Warped Rotors
#21
05-30-2014, 09:59 AM
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Sigh.
Here's some interesting discussion of the subject from two OEMs.
-Warped- Brake Disc and Other Myths
Raybestos Brake Tech School, Part One: Rotors Don't Warp | Hendon Publishing
plus another from an ASE-certified Master Technician
Brake rotors don't warp!! - Car and Driver Backfires
Here's some interesting discussion of the subject from two OEMs.
-Warped- Brake Disc and Other Myths
Raybestos Brake Tech School, Part One: Rotors Don't Warp | Hendon Publishing
plus another from an ASE-certified Master Technician
Brake rotors don't warp!! - Car and Driver Backfires
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MaximA (05-30-2014)
#22
05-30-2014, 12:10 PM
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I agree that uneven distribution of friction material onto the rotor is the main issue. And 'friction material deposits' doesn't equal 'warped brake rotor".
I do have to chuckle a bit, though, at the various (and numerous) articles and opinions....and the semantics of same. It all sorta depends in how (im)precisely the word 'warped' is used.
Opinionators and experts (sometimes it's hard to distinguish between the two....but that's a different story) will say that your rotor surfaces are not parallel, but the rotor isn't warped. Or they'll say that the rotor is 'coved', but it isn't warped. Or merely say that the friction surfaces have worn unevenly...but the rotor hasn't warped. Or hard spots created by heat have created an uneven surface, but the rotor hasn't warped. In other words the brake rotor may have any number of problems but in no way, shape, or form should the word 'warp' be used in the conversation.
OK! OK! We get the idea! :-)
Cheers
DD
I do have to chuckle a bit, though, at the various (and numerous) articles and opinions....and the semantics of same. It all sorta depends in how (im)precisely the word 'warped' is used.
Opinionators and experts (sometimes it's hard to distinguish between the two....but that's a different story) will say that your rotor surfaces are not parallel, but the rotor isn't warped. Or they'll say that the rotor is 'coved', but it isn't warped. Or merely say that the friction surfaces have worn unevenly...but the rotor hasn't warped. Or hard spots created by heat have created an uneven surface, but the rotor hasn't warped. In other words the brake rotor may have any number of problems but in no way, shape, or form should the word 'warp' be used in the conversation.
OK! OK! We get the idea! :-)
Cheers
DD
Last edited by Doug; 05-30-2014 at 01:07 PM. Reason: nothing significant
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Mikey (05-30-2014)
#23
05-30-2014, 12:53 PM
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Oh wait, I wasn't suppose to use that word..... Sorry 
he he
Peace!
Last edited by CleverName; 05-30-2014 at 12:56 PM.
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Doug (05-30-2014)
#24
05-30-2014, 01:08 PM
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#25
05-30-2014, 01:44 PM
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LOL I need the laugh.
I personally just get deeper into the issue and that how the issue is solved. Saying its warped for most people implies it is physically lost its shape, which is near impossible on the street. Understanding the what actually causes the "warped" feeling goes a long way to avoiding it all together. Just my 2 cents.
I personally just get deeper into the issue and that how the issue is solved. Saying its warped for most people implies it is physically lost its shape, which is near impossible on the street. Understanding the what actually causes the "warped" feeling goes a long way to avoiding it all together. Just my 2 cents.
#26
05-30-2014, 01:48 PM
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NOPE, DEPENDS ON THE AREA WARPED. AND HOW TRUE THE HUB AND ROTOR TO HUB SURFACE. THERE ARE SEVERAL ISSUES HERE. AND IM NOT PICKING ON YOU MAXIMA YOU HAVE GREAT POINTS. THESE ARE GENERAL ISSUES I SEE WORKING ON THESE ALL THE TIME
1) ALCANS ARE A FIXED CALIPER AND YOU WILL FEEL MORE BRAKE FEEL, PULSATIONS ETC THAN YOU EVER WOULD A FLOATING CALIPER.
2) REALLY CHECK RUN OUT? AND HOW WITH THE SCALLOPED ROTR OR DO YOU HAVE FLAT SURFACE. YOU CAN BARELY RUN A DIAL INDICATOR ON THE SURFACE EXCEPT THE VERY EDGE WHERE YOU WONT HIT A SCALLOP.
