Sally
Labour costs are relative to whether the shop uses flat rates or actual
time for a job. Three hours does seem excessive for just doing the rear
brake pads, by a competent mechanic. However, removing the rear rotors
is complicated a little by the parking brake mechanism which is inside
the drum on the rear rotors. It usually needs tightened to remove a rear
rotor and reset after reinstalling the rotor. That is a tedious little
job but not overly time consuming.
If the rotors were actually "grinded and turned" then that cost was not
unreasonable but I doubt that they were turned and ground (the order is
important if it is done) and just simply turned.
Unfortunately, you have opened the door to one of my favorite rants.
This is not a Subaru rant. I just installed all calipers rotors and
pads on my `97 Legacy GT and have no complaints other than the price.
Shops use turning for two reasons:
1. When new brake pads are installed on old rotors, the shop will
normally want to turn them to prevent a pulse or shudder when applying
the brakes, at least on the brakes they replaced. Besides this being
somewhat mechanically sound, this removes a potential source of customer
complaint.
I say "somewhat mechanically sound" because since the rotor has warped,
it has been subjected to heat from braking conditions that are likely to
re-occur, if the driving conditions remain the same. Since there is now
less rotor material to absorb the heat, the rotor will warp more easily
than before. This is not necessarily an immediate process but is
relative to time: more aggressive stopping = less time.
This is one reason why I always replace warped rotors.
2. Old rotors can become "glazed", a smoothing of the rotor surface
that makes it difficult for the rotor to quickly remove enough of the
surface of new brake pads to develop full and even contact between the
two surfaces. Without proper contact, braking efficiency can be
significantly reduced.
A secondary effect of improper contact can be chattering or squealing
when braking, something else shops want to avoid because that will
result in customer complaint.
If a rotor is glazed BUT NOT WARPED then rough grinding is a better
mechanical option because much less material is removed from the rotor
and the surface will be rough enough, similar to that of a new rotor, to
properly "wear in" the new pads. I doubt that you will find a standard
shop that grinds rotors and if you do then the price will be more than
that for turning, possibly significantly more.
Now the process of turning a rotor has a problem in and of itself. If
too much heat is generated in the turning process then that can warp the
rotor. There are ways that this can happen, eg.: too much material
removed at once, dull cutting tool, lack of cutting fluid, etc. A
reputable shop should not have this problem but it would be easy for
this to happen intentionally.
Also, a turned rotor has an extremely rough surface. This will
certainly help to properly seat your new pads faster but it also
decreases the life of the pads! The rougher the surface, the more wear,
the less pad life.
This is the second reason why I always replace warped rotors and brings
us to my conspiracy theory about the turning of brake rotors.
Conspiracy Theory
Every time the pads are changed, the rotors are turned. The life of the
pads is shortened, as is that of the rotors. Result: higher turnover of
products. Even on new cars, they know that eventually you will run out
of warranty.
Even if new parts are covered under a warranty, the labour seldom is,
unless you have purchased an extended warranty to cover this.
When you buy new rotors for your unwarrantied vehicle (always use new
pads) then installers will turn the rotors first, unless you insist
otherwise. When you ask that this not be done, they will try to not
guarantee the job, saying not responsible for chatter, squeal, etc. If
the caliper alignment is good, new rotors do not need turned.
Some cars have the "brake caliper alignment to the rotor" so out of
whack that a very rough rotor surface is the only way to get the pads to
seat fast enough to avoid squeal and chatter. This is evidenced by a
very uneven wearing of the break pads. On new cars of this type you
won't need pads until after the warranty runs out since they have made
them extra thick. You won't be able to buy pads exactly like the
originals.
/end Conspiracy Theory
