe will tell me.

The right front rotor measured at .747 to start
I took one pass at .002 on each side
Final measurement was .742

The left front rotor measured at .697 on the outside edge and .703 at the
inside edge to start
I took one pass at .002 on each side. the start of the cut was heavy, I
thought I'd have to do a second cut. Often we will see the O/S edge a
wee bit thinner than the inside edge, but when I returned to the lath one
cut was all that was needed.
Final measurement was .696

I forgot to write it down, but discard was in the .660 range.

Most people who do brakes at home won't measure the rotors and it was
interesting to see the big difference in specs from the left to the right to
start. We thought there would be at least one new rotor needed, but specs
are specs.


You can see by the measurements that the lath action took off very little
metal, not enough to make a difference on heat dissipation, but the little
work guaranteed me that this car (the POS it was) had decent front brakes
when he left.
This is why I turn rotors every time. In the big picture, more metal is lost
in the time between brake jobs by the pads than on a simple clean up on a
lath.





--
Stephen W. Hansen
ASE Certified Master Automobile Technician
ASE Automobile Advanced Engine Performance
ASE Undercar Specialist

http://autorepair.about.com/cs/troub...l_obd_main.htm
http://www.troublecodes.net/technical/

Re: Turning Rotors: a case study...
 

Stephen H wrote:
> With all of the debate about turning rotors I thought I'd do a bit of
> measuring and documenting while doing a brake job. Here is my results.
>
>
> The car 1987(?) Honda accord; poor shape, 200,000K no brakes due to a
> ruptured line. This soaked the pads and as per MAP standards required new
> pads. Now disregarding the brake line (and the springs off in the right read
> drum that he couldn't afford to repair) the car would appear as a prime
> candidate for a DIY brake job in the front driveway. Both rotors had no
> major grooves, very small ridge> I could picture this as a easy pad slap.
>
> Now ASE standards have you measure several different angles to determine if
> a re-cut is needed. We concentrate on the warpage factor. I don't feel like
> buying a few hundred dollars more of measuring tools to tell me what one
> pass on a lathe will tell me.
>
> The right front rotor measured at .747 to start
> I took one pass at .002 on each side
> Final measurement was .742
>
> The left front rotor measured at .697 on the outside edge and .703 at the
> inside edge to start
> I took one pass at .002 on each side. the start of the cut was heavy, I
> thought I'd have to do a second cut. Often we will see the O/S edge a
> wee bit thinner than the inside edge, but when I returned to the lath one
> cut was all that was needed.
> Final measurement was .696
>
> I forgot to write it down, but discard was in the .660 range.
>
> Most people who do brakes at home won't measure the rotors and it was
> interesting to see the big difference in specs from the left to the right to
> start. We thought there would be at least one new rotor needed, but specs
> are specs.
>
>
> You can see by the measurements that the lath action took off very little
> metal, not enough to make a difference on heat dissipation, but the little
> work guaranteed me that this car (the POS it was) had decent front brakes
> when he left.
> This is why I turn rotors every time. In the big picture, more metal is lost
> in the time between brake jobs by the pads than on a simple clean up on a
> lath.
>
>
>
>
>
what does measuring disk thickness tell you about how accurately the
disk was kept axial with the bearing?

Re: Turning Rotors: a case study...
 

"jim beam" <nospam@example.net> wrote in message
news:AP6dndMeh4tniDzenZ2dnUVZ_tidnZ2d@speakeasy.ne t...
> Stephen H wrote:
>> With all of the debate about turning rotors I thought I'd do a bit of
>> measuring and documenting while doing a brake job. Here is my results.
>>
>>
>> The car 1987(?) Honda accord; poor shape, 200,000K no brakes due to a
>> ruptured line. This soaked the pads and as per MAP standards required new
>> pads. Now disregarding the brake line (and the springs off in the right
>> read drum that he couldn't afford to repair) the car would appear as a
>> prime candidate for a DIY brake job in the front driveway. Both rotors
>> had no major grooves, very small ridge> I could picture this as a easy
>> pad slap.
>>
>> Now ASE standards have you measure several different angles to determine
>> if a re-cut is needed. We concentrate on the warpage factor. I don't feel
>> like buying a few hundred dollars more of measuring tools to tell me what
>> one pass on a lathe will tell me.
>>
>> The right front rotor measured at .747 to start
>> I took one pass at .002 on each side
>> Final measurement was .742
>>
>> The left front rotor measured at .697 on the outside edge and .703 at the
>> inside edge to start
>> I took one pass at .002 on each side. the start of the cut was heavy,
>> I thought I'd have to do a second cut. Often we will see the O/S edge a
>> wee bit thinner than the inside edge, but when I returned to the lath one
>> cut was all that was needed.
>> Final measurement was .696
>>
>> I forgot to write it down, but discard was in the .660 range.
>>
>> Most people who do brakes at home won't measure the rotors and it was
>> interesting to see the big difference in specs from the left to the right
>> to start. We thought there would be at least one new rotor needed, but
>> specs are specs.
>>
>>
>> You can see by the measurements that the lath action took off very little
>> metal, not enough to make a difference on heat dissipation, but the
>> little work guaranteed me that this car (the POS it was) had decent front
>> brakes when he left.
>> This is why I turn rotors every time. In the big picture, more metal is
>> lost in the time between brake jobs by the pads than on a simple clean up
>> on a lath.
>>
>>
>>
>>
>>
> what does measuring disk thickness tell you about how accurately the disk
> was kept axial with the bearing?

If this were the only factor in the performance of brakes than I would be
concerned. But by just removing the tire and rotor you can effect the
bearing to rotor play if a small piece of dirt were to fall between them. In
fact, how do you know your "new Honda replacement rotor is true to your old
wheel bearing?. We do have a 5000$ on car lathe, that is suppose to be "the
most accurate way to turn the brakes" but it broke again. (600$ was the last
repair bill) and having a brother-in law that is a machinist, we can see no
great advantage to turning it on the car of off, as long as the turn job is
true.

