RL411 Disc Brake Squeal

[jfbrink]

 

Hi, all,

 

I'm running RL411 factory disc brakes on my sedan, and they squeal loudly and frequently on every drive. Not continuously, just about half the times you press the brakes. It's often on medium braking, and sometimes you can "push through" it with heavy braking, but sometimes not. It's bad enough that I don't want to drive the car.

 

What I've done so far:

 

    -Installed new rotors (long ago eBay find) and new pads -- No effect

    -Put that pad glue on the backs of the pads -- Helped for a few drives, maybe.

    -Greased moving contact points -- No effect.

    -Swapped the old black spring clip sheets in for silver ones that came with new pads  (they differ noticeably in length) -- Maybe made squeals less frequent

 

Does anyone have specific experience with these RL411 discs squealing? Is there some specific pad I should be using or pad shim or something?

 

Thanks,

 

Jesse.

[MikeRL411]

The spring metal clips on the black sheet metal insert that covers the open area on the top of the caliper is subject to deformation and might be rubbing on the rim of the disc.

[mklotz70]

Ended up here looking for something else. lol   Did you ever get this figured out?

 

[jfbrink]

MikeRL, 

 

That's an interesting idea. But, I see no sign of rubbing and the problem happens with equal frequency between my ancient black spring plates and my relatively new silvery spring plates. 

 

Mike K., 

 

I have not figured this out, yet. It's very inconsistent and yet persistent, so it's super frustrating to diagnose. It almost never happens at the start of a drive, and sometimes it doesn't happen at all regardless of distance or braking frequency. And, often after happening for a while during a drive, it will just go away again. Other times, once it starts, they squeal for the entire rest of the drive.

 

The only nearly consistent element is that it happens at medium braking, not really light or hard braking. 

 

Obviously, being factory brakes this should be something I can fix. But, I wonder if current aftermarket pads are dimensionally off in some way? 

 

Meanwhile, I have your kit on my wagon and the brakes are quiet as little mice. 

 

Jesse. 

[jfbrink]

 

Hey, gang, 

 

I forgot that I had a second theory on why this might be happening that I wanted to run past you all. I am using a 77-81 280zx disc/drum master cylinder with my stock RL411 discs. I chose it because it fit and provided a dual circuit setup, which I preferred over the stock single circuit. Because of the area ratio of the M/C plunger to the caliper pistons, the force required at the pedal is VERY high. I was wondering if somehow this could contribute to the squealing somehow? 

 

In contrast, I have this same M/C on my Mike Klotz disc conversion on my wagon, and because of the larger caliper pistons, the force required at the pedal is very low. Coincidentally (or not) those brakes don't squeal at all. 

 

Jesse. 

[mklotz70]

Thanks Jesse. :)

 

Brake squeal is basically just a high pitched vibration.  The pads are vibrating on the discs/rotors.  Under light pedal pressure, you're probably not creating enough drag between the pads and rotors for them to vibrate.  Under heavy, they're squeezed down hard enough that it does not permit vibration.   The goo that you can buy is supposed to stop the vibration by "gluing" the pads to the caliper pistons....thereby pulling the pads away from the rotor.  This only works if the piston actually retracts that far.  Most disc brake calipers pull the pistons back a very tiny bit because of the square seals, but still have the pad surface drag a little bit to keep them warm.  Brake pads don't work very well when cold.  

Did you have the rotors turned(resurfaced) when you put the new pads on?  If your pads are nice and flat, I'd check them for glazing.  You can sand the glazing off....just have a fan blowing the dust away....spray them with water when doing it.....just don't breathe the dust anymore than you have to.  Considering they're factory rotors, I'm guessing they were too thin to turn, so you just put pads on.  I'm also guessing they had some ripples on the rotors too that the new pads just "adjusted" themselves to.  

 

Too bad...I just sold the last upgrade kit for factory discs.

[datzenmike]

Increasing master size will increase effort, that's all. The brake line pressure will be the same stopping, but you will have to push harder. 

 

 

[]2eDeYe]

10 hours ago, jfbrink said:

 

Hey, gang, 
 

I am using a 77-81 280zx disc/drum master cylinder with my stock RL411 discs. I chose it because it fit and provided a dual circuit setup, which I preferred over the stock single circuit.

 

Jesse. 

 

 

Do you have pics of this setup?

 

[jfbrink]

@mklotz70 - The squealing started maybe a year into running very heavily worn stock rotors. But, it continued without change with NOS rotors and a new set of pads. The "goo" did not do me much good. Like most attempts to fix the problem, at the start of the drive, I think "oh, it's better now" and then by some point in the drive I realize, "nope, still there." 

 

@]2eDeYe - Hey, here is a photo of the M/C in place. I can take more later in the week: Engine Bay Overview with Dual M/C

 

 

[datzenmike]

Check your master has a residual valve in it. It's up under the large nut that the front brake line threads into. Tajke the line off and loosen/remove the nut. Up inside is a valve and a spring. It's job is to retain about 2-3 PSI of brake line pressure on the front pads.

 

[mklotz70]

4 hours ago, jfbrink said:

@mklotz70 - The squealing started maybe a year into running very heavily worn stock rotors. But, it continued without change with NOS rotors and a new set of pads. The "goo" did not do me much good. Like most attempts to fix the problem, at the start of the drive, I think "oh, it's better now" and then by some point in the drive I realize, "nope, still there." 

 

@]2eDeYe - Hey, here is a photo of the M/C in place. I can take more later in the week: Engine Bay Overview with Dual M/C

 

 

 

are you completely sure it's not the bearings?  

[]2eDeYe]

17 hours ago, jfbrink said:

 

@]2eDeYe - Hey, here is a photo of the M/C in place. I can take more later in the week: Engine Bay Overview with Dual M/C

 

 

 

Thanks, that looks great.