Power stop brake squeal

[BULL]

Some brake systems have more mass and thus better attenuate brake noise & tuned out of our hearing range. When a pad rubs on a rotor, there is always a Resonance created; hopefully it is always tune out of our hearing range with mass and correct installation. It has nothing to do with break-in procedures. I also don't recommend heating the new brakes up to bed or break them in. Remember, when you heat up the brakes, that heat goes into the pads AND the rotor. I just take it easy for a couple hundred miles to burnish them in. Then, if I need them they are ready...

Best!

Another time we can debate a few of these points.

 

[Slowpoke387]

Some brake systems have more mass and thus better attenuate brake noise & tuned out of our hearing range. When a pad rubs on a rotor, there is always a Resonance created; hopefully it is always tune out of our hearing range with mass and correct installation. It has nothing to do with break-in procedures. I also don't recommend heating the new brakes up to bed or break them in. Remember, when you heat up the brakes, that heat goes into the pads AND the rotor. I just take it easy for a couple hundred miles to burnish them in. Then, if I need them they are ready...

Best!

Bed-in directions if memory serves specifies long stops followed by cooling period. I’m sure it’s to mate the surfaces but the by product will be heat. Heat is certainly not the goal but long stops will create heat so essentially youre heating them up before letting them cool.

 

[Finface]

I installed new Hawk DTC-60 pads on all four corners prior to last weekend's HPDE two day event. I did not experience brake squeal with the stock Bembro's, or the Z-26 pads I had in there for a couple of months. After a session on the track I started getting loud brake squeal right where Bickie mentioned it - from 15 mph down to a stop. Every time. This when the brake pads were very hot, so the idea squeal only happens when cold isn't true in my case. I think it is coming from the rear right wheel, but not sure yet. It's a bit unnerving because it sure sounds like metal on metal (it isn't, I pulled the wheels yesterday and all is well - lots of pad left). I also noticed some mild chatter when hard braking from 125 mph down to 75 mph - hoping this could be the "balled up" paint. The rotors look fine - no detectable warping. The stock rotors are darkened compared to before the weekend with the Hawk pads.

I lubricated the back sides of the brake pads before installing them. Doing this is recommended by people here and in the installation instructions. So is the squeal from the pad edges being painted and paint balling up on the brake pad surface, or from the caliper pistons pushing on the metal backing, or can both cause squealing?

Did I break them in correctly, and if not is that really the reason? Or as Moetrack says it is just going to happen? The Hawk instructions said to do the series of moderate speed braking down to slow speed (not stopping), followed by a series of stops "from track speeds". Well, that can't happen legally and I'm not going to have my license suspended for 90 days if I got tagged for going 26 mph over any posted speed limit (here in Kentucky it is automatic). So I blew that part of the break-in procedure off.

These Hawk pads have as much, if not more, brake dust than the Bembro's, but they don't cost as much. And they are great stoppers.

I welcome any ideas and thoughts. Thanks.

 

[Slowpoke387]

I installed new Hawk DTC-60 pads on all four corners prior to last weekend's HPDE two day event. I did not experience brake squeal with the stock Bembro's, or the Z-26 pads I had in there for a couple of months. After a session on the track I started getting loud brake squeal right where Bickie mentioned it - from 15 mph down to a stop. Every time. This when the brake pads were very hot, so the idea squeal only happens when cold isn't true in my case. I think it is coming from the rear right wheel, but not sure yet. It's a bit unnerving because it sure sounds like metal on metal (it isn't, I pulled the wheels yesterday and all is well - lots of pad left). I also noticed some mild chatter when hard braking from 125 mph down to 75 mph - hoping this could be the "balled up" paint. The rotors look fine - no detectable warping. The stock rotors are darkened compared to before the weekend with the Hawk pads.

I lubricated the back sides of the brake pads before installing them. Doing this is recommended by people here and in the installation instructions. So is the squeal from the pad edges being painted and paint balling up on the brake pad surface, or from the caliper pistons pushing on the metal backing, or can both cause squealing?

Did I break them in correctly, and if not is that really the reason? Or as Moetrack says it is just going to happen? The Hawk instructions said to do the series of moderate speed braking down to slow speed (not stopping), followed by a series of stops "from track speeds". Well, that can't happen legally and I'm not going to have my license suspended for 90 days if I got tagged for going 26 mph over any posted speed limit (here in Kentucky it is automatic). So I blew that part of the break-in procedure off.

These Hawk pads have as much, if not more, brake dust than the Bembro's, but they don't cost as much. And they are great stoppers.

I welcome any ideas and thoughts. Thanks.

Blickie has posted about five thousand times telling people to sand the paint off of the pad sides. Might wanna try it and re-install just to see.