Wear of the rotor and warpage (runout) are the two biggest factors of a
brake job.


--
Stephen W. Hansen
ASE Certified Master Automobile Technician
ASE Automobile Advanced Engine Performance
ASE Undercar Specialist

http://autorepair.about.com/cs/troub...l_obd_main.htm
http://www.troublecodes.net/technical/

Re: Turning Rotors: a case study...
 

Personally I have had very poor results in dealing with warped rotors
through turning them. On my '03 Accord the rotors warped enough to
cause brake shudder. Turning them helped for about 50 miles, when they
warped again. New Brembo rotors cured the problem completely. 20,000
miles later the brakes are still working perfectly.

John

Re: Turning Rotors: a case study...
 

"John Horner" <jthorner@yahoo.com> wrote
> Personally I have had very poor results in dealing with
warped rotors
> through turning them. On my '03 Accord the rotors warped
enough to
> cause brake shudder. Turning them helped for about 50
miles, when they
> warped again. New Brembo rotors cured the problem
completely. 20,000
> miles later the brakes are still working perfectly.

Where did you buy these? How much did they cost? They're not
OEM, right?

Re: Turning Rotors: a case study...
 

Stephen H wrote:

> The left front rotor measured at .697 on the outside edge and .703 at the
> inside edge to start
> I took one pass at .002 on each side. the start of the cut was heavy, I
> thought I'd have to do a second cut. Often we will see the O/S edge a
> wee bit thinner than the inside edge, but when I returned to the lath one
> cut was all that was needed.
> Final measurement was .696

I'm confused. You just told us that you took 0.004" of material off the
rotor, but your initial and final thicknesses only vary by 0.001"?

Re: Turning Rotors: a case study...
 

Stephen H wrote:
> With all of the debate about turning rotors I thought I'd do a bit of
> measuring and documenting while doing a brake job. Here is my results.
>
>
> The car 1987(?) Honda accord; poor shape, 200,000K no brakes due to a
> ruptured line. This soaked the pads and as per MAP standards required new
> pads. Now disregarding the brake line (and the springs off in the right read
> drum that he couldn't afford to repair) the car would appear as a prime
> candidate for a DIY brake job in the front driveway. Both rotors had no
> major grooves, very small ridge> I could picture this as a easy pad slap.
>
> Now ASE standards have you measure several different angles to determine if
> a re-cut is needed. We concentrate on the warpage factor. I don't feel like
> buying a few hundred dollars more of measuring tools to tell me what one
> pass on a lathe will tell me.
>
> The right front rotor measured at .747 to start
> I took one pass at .002 on each side
> Final measurement was .742
>
> The left front rotor measured at .697 on the outside edge and .703 at the
> inside edge to start
> I took one pass at .002 on each side. the start of the cut was heavy, I
> thought I'd have to do a second cut. Often we will see the O/S edge a
> wee bit thinner than the inside edge, but when I returned to the lath one
> cut was all that was needed.
> Final measurement was .696
>
> I forgot to write it down, but discard was in the .660 range.
>
> Most people who do brakes at home won't measure the rotors and it was
> interesting to see the big difference in specs from the left to the right to
> start. We thought there would be at least one new rotor needed, but specs
> are specs.
>
>
> You can see by the measurements that the lath action took off very little
> metal, not enough to make a difference on heat dissipation, but the little
> work guaranteed me that this car (the POS it was) had decent front brakes
> when he left.
> This is why I turn rotors every time. In the big picture, more metal is lost
> in the time between brake jobs by the pads than on a simple clean up on a
> lath.
>

anyway I installed new front rotors on my taurus today, turning the old
ones was $20 ea, new ones was $27...guess I could've saved $14........
Oh well, maybe next time..

A couple years ago my brother asked me to fix his brakes, said they just
quit workin'. The rotors were wore down through the vents, mustaben
steel on steel for at least 10,000 miles..... wonder if they were past
the minimum thickness....

Re: Turning Rotors: a case study...
 

Stephen H wrote:
> "jim beam" <nospam@example.net> wrote in message
> news:AP6dndMeh4tniDzenZ2dnUVZ_tidnZ2d@speakeasy.ne t...
>
>>Stephen H wrote:
>>
>>>With all of the debate about turning rotors I thought I'd do a bit of
>>>measuring and documenting while doing a brake job. Here is my results.
>>>
>>>
>>>The car 1987(?) Honda accord; poor shape, 200,000K no brakes due to a
>>>ruptured line. This soaked the pads and as per MAP standards required new
>>>pads. Now disregarding the brake line (and the springs off in the right
>>>read drum that he couldn't afford to repair) the car would appear as a
>>>prime candidate for a DIY brake job in the front driveway. Both rotors
>>>had no major grooves, very small ridge> I could picture this as a easy
>>>pad slap.
>>>
>>>Now ASE standards have you measure several different angles to determine
>>>if a re-cut is needed. We concentrate on the warpage factor. I don't feel
>>>like buying a few hundred dollars more of measuring tools to tell me what
>>>one pass on a lathe will tell me.
>>>
>>>The right front rotor measured at .747 to start
>>> I took one pass at .002 on each side
>>> Final measurement was .742
>>>
>>>The left front rotor measured at .697 on the outside edge and .703 at the
>>>inside edge to start
>>> I took one pass at .002 on each side. the start of the cut was heavy,
>>>I thought I'd have to do a second cut. Often we will see the O/S edge a
>>>wee bit thinner than the inside edge, but when I returned to the lath one
>>>cut was all that was needed.
>>> Final measurement was .696
>>>
>>>I forgot to write it down, but discard was in the .660 range.
>>>
>>>Most people who do brakes at home won't measure the rotors and it was
>>>interesting to see the big difference in specs from the left to the right
>>>to start. We thought there would be at least one new rotor needed, but
>>>specs are specs.
>>>
>>>
>>>You can see by the measurements that the lath action took off very little
>>>metal, not enough to make a difference on heat dissipation, but the
>>>little work guaranteed me that this car (the POS it was) had decent front
>>>brakes when he left.
>>>This is why I turn rotors every time. In the big picture, more metal is
>>>lost in the time between brake jobs by the pads than on a simple clean up
>>>on a lath.
>>>
>>>
>>>
>>>
>>>
>>
>>what does measuring disk thickness tell you about how accurately the disk
>>was kept axial with the bearing?
>
>
> If this were the only factor in the performance of brakes than I would be
> concerned. But by just removing the tire and rotor you can effect the
> bearing to rotor play if a small piece of dirt were to fall between them.

ok, so now let's /cut/ a disk with a piece of dirt under the rotor. now
we have a disk that is perfectly planar with respect to the dirt, not
the mounting. and that causes brake judder.

