Buildup on brake rotors (1 Viewer)

[ozarkmud]

I'm working on our '93 FZJ-80 with discs all around. I did the calipers and pads a while back. The rotors, from the outside, looked fine and I ignored them.

The typical "warped rotor" feeling came, I think getting progressively worse after the job. Pulsating while on the brakes.

I had heard about rotor buildup before, that the rotors aren't normally warped. but since I didn't see anything obvious, I just let it be.

After buying some rotors and now finally tearing into it, I finally got started on the front right corner. I really ought to get a dial caliper as the spec is pretty tight -- 0.15mm. But nothing obvious visually.

After removing the caliper, I noticed something very odd. Swept area is significantly different from outside to inside. The inside of the rotor has a ton of buildup in one spot. I was able to hammer lightly on it and break it up. Underneath was a layer of rust, which I was able to scratch off fairly easily.

Maybe my rotors are fine and this is just the buildup that people talk about? Is this a common spot for it? How does it usually manifest? Can you clean it off well without removing the calipers? Not too happy about having to take apart the hubs to get the calipers off as it just adds an extra step and some more bits to get wrong. Although I'm thinking it may be the only way.

My inner hub seal looks fine, although was replaced with an aftermarket part. But maybe at one point it was leaking? My theory about the buildup, and I don't know what I'm talking about with this, is that the inner seal may have been leaking a long time ago and some molybdenum rich grease coated around that spot and created this strange deposit. Please let me know if that seems sensible or impossible.

I haven't gotten to the other corners yet.

Thank you!

 

[BILT4ME]

I'm working on our '93 FZJ-80 with discs all around. I did the calipers and pads a while back. The rotors, from the outside, looked fine and I ignored them.

The typical "warped rotor" feeling came, I think getting progressively worse after the job. Pulsating while on the brakes.

I had heard about rotor buildup before, that the rotors aren't normally warped. but since I didn't see anything obvious, I just let it be.

After buying some rotors and now finally tearing into it, I finally got started on the front right corner. I really ought to get a dial caliper as the spec is pretty tight -- 0.15mm. But nothing obvious visually.

After removing the caliper, I noticed something very odd. Swept area is significantly different from outside to inside. The inside of the rotor has a ton of buildup in one spot. I was able to hammer lightly on it and break it up. Underneath was a layer of rust, which I was able to scratch off fairly easily.

Maybe my rotors are fine and this is just the buildup that people talk about? Is this a common spot for it? How does it usually manifest? Can you clean it off well without removing the calipers? Not too happy about having to take apart the hubs to get the calipers off as it just adds an extra step and some more bits to get wrong. Although I'm thinking it may be the only way.

My inner hub seal looks fine, although was replaced with an aftermarket part. But maybe at one point it was leaking? My theory about the buildup, and I don't know what I'm talking about with this, is that the inner seal may have been leaking a long time ago and some molybdenum rich grease coated around that spot and created this strange deposit. Please let me know if that seems sensible or impossible.

I haven't gotten to the other corners yet.

View attachment 3480735

View attachment 3480731

View attachment 3480732

View attachment 3480733

View attachment 3480734

View attachment 3480730

Thank you!

Part of that is from not driving it enough.

Second, have you bedded your brakes properly? This helps prevent that issue.

 

[ozarkmud]

I did a couple of the bedding practices, but definitely not perfectly.

What is the cause from not driving it enough? We do lots of highway driving and only a little bit in the city, so they don't get worked all that much.

 

[Chris Wilcox]

My rotors look like that all the time but we see salt on the roads in the winter and I just assumed it was from that. I go "Cuban Style" on them like you did, hammer off the rust, run a file over it and reinstall. Easier in the back than the front so the fronts just get replaced with new. I've been driving my same 80 in this climate since 2007. If there is some other cause that can prevent this I'm interested to hear it.

 

[BILT4ME]

I did a couple of the bedding practices, but definitely not perfectly.

What is the cause from not driving it enough? We do lots of highway driving and only a little bit in the city, so they don't get worked all that much.

Coming to a stop with your foot on the brakes after a long drive can "melt" the pads into the rotors and cause a buildup like that.
If you're really easy on the brakes or ride them a lot that gets the pads and rotors hot, then when you come to a stoplight and hold your foot on the brakes can do the same.

Bedding the brakes spikes the temps up and down. The heat from it helps cure the pads and make them "harder" and they will last longer and be less likely to do this buildup.
When I do my bedding, my brakes are smoking by the time I'm done, but I do NOT hold my foot on the pedal. I keep rolling until they cool.

Also, if the truck sits for week(s) at a time, the area where the pads are can hold moisture behind them and will cause rusty areas. My wife's van does this because she may not go anywhere for a week or more at a time, then she doesn't drive aggressively enough to get the brakes warmed up and polish off the rust.

We took off on a family trip about 6 months ago and came into a corner on the interstate running about 80 MPH. It started with a helluva vibration, like we suddenly lost a wheel weight or had a tire that lost a band. When I touched the brakes it magnified, then calmed down. So, with that, I waited until traffic was clear, and stood on the brakes to "clean" them. After that, everything was smooth as glass. It was a rusty area that caused the issue. When we got to our destination 5 hours away, the rear rotors were nice and evenly shiny.

Proper bedding:
Speed up to 45 MPH as fast as you can and stand on the brakes as hard as you can WITHOUT locking up the wheels and only slow down to 5 MPH, but do NOT stop.
Do this (3) times in rapid succession.

Drive around for 5 minutes without touching the brakes.

