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.