On Wed, 10 Jan 2018 08:34:43 -0000 (UTC), Mad Roger
> wrote:

> On Tue, 09 Jan 2018 23:55:56 -0500,
> Clare Snyder wrote:
>
>>>It's usually *hard* to find the scoring spec; it's a lot easier to find the
>>>thickness and runout specs, so I'm not saying it's an easy spec to find.
>>
>> not hard at all. here's one:
>> https://www.cbsparts.ca/admin/bullet...nd%20Rotor.pdf
>
>Um... you just proved my point.
>There's no spec for scoring and grooving in that PDF.

Because if there is scoring that cannot be polished out by hand the
drum MUST be refinished or replaced. There is no spec because there is
no tolerance for scoring or grooving. If you can feelit - it fails.
Period - end of discussion.
>And in *anything* on a car, there is no such thing as 0 tolerance. It just
>doesn't exist. 0 may be 0.090 or it might be 0.001 but it's never going to
>be 0 on anything.
>
>Specifically "free of scoring" is not a spec for how thick the scoring can
>be. (Yes, I know you *intimate* zero, but 0 inches is not the OEM spec, as
>I've seen OEM specs when I looked. They're hard to find, but they're
>nowhere near 0 inches).
>
>I'm not chastising you for finding that PDF, as I know it's nearly
>impossible to find any manufacturer's spec for how thick a groove or
>scoring can be before it's rejected - but when you find the spec (as I have
>in the past), you'll be shocked how deep and wide the grooves can be and
>still be within manufacturers' specs.
>

no - the spec you talk of is how deep the scoring can be and still
be correctable, not acceptable - you can machine uot deep scoring as
long as you don't excede the machining limit, which is generally
about 30 thou less than the discard limit - but on the heavy drums of
a 4-runner or land cruiser, is equal to the discard limit.
>> and another:
>> https://www.cbsparts.ca/admin/bullet...20Problems.pdf
>
>Um... this proves point also, which is that there is no spec in there for
>scoring or grooving other than 0, which is a ridiculous number that isn't
>the manufacturer's spec.
>
>Again, I'm not chastising you for finding out what I already knew to be the
>case, because I too looked and it's not easy to find a spec but when you
>find it, you'll be amazed how wide the grooves can be and still be within
>the manufacturers' specs.
>


Give me proof
>> see page 402 at :
>> https://books.google.ca/books?id=O01...limits&f=false
>
>Ch 8 Drum Brakes wasn't visible to me when I looked.
>
>> "If scoring or light grooves cannot be removed by hand (with emery
>> cloth) the drum MUST be refinished or replaced"
>
>Again, this proves my point. Unless you actually believe 0 is the spec, but
>I already know, from my past searches years ago, that it's huge, so it's
>not even close to zero.

Give me proof.

>
>> There is NO ALLOWABLE AMOUNT OF GROOVING ALLOWED ON A DRUM when
>> replacing friction m,aterial- PERIOD.
>
>I see your words and I believe it says that but it's not a manufacturer's
>spec

.. Because there IS no spec.
>
>Now, I did look it up only for the rotors because the vehicle didn't have
>drum brakes, so, maybe drums are different - but that doesn't change the
>fact that none of these are Toyota specs.

It IS different. There is NO spec for drums. There IS a spec for
rotors, but even there, the spec is for "in service" rotors - not for
pad replacement.
>
>> read ALL of:
>> http://www.aa1car.com/library/drum_brakes.htm
>
>Um. Again, it proves my point, saying only that "Minor pitting and scoring
>are acceptable as long as the grooves are not too deep and can be removed
>by resurfacing."



meansd you don't have to throw them away if they can be resurfaced
within spec. It does NOT mean they can be returned to service asis
with new friction material>
>As in the other PDFs, that implies 0 but it's just not 0 IMHO.
>I may be wrong for drums, because what I looked up was the manufacturer's
>spec for scoring of rotors - but the scoring limit for rotors is *huge* so
>why would drums be different?

Because drums are not rotors and you are reading the rotor spec weong.

>
>Maybe drums *are* zero (I'm not saying they're not); all I'm saying is that
>you and I both know that it's damn hard to find the *manufacturers* spec
>for the depth and width of a scoring that will fail a drum.
>

Because, as I said, there IS NO SPEC other than if it cannot be
polished out, it should be resurfaced, and you cannot reserface beyond
the machining limit, which is GENERALLY less than the in-service wear
limit
>To be clear, I'm not trying to argue with you as you found exactly what I
>found, which is that it's damn hard to find the manufacturers' spec for the
>size of scoring where it's *easy* to find their spec for the diameter and
>other things.
>
>That last article does say the following:
> "One way to tell if the surface finish is in the recommended range
> of 80 microinches or less"

And seldom is a tolerance plus or minus 50% - so that leaves you, at
the outside, with 120 mict=roinches with a "50%/-0 TOLERANCE.
>
>Ok. That's 80 millionths of an inch, or 0.000080 inches, but that's the
>overall "roughness" factor and not scoring per se. And, notice it's not 0
>simply because nothing in a vehicle is at 0 tolerance.
>
>My main comment stands which is that, at least for rotors, scoring has to
>be huge to fail a rotor, according to the specs I don't have now but that I
>unearthed in the past from a vehicle manufacturer.
>

With rotors directly exposed to road grit, stones, ets it is obvious
they WILL suffer some scoring in use, wheras drums, being enclosed
should not. WHAT is going to cause scoring in drums?????

And the spec for rotors is for in-service failure - NOT for tolerance
for replacing friction material.

If rotors are scored, you don't get full friction surface engagement,
and the "high spots" overheat as they wear in - then when wornin the
surface area increases by the annular surface of the groove, and the
friction co-efficient of the pads to rough rotors is different than
the co-efficient oif friction with proiperly machined rotors (and
glazed rotors are different again)

For someone so fixated on friction ratings, you are certainly missing
the point on damaged rotors and drums, which have SIGNIFICANT effects
on the friction effects of the brakes.

I'm going to step right out and say it - you are an IDIOT if you
cannot grasp the significance of what has been said, bothabout
friction materials and rotor/drum condition.
>Whether rotor scoring is similar is unknown to me but it's a good question
>of what Toyota things is a scoring limit. But really this is theoretical
>since I'm keeping the drums as they're in fine shape with no "visible"
>scoring.
Your drums did look OK in the pictures. Now just buy the OEM SPEC
linings and get it done!!!! - and before you install the drums on the
new shoes DEGLAZE THEM WITH 80 GRIT ABRASIVE PAPER tocondition the
surface to properly break in the new friction material.