What are some car-repair jobs you always wished you could do but have never done?

On Mon, 6 Nov 2017 04:49:14 +0000 (UTC), RS Wood >
wrote:

>Steve W. wrote:
>
>> Chains don't mean a lot when they drop them down to bicycle sizes with
>> small pins. Things stretch like cheap rope.
>
>I think the only reason manufactures went to belts is to increase their
>profits, so I wonder if there is any value to a belt AFTER you look at the
>tradoffs.

No, chains stretch - belts don't. Belt timing is more accurate and
consistant. Belts are more efficient at transmitting power.
Belts are much easier and cheaper to replace
>
>The real question for a repair group would be the main factors:
>1. Reliability of chain versus belt
It can be pretty much a wash
>2. Damage potential of chain versus belt
When a chain goes bad, it does more damage than a belt
>3. Repair hassle of chain versus belt
A lot more hassle when a chain brakes.
>
>Let's ignore the marketing bull**** (e.g., lighter, quieter, etc.) for this
>thread to concentrate on the reliability and repair-related issues.
>
>As I already noted, I *wish* I had replaced a timing chain in my life, but
>just like I've never owned a FWD vehicle (and I lived in a "snow state" for
>decades), I have never had a belt car and I've never had a chain break on
>me.
>
>So I have no experience.
>But....
>
>I posit that:
>1. The chain is *far* more reliable than the belt
Not necessarilly true
>2. Both can ruin an interference engine if they break
Correct - and the cain causes more damage and is more expensive to
repair
>3. Repair hassle is probably about the same
Nope - an order of magnitude worse with a chain
>
>The question is how long is the typical MTBF for a belt versus a chain?

Belts - 60- 100 thousand Km in the past - some last a lot longer but
don't take the chance on an interference engine. an hour or 2 to
change it, and mabee 50 bucks for the belt vs 6 hours plus the cost
of tensioners and sprockets and chain (often over $200) for the chain
- which SHOULD last longer than 2 or 3 belts - but the average car
will only have the belt changed 3 times in it's lifetime

On Mon, 6 Nov 2017 04:49:16 +0000 (UTC), RS Wood >
wrote:

>Xeno wrote:
>
>>>> I have Toyotas precisely because they have a chain.
>>> Some do, some don't. (perhaps today they all do - not sure)
>>>
>> The ones I buy sure do! ;-)
>
>Two vehicles that are worthless to me:
>1. FWD
>2. Belt
Absoltely no biggy, on either count.
I like FWD. I like RWD. in NORMAL driving, there is basically no
difference - and the flat floor of a FWD is nice - and with the weight
of the engine over the drive wheels traction is snow is MUCH superior
to the traction of a rear wheel drive car with no extra weight in the
rear - - -

I've had my say on belts

On Mon, 6 Nov 2017 04:49:21 +0000 (UTC), RS Wood >
wrote:

>Frank wrote:
>
>> Chains are hardly ideal. Chains wear. The wear changes the pitch
>> between the links and the links no longer quite fit on the sprockets. It
>> turns into a self reinforcing cycle. More wear = worse fit, worse fit =
>> accelerated wear. Eventually the poorly fitting chain will jump one or
>> more teeth on the crank gear or start breaking the teeth on the cam gear.
>
>What are our choices?
>1. Chain
>2. Belt
>3. Pushrod
>
>Anything else?
Pushrod can be gear or chain
>
>> The other effect of chain wear is retarded cam timing. The more worn
>> links between the crank and cam, the more the camshaft timing gets
>> retarded. I changed timing sets on conventional OHV engines and that
>> usually advanced the ignition timing from 5 to 10 degrees, suggesting
>> that chain wear had retarded the timing by that amount.
>
>From a repair standpoint, how long do each typically last?
>1. Chain ?
>2. Belt ?
>3. Pushrod ?

