lousy brake peformance / best practices for DIY brake job

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.

2001 Legacy Outback Wagon, 2.5L H-4 Chicago, Illinois USA
Reply to
Todd H.
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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.

Reply to
johninky

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.

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Reply to
1 Lucky Texan

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

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!)) 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.

Reply to
1 Lucky Texan

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.

2001 Legacy Outback Wagon, 2.5L H-4 Chicago, Illinois USA
Reply to
Todd H.

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.

2001 Legacy Outback Wagon, 2.5L H-4 Chicago, Illinois USA
Reply to
Todd H.

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

Reply to
XR650L_Dave

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

Reply to
XR650L_Dave

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.

Reply to
johninky

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.

Reply to
clare

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.

Reply to
clare

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.
Reply to
clare

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

Reply to
StephenH

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.

Reply to
Chico

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

Reply to
XR650L_Dave

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