3) JAGUAR SPECS .008" OR LESS AS ACCEPTABLE
TOTAL BS. .003" AND HIGHER I FEEL.
4) A HUB SHOULD HAVE 0.000 RUNOUT PERIOD. IF ANY ITS BAD
5) AND RUNOUT IS MAGNIFYED THE FURTHER OUT YOU GO ON A ROTOR. SO A INNER READING CLOSE TO THE HUB MIGHT BE .002" AND FINE. NOW GO OUT TO THE EDGE AND ITS MULTIPLIES EVEN MORE AND MIGHT BE
.008-.012"
6)ALIGNMENT AND WORN BAD CONTROL ARM BUSHINGS CAN ALSO CAUSE THIS AS THE FORCES IMPARTED TO THE SUSPENSION ARE VERY DIFFERANT WHEN BRAKING AND VERY LITTLE FEEL /FEEDBACK WHEN DRIVING CAN BE MUCH MORE MAGNIFYED UNDER BRAKING FORCES.
AND IS IT A BRAKE ROTOR/PAD SHIMMY OR TOLERANCES IN SUSPENSION. OR STEERING RACK PINION BACKLASH CLEARANCE OR TIRES. 2011 XFR I DID TODAY WAS TIRES FOR SHIMMY OR I CALL IT A KIBBLE. WETHER BRAKING OR NOT BUT WAS WORSE BRAKING. AND LESS AIR PRESSURE MADE IT WORSE TO(ROAD MORE ON THE FEATHER EDGED CUPPED PORTION. NEW TIRES AND TOTALLY GONE.
HER DESCRIPTION( AND SHE IS A CAR NUT) WAS VIBRATION. BUT AFTER DRIVING I CALLED HER AND AGREED IT WAS NOT A VIBRATION BUT SHIMMY OR KIBBLE IN THE STEERING WHEEL. TIGHTENED PRELOAD ON RACK SLIGHTLY, ALIGNED CAR AND REPLACED ALL 4 TIRES(THEY WHERE CLOSE TO WEAR BARS ANYWAY SO NOT A WASTE) AND WHEN DONE IS NICE AND SMOOTH.
HOPE I SHED A LITTLE MORE LIGHT IN OTHER NOT MENTIONED AREAS THAN THE ALREADY GREAT POINTS BROUGHT UP.
CRAP AND A LONG WINDED POST IN CAPS
IM GOING HOME
DAMN AND I THINK OF MORE... NEED TO CHECK PARALELLISM THCKER/THINNER IN SPOTS. THIS IS MOST OFEN CAUSE BY YES SLIGHT RUST THE HAPPENS OVER NIGHT OR DAY OR 2 NOT DRIVEN IN HUMIDITY OR RAIN EVEN FASTER. WHEVER THE PADS ARE ON THE ROTORS THE Y DONT RUST, THE EXPOSED AREAS DO. THEN WHEN YOU BRAKE AND CLEAN THE ROTORS THE RUSE IS GONE, PROBLEM IS THE RUSTED AREAS ARE SLIGHTLY THINNER NOW THAN WHERE THE PADS SAT. YOULL FEEL THIS TOO.
OK NOW IM GOING HOME
1) ALCANS ARE A FIXED CALIPER AND YOU WILL FEEL MORE BRAKE FEEL, PULSATIONS ETC THAN YOU EVER WOULD A FLOATING CALIPER.
2) REALLY CHECK RUN OUT? AND HOW WITH THE SCALLOPED ROTR OR DO YOU HAVE FLAT SURFACE. YOU CAN BARELY RUN A DIAL INDICATOR ON THE SURFACE EXCEPT THE VERY EDGE WHERE YOU WONT HIT A SCALLOP.
3) JAGUAR SPECS .008" OR LESS AS ACCEPTABLE
TOTAL BS. .003" AND HIGHER I FEEL.