Chevy pushrod engines often took out the plastic timing gears in
under 100,000 km. Lots of timing chains on pushrod engines never made
100,00 miles.
>
>I don't hear anyone talking about pushrods, so, all I see here are that
>chains last a *lot* longer in general than do belts, where if either one
>broke on an interference engine, expensive things can happen.
>
>> But I still prefer belts. Even on a tight package like a Dodge Neon with
>> the 4 speed auto, the replacement isn't too bad, once you know the
>> routine.
>
>If the replacement isn't bad, then the belt isn't 'as' bad.
>
>In the general sense though, belts, I posit, are bad news multiplied.
>I try not to take things from the marketing-bull**** standpoint.
The belt is just a maintenance item like plugs
>
>My take is always from the *why* standpoint.
>Why did the automakers go to belts over chains?
Because in SO many ways they are better and they are not affected by
lubrication issues.
>
>My supposition is that they did it to save them money.
>No other reason.
You are wrong
>
>The tradoffs are legendary where the owner is the one who loses in the end
>calculation.
>
Not necessarily
>
>>> Just like FWD cars and tricked-out cars are, to me, nearly worthless.
>>
>> I love front wheel drive, especially in the snow.
>
>Lots of cars are FWD that never see snow.
>
>In the general sense though, FWD, I posit, is bad news multiplied.
>I try not to take things from the marketing-bull**** standpoint.
>
>My take is always from the *why* standpoint.
>Why did the automakers go to FWD over RWD?
For many reasons which I have already given you.
>
>My supposition is that they did it to save them money.
>No other reason.
Nope,
>
>The tradoffs are legendary where the owner is the one who loses in the end
>calculation (particularly since deep snow is still on the road for what,
>maybe 10 days out of 365?)
Not up here. and they make cars for world markets -
>
>Anyone who mentions snow with FWD is falling directly into marketing hell.
>Just like anyone who mentions belts are "quieter" and "lighter" is doing.
>
>The sole reason for belts and FWD is to increase manufacturer's profits.
>Everything else is marketing bull**** because the tradeoffs are legendary.
You can believe what you like - but my FWD cars get around in snow
al LOT better than my old RWD cars. Try driving a new mustang or
camaro in snow.

On Mon, 6 Nov 2017 04:49:25 +0000 (UTC), RS Wood >
wrote:

>Ed Pawlowski wrote:
>
>> The $50 figure is about 30 years old. If it was accurate at the time is
>> would be double that today and there was still a lot of engineering and
>> new tooling to pay for. That said, I have no ideal today.
>
>I remember $1000 but they didn't pass that on to the consumer in toto.
>
>What irks me the most isn't that they make FWD cars, just like it doesn't
>irk me that they make convertibles or muscle cars or economy cars or luxury
>cars.
>
>What irks me about FWD is that the hoi polloi do not UNDERSTAND what FWD
>gets them.
>
>I posit it gets them almost nothing.
>
>Then the hoi polloi don't understand what they lose.
>
>I posit they lose handling.
>
>Maybe FWD is better now ... but I think I'll have to go to my deathbed
>before owning a FWD car... simply because I don't want to fall for the
>marketing trap that everyone else easily falls into.
You are not drinking the coolade, but you are certainly falling for
the bull****.

On Mon, 6 Nov 2017 04:54:55 +0000 (UTC), RS Wood >
wrote:

>Xeno wrote:
>
>>> Hrm.+AKA- I thought that was done to lighten them -- bicyclists are
>>> sometimes also called gram-shavers.+AKA- It provides better cooling too?
>>>
>> Removing mass reduces heat holding ability. The material removed does
>> not provide a gain in surface exposure. The real gain is providing a
>> path for the gasses coming off the pad surfaces to escape from between
>> the pad and rotor. Reduces the hovercraft effect.
>
>I can spout marketing bull**** as well as anyone can.
>I just choose not to.
>
>If you can find a scientific study that proves for street cars that a
>drilled/slotted rotor makes *any* difference over a solid rotor in braking
>performance, let me know.
>
>I'm all about logic.
Not for normal legal street driving

On Mon, 6 Nov 2017 16:25:31 +1100, Xeno >
wrote:

