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rslifkin
rslifkin UltraDork
8/5/18 8:55 a.m.

In reply to dj06482 :

Those pictures look a lot like what I was seeing with the Prius rotors, but yours aren't quite as bad.  How old (in years) were the rotors when that happened?

spitfirebill
spitfirebill MegaDork
8/5/18 10:35 a.m.
pres589 said:

There's Raybestos rotors listed on Rock Auto, I'd probably give them a shot.  Grain of salt, no experience with them on something not from America.

I’ve bought their advanced performance rotors and am pleased with them.    

Knurled.
Knurled. GRM+ Memberand MegaDork
8/5/18 1:20 p.m.
rslifkin said:

Out of the Centric, Raybestos and a couple others that I can't remember that I've bought over the last few years, I've yet to have a rotor give me issues before I replaced it either due to rust or wear.  The only real failure I've seen is from the OEM rotors on my girlfriend's Prius.  9 years and 150k miles and they got rusty enough that pieces of the braking surface started to flake off (despite being shiny and in apparently good shape beyond rusty cooling vanes). 

For the most part, cast iron rotors don't warp.  They can have runout, but that'll be there from day 1.  If they "warp" afterwards, it's almost always due to burned in pad deposits (which can cause uneven wear and make them feel warped).  And the pad deposits are driver error in most cases. 

If the brakes are good and warm (such as from stopping from 70 on a downhill highway off-ramp) and you sit with your foot on the brakes firmly once you've stopped (especially if the pads aren't well bedded yet), you can end up burning a little bit of pad material onto the rotor.  Do this a few times and you get an uneven rotor surface and hot spots on the rotor where the surface is a little higher (which causes a metallic change in the rotor in those spots, so the unevenness never goes away and often comes back even if the rotors are turned). 

Rotora can and do warp.  Tempos were infamous for this.  They would develop a pulsation but only when hot.

 

As you say, it ia usually a runout issue, but when the rotor is new, there will be no thickness variation and the caliper/pads will track the rotor.  Over time, though, when NOT braking, the pads will continually be glancing off of the high spots, and this WILL lead to thickness variation (felt as a pulsation in the pedal) and/or uneven pad transfer (felt more in the floor/seat of pants).

 

 

Knurled.
Knurled. GRM+ Memberand MegaDork
8/5/18 1:22 p.m.
dj06482 said:

I actually took pictures and sent them to Centric, but never heard a reply.  These were Centric premiums with Akebono pads.  I bedded them in properly immediately after installation (by me). I sprayed the rotors with Brake Clean prior to installing,  as well.  The other side was perfectly fine.

Caliper slides are stuck, or the piston is stuck, or the pads are stuck in the hangers.

 

This is 95% of the reason for rear brake service that I see.

dj06482
dj06482 GRM+ Memberand SuperDork
8/5/18 4:30 p.m.
rslifkin said:

In reply to dj06482 :

Those pictures look a lot like what I was seeing with the Prius rotors, but yours aren't quite as bad.  How old (in years) were the rotors when that happened?

It happened pretty quickly - say after the first winter (we're in CT).

When I took everything apart I didn't notice any major issues with the piston or caliper bolts, but it wouldn't surprise me if something was hanging up.  In the last few thousand miles, they made some noise when first backing up in the morning, but I never noticed anything from the pedal.

Based on our winters, I'm thinking I should go over and clean/regrease all our brakes during the winter.  Is anyone else doing this?

former520
former520 HalfDork
8/5/18 5:57 p.m.
dj06482 said:

I actually took pictures and sent them to Centric, but never heard a reply.  These were Centric premiums with Akebono pads.  I bedded them in properly immediately after installation (by me). I sprayed the rotors with Brake Clean prior to installing,  as well.  The other side was perfectly fine.

Were you using this rotor as an anchor for a sea going vessel prior to installing?  

Knurled.
Knurled. GRM+ Memberand MegaDork
8/5/18 6:59 p.m.

In reply to dj06482 :

That's about normal after a year or two here unless you really keep up with your maintenance - make sure the pads move freely in the hangers and the slide pins move freely every oil change or so.

 

Rear disks on most vehicles rarely get hot enough to burn off overnight rust completely, and the wear rate is so slow that everything just sort of seizes up and dies of boredom rather than wearing out.

 

I make sure to get in a good firm braking event while the pads and rotors are still cold every morning, since that is when pads are the most "abrasive" (they wear the rotor instead of transferring material to the rotor).  Even then, I think I replaced the rear calipers twice in three years of owning my S40.  Pads were $30 a set and rotors maybe ten bucks each for rears, but that is no good if the calipers are junk.

 

You shoulda seen the brakes on my Quantum.  The FRONTS looked like that too.   Between being manual trans and having not enough power to need the brakes, they never got hot ever...

rslifkin
rslifkin UltraDork
8/5/18 7:05 p.m.

I generally make a point to lube pad and calipers slides any time I have the wheels off a car, so at least twice a year for something that gets driven through the winter. 

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