 

[Finface]

Blickie has posted about five thousand times telling people to sand the paint off of the pad sides. Might wanna try it and re-install just to see.

Thanks, Slowpoke. I saw his posts and he is quite certain it works every time. I googled the subject just now and eliminating break squeal advice varies from, "always replace all brake hardware", to greasing the backs of the plates, to cleaning the pads, to using special brake adhesive on the back of the plates, to just living with it that's what racing pads do. Didn't see anything about sanding the sides of the brake pads "out there" so far, but it doesn't sound like it would hurt to try it.

 

[Finface]

Here is the Technical Explanation why the paint should be removed from the sides of Friction Pucks:

Brake heat softens the paint and it balls up, rolls onto the brake pad. The sticky, soft paint causes the brake pad to "chatter" on the rotor instead of sliding. We hear that "chatter" as a high frequency brake noise. Most of the time, this noise usually occurs at or near the end of a normal stop at or below 15 MPH. Increasing brake pedal pressure may help attenuate the brake noise which can be a diagnosis confirmation of this issue. To prevent any and all of this brake noise, just whiz the paint off the friction puck and lube with a good, high quality silicone brake lube. You can remove the paint prior to initial pad install or you can perform this procedure to existing pads and then reinstall. If existing pads, also whiz the surface of the pad off as well to removed any imbedded paint (you can't see).

Hi Blickie,

I appreciate you telling us how you've stopped brake squeal. I just removed the offending rear right wheel Hawk brake pads. The contact surfaces of the pads to the rotor did not have any foreign debris or sticky areas I could see. These rear pads were hardly worn at all (actually, undetectably worn to me), even after 4 hours of on-track brake workouts. The paint you refer to on the edges looked intact. It may be there is some kind of hard to see stickier smeared paint (if that is what you're saying by a paint ball getting smooshed between pad and rotor) on the pad material I just can't see it.

I saw that a caliper piston contact point on each brake pad's outside surface - and these faced each other - had worn away the black paint in about a half circle indicating a lot of force had been applied and not entirely symmetrically - don't know what to make of that. I had used a handy spray can white grease lubricant with the Hawks (Hawks didn't come with lube packets) and at the time of installation I had the thought it was not as thick as the white grease that came with the Z26 pads. I'm thinking that didn't hold up well enough and may have contributed to the squeal.

I also saw that both the retaining pins were not fully driven through their holes - and that is my bad because I had only tapped the inside ends of those pins flush with the caliper. They hadn't backed out, but properly seated the points come outside of the caliper about 1/8" and aren't flush. It is possible this introduced some asymmetric forces from the pistons to the brake pads, accounting for the squeal, the semi-circle wearing on the back of the pads, and that little shimmy (slight chatter) I felt romping on the binders at the track.

I cleaned everything, found some thick lithium grease for the back of the pads, and fully tapped in the retaining pins (on both sides of the car). If it still squeals when next I drive the car, or at NCM at the end of May, I'll give sanding off the paint a try. Was that the Binford 5,000 Thermonuclear Brake Pad Edge Paint Remover, or the Binford 8,000 Superthermonuclear model? I know one doubles as a fabulous can opener - just can't remember which.

Finface

 

[Blickie]

Thanks, Slowpoke. I saw his posts and he is quite certain it works every time. I googled the subject just now and eliminating break squeal advice varies from, "always replace all brake hardware", to greasing the backs of the plates, to cleaning the pads, to using special brake adhesive on the back of the plates, to just living with it that's what racing pads do. Didn't see anything about sanding the sides of the brake pads "out there" so far, but it doesn't sound like it would hurt to try it.

Yes, I am certain... I've done this fix more times than I can count and so had many of my former customers. That's why I made the effort to create a graphic with instructions on how to remove the paint to prevent low-speed brake noise.

All pads are the same....remove the paint. Lubricate ALL steel plate contact points with a good high-temp Silicone Brake Lube, backs (on top of shim) and sides where the steel plate rides in the caliper slots. Also, lubricate on top of the steel plate where the spring steel hardware contacts the center of the plate.

Our Cats don't have a lot of brake hardware that contribute to brake noise.

 

[DGatzby]

@Finface you did what??

“found some thick lithium grease for the back of the pads”

Now you go find out what the melting point of that shit is, and simultaneously remove those wheels, pull those pads and wipe every spec of that shit off your brakes before you kill yourself.

Racing pads squeal, @TraxMoe and I and a bunch here know that is absolutely expected! Matter of fact when I move my car very slow, I am proud to say I can get that pedal just right and play music with my DTC-70’s! I have been driving the Hellcat on the street with my Hawk pads for a couple of weeks now. I just did not want to change them out before trailering it again Friday. Hell yes, they squeal sometimes, and I am using my “track” wheels because it is so easy to clean the mess (dust) off. That is life and it is expected.