>On 6/11/2017 3:48 PM, RS Wood wrote:
>> wrote:
>>
>>> Some of the best rotors out there are Chinese - but also some of the
>>> worst. Consistency is the problem
>>
>> I can't argue but my point is that I've heard everything.
>> The problem is that the advice has to be both logical and actionable.
>>
>> Saying "buy only Brembo or Meyle" is actionable, but not logical.
>> Saying "don't buy Chinese crap" is logical but not actionable.
>>
>> For advice to be useful, it has to be both actionable and logical.
>> I've never heard that in rotors other than buy solid and don't buy
>> drilled/slotted rotors.
>>
>> Other than that, there's no way for a person to tell if one rotor is gonna
>> be better than another.
>>
>> Hence pragmatically ... a rotor is a rotor is a rotor is a rotor.
>>
>>> In some instances (virtually never normal street use) grooved and
>>> slotted rotors DO provide better braking. We are talking competition
>>> use, where the rotors are glowing red hot half the time, and the pads
>>> are off-gassing like crazy - where even 100% dry DOT4 brake fluid
>>> boils in the calipers. Under those conditions, rotors can warp - and
>>> even fracture (in Rallye use I've seen red hot rotors hit an icy
>>> puddle and totally fracture)
>>
>> I'm never talking racing.
>> They drive on bald tires for heaven's sake in racing!
>>
>
>Yep, far better coefficient of friction - in dry conditions.
>
>>
>>> Actually, on SOME cases you can. Look at the consistancy of the fins
>>> in the rotors, and the even-ness of the thickness of the braking
>>> surfaces on both sides of the fins.
>>
>> I'm not gonna disagree that we all can see the mark of good quality on some
>> things when we have two to compare in our hand, but it's too late if you
>> order on the net.
>>
>>>> How are you gonna know the metallurgy?
>>>
>>> You don't - that's the hard part - but when you are in the business
>>> you get to know which suppliers stand up, and which don't. If you
>>> know the suppliers well, they will tell you which ones they have
>>> trouble with, and which ones they don't.
>>
>> Yup. I have nothing against good suppliers. I use Brembo and Meyle but if
>> someone else gave me a rotor at a better price, I'd consider them too.
>>
>>> And some rotors DO WARP. Not many - but I've had at least a bushel
>>> basket full of genuinely warped rotors in my 25 year carreer. Most
>>> "warped" rotors are not warped - but some are. Some DRASTICALLY - to
>>> the point the caliper moves visibly when the wheel is turned - and if
>>> the sliders stick the pedal jumps and the steering wheel twitches.
>>
>> That's not the measure of warp.
>> Warp is measured on a flat bench.
>> Just like head warp is measured.
>
>Or with a dial indicator - on both sides - for comparison.
>>
>>> More often than not though, they are either pitted or have deposit
>>> buildup, ot they have "hard spots" due to metalurgical inclusions
>>
>> The only person who says their rotors warped that I will ever trust is one
>> who measured the warp just like you'd measure head warp.
>
>Use to check for warp every time.
>>
>> If they haven't measured it, it's not happening.
>> And nobody measures it.
>> So it didn't happen.
>
>Some do. I did. I also taught apprentices to measure for it.
>>
>> It "could" happen. But it doesn't (on street cars).
>> The problem is the temperature never gets hot enough.
>
>It can under specific circumstances. See it most often on autos in very
>hilly country.
>>
>> Now they can be "warped" from the factory; but that's different (and rare).
>>
>>> Wrong tool. The one I'm talking about has tabs that fit into the
>>> notches on the piston face to "thread" it in as you squeese. Can
>>> sometimes get away with the $17 "cube" but the kit you KNOW is going
>>> to work starts at about $35 for one of questionable quality, and goes
>>> up very quickly from there (and IT won't turn back Mazda rear calipers
>>> - they use a different system
>>
>> I think we're talking about two different kinds of disc brake systems.
>> I had the Nissan 300Z which had the rear disc also as the rear parking
