what's better about higher priced rotors?

In article >, jim wrote:
>> But it's not just those three, there are countless grades within each
>> generic catagory.
>
> The grades within the categories are based on the mechanical properties
> of the iron. It's relatively easy to determine the grades if you are
> willing to do destructive testing. After you have determined the grade
> of a batch of castings there are non-destructive tests that can be used
> to determine if the quality is maintained through out. The metal casting
> industry didn't just crawl out from under a cabbage leaf yesterday they
> have had this sort of stuff worked out for along time.

Thank you captain obvious.


>>Given general practices in China, I would suspect that
>> process controls and material substitutions would result in very poor
>> parts. One could get a 'grey cast iron' rotor made of a low grade that is
>> suspect of even meeting those requirements that performs poorly but that
>> doesn't mean all grey cast iron is bad for brake rotors.

> I don't know why process control would be any different for a Chinese
> foundry than an American. If any thing they may be more quality
> conscious. Considering the cost of shipping something so heavy from
> China if they get a batch of castings rejected they are going to be out
> a lot more than when it happens to an American foundry.

The culture in china is entirely different. They don't know and/or just
don't care for the most part.

>> >> The Bosch automotive handbook reads:
>> >> "Gray cast iron brake disks with bilaterally acting calipers have proven
>> >> to be the most satisfactory layout."
>>
>> > Given that many ( most? ) cars don't have that particular configuration
>> > we can assume that opinion isn't the definitive word on the subject.
>>
>> You were saying what was better, I just brought up another source that
>> has a differing opinion.

> I merely said that the rotors you see in parts stores are most often not
> gray iron. I made the mistake of expanding on that and offering a
> possible reason. From that you conclude I have something against gray
> iron?

No. I want to say: A) what they are and why it's better. goose, gander,
all that sort of thing.

>> >> Now, since you disagree, what is 'better'?
>>
>> > Better in what way?
>>
>> You're the one making the claim... up to you.

> I didn't claim anything. I simply observed what it is the market place
> finds better and why.

Read your own words back to yourself.

>> > Where I live corrosion from road salt is the main
>> > thing that shortens the life of brake rotors. If you want corrosion
>> > resistance then stainless steel is better. But it won't be better in
>> > price or in the ability to bring the vehicle to a stop.
>> > At any rate that wasn't the question. The biggest advantage of gray
>> > iron is its ability to dampen noise and vibration. So when you see one
>> > set of rotors advertised as being made of "noise dampening iron" you can
>> > be certain that one is gray iron. That property alone would seem to make
>> > it the perfect material for brakes. The problem is that it is not as
>> > tough or strong as steel or ductile iron. So there is a greater danger
>> > of catastrophic failure. I suspect that property is what is given the
>> > most consideration by manufacturers.

>> There are various grades of each and there is considerable overlap in the
>> ranges. The specific grade and manufacturing processes is what it all
>> comes down to.

>> Noise dampening iron seems to refer to carbon content. For instance,
>> Brembo uses a high carbon content for noise reduction.

> Well, that may be how you and the marketing people at Brembo understand
> it. But if they are pushing noise reduction you can be sure it is gray
> iron. And if a company is not advertising a particular rotor is good for
> noise reduction then it probably isn't (unless their marketing people
> are just dimwits).

You know that exactly how? You cut up rotors and examine the microstructure?

Brent P wrote:

>
> You know that exactly how? You cut up rotors and examine the microstructure?

Well no, but I did that once back in a different life. Determining
whether something is made of gray iron is pretty simple. Hit it with
something hard (like a screw driver handle) if it goes thud its gray
iron. If it rings (like a bell) it is not. The vibration damping
properties of gray iron is quite obvious.

-jim

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jim wrote:
>
> Brent P wrote:
>
>>> Yes you are right most people can't tell the difference between gray
>>> iron and ductile iron. White iron is not very machinable so it's
>>> unlikely you will ever see any of that in a brake rotor.
>> But it's not just those three, there are countless grades within each
>> generic catagory.
>
> The grades within the categories are based on the mechanical properties
> of the iron. It's relatively easy to determine the grades if you are
> willing to do destructive testing. After you have determined the grade
> of a batch of castings there are non-destructive tests that can be used
> to determine if the quality is maintained through out. The metal casting
> industry didn't just crawl out from under a cabbage leaf yesterday they
> have had this sort of stuff worked out for along time.
>

Uh huh... I'm sure you can do all this testing in a parts store or over
the internet while you're trying to determine if you should buy the $19
rotor, the $49 rotor, or the $99 rotor.

Ray

Ray > wrote:
>
>Uh huh... I'm sure you can do all this testing in a parts store or over
>the internet while you're trying to determine if you should buy the $19
>rotor, the $49 rotor, or the $99 rotor.

Most of the time you don't care. Tap it on the parts counter and see if
it goes clang or it goes thunk. That tells you most of what you want to
know. Look at the surface. Does it look nice and clean or does it look
like the Three Stooges got their hands on a turret lathe?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Ray wrote:
>
> jim wrote:
> >
> > Brent P wrote:
> >
> >>> Yes you are right most people can't tell the difference between gray
> >>> iron and ductile iron. White iron is not very machinable so it's
> >>> unlikely you will ever see any of that in a brake rotor.
> >> But it's not just those three, there are countless grades within each
> >> generic catagory.
> >
> > The grades within the categories are based on the mechanical properties
> > of the iron. It's relatively easy to determine the grades if you are
> > willing to do destructive testing. After you have determined the grade
> > of a batch of castings there are non-destructive tests that can be used
> > to determine if the quality is maintained through out. The metal casting
> > industry didn't just crawl out from under a cabbage leaf yesterday they
> > have had this sort of stuff worked out for along time.
> >
>
> Uh huh... I'm sure you can do all this testing in a parts store or over
> the internet while you're trying to determine if you should buy the $19
> rotor, the $49 rotor, or the $99 rotor.

