Topic: Re: '76 Honda CB550F: Constant Disk Brake Squeal!!

[magner]

Hey guys, loving my first bike so far, but I absolutely can't stand all the squeaking from my front brake! It really takes the bike from seeming like a vintage hot rod, to an old clunker... I am getting a constant brake squeak/screech from my front disk brake (without it applied at all) when rolling the bike around in neutral, going slow, and even at high speeds: just at all times. I first sprayed it with brake cleaner, and then resorted to swapping out the pads for brand new ones and even applying disk brake quiet to the back of the pads. Might be even worse now. I also notice now that it feels like the brake is constantly slightly applied, because when walking the bike around my garage with it off and in neutral it is much harder to push and not rolling freely. I am new to bikes so I'm assuming that part is from human error upon reassembly... Any suggestions on how to fix this for a newbie?

Cheers,
Andy

[bryanj]

Start by stripping out the swinging bracket pivot, cleaning and greasing it then rebuild the caliper PROPERLY using at least a new seal and maybe piston. If those do not stop it dragging move onto the master cylinder and hoses

[Deltarider]

... and then resorted to swapping out the pads for brand new ones ...

What brand pads are your 'brand new ones'.
I had a noisy frontbrake several times, long time ago now. I was about to dissassemble the swinging bracket pivot, but with the front wheel removed, it struck me how easy and frictionless the assembly could swing, so I decided not to take it apart and I still have the O-rings unpacked.
This what I did instead:
1. I have several brake pads lying around but installed genuine Honda pads.
2. Prior to that I cleaned where the piston and seal sits. That spot is known to collect dirt (this concerns all CB's btw).
3. I greased - very, very lightly - the backs and sides of the pads with ATE grease.
4. Made sure the nylon ring was at the back of PAD A.
Problem gone.
Now that we're on the subject. Among the brake pads lying around, there's a pair of EBC FA13. Did I read somewhere that they'll sqeal like hell (on mine they did) unless you remove the paint from the sides and that for the rest they're fine?
My brakelines are 43 years old and don't leak. The feel is not great however and I need quite some force to apply the brake (the advantage is you can brake like a fool). I'm tempted to fit Stahlflex brakelines. Anything against it? Anyone regretted fitting them? Is there more chance of a dragging brake? What should I observe fitting them? Is there a particular working order? BTW, what's inside the genuine Honda lines? Rubber only?

[dave500]

the hoses and master wont have #$%* to do with squeal!itll have a combination of sloppy pivot and non asbestos pads!try deglazing the disc and hacksaw a cross over the pads bout a mm deep.

[bryanj]

Dave, i have had partialy collapsed hoses not releasing all the pressure and that tiny hole blocked holding some pressure, both not enough to lock the wheel but just enough to hold pads against disc.
I also had one where the fluid had gone solid in the flexi which stopped any fluid being bled out and that one caused some head scratching till found!

[dave500]

#$%* if I found fluid gone solid id be replacing the lot?

[jlh3rd]

there is an adjustment to the brake caliper that can be made on these bikes. See the bolt #11 ? It has a slot at the end. Turning this bolt moves the caliper in or out. Where i can't help you is how to set this adjustment. It might be in the manual, my manuals are out in the shed, i can look later....but maybe someone else on here can chime in.
Also, the other suggestions on here can help fix this .

[bryanj]

6 thou between fixed pad and disc.

[Bodi]