>> brake, but my bimmer has the rear disc and a separate rear parking brake.
>>
>> The piston arrangement is different as is the way to retract them.
>>
>> You don't *twist* pistons in disc brakes that I own that don't have the
>> parking brake as part of the disc brake itself.
>>
>> At least I don't.
>>
>>
>>>> Never once in my life have I found a single person who has *measured* the
>>>> warp.
>>>
>>> I have. many times.
>> How?
>>
>>>> You know why?
>>>> They don't even know *how* to measure rotor warp.
>>>> They don't have the tools to measure rotor warp
>>> A somple dial indicator tells the tale
>>
>> Nope.
>> How you gonna tell runut from warp with a dial gauge?
>
>Measure disc thickness at various points around the disc. If the
>thickness doesn't vary, then any runout measured on the dial indicator
>is warp. Verified by back and front runout comparisons.
>
>By the way, thickness variation checks are part of a standard disc
>inspection process.
>
>>
>>> - and sometimes one side is
>>> straight, and the other side is not - parallelism warpage - where some
>>> fins collapse and one side of the rotor "caves in" - 1 inch thick on
>>> one "side" of the rotor, and .875 or something like that diametrically
>>> across the rotor. - and sometimes virtually deead flat on both
>>> surfaces - other times with about hald paralel and the other half
>>> "sloped"
>>
>> Now you're straining credularity.
>>
>>>> (Hint: It requires a flat benchtop and feeler gauges and it's not hard -
>>>> but they don't know that because they didn't measure a single thing.)
>>>
>>> That won't necessarilly tell you anything. The only way to KNOW is to
>>> use a dial indicator properly.
>>
>> How you gonna tell runut from warp with a dial gauge?
>
>Compare measurements.
>>
>>> And that is where YOU are WRONG.
>>> Many technicians measure brake rotors virtually every day of their
>>> working lives.
>>
>> On the entire freaking Internet, find *one* picture (just one) of a
>> technician actually properly measuring brake rotor *warp*.
>>
>> Just find a *single* picture please. Just one.
>> On the entire freakin' Internet.
>>
>> Find one.
>>
>>> Dealerships were then REQUIRED to buy an "on-the-car lathe" to true
>>> up rotors.
>>
>> That's not warp.
>> Nothing on this planet is going to fix warp.
>> There's not enough metal to remove.
>
>Depends on the warp severity.
>>
>>> A wize man learns from the mistakes of others - a fool never learns
>>> because he "never makes mistakes"
>>
>> Which is why I wish I had done these half-dozen jobs:
>> 1. Alignment
>> 2. Transmission
>> 3. Engine
>> 4. Tires
>> 5. paint
>
>Done all, taught 1 thru 4 at a technical college.
>>
>>> Yes - you are right to the extent that MOST "warped rotors" are not.
>>> But you are absolutely WRONG when you say they never warp in
>>> street/highway use and anyone who says they have had a warped rotor is
>>> lying and hasn't measured the rotor to prove it.
>>
>> I never once said "never" but "almost never" which is different, and we're
>> only talking street, and I have references that back up everything I say
>> whereas you provided zero references for what you said.
>>
>> I'm not here to argue opinions.
>> I only argue using logic.
>>
>> Just read the references I provided and then provide some references that
>> back up your point of view.
>>
>> The "Warped" Brake Disc and Other Myths of the Braking System
>> <http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths>
>>
>> The 'Warped Rotor' Myth
>> <http://www.10w40.com/features/maintenance/the-warped-rotor-myth>
>>
>> Warped Brake Rotors - Vibrating Reality or Internet Myth?
>> <https://blog.fcpeuro.com/warped-brake-rotors-vibrating-reality-or-internet-myth>
>>
>> Stop the +IBg-Warped+IBk- Rotors Myth and Service Brakes the Right Way
>> <http://www.brakeandfrontend.com/warped-rotors-myth/>
>>
>> Raybestos Brake Tech School, Part One: Rotors Don't Warp
>> <http://www.hendonpub.com/resources/article_archive/results/details?id87>
>>
Notice amateur Woody is arguing with 2 former professional mechanics
and trade school instructors???? I'm done with him. A waste of time,
effort and breath. PLONK!!