Rapidly speed up to 45 MPH, then slowly ride the brakes from 45 down to 5 MPH but do NOT stop. This should take about 15-20 seconds of slowing down.
Accelerate hard back up to 45 MPH, and repeat the process (3) times.

Drive around for about 20 minutes to let the brakes system completely cool without stopping and without your foot on the brake pedal at any must-stop situation (stop sign)

After this, you can go back to driving normally or park it for the night.

After the first couple rounds, there will be a bluish smoke that smells like burning electrical (or just burning brakes). That means you're doing it right. I know it seems counter-productive, but it truly makes them last longer. it also makes a difference if you have the cheap pads or the quality pads. The cheap pads will smoke more and will eject a lot more brake dust.

 

[Kernal]

IMO you'll spend more time cleaning those rotors up than they're worth, new OEM rotors are inexpensive and high quality.

Next is to get a set of early 100 series front brake pads (1998-2002 IIRC) (for the front calipers). They're slightly larger than the stock 80 Series front pads and cover the front rotor out to the edge. OEM pads are also great quality or IMO a good second choice would be Akebono pads. (note: you can't use 100 series pads for the rear pads, those stay stock 80 series pads (size)).

Some people had issues fitting the 100 series front pads in an 80 Series, they didn't drop in (I had to lightly tap them in), but the front brakes did not run hot and I'm still running the same set with 90,000 miles on them. FWIW.

Also check that your calipers aren't sticking/stuck. Might be a good time to rebuild or replace the calipers.

For the hub seals, consider Terrain Tamer HD hub seals, cuts down on wear into the spindle from the OEM style hub seal.



FWIW

 

[mudgudgeon]

I agree with @Kernal above, i wouldn't bother cleaning up those.

Also, have similar experience to what @BILT4ME described. Vibration felt through the brake pedal in a work car that mostly saw easy city use.
On the highway on a downhill, without to much traffic about, stand on the brakes hard, wash off speed from around 50mph down to 25-30. Come back up to speed, repeat 4 or 5 times. Stop before your brakes fade fully.

I've done this a few times, and it will help if there's a light build up on rotors causing a vibration. I wouldn't expect it to fix what you pictured though

 

[ozarkmud]

Thank you all for the replies! Will definitely do the bedding process with these rotors once I get it back together. I've heard of the Terrain Tamer seals. I looked into ordering them in the US and think I got a lead on it, but never ordered them.

I finished all but the rear right rotor. Rear right ended up giving me some grief. My nemesis, the rear disc brake, has struck again.

The rear left rotor came off without any struggle, so I was expecting none for rear right. I didn't back off on the parking brake adjuster on either, and it seems that was a mistake for rear right. I was too aggressive getting the rotor off and didn't realize the parking brake was sticking to the rotor (must've been misadjusted?).

Parking brake is all apart and the rotor is off. Rear left rotor wasn't bad looking, but rear right is looking rough and definitely worth replacing.

I'm hoping I didn't bend up any of the parking brake parts and that I can manage to put the contraption back together.

I am seeing some weeping on the inside hub seal, so maybe it is time for those Terrain Tamers after all. Way less than the other side though, and makes me wonder if it was leaking but the leak was stopped and never fully cleaned up.

 

[ZackR]

Just to drive the point home don't come to a stop when bedding in new brakes. Follow @BILT4ME 's procedure above (or something really similar). When I did mine I had a pretty open road to work with and went from 55mph to 20mph but it was the same idea.

 

[alia176]

Additionally, if you're re-using rotors (between pad changes), I suggest resurfacing them yourself using the technique in this video. Also, I tend to cheap out on rotors but spend money on the pads but everyone is different. I use NAPA rotors and EBC Greenstuff pads.

 

[Kernal]

Cruiser Brothers in the US sells the Terrain Tamer HD hub seals.

T/T90311-62001HD Hub Seal, HD Terrain Tamer - CruiserBrothers

Click here to learn about Terrain Tamer Heavy Duty Wheel Hub Seals Heavy duty wheel hub seal, inner 40 60 80 series front, rear full float

cruiserbrothers.com

 

[ozarkmud]

I managed to sort out the parking brake and put it back together. Little tedious, but not too bad.

Brakes feel really nice now! But not surprising there's an improvement given how nasty some of the rotors were.

Rear left:

(Note the well oiled parking brake surface.)

Rear right:

Not sure what those two dimples are about.

Rear right also had stuck sliding pins. I must've forgot to grease them, but might've also been from parts being delayed. Moving much better now. Hoping the uneven pad wear sorts itself out.

This explains a lot about brakes and gives me a lot to think about. Thank you all for your help!

Good idea as well about rotor resurfacing. I can see why it's helpful that they surface the rotors when new.

 

[mudgudgeon]

Additionally, if you're re-using rotors (between pad changes), I suggest resurfacing them yourself using the technique in this video.

Hard pass

 

[Malleus]

Yeah, that's not exactly a brake lathe.

 

[Malleus]

FWIW, the brake grease that comes in the rebuild kits in those infuriating little square plastic packages is available in a manageable size:

Also good for sticking the anti-squeal pads to the backs of the brake pads.

 

[alia176]

Yeah, that's not exactly a brake lathe.

ya don't need a lathe unless the rotors are technically warped. For most of us, we're only dealing with pad material buildup for whatever reason and this takes care of it. Most of us aren't doing track days heating the crap out of our pads and rotors Easy enough to do at home with some elbow grease.

 

[LXDOC]

Ummmmm. Your Right rear appears to have a pad inserted with backing plate against rotor surface and fused to the rotor surface Itself. That one is done.