> In
> fact, how do you know your "new Honda replacement rotor is true to your old
> wheel bearing?.

well, i've never had a problem with a new disk. i've had repeated
problems with skimmed disks. you figure it out. labor and a $5k
machine to futz about with a part that can be replaced with a flawless
new disk for $50-$60 in about 10 minutes? forget it.

> We do have a 5000$ on car lathe, that is suppose to be "the
> most accurate way to turn the brakes" but it broke again. (600$ was the last
> repair bill) and having a brother-in law that is a machinist, we can see no
> great advantage to turning it on the car of off, as long as the turn job is
> true.
>
> Wear of the rotor and warpage (runout) are the two biggest factors of a
> brake job.

no kidding.

Re: Turning Rotors: a case study...
 

Elle wrote:
> "John Horner" <jthorner@yahoo.com> wrote
>
>>Personally I have had very poor results in dealing with
>
> warped rotors
>
>>through turning them. On my '03 Accord the rotors warped
>
> enough to
>
>>cause brake shudder. Turning them helped for about 50
>
> miles, when they
>
>>warped again. New Brembo rotors cured the problem
>
> completely. 20,000
>
>>miles later the brakes are still working perfectly.
>
>
> Where did you buy these? How much did they cost? They're not
> OEM, right?
>
>
summitsportcompact.com has great prices on brembo disks. quality is
very good.

Re: Turning Rotors: a case study...
 

John Horner wrote:
> Personally I have had very poor results in dealing with warped rotors
> through turning them. On my '03 Accord the rotors warped enough to
> cause brake shudder. Turning them helped for about 50 miles, when they
> warped again.

my experience exactly. thank you.

> New Brembo rotors cured the problem completely. 20,000
> miles later the brakes are still working perfectly.
>
> John

Re: Turning Rotors: a case study...
 

Elle wrote:
> "John Horner" <jthorner@yahoo.com> wrote
>

>>warped again. New Brembo rotors cured the problem
>
> completely. 20,000
>
>>miles later the brakes are still working perfectly.
>
>
> Where did you buy these? How much did they cost? They're not
> OEM, right?
>
>

One of the online parts sources, though I forget which one. It was
probably one of: rockauto.com, alleurasianautoparts.com or
discountautoparts.com.

Personally I trust professional level aftermarket brands, but stay away
from the no name and "value" brands of auto parts.

No need to go with OEM for these. I hated the rotors which came on the
car, so why give Honda more of my money?

John

Re: Turning Rotors: a case study...
 

User wrote:

> anyway I installed new front rotors on my taurus today, turning the old
> ones was $20 ea, new ones was $27...guess I could've saved $14........
> Oh well, maybe next time..


Not worth the $14 "savings" IMO.

John

Re: Turning Rotors: a case study...
 

"John Horner" <jthorner@yahoo.com> wrote
> One of the online parts sources, though I forget which
one. It was
> probably one of: rockauto.com, alleurasianautoparts.com
or
> discountautoparts.com.
>
> Personally I trust professional level aftermarket brands,
but stay away
> from the no name and "value" brands of auto parts.
>
> No need to go with OEM for these. I hated the rotors
which came on the
> car, so why give Honda more of my money?

Sounds good; appreciate the info.

Re: Turning Rotors: a case study...
 

> well, i've never had a problem with a new disk. i've had repeated
> problems with skimmed disks. you figure it out. labor and a $5k machine
> to futz about with a part that can be replaced with a flawless new disk
> for $50-$60 in about 10 minutes? forget it.
>
>> We do have a 5000$ on car lathe, that is suppose to be "the most accurate
>> way to turn the brakes" but it broke again. (600$ was the last repair
>> bill) and having a brother-in law that is a machinist, we can see no
>> great advantage to turning it on the car of off, as long as the turn job
>> is true.
>>
>> Wear of the rotor and warpage (runout) are the two biggest factors of a
>> brake job.
>
> no kidding.


You may have had problems, and in a perfect world everyone would replace
parts with new when worn with high quality stuff, but many want it done
cheap.

Anyway my point was to show how little metal comes off during a lathe job.



--
Stephen W. Hansen
ASE Certified Master Automobile Technician
ASE Automobile Advanced Engine Performance
ASE Undercar Specialist

http://autorepair.about.com/cs/troub...l_obd_main.htm
http://www.troublecodes.net/technical/

Re: Turning Rotors: a case study...
 

>
> anyway I installed new front rotors on my taurus today, turning the old
> ones was $20 ea, new ones was $27...guess I could've saved $14........ Oh
> well, maybe next time..
>
> A couple years ago my brother asked me to fix his brakes, said they just
> quit workin'. The rotors were wore down through the vents, mustaben steel
> on steel for at least 10,000 miles..... wonder if they were past the
> minimum thickness....


Seen that before; and had customers drive out of the store like that too!

As for the Taurus, You did just fine
Ford Taurus factory rotors were crap. Wouldn't hold a clean cut for 2
months. Almost all Taurus brake jobs would have pulsation when they came in
and most cutting would help, but on a few they would come back. we learned
new rotors were the only real solution. Even on My and my Mom's Taurus.