Yes, many things can cause brake squeal. Definitely the pads are touching the disk with brake released though, they really shouldn't (not enough to squeal at least).
Adjustment of the inner pad spacing should be first, during that check that the arm pivot is free: disassemble, clean, and grease it if not. The spring should push the inner pad about a business card thickness away from the disk. You have to push the outer pad in (push caliper the piston in) to get clearance for this adjustment. That should be not easy to push in but not super difficult, if it doesn't push in without Herculean effort something is wrong. The caliper piston and/or seal may be bad, the master cylinder return orifice could be blocked.
If it's swinging free and the clearance is good, the caliper must be staying clamped to the disk after you release the brake.
Pad material and disk surface condition contribute to squealing. Deglazing the disk with a bench stone or very fine sandpaper may help. Sanding or filing the pads to get a fresh surface also may help. If the pads are contaminated with brake fluid or oil there is no way to clean them: they must be replaced.
"the hoses and master wont have #$%* to do with squeal!" - not true. The caliper piston should retract a tiny bit when the brake is released. That's partly done by the master cylinder, when released it sucks back on the brake line slightly and helps retraction. A worn out rubber line way past it's best-before date stretches and expands under pressure, and springs back when pressure is released... that eliminates any suction from the master cylinder. Air bubbles in the fluid does the same.
The caliper piston seal does most of the retraction. It gets pushed outward under hydraulic pressure, and when it relaxes as pressure is released it pulls the piston back with it. A corroded piston surface or corroded and gummed up seal groove will defeat this action.

[Deltarider]

... If the pads are contaminated with brake fluid or oil there is no way to clean them: they must be replaced...

Don't I know it... I once made the mistake to clean the front fender after spraying some WD-40, to later find out - you guessed it - brake performance was gone almost completely. This is the kind of mistake one makes easily: your mind concentrated on one thing temporarely looses oversight over the consequences: tunnel vision. I got the pads out to rub them over sandpaper, but I'm not really satisfied. Here's something I always wanted to know. With Honda you can order pads A and B separately. Is there anything against replacing one pad only? I expect the hump on its back will allow pad B to line up parallel to pad A or am I mistaken?   

[BenelliSEI]

Take note of BryanJ comment on the original rubber hoses. On my K1 I did caliper rebuild, got the pivot working, then the master. When I tried to bleed the system, my MityVac just couldn’t pull brake fluid from the master to the caliper......... discovered the original rubber hoses had collapsed internally. Pressure from the master would get fluid through, but the hoses were acting like check valves and the pressure would not release! New hoses, no more squeaks!

[AwesomeCB]

I had a persistent brake squeal. Rebuilt the caliper, tried different pads... Finally rebuilt the MC and the racket stopped.

[PeWe]

Same as old cars, place a dollop of copper paste behind the pad. I think it is the fixed one that need it.

[dave500]

hose and master cylinder rebuild that stops squeal is a fluke.

[robvangulik]

hose and master cylinder rebuild that stops squeal is a fluke.

When either of those stops fluid from flowing back to the reservoir, they can very well be resposible for that extra noise!

[Clinto]

I have tried all the tricks and tips to try to get my brakes to stop squealing to no avail. I have a new nissin MC, stainless lines, correctly rebuilt calipers with new seals and brake assembly fluid, greased pivot arms, cut small lines in the pads for dust to escape, tried no-squeal on the backs of the pads, etc.  The only thing left for me to try is a different brand of pads. I believe the ones I have on now are the "organic" EBC pads. I remember someone posting Honda's official statement on the issue being "most will squeal, some won't"

Temporary fixes include sanding down pads, sanding down rotors (making sure you're sanding flatly on both) -- but the squeal will be back.

Good luck!

[Deltarider]

I'm afraid you can't sand down the type of rotors (stainless steel) we have...

[BomberMann650]

Had luck myself just using the factory caliper alignment method.  Think it was a .05 feeler gauge to clearance the rear pad off the rotor.  Didn't go overboard cleaning the pivot but the sqeak stopped.

[sixthwisconsin]

Godffery makes a shim for the inside pad.
https://godfferysgarage.com/project/anti-squeal-brake-shim/

I made my own after a complete rebuild of the caliper, new SS lines and new MC. The front brake squealed until I added the gasket shim.

[scottly]

I also notice now that it feels like the brake is constantly slightly applied, because when walking the bike around my garage with it off and in neutral it is much harder to push and not rolling freely. I am new to bikes so I'm assuming that part is from human error upon reassembly... Any suggestions on how to fix this for a newbie?

Cheers,
Andy

Andy, a common reassembly error is to fit the fender brace between the upper caliper mount and the lower fork leg, cocking the caliper. The caliper mount should be directly against the fork, with the fender brace on the tire side of the caliper bracket.

