lousy brake peformance / best practices for DIY brake job

Discussion in 'General Motoring' started by Todd H., Sep 10, 2009.

  1. Todd H.

    Todd H. Guest

    I'd be grateful for any sage advice on a long standing brake puzzler.

    I can barely recall the last time I was happy with my brakes on this
    frigin vehicle. :) My 140k mile 01 Outback has warped its rotors
    again, and has had lousy braking performance since about a month after
    the latest top-of-line third party pads and new top quality third
    party rotor went on it (done by a non-Sube tech)...oh, probably just
    25k miles ago. The brakes since the most recent set of top of the
    line pads have felt soft to me, and stopping performance seems lousy.
    Pedal travel seems to be a bit more than it should as well, though the
    techs did bleed the brake system, and on a return trip insist that a
    hydraulic issue isn't at play and that those particulra pads are just
    a bit soft in feeling. I'm a family guy with an anemic engine'd
    vehicle, drive with one foot, and decelerate slowly and smoothly, so
    aggressive driving certainly can't be the issue. :) My brake rotors
    don't look shiny on the front for what it's worth--they look more
    black.

    Q1: is this blackness of the rotors indicative of an overtemp
    condition at some point in the past?

    Q2: if so, what could be causing that? Tab of non-OEM brake pad a
    bit too large causing it to hang up? Or could there be an issue with
    booster or master cylinder at play? How do they test for booster or
    master cylinder issues?

    Q3: is it true that if a pad overheats, it chemically changes and will
    never stop the same ever again? Most recently a tech who looked at
    the issue mentioned this and shook off any of my questions about
    possible master cylinder or booster problems.

    Q4: on pad replacement, aside from going OEM with pad and rotor (which
    I'm going to do this time), I'd like to know what are the best
    practices to doing the brake job.

    I plan to do this one myself again--since the pros I left it to the
    last 2 times it'd been in didn't seem to do any better, and want to
    leverage the savings of subarugenuineparts.com--and am interested in
    what goodies are best to clean up the calipers, caliper slides, and
    that and what sort of lubricant should be used on the slides (does
    Subaru sell a kit for such?).

    Also, looking in the OEM catalog--anyone know what the front brake
    backing plate is that sells for about $15 each? Is that the backing
    plate for the pads?

    Thanks for any insight or time in hanging with an overlong question.
    :)
     
    Todd H., Sep 10, 2009
    #1
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  2. Todd H.

    johninky Guest

    Have been driving now for 40+ years and have never experienced warped
    rotors. My understanding is just about the only thing that will warp
    a rotor is overtorqued lug nuts. If the rotors are "black" that
    suggests to me the calipers are not working. Don't believe
    overheating the brake pads changes them in any way. I once many years
    ago had a 66 Corvette with the 427/425 and turned all 4 rotors red
    after a panic stop from 100 m/hr. Never noticed any difference in the
    braking performance after the rotors cooled. The brake pedal will be
    super hard if the booster fails. Bad MC and the pedal goes to the
    floor when pushed. I installed front rotors and calipers from a 2002
    WRX on my 95 wagon about 4 years ago and haven't had a bit of problems
    with them. Thinking your newer wagon uses the same parts as the WRX.
    When you install the new rotors, make sure the surface behind the
    rotor where the rotor presses up against the hub is clean. Not much
    help but like I said, never had this problem.

    Did take your advice when I had all the rear wheel bearing problems
    and went with a used knuckle. So far so good.
     
    johninky, Sep 11, 2009
    #2
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  3. I only know what I've read and a little experience. I DO believe that
    less-than-careful torqueing of wheel lugnuts can cause problems with
    drums and rotors but that MOST of the so-called brake warpage is
    actually 'cementite' or pad deposits or other localized changes in the
    rotor material from overheated pads and rotors. Just about the worst
    thing that you can do is have an emergency stop followed by a lengthy
    time sitting with the pads clamped in one spot. The heat under the pad
    will not dissipate and can alter the 'temper' of the rotor in one spot
    and/or deposit pad material in that one area. And supposedly having
    rotors turned will not remove the altered metal sufficiently in many
    cases. Possibly driving through a deep puddle after heating up the
    rotors could cause a problem ? - dunno.

    I've also read that mix/matching rotors and pads can lead to
    suboptimal brake performance. That is, Akebono pads may not work as
    well on Stoptech rotors as Stoptech pads would. I can tell you I am
    experiencing this at present with some Wagner pads I put on the wife's
    03 Outback. They are noticeably worse than the OEMs were. I will go
    back to OEM after these become worn-out, (or maybe a little before)

    Brakes stop your wheels, TIRES stop your car. Don't run low
    performance tires and expect high performance from high performance
    brakes.