4) A HUB SHOULD HAVE 0.000 RUNOUT PERIOD. IF ANY ITS BAD
5) AND RUNOUT IS MAGNIFYED THE FURTHER OUT YOU GO ON A ROTOR. SO A INNER READING CLOSE TO THE HUB MIGHT BE .002" AND FINE. NOW GO OUT TO THE EDGE AND ITS MULTIPLIES EVEN MORE AND MIGHT BE
.008-.012"
6)ALIGNMENT AND WORN BAD CONTROL ARM BUSHINGS CAN ALSO CAUSE THIS AS THE FORCES IMPARTED TO THE SUSPENSION ARE VERY DIFFERANT WHEN BRAKING AND VERY LITTLE FEEL /FEEDBACK WHEN DRIVING CAN BE MUCH MORE MAGNIFYED UNDER BRAKING FORCES.
AND IS IT A BRAKE ROTOR/PAD SHIMMY OR TOLERANCES IN SUSPENSION. OR STEERING RACK PINION BACKLASH CLEARANCE OR TIRES. 2011 XFR I DID TODAY WAS TIRES FOR SHIMMY OR I CALL IT A KIBBLE. WETHER BRAKING OR NOT BUT WAS WORSE BRAKING. AND LESS AIR PRESSURE MADE IT WORSE TO(ROAD MORE ON THE FEATHER EDGED CUPPED PORTION. NEW TIRES AND TOTALLY GONE.
HER DESCRIPTION( AND SHE IS A CAR NUT) WAS VIBRATION. BUT AFTER DRIVING I CALLED HER AND AGREED IT WAS NOT A VIBRATION BUT SHIMMY OR KIBBLE IN THE STEERING WHEEL. TIGHTENED PRELOAD ON RACK SLIGHTLY, ALIGNED CAR AND REPLACED ALL 4 TIRES(THEY WHERE CLOSE TO WEAR BARS ANYWAY SO NOT A WASTE) AND WHEN DONE IS NICE AND SMOOTH.
HOPE I SHED A LITTLE MORE LIGHT IN OTHER NOT MENTIONED AREAS THAN THE ALREADY GREAT POINTS BROUGHT UP.
CRAP AND A LONG WINDED POST IN CAPS
IM GOING HOMEDAMN AND I THINK OF MORE... NEED TO CHECK PARALELLISM THCKER/THINNER IN SPOTS. THIS IS MOST OFEN CAUSE BY YES SLIGHT RUST THE HAPPENS OVER NIGHT OR DAY OR 2 NOT DRIVEN IN HUMIDITY OR RAIN EVEN FASTER. WHEVER THE PADS ARE ON THE ROTORS THE Y DONT RUST, THE EXPOSED AREAS DO. THEN WHEN YOU BRAKE AND CLEAN THE ROTORS THE RUSE IS GONE, PROBLEM IS THE RUSTED AREAS ARE SLIGHTLY THINNER NOW THAN WHERE THE PADS SAT. YOULL FEEL THIS TOO.
OK NOW IM GOING HOME
My brakes don't squeal shudder shake shimmy or anything that I don't want them to do as I take care of them that was my point. Sorry for trying help.
Have a good day,
Max
Last edited by MaximA; 05-30-2014 at 01:50 PM.
#27
05-30-2014, 04:54 PM
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i can agree with you on the majority of what you are saying and thank you for the post. I also could care less if your picking on me i'm stating my experience dealing with brakes obviously yours is different.
My brakes don't squeal shudder shake shimmy or anything that i don't want them to do as i take care of them that was my point. Sorry for trying help.
Have a good day,
max
My brakes don't squeal shudder shake shimmy or anything that i don't want them to do as i take care of them that was my point. Sorry for trying help.
Have a good day,
max
#28
05-30-2014, 06:01 PM
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#29
05-31-2014, 02:04 PM
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Irrespective of whether some people dislike the word "warped" as applied to brake rotors, when engineers write for other engineers, I think they can be expected to choose their words carefully. If they say "warped", they probably mean "warped" as opposed to any other descriptive term that they might have chosen.
When they further clarify the causes and classes of what they consider to fall into the scope, then the reader gains a sense that they truly have a basis for what they have written.
If independent industry engineering sources say that "warping" exists, then it exists despite any claims to the contrary. That does not preclude other causes of problems, but rather that "warping" is not precluded either.
When they further clarify the causes and classes of what they consider to fall into the scope, then the reader gains a sense that they truly have a basis for what they have written.
If independent industry engineering sources say that "warping" exists, then it exists despite any claims to the contrary. That does not preclude other causes of problems, but rather that "warping" is not precluded either.