One other thing. If anyone believes their Track Mode Hellcat downshifts going into turns is interfering or if you can feel that over your brakes, you are NOT pressing that pedal down hard enough! It is good to have the rears use the engine to help slow, because up front those pads are working their ass off nearly alone to slow you down. @Finface that is why you found little or no wear on the rears. They don’t work much until you hammer those brakes like @TrackDay. He is so aggressive with that left pedal @BULL uses his data to test new brakes!

On those Z26’s. When I have mine on they squeal coming out of my garage nearly every time. I use brake grease as is shown above, it don’t matter, it is just the way it is. Turn up your stereo and enjoy.

 

[Finface]

@Finface you did what??

“found some thick lithium grease for the back of the pads”

Now you go find out what the melting point of that shit is, and simultaneously remove those wheels, pull those pads and wipe every spec of that shit off your brakes before you kill yourself.

Racing pads squeal, @TraxMoe and I and a bunch here know that is absolutely expected! Matter of fact when I move my car very slow, I am proud to say I can get that pedal just right and play music with my DTC-70’s! I have been driving the Hellcat on the street with my Hawk pads for a couple of weeks now. I just did not want to change them out before trailering it again Friday. Hell yes, they squeal sometimes, and I am using my “track” wheels because it is so easy to clean the mess (dust) off. That is life and it is expected.

One other thing. If anyone believes their Track Mode Hellcat downshifts going into turns is interfering or if you can feel that over your brakes, you are NOT pressing that pedal down hard enough! It is good to have the rears use the engine to help slow, because up front those pads are working their ass off nearly alone to slow you down. @Finface that is why you found little or no wear on the rears. They don’t work much until you hammer those brakes like @TrackDay. He is so aggressive with that left pedal @BULL uses his data to test new brakes!

On those Z26’s. When I have mine on they squeal coming out of my garage nearly every time. I use brake grease as is shown above, it don’t matter, it is just the way it is. Turn up your stereo and enjoy.

DGatzby,

The use of lithium grease - a mistake someone else already set me straight about. It looked exactly like the stuff that was included in the Z26 pads. I am wiping it all off and will use a silicone lubricant.

The rear brake pads were making contact, in case anyone was thinking I said they didn't. As far as the Track Mode for transmission goes I accept your verdict I wasn't braking hard enough to mask the abrupt downshifting effect on the smoothness of the deceleration. Still learning here...(this, for the thread followers in this threat is part of another discussion).

My Z26's didn't squeal at all - probably that damn lithium grease *grin*.

 

[TrackDay]

I don't lube any of my pads anymore. I used to try and spray some Permatex blue sticky stuff on the back and it was fine for street pads but with this car I don't scrape paint off or lube anything with my race pads. The paint melts off and goes away with no issue. The pads can squeal some when cold but once they heat up it's all gone. That's in about a half lap. 😉
I use the Z26 pads on the street with no squeal at all. No lube.
BTW, consider DTC70 for the front next time. The pedal feel is a little better to me and they have a little higher heat range. You can run the DTC60 on the rear with them.

 

[2017 Redline HC]

I tried buffing the paint off around the edge of all 8 pads last weekend after flushing the brake fluid. I will say it may have reduced the squeal a slight bit, but not really worth the effort of doing it. As I had mentioned it only does it when cold so I’ll learn to live with it. I can put up with the noise to not have all the dust created with the Brembo pads.

 

[Finface]

BTW, consider DTC70 for the front next time. The pedal feel is a little better to me and they have a little higher heat range. You can run the DTC60 on the rear with them.

Thanks for the tip, TrackDay.

 

[Finface]

All,

I always believed as a single seat Navy pilot years ago that only when you could stand up in front of your fellow pilots, including your CO, and tell them how you almost smoked yourself, could you consider yourself truly a mature naval aviator. Everybody had close calls fulfilling the attack pilot mission and in the A-7 "single seat pride of the fleet" the screw-ups that almost bought you the farm...well, no one could ever be the wiser. To share the sequence of events that led to almost hitting the ground, or another jet, in the hope you might save someone else was maturity, even if it might cost you "ace of the base" respect in the eyes of the boss.

So in the spirit of sharing a screw-up...yes, I put white lithium grease on the backs of my new Hawk DTC-60 brake pads before I went to Putnam Park on May 15/16 for four hours of curvy road course fun. Blickie and DGatzy set me straight this is an absolute no-no, due to the effect mineral (petroleum) lubricants have on rubber (destructive). I want to say thank you to them again. This was a potentially very serious error and everybody, not just people who track their cars, needs to know about it.