On Mon, 6 Nov 2017 17:23:01 +1100, Xeno >
wrote:

>On 6/11/2017 3:49 PM, RS Wood wrote:
>> Xeno wrote:
>>
>>>>> I have Toyotas precisely because they have a chain.
>>>> Some do, some don't. (perhaps today they all do - not sure)
>>>>
>>> The ones I buy sure do! ;-)
>>
>> Two vehicles that are worthless to me:
>> 1. FWD
>> 2. Belt
>>
>The past half dozen cars I've had have been FWD. I don't have a problem
>with them. My first FWD car was a Morris Mini back in 74 and I have had
>heaps of them since. Had heaps of RWD cars too. Totals in the hundreds.
2 mechanics/trade school instrctors who drove Morris Minis ----

On Mon, 06 Nov 2017 02:57:16 -0500, wrote:


> Only the stop-tech article is written by a pro (Can't open the
>raybestos link so it's useless)

That "pro" says to replace brake fluid once a year.
I wonder how many people do that.
I never replace brake fluid unless I've got the system open.

On 6/11/2017 6:57 PM, wrote:
> On Mon, 6 Nov 2017 04:48:28 +0000 (UTC), RS Wood >
> wrote:
>
>> wrote:
>>
>>> Some of the best rotors out there are Chinese - but also some of the
>>> worst. Consistency is the problem
>>
>> I can't argue but my point is that I've heard everything.
>> The problem is that the advice has to be both logical and actionable.
>>
>> Saying "buy only Brembo or Meyle" is actionable, but not logical.
>> Saying "don't buy Chinese crap" is logical but not actionable.
>>
>> For advice to be useful, it has to be both actionable and logical.
>> I've never heard that in rotors other than buy solid and don't buy
>> drilled/slotted rotors.
>>
>> Other than that, there's no way for a person to tell if one rotor is gonna
>> be better than another.
>>
>> Hence pragmatically ... a rotor is a rotor is a rotor is a rotor.
>>
>>> In some instances (virtually never normal street use) grooved and
>>> slotted rotors DO provide better braking. We are talking competition
>>> use, where the rotors are glowing red hot half the time, and the pads
>>> are off-gassing like crazy - where even 100% dry DOT4 brake fluid
>>> boils in the calipers. Under those conditions, rotors can warp - and
>>> even fracture (in Rallye use I've seen red hot rotors hit an icy
>>> puddle and totally fracture)
>>
>> I'm never talking racing.
>> They drive on bald tires for heaven's sake in racing!
>>
>>
>>> Actually, on SOME cases you can. Look at the consistancy of the fins
>>> in the rotors, and the even-ness of the thickness of the braking
>>> surfaces on both sides of the fins.
>>
>> I'm not gonna disagree that we all can see the mark of good quality on some
>> things when we have two to compare in our hand, but it's too late if you
>> order on the net.
>
> And only a total fool buys everything on the net. I can generally buy
> off the shelf for close to the same price, with no hassle returns and
> I get to see-feel EXACTLY what I'm buying.
>>
>>>> How are you gonna know the metallurgy?
>>>
>>> You don't - that's the hard part - but when you are in the business
>>> you get to know which suppliers stand up, and which don't. If you
>>> know the suppliers well, they will tell you which ones they have
>>> trouble with, and which ones they don't.
>>
>> Yup. I have nothing against good suppliers. I use Brembo and Meyle but if
>> someone else gave me a rotor at a better price, I'd consider them too.
>
> Can't even BUY Brembo for my daughter's car.
>>
>>> And some rotors DO WARP. Not many - but I've had at least a bushel
>>> basket full of genuinely warped rotors in my 25 year carreer. Most
>>> "warped" rotors are not warped - but some are. Some DRASTICALLY - to
>>> the point the caliper moves visibly when the wheel is turned - and if
>>> the sliders stick the pedal jumps and the steering wheel twitches.
>>
>> That's not the measure of warp.
>> Warp is measured on a flat bench.
>> Just like head warp is measured.
>
> Not in the real world. On a large percentage of rotors doing it your
> way is totally impossible. And my way (the industry standard) I can
> measure warpage/runout ON THE CAR and know if it's a problem before
> taking ANYTHING apart beyond moving the rim.
>>
>>> More often than not though, they are either pitted or have deposit
>>> buildup, ot they have "hard spots" due to metalurgical inclusions
>>
>> The only person who says their rotors warped that I will ever trust is one
>> who measured the warp just like you'd measure head warp.
>>
>> If they haven't measured it, it's not happening.
>> And nobody measures it.
>> So it didn't happen.
>>
>> It "could" happen. But it doesn't (on street cars).
>> The problem is the temperature never gets hot enough.
>>
>> Now they can be "warped" from the factory; but that's different (and rare).
>>
>>> Wrong tool. The one I'm talking about has tabs that fit into the
>>> notches on the piston face to "thread" it in as you squeese. Can
>>> sometimes get away with the $17 "cube" but the kit you KNOW is going
>>> to work starts at about $35 for one of questionable quality, and goes
>>> up very quickly from there (and IT won't turn back Mazda rear calipers
>>> - they use a different system
>>
>> I think we're talking about two different kinds of disc brake systems.
>> I had the Nissan 300Z which had the rear disc also as the rear parking
>> brake, but my bimmer has the rear disc and a separate rear parking brake.
>
> Really crappy system - sorry.
>
>
> I've worked on everything from a moskovitch to a Rolls, with Jags,
> Rovers, Toyotas, Fiats, Ladas, VWs, Nissans as well as just about
> every North American brand
>>
>> The piston arrangement is different as is the way to retract them.
>>
>> You don't *twist* pistons in disc brakes that I own that don't have the
>> parking brake as part of the disc brake itself.
>
> I'm talking in general - not the limited vehicles of your experience.
>>
>> At least I don't.
>>
>>
>>>> Never once in my life have I found a single person who has *measured* the
>>>> warp.
>>>
>>> I have. many times.
>> How?
>>
>>>> You know why?
>>>> They don't even know *how* to measure rotor warp.
>>>> They don't have the tools to measure rotor warp
>>> A somple dial indicator tells the tale
>>
>> Nope.
>> How you gonna tell runut from warp with a dial gauge?
> \Measure in more than 2 places -
>>
>>> - and sometimes one side is
>>> straight, and the other side is not - parallelism warpage - where some
>>> fins collapse and one side of the rotor "caves in" - 1 inch thick on
>>> one "side" of the rotor, and .875 or something like that diametrically
>>> across the rotor. - and sometimes virtually deead flat on both
>>> surfaces - other times with about hald paralel and the other half
>>> "sloped"
>>
>> Now you're straining credularity.
>
> No I'm not. Seen it many times
>>
>>>> (Hint: It requires a flat benchtop and feeler gauges and it's not hard -
>>>> but they don't know that because they didn't measure a single thing.)
>>>
>>> That won't necessarilly tell you anything. The only way to KNOW is to
>>> use a dial indicator properly.
>>
>> How you gonna tell runut from warp with a dial gauge?
>
> Watch the needle move.
>>
>>> And that is where YOU are WRONG.
>>> Many technicians measure brake rotors virtually every day of their
>>> working lives.
>>
>> On the entire freaking Internet, find *one* picture (just one) of a
>> technician actually properly measuring brake rotor *warp*.
>
> The internet doesn't show EVERYTHING. What you know comes from the
> web. What I know comes from tears in the trade (including teaching the
> trade)