--
Stephen W. Hansen
ASE Certified Master Automobile Technician
ASE Automobile Advanced Engine Performance
ASE Undercar Specialist

http://autorepair.about.com/cs/troub...l_obd_main.htm
http://www.troublecodes.net/technical/

Re: Turning Rotors: a case study...
 

"Eric" <say.no@spam.now> wrote in message news:43A22640.D8F5EFC9@spam.now...
> Stephen H wrote:
>
>> The left front rotor measured at .697 on the outside edge and .703 at the
>> inside edge to start
>> I took one pass at .002 on each side. the start of the cut was heavy, I
>> thought I'd have to do a second cut. Often we will see the O/S edge a
>> wee bit thinner than the inside edge, but when I returned to the lath one
>> cut was all that was needed.
>> Final measurement was .696
>
> I'm confused. You just told us that you took 0.004" of material off the
> rotor, but your initial and final thicknesses only vary by 0.001"?

Because the rotor wasn't true-- the outside edge was thinner than the inside
edge, so only 001 was removed from the outside.


--
Stephen W. Hansen
ASE Certified Master Automobile Technician
ASE Automobile Advanced Engine Performance
ASE Undercar Specialist

http://autorepair.about.com/cs/troub...l_obd_main.htm
http://www.troublecodes.net/technical/

Re: Turning Rotors: a case study...
 

Stephen H wrote:
>>well, i've never had a problem with a new disk. i've had repeated
>>problems with skimmed disks. you figure it out. labor and a $5k machine
>>to futz about with a part that can be replaced with a flawless new disk
>>for $50-$60 in about 10 minutes? forget it.
>>
>>
>>>We do have a 5000$ on car lathe, that is suppose to be "the most accurate
>>>way to turn the brakes" but it broke again. (600$ was the last repair
>>>bill) and having a brother-in law that is a machinist, we can see no
>>>great advantage to turning it on the car of off, as long as the turn job
>>>is true.
>>>
>>>Wear of the rotor and warpage (runout) are the two biggest factors of a
>>>brake job.
>>
>>no kidding.
>
>
>
> You may have had problems, and in a perfect world everyone would replace
> parts with new when worn with high quality stuff, but many want it done
> cheap.
>
> Anyway my point was to show how little metal comes off during a lathe job.
>
>
>
i have two points:

1. it ain't cheap enough to be worth bothering with [unless it's a disk
that requires complete disassembly of the hub] AND

2. the results frequently aren't good enough to be worth the trouble.
in fact it often /causes/ problems.

i'd much rather live with a slightly scored disk than one that's been
machined wrong and is now ruined.

Re: Turning Rotors: a case study...
 

Stephen H wrote:
>>anyway I installed new front rotors on my taurus today, turning the old
>>ones was $20 ea, new ones was $27...guess I could've saved $14........ Oh
>>well, maybe next time..
>>
>>A couple years ago my brother asked me to fix his brakes, said they just
>>quit workin'. The rotors were wore down through the vents, mustaben steel
>>on steel for at least 10,000 miles..... wonder if they were past the
>>minimum thickness....
>
>
>
> Seen that before; and had customers drive out of the store like that too!

there's laws about letting a vehicle leave the shop in that condition,
regardless of how it drove in. you need to check into them.

>
> As for the Taurus, You did just fine
> Ford Taurus factory rotors were crap. Wouldn't hold a clean cut for 2
> months.

but that's the point guy!!! you get /trained/ to skim disks as the
"solution", but [and here's the point that i find fascinating] your
experience contradicts what you were told! but you still /repeat/ what
you were told! can you tell what's wrong with this picture?

> Almost all Taurus brake jobs would have pulsation when they came in
> and most cutting would help, but on a few they would come back. we learned
> new rotors were the only real solution. Even on My and my Mom's Taurus.
>
>
>

Re: Turning Rotors: a case study...
 

"jim beam" <nospam@example.net> wrote in message
news:pq6dnWz14uq5Uz_eRVn-qA@speakeasy.net...
> Stephen H wrote:
>>
>> You may have had problems, and in a perfect world everyone would replace
>> parts with new when worn with high quality stuff, but many want it done
>> cheap.
>>
>> Anyway my point was to show how little metal comes off during a lathe
>> job.
>>
>>
>>
> i have two points:
>
> 1. it ain't cheap enough to be worth bothering with [unless it's a disk
> that requires complete disassembly of the hub] AND
>
> 2. the results frequently aren't good enough to be worth the trouble. in
> fact it often /causes/ problems.
>
> i'd much rather live with a slightly scored disk than one that's been
> machined wrong and is now ruined.

I don't think this issue can be resolved into a single best course of
action. In another recent thread the subject of professional standards vs
DIY standards came up, and I think that applies here. A DIYer who routinely
leaves untouched disks that look good and have performed well is frugal and
smart. A shop that routinely leaves untouched any disk is being sloppy.

Jim, I gather you and I are on the same page on the DIY way of doing it. If
the disks are serviceable as-is there is no point in doing anything to them
except a quick wash with brake cleaner when we get our mitts off them. If
they need more, replacement is the way to go. If we had free access to a
lathe we might do the same as Stephen does - clean the surface up. Or maybe
not.

Mike

Re: Turning Rotors: a case study...
 

"jim>> Anyway my point was to show how little metal comes off during a lathe
job.
>>
>>
>>
> i have two points:
>
> 1. it ain't cheap enough to be worth bothering with [unless it's a disk
> that requires complete disassembly of the hub] AND
>
> 2. the results frequently aren't good enough to be worth the trouble. in
> fact it often /causes/ problems.
>
> i'd much rather live with a slightly scored disk than one that's been
> machined wrong and is now ruined.

My point is different;
We do it for free with a brake job
It takes about 10 minutes to do total

We have never had an issue with machining them wrong. Its to simple.
But and idiot could play with the settings on the lath and screw it up...
Perhaps the people who turned your rotors in the past were idiots?


