If it is not grooved , pitted, or discoloured just scuffing with "40
grit abbrasive will allow them to seat just fine.
HOWEVER, in at least half of North America finding rotors in that
condition while requiring pad replacement is getting to be a rare
occurrence. (Particularly on the inner surface of the rotor)
Most car makers do NOT recommend routine turning of the rotors when
pads are replaced. And the worst that would happen if you don't turn
them is that the pads last longer, hardly a reason not to honor the
warranty on the pads. It's just another excuse the shops use to avoid
doing inexpensive work.
Group 06- Section 00, pages 17 to 19 of the Ford PG2040 manual for
the 1996 Mystique /Contour states "each time the brakes are serviced,
the front and rear disk rotors should be checked for scoring, runout,
parallelism and thickness"
Runout of over 0.006" is unacceptable, and parallelism (variation in
thickness) must not excede 0.0006" and there is half a page dedicated
to how to refinish a rotor. They also stipululate that you NEVER
machine to miinimum thickness spec. Front rotor discard thickness is
22.2mm, or 0.87". Original spec is 25MM (0.984").
That leaves 0.114" MAXIMUM cut/wear to scrap - aprox 0.040" per side
to the service limit - and .057" to scrap.
So it is OBVIOUS they intend/expect that the rotors will often
require refinishing or replacement.
"often"?? that's just your assumption.It's not so obvious to me.
I doubt many brake techs actually measure runout,parallelism,or rotor
thickness;they just quote new rotors,and add the cost to your bill.
How much rotor material wears off if the car's brought in before the pads
reach minimum thickness?
How much does a ordinary refinishing job remove?
(On a rotor that is not grooved.)
(I don't know.)
That depends on the pads, to a large extent - and also on the rotor
I've seen rotors worn to below the limit, with NO grooves, without
ever being machined.
I've seen rotors that were not machinable any more with half the
frictionnmaterial still left on the pads - after having pads and
rotors replaced at the same time less than a year before.
That depends, but you won't get away with ten thou per side - almost
guaranteed. This is assuming there is a requirement to machine them in
the first place.
If the rotor is dead smooth, but badly glazed, an abrasive disk will
do the job at about one thou per side. If a cut is required, (shop
doesn't have the "grinder pucks" generally closer to five thou per
side. Any less leaves a bad finish because the cutter needs to get
UNDER the glaze to remove it. It's too hard to cut the glaze itself.
Kinda like being case hardened.
Prep discs on a die grinder can take off the glaze without removing
much metal - spin the rotor up (car running in gear) and run the prep
disk on the grinder untill the glaze is gone - generally 80 grit does
the job, but 120 could also be used
If you never want to replace your calipers again, flush your brake fluid
every two years. I have a Motive PRoducts pressure bleeder and it's
inexpensive and works great. Whenever you change pads, make sure to
lube up all the caliper sliders and replace any corroded hardware. If
you do this, your calipers should last at least as long as your hoses.
replace "roosters" with "cox" to reply.
With some shops that is a definite truth - they will replace anything
if you let them.
However, a shop makes MORE money machining a set of rotors than they
do replacing that same set of rotors, all things considered.
Assuming nothing goes wrong with the job and they don't end up having
to do the job over on their dime a month or two down the road.
In some parts of North America 125,000 miles on the original calipers
is no stretch at all. Perhaps even on the original rotors - and with
strictly highway miles?? Even a chance on the first set of pads if the
driver is conservative in his driving habits.
In other parts of North America, in urban driving conditions, 30,000
miles on a set of pads and rotors would be almost miraculous, and
50,000 on the calipers would be uncommon, particularly without that
"un-neccesary" bi-annual brake service that all the "crooked,
unscrupuolous" mechanics try to stuff down your throat.
Like the manufacturer of that orange oil filter used to say back in
the sixties and seventies "you can pay me now, or you can pay me
Hmm, a bit off topic, are we?
If the shop routinely replaces the rotors, ask them why. I personally would
avoid a shop that routinely replaces rotors without first checking to see
if the old ones can be machined. The exception might be newer cars that
come with pretty thin rotors, and they often can't be machined. Some rotors
can be machined, but will warp easily afterwards because they are too
thing. With a bit of experience, you know which cars will probalby need new
rotors and you learn not to waste time machining them.
Most older cars come with nice fat rotors that can be machined many times.
There are good reasons to routinely replace rotors on some models, but it
is unnecessary and wastefull with other models.
The limit on even the "old fat" ones was usually 2, or at the very
best, 3 times.
As for machining vs replacing? On today's cars, with rotors often
available for less than $40 and machining costing 30+, why would you
EVER machine the rotor??
It cost me $25 to machine my rotors, $90 to replace them. If it really
was $40 versus $30, phht, ten bucks more gets me new rotors? Replace
In the end I replaced them anyhow because within six months the had
warped. Next time I pay $90 to replace them instead of $25 to machine
TELL THEM IN ADVANCE YOU MUST HAVE ALL WORN OUT PARTS!
I giot into a 6 month hassle with Midas Muffler, they found a bad CV
joint boot, and inssted the joint was bad too. So I said OK give me
It was fine, but before it was thru i had talked to the president of
midas muffler he assured me the local franchissee was honest as the
day was long. talked to a former employee wo left cause he got tired
of ripping off customers, talked to a bunch of victims err customers
in their waiting room and warned them they are going to pick your
less than a month later a inverstigative report came out, midas lost
their state inspection license, many stores closed, would of loved to
see the people i warned say that guy was right when he nearly got
thrown out of the store warning us.
a small local mechanic is often a better choice.
but in this case i support replacing the rotors.
if they dont and you leave and have a accident they run the risk of
Another way to look at it. the absolute worst thing that can happen is that
you pay a bit more money. Your brakes will work like new, guaranteed. At
least in this case, if you are getting ripped off, you are getting new
brake parts in return so the money isn't being wasted.
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