    Stoptech has a 'white paper'/w'ever on warpage as well as other good
    info.

    http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml
     
    1 Lucky Texan, Sep 11, 2009
    #3
  4. Another thought - sometimes with age the rubber brakelines can balloon
    with pressure and will feel a little spongy. New OEM or perhaps
    stainless braided brakelines might restore some more 'solid'-feeling
    performance.

    as for parts pricing - try an on-line source like
    subarugenuineparts.com.(Jamie is the contact there - she's helped me a
    lot. and she rallies www.subiegal.com !)) Sometimes you can even get
    the local dealer to match prices. I think the backing plate is spot
    welded on? maybe that depends on the model.
     
    1 Lucky Texan, Sep 11, 2009
    #4
  5. Todd H.

    Todd H. Guest

    I've exepreinced that before. It's possible, but I do manually
    retorque after wheel servicing and have a torque wrench. I'm also
    annoying in making a point of asking for manual or at least torque
    stick torquing to avert that, yet here I am. . :-\
    Hanging up ?

    I'm wondering if maybe teh aftermarket pad maybe has tabs that are
    just a tad too large preventing them from sliding easily. I recall
    someone saying here that they've ground those down a bit to address a
    difference between aftermarket and OEM. I guess I'll find out when my
    oem pads get here and I can measure them against what I'm taking out.
    Hard how? As in you have to put a lot of pressure on the pedal to get
    braking? If so, that may be an issue I have. If you mean hard as in
    it doesn't move at all and feels like you're pushing on a solid piece
    of metal, then it's definitely not that. I have to push pretty hard
    and the pedal will nearly go the the floor, but does stop shy.
    Squishy is the best way I can describe it.
    Hrmm. I don't have that either, so I don't have what I envision MC
    blow by would feel like.
    What pads/rotors did you use?
    Woo hoo!

    Thanks for the response. I'm feeling a bit more relieved that at
    least I probably don't have mc or booster problems.

    Carl's theory about bulging brake lines has me intrigued though--that
    makes sense to me. We'll see how it feels when my new OEM rotors and
    pads get here.

    Thanks also for the reminder to clean up the hub where the rotor
    interfaces.
     
    Todd H., Sep 11, 2009
    #5
  6. Todd H.

    Todd H. Guest

    I've gathered a few of those over the years here too. These pads
    though I never got told exactly what they were were expensive and
    matched to the rotors, and were requested to be high-end aftermarket.
    Who knows what the guy selected though--I've had soem issues where he
    wasn't entirely straight with me and I've since moved on, so who
    knows!
    I've got some non-cheap Michelin's on em so that shouldn't be too
    awful, but it's really a matter of pedal feel vs every rental car and
    the 1 year old van I have that lets me know something is definitely
    amiss in how much deceleration I get for how much I have to push on
    the pedal. The pads and rotors just don't seem to be all that grippy
    to each other.
    Cool. I 'll give it a look.

    Thanks also for the subarugenuineparts/Jamie lead years ago. I'd
    actually just traded emails with her and ordered pads/rotors from her
    before posting that yesterday!
     
    Todd H., Sep 11, 2009
    #6
  7. Todd H.

    XR650L_Dave Guest

    I had what felt like a warped rotor on my '03 OBW, but it was actually
    pad material that had transferred to the rotor and made an extra-high-
    friction high-spot.

    I have had to file brake pad backing plates to get them to fit on my
    car.

    I'd advise using the good pads that come with the stainless shims, get
    at least mid-grade rotors (the $35 ones at napa seem to be decent),
    and clean the rust off the caliper/pad holders where the shims/pads go
    on.

    Make sure the caliper pistons slide back smoothly, make sure the
    sliders the caliper bolts to slide easily, make sure the pads go into
    place and can move back and forth without a lot of effort, and use the
    high-temp silicone grease both on and under the stainless shims (if
    the material under the shims rusts it could force the shim into the
    pad, causing it to bind).

    Make sure the hub where the rotor goes is clean and smooth, and put
    some anti-seize on it.Scrape it with a screwdriver and a wire brush,
    whetever it takes.

    Make sure the wheel where it goes on the hub is clean and smooth, my
    AL rims had a nasty, hard glassy buildup where the AL and the rust
    reacted, I had to break it off with a screwdriver (it was like welding
    slag).


    Dave
     
    XR650L_Dave, Sep 11, 2009
    #7
  8. Todd H.

    XR650L_Dave Guest

    Oh, and maybe you're not using the brakes hard enough?

    After the rotors get wet (dew, rain) you have to use them hard enough
    to clean off the rust, and you have to use them hard enough early on
    to bed the pads in, and wear the rotor in. It is possible you glazed
    the pads by being too gentle on 'em, especially early on.

    I don't really reccommend sanding the pads to break glazing, but you
    can wet sand them. If the rotors are really pretty new (and really the
    good ones) it may be worthwhile to turn them. Also, turning them will
    leave a rougher finish, which is better if you are having glazing
    problems from being a very gentle braker.