I agree with pressed on rotors... What a wonderful idea someone had...

Take care,


--
Stephen W. Hansen
ASE Certified Master Automobile Technician
ASE Automobile Advanced Engine Performance
ASE Undercar Specialist

http://autorepair.about.com/cs/troub...l_obd_main.htm
http://www.troublecodes.net/technical/

Re: Turning Rotors: a case study...
 

"Stephen H" <hansensw@hotmail.com> wrote in message
news:64tof.293882$zb5.30072@bgtnsc04-news.ops.worldnet.att.net...
> As for the Taurus, You did just fine
> Ford Taurus factory rotors were crap. Wouldn't hold a clean cut for 2
> months. Almost all Taurus brake jobs would have pulsation when they came
> in and most cutting would help, but on a few they would come back. we
> learned new rotors were the only real solution. Even on My and my Mom's
> Taurus.
>
The only Taurus experience I've had was on one my #2 son owned for a couple
years. I didn't get into the brakes, but when he was in Montana the clutch
went out. Turns out the clutch on the 2.4L 4 cyl is only 6 inches diameter!
It seems to me the Ford strategy for cars (but not for trucks) is to make
something that gives three years good service, and anything goes after that.

Mike

Re: Turning Rotors: a case study...
 

Michael Pardee wrote:
> "Stephen H" <hansensw@hotmail.com> wrote in message
> news:64tof.293882$zb5.30072@bgtnsc04-news.ops.worldnet.att.net...
>
>>As for the Taurus, You did just fine
>>Ford Taurus factory rotors were crap. Wouldn't hold a clean cut for 2
>>months. Almost all Taurus brake jobs would have pulsation when they came
>>in and most cutting would help, but on a few they would come back. we
>>learned new rotors were the only real solution. Even on My and my Mom's
>>Taurus.
>>
>
> The only Taurus experience I've had was on one my #2 son owned for a couple
> years. I didn't get into the brakes, but when he was in Montana the clutch
> went out. Turns out the clutch on the 2.4L 4 cyl is only 6 inches diameter!
> It seems to me the Ford strategy for cars (but not for trucks) is to make
> something that gives three years good service, and anything goes after that.
>
> Mike
>
>
yes indeed! it's all about the first owner; all the others can go hang.

buddy of mine used to work at one of their r&d facilities. all their
time & money was going into cost control [which is ok] and life
limitation [which is not, since the price differential between say ford
& honda is minimal]. if a ford was 1/3 the price of a honda, i'd have
no problem with it, but i'm wierd like that.

Re: Turning Rotors: a case study...
 

"jim beam" <nospam@example.net> wrote in message
news:zOGdnQuSG-ZtTT_eRVn-iw@speakeasy.net...
> Stephen H wrote:
>> Seen that before; and had customers drive out of the store like that too!
>
> there's laws about letting a vehicle leave the shop in that condition,
> regardless of how it drove in. you need to check into them.
>
Realistically, there isn't much that can be done. The customer can't be
forced to pay for repairs he doesn't want, and restraining either the
customer or his property isn't allowed - those are crimes. If a peace
officer shows up in time he can take the car off the road but a citizen
legally can't (at least not in the US - in any state I know if.)

When I was in aviation we would occasionally see planes in obviously
unairworthy condition come through and all we could do was inform our FAA
safety inspector.

Mike

Re: Turning Rotors: a case study...
 

">>
>>
>>
>> Seen that before; and had customers drive out of the store like that too!
>
> there's laws about letting a vehicle leave the shop in that condition,
> regardless of how it drove in. you need to check into them.

Some states yes, not this one (we wish there was!)


>>
>> As for the Taurus, You did just fine
>> Ford Taurus factory rotors were crap. Wouldn't hold a clean cut for 2
>> months.
>
> but that's the point guy!!! you get /trained/ to skim disks as the
> "solution", but [and here's the point that i find fascinating] your
> experience contradicts what you were told! but you still /repeat/ what
> you were told! can you tell what's wrong with this picture?
>

It has to do with the quality of the OEM part. Sometimes they are better,
other times (as in the Taurus) there worse.
BMW, VW Volvo and now even Ford Focus have a extremely soft metal for the
rotors. Replace them with the pads they wear that quick.



--
Stephen W. Hansen
ASE Certified Master Automobile Technician
ASE Automobile Advanced Engine Performance
ASE Undercar Specialist

http://autorepair.about.com/cs/troub...l_obd_main.htm
http://www.troublecodes.net/technical/

Re: Turning Rotors: a case study...
 

"Michael Pardee" <michaeltnull@cybertrails.com> wrote in message
news:a-qdnYZnMeB2TD_enZ2dnUVZ_sCdnZ2d@sedona.net...
>
> I don't think this issue can be resolved into a single best course of
> action. In another recent thread the subject of professional standards vs
> DIY standards came up, and I think that applies here. A DIYer who
> routinely leaves untouched disks that look good and have performed well is
> frugal and smart. A shop that routinely leaves untouched any disk is being
> sloppy.
>
> Jim, I gather you and I are on the same page on the DIY way of doing it.
> If the disks are serviceable as-is there is no point in doing anything to
> them except a quick wash with brake cleaner when we get our mitts off
> them. If they need more, replacement is the way to go. If we had free
> access to a lathe we might do the same as Stephen does - clean the surface
> up. Or maybe not.
>
> Mike



Well said.



--
Stephen W. Hansen
ASE Certified Master Automobile Technician
ASE Automobile Advanced Engine Performance
ASE Undercar Specialist

http://autorepair.about.com/cs/troub...l_obd_main.htm
http://www.troublecodes.net/technical/

Re: Turning Rotors: a case study...
 

Stephen H wrote:

> > I'm confused. You just told us that you took 0.004" of material off
> > the rotor, but your initial and final thicknesses only vary by 0.001"?
>
> Because the rotor wasn't true-- the outside edge was thinner than the
> inside edge, so only 001 was removed from the outside.
>

That's what I suspected, i.e., a lack of parallelism. Thanks for
confirming it.