Right. For all you know they are all identical and the only difference
is the box and the price and they all could be from the same foundry in
Kansas.

-jim

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Scott Dorsey wrote:
> Ray > wrote:
>> Uh huh... I'm sure you can do all this testing in a parts store or over
>> the internet while you're trying to determine if you should buy the $19
>> rotor, the $49 rotor, or the $99 rotor.
>
> Most of the time you don't care. Tap it on the parts counter and see if
> it goes clang or it goes thunk. That tells you most of what you want to
> know. Look at the surface. Does it look nice and clean or does it look
> like the Three Stooges got their hands on a turret lathe?
> --scott

I don't even do that - I just buy the cheap stuff usually unless I NEED
it for heavy duty/hi perf type application. For those, I go with brand
name parts only, and only brand names that I trust.

an example -> after bending/breaking two balljoints on my dirt track
camaro, I only use Moog balljoints.

Ray

Scott Dorsey wrote:
> Ray > wrote:
>> Uh huh... I'm sure you can do all this testing in a parts store or over
>> the internet while you're trying to determine if you should buy the $19
>> rotor, the $49 rotor, or the $99 rotor.
>
> Most of the time you don't care. Tap it on the parts counter and see if
> it goes clang or it goes thunk. That tells you most of what you want to
> know.

So thunk is the gray iron and clang isn't. Which is good and which is bad?

i thought i'd follow up and let y'all know what
the eventual outcome of my rotor post, since
the parts arrived today:

if nothing else, i'm impressed with the packaging
of the Monroe pads. inside the sturdy box, the
pads are shrink-wrapped to a cardboard insert.
the outside of the box has, "Printed in Canada"
and "Made in Canada".

the Wagner rotors came in the typical square box.
the "Wagner Brake Products" sticker on the outside
of the box claims, "Printed in China" and
"Made in China".

the rotor, wrapped in a plastic cover, looks EXACTLY
like the $19 rotors i bought for the '90 Trooper a few
months ago. the casting and machining looks of high
quality, the fins are symmetrical and very clean,
with no casting side-effects in the fins. there are no
stampings anywhere on the rotors.

when i stand the rotor on its edge on a formica surface
and tap the inner ring, the result is a "RING" that lasts
for a few seconds.

although i'll (we'll) never know the difference in metal
content between this rotor and the Trooper's rotor, i will
say the "workmanship" looks the same.

regards, michael

i thought i'd follow up and let y'all know what
the eventual outcome of my rotor post, since
the parts arrived today:

if nothing else, i'm impressed with the packaging
of the Monroe pads. inside the sturdy box, the
pads are shrink-wrapped to a cardboard insert.
the outside of the box has, "Printed in Canada"
and "Made in Canada".

the Wagner rotors came in the typical square box.
the "Wagner Brake Products" sticker on the outside
of the box claims, "Printed in China" and
"Made in China".

the rotor, wrapped in a plastic cover, looks EXACTLY
like the $19 rotors i bought for the '90 Trooper a few
months ago. the casting and machining looks of high
quality, the fins are symmetrical and very clean,
with no casting side-effects in the fins. there are no
stampings anywhere on the rotors.

when i stand the rotor on its edge on a formica surface
and tap the inner ring, the result is a "RING" that lasts
for a few seconds.

although i'll (we'll) never know the difference in metal
content between this rotor and the Trooper's rotor, i will
say the "workmanship" looks the same.

regards, michael

> wrote in message
ups.com...
>i thought i'd follow up and let y'all know what
> the eventual outcome of my rotor post, since
> the parts arrived today:
>
> if nothing else, i'm impressed with the packaging
> of the Monroe pads. inside the sturdy box, the
> pads are shrink-wrapped to a cardboard insert.
> the outside of the box has, "Printed in Canada"
> and "Made in Canada".
>
> the Wagner rotors came in the typical square box.
> the "Wagner Brake Products" sticker on the outside
> of the box claims, "Printed in China" and
> "Made in China".
>
> the rotor, wrapped in a plastic cover, looks EXACTLY
> like the $19 rotors i bought for the '90 Trooper a few
> months ago. the casting and machining looks of high
> quality, the fins are symmetrical and very clean,
> with no casting side-effects in the fins. there are no
> stampings anywhere on the rotors.
>
> when i stand the rotor on its edge on a formica surface
> and tap the inner ring, the result is a "RING" that lasts
> for a few seconds.
>
> although i'll (we'll) never know the difference in metal
> content between this rotor and the Trooper's rotor, i will
> say the "workmanship" looks the same.
>
> regards, michael
>

So, what is the bottom line here? Is there actually little or no difference
in all these parts? Brembo rotors ar available for my car for $43 apiece.
Is that a waste of money? It seems like the whole thing is quite a
crapshoot, considering the very high importance of properly operating
brakes.

mg



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