    Dave
     
    XR650L_Dave, Sep 11, 2009
    #8
  9. Todd H.

    johninky Guest

    When the booster fails, best way I can describe the sensation is it
    takes both feet to stop the car. Your booster is probably not bad.
    Would think the engine would also idle badly with the huge vacuum
    leak.

    The WRX rotors/pads/calipers all came from a low-mileage wreck. I
    didn't do anything to any of the parts other than install them.

    You stated something about top of the line pads. Do know lots of high-
    performance pads don't stop worth crap until the pad temperature is
    increased to some value.

    The braking system has a proportioning block somewhere. Never heard
    of one going badbut something else to think about.
     
    johninky, Sep 11, 2009
    #9
  10. Todd H.

    clare Guest


    Well you are one lucky son-of-a-gun, because warped rotors ARE a
    reality, and not just (or even) from overtorqued lug nuts.

    And as for overheated brake pads, a lot of the crap being sold out
    there today (and for the last 20 years) WILL deteriorate from repeated
    overheating. The pad material gets hard and brittle, and in extreme
    cases comes right off the pad. In less extreme cases the brakes just
    lose their effectiveness, requiring more pressure to stop, or they get
    noisy.

    In several decades working as a mechanic, from the inception of disc
    brakes on american cars, I've seen a lot of both.
     
    clare, Sep 11, 2009
    #10
  11. Todd H.

    clare Guest

    It's not pad material transfer - it is corrosion - intergranular
    corrosion that causes the rotor to "swell". If you go to machine it,
    you will find a "crater" under the bulge.
    Generally the pad mountings SWELL with rust - cleaning up the steel
    makes tha new pads fit just fine.
     
    clare, Sep 11, 2009
    #11
  12. Todd H.

    clare Guest

    I read some brake break-in instructions a week or two ago - said to
    stop from 60mph to almost a stop 3 times in a row, then let cool by
    driving for 5 - 10 minutes and repeat - do it 3 times and the pads are
    mated to the rotors and the brakes are broken in. By the third stop of
    each cycle you should be feeling the brakes fade - but eack set of 3
    they will get better and the pedal will get firmer.

    If using the ATE premium rotors (with the special coating and grooves)
    2 or 3 good hard stops will seat the pads adequately. I figured they
    were a "gimmick", but they were something like 30% off when I needed
    to do the brakes on my wife's car so I tried them. They've been
    excellent so far (almost 2 years now) and I just put a set on my car.
    Kevlar pads on the wife's and hybrid ceramics on mine.
     
    clare, Sep 11, 2009
    #12
  13. Todd H.

    StephenH Guest

    I will speak from the other side of the brake pads.
    I have seen countless warped rotors, On customers vehicles and my own.
    It does happen. Ford Taurus were famous until you put aftermarket
    rotors on it.
    Warping rotors by excessive torque is a possibility, especially in the
    older style rotors where the hubs were part of the assembly. I think
    the amount of warpage from torque issues is smaller due to the fact
    that the rotors are now trapped between the hub and the wheel, the
    force doesn't pull on the rotor as much.
    Why do they warp? I don't know. Poorer metal content. too hard of
    pads, riding brakes.
    just my opinion
     
    StephenH, Sep 12, 2009
    #13
  14. Todd H.

    Chico Guest

    Not too long ago, I decided that I was well overdue for new brake
    fluid on m 03 OBS. I figured I was close to 100k kms on the same
    fluid. The brakes were feeling a little squishy, so I got the brake
    fluid replaced.

    Afterwards, the brakes felt worse. I was suspicious that they were
    not properly bled, as unlikely as that seemed. I even scheduled a
    subsequent check-up with the dealer, but just before the appointment
    it started feeling better so I cancelled.

    Now they feel reasonable, although still not nearly as good as a
    rental car I recently had.

    My suspicion is that the seals in the master cylinder were at the same
    water saturation point as the old fluid, but the new fluid was nice
    and dry. Water seeps from the seals to the fluid, and the seals
    shrink, no longer providing a good seal. Brakes feel squishy.
    Eventually, a new equilibrium is reached, and things felt better.

    That's the best I can come up with!

    Good luck. I would have done the brakes myself if I wasn't afraid of
    brake fluid! I did the pad / shoes / drums / rotors last year.
     
    Chico, Sep 13, 2009
    #14
  15. Todd H.

    XR650L_Dave Guest

    Well, caused by the pad somehow- the area was in the shape of the pad.

    I had already cleaned the bracket under the shims, the shear line on
    the pad backer was smeared because they were stamped with a poorly
    made or worn die.


    Dave
     
    XR650L_Dave, Sep 14, 2009
    #15
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