Chronic brake rotor warping - 2001 Outback Legacy

[Jim Stewart]

I wasn't aware of a special coating either, but maybe so. But Ed's
definitely right that the torque values take into account dry surfaces,
and that if you lube them, all bets are off.

Thanks for the info, but I'll keep doing what works
for me. I've seen far too many rusted, binding,
snapped-off studs to change my ways.

As I said earlier, I tighten them by feel, crisscross
and in 3 stages, just like my dad taught me and I've
never had one loosen and come off or rust and
bind up. I've also never had a bit of trouble with
warped rotors.

 

[Bill Putney]

Thanks for the info, but I'll keep doing what works
for me. I've seen far too many rusted, binding,
snapped-off studs to change my ways.

As I said earlier, I tighten them by feel, crisscross
and in 3 stages, just like my dad taught me and I've
never had one loosen and come off or rust and
bind up. I've also never had a bit of trouble with
warped rotors.

I agree about having what I call "calibrated arms" - probably pretty
consistent torque once you develop a feel in early life.

Might I suggest using anti-seize instead of oil? I say that because I
suspect that torque with anti-seize is much closer to dry torque than
torque with oil is. I've never seen any numbers on that, but I believe
it to be true (due to metal particles in the anti-seize). It would
prevent the corrosion at least as well as the oil (i.e., no down sides
that I can think of).

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

[null_pointer]

I also make sure the nuts and studs are clean and

have a light coat of oil on them. I've never re-
torqued them and I've never had them loosen up.

If you've worked around equipment most of your life,
you develop a pretty good biological torque wrench.

I know what you're talking about: When my elbows make a cracking
sound, it's tight enough.....

 

[Tony Hwang]

Can you cite a reference? Sound like a legend to me.

Hi,
Go to a your neighborhood tire shop and ask. It's not a legend.
Only time you need oil is when trying to free up the rust frozen lugs.
Tony

 

[Tony Hwang]

I know what you're talking about: When my elbows make a cracking
sound, it's tight enough.....

Hi,
And when you get older, your forearm will fall off, LOL.
Tony

 

[Al]

Hi,
And when you get older, your forearm will fall off, LOL.
Tony

FYI -- Porsche is now using ceramic rotors on some of their very
expensive models. Do those warp or just explode?

Al

 

[Tony Hwang]

FYI -- Porsche is now using ceramic rotors on some of their very
expensive models. Do those warp or just explode?

Al

Hi,
It is possible to make a ceramic engine block, so I guess it is strong.
Tony

 

[Father Guido]

Read it again and pay attention to the third paragraph! Looks like he
made his point there about wheel nut torquing.

I was referring to the link to the expert on warped rotors -- he never
mentioned torquing wheels more than once in the entire article. By far
he was much more concerned with peoples braking habits, than mis-torqued
wheels.


Father Guido
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
I plan on living forever... so far, so good

 

[Felix Crashalot]

It may not be a matter of rotor warping. Floating disks may shake
because of rust at the surface where the rotor contacts the hub. They
may also shake because the bearing is not properly seated in the hub.
You laugh? Both of my Legacys show the symptom, on both front wheels.
My in-law's laughable Plymouth Acclaim had its rotors perfectly
straight.

The shop manuals say that the runoff should not exceed 7 mils. This
is the thickness of a sheet of paper. Take the wheel off, put the
bolts back on the rotor, run the engine and get the wheel rolling,
then look at the caliper. If you see it moving laterally on its pins,
there's the problem. There's much more than seven mils of runoff.
When the caliper puts the pressure, the movement is transmitted to the
whole suspension. I've seen this with new and reshaved rotors. It
may be rust, it may be the hub, it may be the bearing.

Reinstalling the rotor one or two bolt holes further may diminish the
movement.

 

[TM]

Finally Felix came with a true approach:

Measure the disc runout. You may find that they are within specs. If
only one disc warps, there might be a problem with the caliper.

Did anyone in the thread mention the possibility of erroneous front
toe-in? I found this on the Bosch Automotive Technology manual and it
solved the vibration when braking, vibration that occurred when braking
at high speed only.

 

[Mike B.]

I had that problem when the brakes were hot from stopping.

I replaced the pads with semi-metalic... problem gone

 

[Mike B.]

I read somewhere that some auto shop did a big investigation of "warped rotors"
and they came up with the pad going bad.
I had a Chrysler 300M that had brake vibration problems every 20K.
I cut them, replaced pads, replaced pads with $80 ceramic pads and new rotors.
Still sold the car at 70K with "braking vibration"
the replacement pads are on for 800 miles and no more "breaking vibration"

I had that problem when the brakes were hot from stopping.

I replaced the pads with semi-metalic... problem gone

 

[L. Kreh]

I'm interested in feedback, but isn't it fairly typical with any brand
of car that disks need shaving at 30K and 60K, with disk replacement
at about 90K? At least that's always been my experience, and not only
with Subarus.

Regards,
LK
'99 OBW

 

[Dominic Richens]

I'm interested in feedback, but isn't it fairly typical with any brand
of car that disks need shaving at 30K and 60K, with disk replacement
at about 90K? At least that's always been my experience, and not only
with Subarus.

It must depend on how you drive. My Soobie, with over 160,000km has never
had more than the pads changed.