Teaching the trade, yes, bound to cause tears at times.
>>
>> Just find a *single* picture please. Just one.
>> On the entire freakin' Internet.
>>
>> Find one.
>>
>>> Dealerships were then REQUIRED to buy an "on-the-car lathe" to true
>>> up rotors.
>>
>> That's not warp.
>> Nothing on this planet is going to fix warp.
>> There's not enough metal to remove.
>
> That is totally dependent on how much warp. And what, other than
> "warp" will cause a rotor to develop "runout" if it is totally true
> when installed.
>>
>>> A wize man learns from the mistakes of others - a fool never learns
>>> because he "never makes mistakes"
>>
>> Which is why I wish I had done these half-dozen jobs:
>> 1. Alignment
>> 2. Transmission
>> 3. Engine
>> 4. Tires
>> 5. paint
>
> Ond I've dome them all at least once.

Done hundreds and hundreds of alignments.
>>
>>> Yes - you are right to the extent that MOST "warped rotors" are not.
>>> But you are absolutely WRONG when you say they never warp in
>>> street/highway use and anyone who says they have had a warped rotor is
>>> lying and hasn't measured the rotor to prove it.
>>
>> I never once said "never" but "almost never" which is different, and we're
>> only talking street, and I have references that back up everything I say
>> whereas you provided zero references for what you said.
>
> You have references I have experience.