The sequence of events leading to this error on brake pad lubricants was simple enough. I was completely unaware of the destructive effect on rubber - in the case of our brakes the little rubber boots around the brake pistons that are in direct contact with the brake pad backing plate - that any mineral-based lubricant will have. I read product labels - nothing stated. I find it interesting that there is a truck-load of directly conflicting information about this "out there" on the internet which I've found since being alerted to this property of mineral-based products. Some recommendations to use mineral-based lubricants come from authoritative sounding sources, like this one, that says you can use white lithium grease on rubber;

How to Lubricate Rubber Bushings - And When to Replace Them
"The best lubricants for rubber bushings are silicon based lubricants, white lithium grease or a particular rubber lubricant. You should be able to find these different lubricant types at any motor product store. Polyurethane bushings shouldn't be lubricated with oil or petroleum based lubricants. May 7, 2020.

But not on polyurethane bushings according to this source.

I tried to find warnings about using lithium grease on rubber, and the manufacturers of it don't really seem concerned about it. In fact, from WD-40 (not a lubricant, technically) on down the line of mineral-based lubricants the destructive effect of mineral/petroleum based lubricants on rubber seems to be one of opinion rather than established fact. If there ever was an example of "don't believe everything you read on the internet" this would seem to be one of them.

Anyway, you learn something new every day, or maybe you get conflicting information every day, or maybe these manufacturers know their product isn't good for rubber and just don't want to limit sales by mentioning it. The white lithium grease squeeze tube and a white lithium spray can I have - neither cautions about using it on rubber.

Second step in the chain of events...I have Z26 brake pads and they were the first brake pads I ever installed. They come with a little packet of lubricant. Doesn't say what it is on the packet, and their website doesn't say, and their "how to lubricate" their brake pad video doesn't say. In my ignorance about using lithium grease on the Hawk pads...whatever Powerstop includes as their "high temperature grease" it sure looks like white lithium grease. I'm raising my "I'm a dummy" hand because what something looks like isn't a reliable way to know what anything really is. I called Powerstop this morning and their rep said they include a silicone-based lubricant with all their pads.

DGatzy mentioned the melting point of lithium grease. I found a manufacturer of it who extolls its melting resistance to high temperatures - up to 200 degrees C, but really best recommended for applications up to 120 C - said this product guide. Wow, high temperature? Not when you buy track pads because they resist fading up to 700 C (or higher!). So "high temperature" claims are relative.

I believed the experienced pilots when I was a new guy in the squadron - I appreciated their recounting how they almost bought the farm and I tried to learn from it. Never again any mineral-based product on rubber.

And now for my burning question...what caused this?? These are the backs of the new Hawk DTC-60 front brake pads I removed yesterday from my Challenger Red Eye. I swear I put very little lithium grease on these surfaces - just rubbed some where the pistons would contact the plate. What caused the black paint to do this? Getting these plates out wasn't easy either.



Finface

 

[Paladin06]

The effect is heat. Now to determine the cause. That will require a smarter brake guy than me. Good luck.

 

[BULL]

As above... ^^^^^

Heat...

The whole point of the 50/60/70/80 series pads from Hawk is to handle higher and higher heat ranges...

Not everything will stay "pretty" when it's running at 700c+...

 

[BULL]

Pads from our last Dyno run.

These were instrumented with thermocouples

The peaked at ~975c

500-800c typical

 

[Finface]

Pads from our last Dyno run.

These were instrumented with thermocouples

The peaked at ~975c

500-800c typical

View attachment 45098

DGatzby mentioned you did stuff with brake pads, a la Track Day data. These Hawks are my first set. The Bembros didn't have anything on the back plate blister up and I think I ran them as hard.

If it's normal I'll just clean them up and reinstall them.

Appreciate your response, Bull.

 

[TrackDay]

The Hawk paint just flakes and crinkles for me. I brush it off after I remove them after an event. The pads barely last more than 1 track day of 4 sessions on the front for me partially because of taper. I'm building up a collection of 3/4 gone front pads with the stupid idea I might burn them up as pads for a low speed track around here.

 

[Finface]

The Hawk paint just flakes and crinkles for me. I brush it off after I remove them after an event. The pads barely last more than 1 track day of 4 sessions on the front for me partially because of taper. I'm building up a collection of 3/4 gone front pads with the stupid idea I might burn them up as pads for a low speed track around here.

That is what has happened - crinkled and flaky paint. The pads themselves don't look too worn after my 4 hours of track use last weekend. I must not be braking hard enough, but at least I cooked the paint.

 

[BULL]

Ok, who wants to see a dyno run video???

(For those that haven't already seen it.)