Eric

Re: Turning Rotors: a case study...
 

"Stephen H" <hansensw@hotmail.com> wrote in message
news:wJMof.163324$qk4.127466@bgtnsc05-news.ops.worldnet.att.net...
>
> ">>
>>>
>>>
>>> Seen that before; and had customers drive out of the store like that
>>> too!
>>
>> there's laws about letting a vehicle leave the shop in that condition,
>> regardless of how it drove in. you need to check into them.
>
> Some states yes, not this one (we wish there was!)
>
>
>>>
>>> As for the Taurus, You did just fine
>>> Ford Taurus factory rotors were crap. Wouldn't hold a clean cut for 2
>>> months.
>>
>> but that's the point guy!!! you get /trained/ to skim disks as the
>> "solution", but [and here's the point that i find fascinating] your
>> experience contradicts what you were told! but you still /repeat/ what
>> you were told! can you tell what's wrong with this picture?
>>
>
> It has to do with the quality of the OEM part. Sometimes they are better,
> other times (as in the Taurus) there worse.
> BMW, VW Volvo and now even Ford Focus have a extremely soft metal for the
> rotors. Replace them with the pads they wear that quick.
>
I replaced the front rotors on our '85 Volvo with aftermarket rotors from
NAPA and pads from Volvo when money was tight (the Volvo pads don't rattle
like aftermarket pads do). Now the pads are about half worn and the rotors
are severely worn.

Mike

Re: Turning Rotors: a case study...
 

"John Horner" <jthorner@yahoo.com> wrote in message
news:0Kgof.1352$Jr1.1252@trnddc01...
> Personally I have had very poor results in dealing with warped rotors
> through turning them. On my '03 Accord the rotors warped enough to cause
> brake shudder. Turning them helped for about 50 miles, when they warped
> again. New Brembo rotors cured the problem completely. 20,000 miles
> later the brakes are still working perfectly.
>
> John

A rotor that is "warped", not simply scored, is a very poor candidate for
resurfacing. The metal's properties have been changed by the level of heat
it has been exposed to, causing a permanent change in its structure. After
machining, once heat is applied, it will revert to its prior condition.

I went through this issue with my wife's Malibu, arguing with the Chevrolet
service manager every step of the way. They resurfaced the rotors 3 times to
cure pedal shudder, but it never worked because the rotors were warped. In
this case. it was a design flaw by GM - they made them too thin in the first
place, and paired them up with lousy pads. When I finally gave up dealing
with them and did the job myself, the rotors were ~0.003" thicker than the
bare minimum, suggesting that they were able to shave off a minimal amount
of metal each time they turned them. But so what? The rotors were junk the
first time they warped.

OTOH, a rotor that is merely scored can be effectively resurfaced and
returned to service, providing that not too much metal is removed. I've done
this on cars when the pad wore too far and "kissed" ther rotor. A competent
technician can do this.

Doug

Re: Turning Rotors: a case study...
 

doug wrote:
> "John Horner" <jthorner@yahoo.com> wrote in message
> news:0Kgof.1352$Jr1.1252@trnddc01...
>
>>Personally I have had very poor results in dealing with warped rotors
>>through turning them. On my '03 Accord the rotors warped enough to cause
>>brake shudder. Turning them helped for about 50 miles, when they warped
>>again. New Brembo rotors cured the problem completely. 20,000 miles
>>later the brakes are still working perfectly.
>>
>>John
>
>
> A rotor that is "warped", not simply scored, is a very poor candidate for
> resurfacing. The metal's properties have been changed by the level of heat
> it has been exposed to, causing a permanent change in its structure. After
> machining, once heat is applied, it will revert to its prior condition.

sorry - unless this disk has been operated well into red heat, you're
not going to get much change in microstructure. you can however have
problems with a bad disk if it was not heat treated properly after
casting. when operated hot, /that/ disk will distort. more likely is
that there are simply different cooling rates on different parts of the
disk leading to local temporary distortion. that shouldn't happen on a
disk of sufficient thickness and whose internal vanes have not lost too
much material through rust.

my experience is that the disk cutting process is far from perfect -
those cutting machines see heavy usage, and you can mount the same disk
up a dozen times and get 13 different centers.

>
> I went through this issue with my wife's Malibu, arguing with the Chevrolet
> service manager every step of the way. They resurfaced the rotors 3 times to
> cure pedal shudder, but it never worked because the rotors were warped. In
> this case. it was a design flaw by GM - they made them too thin in the first
> place, and paired them up with lousy pads. When I finally gave up dealing
> with them and did the job myself, the rotors were ~0.003" thicker than the
> bare minimum, suggesting that they were able to shave off a minimal amount
> of metal each time they turned them. But so what? The rotors were junk the
> first time they warped.
>
> OTOH, a rotor that is merely scored can be effectively resurfaced and
> returned to service, providing that not too much metal is removed. I've done
> this on cars when the pad wore too far and "kissed" ther rotor. A competent
> technician can do this.
>
> Doug
>
>

Re: Turning Rotors: a case study...
 

Stephen H wrote:
> ">>
>
>>>
>>>Seen that before; and had customers drive out of the store like that too!
>>
>>there's laws about letting a vehicle leave the shop in that condition,
>>regardless of how it drove in. you need to check into them.
>
>
> Some states yes, not this one (we wish there was!)
>
>
>
>>>As for the Taurus, You did just fine
>>>Ford Taurus factory rotors were crap. Wouldn't hold a clean cut for 2
>>>months.
>>
>>but that's the point guy!!! you get /trained/ to skim disks as the
>>"solution", but [and here's the point that i find fascinating] your
>>experience contradicts what you were told! but you still /repeat/ what
>>you were told! can you tell what's wrong with this picture?
>>
>
>
> It has to do with the quality of the OEM part. Sometimes they are better,
> other times (as in the Taurus) there worse.
> BMW, VW Volvo and now even Ford Focus have a extremely soft metal for the
> rotors. Replace them with the pads they wear that quick.
>
>
>
if you do a basic surface scratch test for these disks vs. others of
"harder" metal, you'll not find much difference. what i know for sure
is that some oem pads have a high silica content [with some aftermarket
pad producers copying their lead]. silica is an aggressive abrasive.
this is specified by the manufacturers you cite allegedly to eliminate
disk glazing and cope with surface rust on salted roads, and it does
have some benefit for those purposes. reality however is that it's all
about life limitation.