#30
05-31-2014, 02:38 PM
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TRW not RAYBESTOS
Sorry, should have been TRW and not RAYBESTOS. The document is a copy of the powerpoint slides used for a tutorial presentation at SAE. (Society of Automotive Engineers). The timestamp on the document is 11/7/2003.
So, not only is the source a brake engineer from a major manufacturer, the material was presented at SAE in front of peers. In my books, that trumps "it was said on the internet".
Introduction to Gray Cast Iron Brake Rotor Metallurgy
Here is the passage at page 84 of the document:
Here is another passage at page 88:
The "in service" clause of the two passages would support the old racer trick of running rotors hard on the street to season them before turning the rotors and putting them into service on a race car. The rotor can be machined to dimensional perfection, but a few heating and cooling cycles will bring out any latent warpage due to stress. Turning the rotor after bringing out the latent warpage results in a rotor that remains dimensionally stable under further stress.
Notice that the greatest contributor to a dimensionally stable casting in those two passages is time and temperature. Time and the energy required to maintain the elevated temperatures costs money.
And finally, citation of source as a direct PDF download from sae.org:
http://www.sae.org/events/bce/tutorial-ihm.pdf
++
So, not only is the source a brake engineer from a major manufacturer, the material was presented at SAE in front of peers. In my books, that trumps "it was said on the internet".
Introduction to Gray Cast Iron Brake Rotor Metallurgy
Here is the passage at page 84 of the document:
Casting Cooling in the Sand Mold
• The time the casting spends in the sand mold is typically 20 to 60 minutes. This time is often referred to as the “shake-out” time.
• The time the casting spends in the sand provides slow uniform cooling of the castings.
– A long shake-out time can help minimize residual stresses that can lead to rotor warpage in service.
– A long shake-out time could result in free ferrite formation and soften the castings. This is especially true for high carbon gray cast irons.
– Too short of a shake-out time may lead to possible austenite transformations to martensite or bainite.
• The time the casting spends in the sand mold is typically 20 to 60 minutes. This time is often referred to as the “shake-out” time.
• The time the casting spends in the sand provides slow uniform cooling of the castings.
– A long shake-out time can help minimize residual stresses that can lead to rotor warpage in service.
– A long shake-out time could result in free ferrite formation and soften the castings. This is especially true for high carbon gray cast irons.
– Too short of a shake-out time may lead to possible austenite transformations to martensite or bainite.
Stress Relieving Heat-Treatment of Gray Cast Iron Rotors
• Stress relieving of gray cast iron rotors can be performed to minimize rotor warpage that can occur under extreme service conditions.
• Stress relieving of semi-finished rotors is done in Europe for many rotors designed for high performance vehicles.
• Stress relieving is typically performed in the temperature range of 500°C and 650°C for periods up to 24 hours.
• Stress relieving has no significant effect on microstructure or mechanical properties.
• Stress relieving of gray cast iron rotors can be performed to minimize rotor warpage that can occur under extreme service conditions.
• Stress relieving of semi-finished rotors is done in Europe for many rotors designed for high performance vehicles.
• Stress relieving is typically performed in the temperature range of 500°C and 650°C for periods up to 24 hours.
• Stress relieving has no significant effect on microstructure or mechanical properties.
Notice that the greatest contributor to a dimensionally stable casting in those two passages is time and temperature. Time and the energy required to maintain the elevated temperatures costs money.
And finally, citation of source as a direct PDF download from sae.org:
http://www.sae.org/events/bce/tutorial-ihm.pdf
++
Last edited by plums; 05-31-2014 at 02:45 PM.
#31
05-31-2014, 06:14 PM
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#32
05-31-2014, 08:41 PM
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spin time!
Despite one lay person "never seeing it in service", the fact is that the phenomona of brake rotor warpage exists. Of course, one person cannot have seen all brake rotors that have ever been in service, or even all brake rotors that are in current use. Therefore, it is limited to personal experience and is thus personal opinion at best.
There is an expense involved in tempering and heat relieving brake rotors. There is also an expense involved in quality control and throwing out marginal rotors.