Ditto. Been there, measured that. ;-)
>>
>> I'm not here to argue opinions.
>> I only argue using logic.
>
> Reality defies logic.
>>
>> Just read the references I provided and then provide some references that
>> back up your point of view.
>>
>> The "Warped" Brake Disc and Other Myths of the Braking System
>> <http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths>
>>
>> The 'Warped Rotor' Myth
>> <http://www.10w40.com/features/maintenance/the-warped-rotor-myth>
>>
>> Warped Brake Rotors - Vibrating Reality or Internet Myth?
>> <https://blog.fcpeuro.com/warped-brake-rotors-vibrating-reality-or-internet-myth>
>>
>> Stop the +IBg-Warped+IBk- Rotors Myth and Service Brakes the Right Way
>> <http://www.brakeandfrontend.com/warped-rotors-myth/>
>>
>> Raybestos Brake Tech School, Part One: Rotors Don't Warp
>> <http://www.hendonpub.com/resources/article_archive/results/details?id87>
> Only the stop-tech article is written by a pro (Can't open the
> raybestos link so it's useless)
>
> The rest could be written by you - same level of cred. They are
> written by enthusiasts who have read articles.
>
> They are correct in most of what they say - but real warpage DOES
> exist, because not all rotors are properly manufactured and stress
> relieved and heat treated - like the problem Toyota had in the early
> '80s, and many of the "crap" rotors in the aftermarket - as I have
> explained before. In the "ideal world" they would never warp. Also,
> not all rotors spend their life in "normal" conditions - other
> problems in the braking system, or abuse, can cause a lot more heat
> than normal driving - which is why the accurate stement is:

Overtightening wheel nuts or uneven tightening of same will cause
warpage of discs.
>
> "Under normal operating conditions, properly manufactured and
> installed brake rotors very seldom actually WARP. Poor quality rotors
> can warp, as can rotors that are severely overheated due to abuse or
> certain braking system falures. When you experience brake pulsation,
> actual brake rotor warpage is UNLIKELY to be the problem - but
> stranger things HAVE happened. Uneven friction material transfer due
> to either poor intial bedding of the pads or improper use of the
> brakes is much more likely, and some brake pads are more prone to
> causing these issues due to their composition. In areas where winters
> are more severe and salt is used on the roads some pad compostions are
> more likely to cause problems - particularly the hard-spotting and
> pitting of rotors due to localized overheating caused by uneven
> friction material transfer. Many brake problems tend to be regional in
> nature for this reason. Rustout of cooling fins of a rotor, for
> instance, would be unheard-of in arizona or alabama, but fairly common
> in the northeat and the "rust belt".
>
>
> NEVER say never and ALWAYS avoid always.
>


--

Xeno

On 6/11/2017 7:02 PM, wrote:
> On Mon, 6 Nov 2017 04:48:30 +0000 (UTC), RS Wood >
> wrote:
>
>> Xeno wrote:
>>
>>> Any scoring on a rotor will fail it. As you say, there might be less
>>> than 50% of the pad surface in contact with the rotor surface. No way
>>> will that bed in properly. You will get localised overheating both on
>>> the pad and on the rotor.
>>
>> I'm not gonna argue vehemently because, in practice, while I've seen those
>> "wavy" rotors too, my rotors tend to be smooth so I don't deal with
>> "scoring".
>>
>> However, anyone who says "any scoring of rotors will fail it" has NOT looke
>> up the manufacturer's spec for scoring tests.
>>
>> I have. Long ago.
>>
>> The result was shockingly huge.
>>
>> I don't remember the actual number but I remember being shocked at how huge
>> it is. Something like tens of thousanths of an inch in width huge.
>>
>> We're talking Grand Canyon in rotors.
>>
>> I may be wrong but if someone says "any" scoring, that's just preposterous.
>> Let's see a manufacturer's spec for anyone who says that.
>>
>> Sorry. It's just not logical that 'any' scoring fails a rotor.
> ANY mechanical damage fails the rotor on DOT test. Some smoth wear is
> allowed - but you NEVER install new pads on rotors that have an uneven
> friction surface because it is virtually impossible to properly bed
> the new pads to the uneven rotor withot localized overheating

Exactly. The new pads will charcoal grill on the high spots and *never*
properly bed in.
>
> At the price of rotors today even on your Bimmer, it just is not
> worth it. The pads cost more than the rotors on MOST vehicles today.
> No reputable shop will do it because comebacks are expensive - and
> real mechanics KNOW the comebacks will happen if they do something
> stupid like installing new pads on badly worn rotors.
>
Brake pulling is most likely as the most grooved disc will have less
surface contact.

--

Xeno