Re: Turning Rotors: a case study...
 

Michael Pardee wrote:
> "jim beam" <nospam@example.net> wrote in message
> news:pq6dnWz14uq5Uz_eRVn-qA@speakeasy.net...
>
>>Stephen H wrote:
>>
>>>You may have had problems, and in a perfect world everyone would replace
>>>parts with new when worn with high quality stuff, but many want it done
>>>cheap.
>>>
>>>Anyway my point was to show how little metal comes off during a lathe
>>>job.
>>>
>>>
>>>
>>
>>i have two points:
>>
>>1. it ain't cheap enough to be worth bothering with [unless it's a disk
>>that requires complete disassembly of the hub] AND
>>
>>2. the results frequently aren't good enough to be worth the trouble. in
>>fact it often /causes/ problems.
>>
>>i'd much rather live with a slightly scored disk than one that's been
>>machined wrong and is now ruined.
>
>
> I don't think this issue can be resolved into a single best course of
> action. In another recent thread the subject of professional standards vs
> DIY standards came up, and I think that applies here. A DIYer who routinely
> leaves untouched disks that look good and have performed well is frugal and
> smart. A shop that routinely leaves untouched any disk is being sloppy.
>
> Jim, I gather you and I are on the same page on the DIY way of doing it. If
> the disks are serviceable as-is there is no point in doing anything to them
> except a quick wash with brake cleaner when we get our mitts off them. If
> they need more, replacement is the way to go. If we had free access to a
> lathe we might do the same as Stephen does - clean the surface up. Or maybe
> not.
>
> Mike
>
>
i used to work in a shop and had access - that's how i know these things
can be difficult to center, giving inconsistent results.

Re: Turning Rotors: a case study...
 

> sorry - unless this disk has been operated well into red heat, you're
> not going to get much change in microstructure. you can however have
> problems with a bad disk if it was not heat treated properly after
> casting. when operated hot, /that/ disk will distort. more likely is
> that there are simply different cooling rates on different parts of the
> disk leading to local temporary distortion. that shouldn't happen on a
> disk of sufficient thickness and whose internal vanes have not lost too
> much material through rust.

Your opinion and a dollar will get you a cup of coffee. That's all it's
worth . Repeated heating and cooling cycles will definitely change the
distribution of carbon atoms in an iron matrix - and it doesn't have to be
"red" hot. The temperatures created by the crappy pads used by GM did the
job in less than 15,000 miles.
>
> my experience is that the disk cutting process is far from perfect - those
> cutting machines see heavy usage, and you can mount the same disk up a
> dozen times and get 13 different centers.
>
If that's your experience, that's too bad. You need to find a better
technician, or learn to do it yourself.

Re: Turning Rotors: a case study...
 

Ahhh, New equipment.... Some are sweet!


--
Stephen W. Hansen
ASE Certified Master Automobile Technician
ASE Automobile Advanced Engine Performance
ASE Undercar Specialist

http://autorepair.about.com/cs/troub...l_obd_main.htm
http://www.troublecodes.net/technical/


>> Mike
> i used to work in a shop and had access - that's how i know these things
> can be difficult to center, giving inconsistent results.

Re: Turning Rotors: a case study...
 

> == 1 of 6 ==
> Date: Sat, Dec 17 2005 3:54 am
> From: Eric
>
> Stephen H wrote:
>
> > > I'm confused. You just told us that you took 0.004" of material off
> > > the rotor, but your initial and final thicknesses only vary by 0.001"?
> >
> > Because the rotor wasn't true-- the outside edge was thinner than the
> > inside edge, so only 001 was removed from the outside.
> >
>
> That's what I suspected, i.e., a lack of parallelism.
> Thanks for confirming it.



Thanks for "confirming" suspicion of lack of parallelism
are superfluous - Stephen H had told us of it:


> Date: Thurs, Dec 15 2005 4:48 am
> From: "Stephen H"
snip
> The left front rotor measured at .697 on the outside
> edge and .703 at the inside edge to start

Re: Turning Rotors: a case study...
 

> == 4 of 6 ==
> Date: Sat, Dec 17 2005 8:41 am
> From: jim beam
snip
> you can mount the same disk
> up a dozen times and get 13 different centers.

and

> == 6 of 6 ==
> Date: Sat, Dec 17 2005 9:02 am
> From: jim beam
snip
> i used to work in a shop and had access - that's how i
> know these things can be difficult to center, giving
> inconsistent results.



Why bring up coaxiality, or lack thereof? It is
irrelevant as long as the contact surface with the pad
gets machined.

Relevant is that the machined surface and the mounting
surface are perpendicular to the axis, and it is therefor
important that the mounting surfaces are clean. This is
the area you have to concentrate on, not centering. No
wonder why you got "inconsistent results."

Re: Turning Rotors: a case study...
 

> Date: Sat, Dec 17 2005 6:21 pm
> From: doug
>
> > Date: Sat, Dec 17 2005 8:41 am
> > From: jim beam
snip
> > my experience is that the disk cutting process is far
> > from perfect - those cutting machines see heavy usage,
> > and you can mount the same disk up a dozen times and
> > get 13 different centers.
>
> If that's your experience, that's too bad. You need to
> find a better technician, or learn to do it yourself.