A reasonable person would conclude that there are differences between one manufacturer and another. The expense incurred by one manufacturer in producing a top notch product is likely reflected in the price and the savings of another in letting things slide is also likely reflected in the price. In fact the cheapest no-name brand rotors on the market might even be discards from a premium brand manufacturers. Pre-use recycling as it were.
Even from the same production line, there are enough variables that having some not so great rotors slip past is within the realm of possibility.
Thus, owners who have multiple replacements due to warpage have first hit some of the bad apples, and second have had further bad luck because the replacements came from the same batch.
Maybe not as possible with a VW Golf, but since Jaguar has much smaller production numbers, then any bad batch hangs around longer.
Do such things happen? Yes. A few years ago, there was a bad batch of Jaguar oil filters that blew out the seal ring in service.
When oil filter seal rings start blowing out, it gets reported upstream pretty fast. Brake rotor warpage is somewhat less obvious and might not get caught for some time as a production line caused defect.
++
There is an expense involved in tempering and heat relieving brake rotors. There is also an expense involved in quality control and throwing out marginal rotors.
A reasonable person would conclude that there are differences between one manufacturer and another. The expense incurred by one manufacturer in producing a top notch product is likely reflected in the price and the savings of another in letting things slide is also likely reflected in the price. In fact the cheapest no-name brand rotors on the market might even be discards from a premium brand manufacturers. Pre-use recycling as it were.
Even from the same production line, there are enough variables that having some not so great rotors slip past is within the realm of possibility.
Thus, owners who have multiple replacements due to warpage have first hit some of the bad apples, and second have had further bad luck because the replacements came from the same batch.
Maybe not as possible with a VW Golf, but since Jaguar has much smaller production numbers, then any bad batch hangs around longer.
Do such things happen? Yes. A few years ago, there was a bad batch of Jaguar oil filters that blew out the seal ring in service.
When oil filter seal rings start blowing out, it gets reported upstream pretty fast. Brake rotor warpage is somewhat less obvious and might not get caught for some time as a production line caused defect.
++
#33
05-31-2014, 09:57 PM
#34
05-31-2014, 10:04 PM
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Seems to me that the most important thing here is to avoid assuming you have a rotor problem (or even a brake problem) just because you have brake shudder.
- It could be a suspension problem or a hub problem. If faults here are overlooked then rotors might be replaced or resurfaced needlessly
- If it does come down to a rotor problem then it is likely to be friction material transfer which can often simply be sanded off. If this is overlooked then rotors might be replaced or resurfaced needlessly, as, actually, there is nothing wrong with the rotor per se.
- If a rotor is scalloped, coved, non-parallel, or uneven (conditions that might fall under a a definition of 'warped' *, if you dare use the word at all...tee hee) it will need resurfacing or replacing.
How's that ?
Cheers
DD
*I checked several dictionaries for the definition of 'warp' . Several say pretty much the same thing: "Twisted or bent out of shape". Hmmm. Not quite spot-on relative to brake rotors...except perhaps those that have been improperly torqued down. A couple, though, said to "bend or twist out of shape, especially from a straight or flat form". That holds a bit of promise. Only one mentioned heat in the definition.
<shrug>
This is fun. I love picking fly **** out of the pepper
Cheers
DD
- It could be a suspension problem or a hub problem. If faults here are overlooked then rotors might be replaced or resurfaced needlessly
- If it does come down to a rotor problem then it is likely to be friction material transfer which can often simply be sanded off. If this is overlooked then rotors might be replaced or resurfaced needlessly, as, actually, there is nothing wrong with the rotor per se.
- If a rotor is scalloped, coved, non-parallel, or uneven (conditions that might fall under a a definition of 'warped' *, if you dare use the word at all...tee hee) it will need resurfacing or replacing.
How's that ?
Cheers
DD
*I checked several dictionaries for the definition of 'warp' . Several say pretty much the same thing: "Twisted or bent out of shape". Hmmm. Not quite spot-on relative to brake rotors...except perhaps those that have been improperly torqued down. A couple, though, said to "bend or twist out of shape, especially from a straight or flat form". That holds a bit of promise
. Only one mentioned heat in the definition. <shrug>
This is fun
. I love picking fly **** out of the pepper Cheers
DD
#35
06-01-2014, 08:24 AM
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06-01-2014, 09:04 AM
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