Actually, he is talking about himself. He does not
understand the physical relationship between runout (I
believe this is the name - I am no mechanic) and
perpendicularity of axis and contact surfaces - he
concentrated on irrelevant coaxiality!:


> Date: Sat, Dec 17 2005 9:02 am
> From: jim beam
snip
> i used to work in a shop and had access - that's how i
> know these things can be difficult to center, giving
> inconsistent results.

Re: Turning Rotors: a case study...
 

> Date: Sat, Dec 17 2005 9:20 pm
> From: "karl"
>
snip
> > i used to work in a shop and had access - that's how i
> > know these things can be difficult to center, giving
> > inconsistent results.
>
>
> Why bring up coaxiality, or lack thereof? It is
> irrelevant as long as the contact surface with the pad
> gets machined.
>
> Relevant is that the machined surface and the mounting
> surface are perpendicular to the axis, and it is therefor
> important that the mounting surfaces are clean. This is
> the area you have to concentrate on, not centering. No
> wonder why you got "inconsistent results."


In a number of messages (maybe in all of his "cutting
rotor" messages) jim beam emphasized the importance of
centering the disks when their surfaces are being
machined. This is what I was replying to - centering,
within limits, is irrelevant, but I used the wrong term
"coaxiality." Once again, important is the
"perpendicularity of axes and contact surfaces," and
anything that throws this off will cause problems.

In fact, there is the possibility that jim beam, too, is
talking about this when he writes about the importance of
centering: in a message at another list he wrote of the
importance of cleaning the mounting surfaces of the lathe
and of the disk.

Re: Turning Rotors: a case study...
 

> Date: Sat, Dec 17 2005 10:15 pm
> From: "karl"
>
> > Date: Sat, Dec 17 2005 6:21?pm
> > From: doug
> >
> > > Date: Sat, Dec 17 2005 8:41?am
> > > From: jim beam
> snip
> > > my experience is that the disk cutting process is far
> > > from perfect - those cutting machines see heavy usage,
> > > and you can mount the same disk up a dozen times and
> > > get 13 different centers.
> >
snip
>
> Actually, he is talking about himself. He does not
> understand the physical relationship between runout (I
> believe this is the name - I am no mechanic) and
> perpendicularity of axis and contact surfaces - he
> concentrated on irrelevant coaxiality!:


In a number of messages (maybe in all of his "cutting
rotor" messages) jim beam emphasized the importance of
centering the disks when their surfaces are being
machined. This is what I was replying to - centering,
within limits, is irrelevant, but I used the wrong term
"coaxiality." Once again, important is the
"perpendicularity of axes and contact surfaces," and
anything that throws this off will cause problems.

In fact, there is the possibility that jim beam, too, is
talking about this when he writes about the importance of
centering: in a message at another list he wrote of the
importance of cleaning the mounting surfaces of the lathe
and of the disk.

Re: Turning Rotors: a case study...
 

karl wrote:
>> Date: Sat, Dec 17 2005 10:15 pm
>> From: "karl"
>>
>>> Date: Sat, Dec 17 2005 6:21?pm
>>> From: doug
>>>
>>>> Date: Sat, Dec 17 2005 8:41?am
>>>> From: jim beam
>> snip
>>>> my experience is that the disk cutting process is far
>>>> from perfect - those cutting machines see heavy usage,
>>>> and you can mount the same disk up a dozen times and
>>>> get 13 different centers.
>>>
> snip
>>
>> Actually, he is talking about himself. He does not
>> understand the physical relationship between runout (I
>> believe this is the name - I am no mechanic) and
>> perpendicularity of axis and contact surfaces - he
>> concentrated on irrelevant coaxiality!:
>
>
> In a number of messages (maybe in all of his "cutting
> rotor" messages) jim beam emphasized the importance of
> centering the disks when their surfaces are being
> machined. This is what I was replying to - centering,
> within limits, is irrelevant, but I used the wrong term
> "coaxiality." Once again, important is the
> "perpendicularity of axes and contact surfaces," and
> anything that throws this off will cause problems.
>
> In fact, there is the possibility that jim beam, too, is
> talking about this when he writes about the importance of
> centering: in a message at another list he wrote of the
> importance of cleaning the mounting surfaces of the lathe
> and of the disk.

Another factor is also how the disk is actually cut. Not only is each axis
perpendicular to each other, but the surfaces for the pads to be parallel.
A poor cutting bit, taking off too much at a time, or a crossfeed that is
too high can cause these kinds of problems.

I just went through all of this with Chrysler, as the Jeep Cherokee's from
2000-2003 are notorious for premature warping of the front rotors (TSB
issued). They (Chrysler) went through the trouble of changing the calipers
and pads to another design in accordance with the TSB recommendations, but
only cut the rotors (which I argued against), and they were warped again
within 4K miles. I gave up arguing with them and purchased and installed a
set of high performance rotors and pads.

Re: Turning Rotors: a case study...
 

karl wrote:
>>== 4 of 6 ==
>>Date: Sat, Dec 17 2005 8:41�am
>>From: jim beam�
>
> snip
>
>>you can mount the same disk
>>up a dozen times and get 13 different centers.
>
>
> and
>
>
>>== 6 of 6 ==
>>Date: Sat, Dec 17 2005 9:02�am
>>From: jim beam
>
> snip
>
>>i used to work in a shop and had access - that's how i
>>know these things can be difficult to center, giving
>>inconsistent results.
>
>
>
>
> Why bring up coaxiality, or lack thereof? It is
> irrelevant as long as the contact surface with the pad
> gets machined.
>
> Relevant is that the machined surface and the mounting
> surface are perpendicular to the axis, and it is therefor
> important that the mounting surfaces are clean. This is
> the area you have to concentrate on, not centering. No
> wonder why you got "inconsistent results."
>
you need to read around a bit more. if the disk plane is not
exactly perpendicular to the rotation axis, on a floating [single
piston] caliper, you have pulsing in the hydraulics because of momentum
differences due to the mass of the caliper vs. the piston. with a
fixed caliper and 2 [or 4 or 6] pistons, the mass on each side is the
same and there's little net effect.