[magner]

I cleaned out and rebuilt the piston, and got some fresh brake fluid in there. It seems like it retracts well now as there is no longer any resistance when pushing the bike around, and the brake works a lot better, BUT I’m still getting terrible brake squeal. It’s iust a constant scream when I’m at 40mph! I’ve got a thin layer of that red brake quiet stuff that forms a rubbery surface on the back of the pad, should I make a thicker layer?? The pivot arm moves easily. Master Cylinder is new.  The rubber line is definitely old, but the brake fluid was very easy to bleed so I doubt it’s collapsed. What would y’all do next?

[magner]

Andy, a common reassembly error is to fit the fender brace between the upper caliper mount and the lower fork leg, cocking the caliper. The caliper mount should be directly against the fork, with the fender brace on the tire side of the caliper bracket.

Thanks Scotty, however I do not have any fender on the bike. Although I did notice after a ride on the fresh pads that only the front half of the pad was worn, like it may be hitting the disc at an angle. I know on bicycles this is actually done on purpose to avoid squeal, but maybe that’s different on motorcycles?

[scottly]

BUT I’m still getting terrible brake squeal. It’s iust a constant scream when I’m at 40mph!

The few times I've experienced the dreaded brake squeal, it was only when applying the brakes, not constant. You might try removing the adjuster screw and spring and see if it improves?

[scottly]

Which side of the forks is the hex of the axle nut on?

[luckydave]

Many years ago I had a persistent squeal on a Triumph T140,cured by simply filing a chamfer on the pad leading edge.Simple fix can often work

[dave500]

I'm afraid you can't sand down the type of rotors (stainless steel) we have...

ive scratched em up with a flapper wheel before,ive also sand blasted them,dont last long though,its a some special hard stainless,in the day selling a new bike with shiney new to the world hydraulic disc brake was paramount,had they been plain cast iron they would work better but look terrible rusty on the showroom floor!

[AwesomeCB]

hose and master cylinder rebuild that stops squeal is a fluke.

Naw.

[dave500]

#$%* im glad you know everthing.

[Deltarider]

I'm afraid you can't sand down the type of rotors (stainless steel) we have...

ive scratched em up with a flapper wheel before,ive also sand blasted them,dont last long though,its a some special hard stainless,in the day selling a new bike with shiney new to the world hydraulic disc brake was paramount,had they been plain cast iron they would work better but look terrible rusty on the showroom floor!

Exactly! It had to look good in the brochure and the showroom. If they only had fitted the Brembo's the Guzzi's had...

[Korven]

This is what worked for me on my cb. it had a squeaking sound until applying the brakes lightly. It had no rolling resistance in neutral like yours did so that might need a rebuild. Copperpaste didnt work for me (was alu there from previous owner) Ive heard the Sound comes from microvibration, 6 layer rubber/glassfiber should remove these vibrations. Not much international info about these seem to be found but must be other manufacturers for similar products.

[Deltarider]

Although I did notice after a ride on the fresh pads that only the front half of the pad was worn, like it may be hitting the disc at an angle. I know on bicycles this is actually done on purpose to avoid squeal, but maybe that’s different on motorcycles?

That could very well be it. I remember that on my Koga Miyata Terraliner, a hybrid bike, I used to fit the V-brakes so, that the front part would contact the rim first. I did this on purpose, after I had learned in a bicycle workshop that that would make your brakes screech and it did. I admit I was very childish.

[przjohn]

Here is what has worked for me on a few vintage bikes including H model Kawasakis that are notorious for brake squeal. As has been stated, chamfer a 45 on the leading edge of the pads. The leading edge is actually the back of the brake pads as that is what comes in contact with the disc first. Then, with doubled up hacksaw blades, cut a line through the center of the pad in parallel with the road surface. Don't cut all the way through to the metal just about half way. Then use brake quiet on the back of the pads. Finally, with a very small amount of grease apply a thin coat to where the movable pad slides against the metal caliper. If you want to kick it in the ass send the disc out to True Disc for drilling and grinding. I guarantee your squealing problem will be gone. Below is a pic of the front disc of a 76 750F I restored a couple of years ago. This disc has about 2,000 miles on it since resto and you can see the line that is from the parallel to the ground cut on the pad will leave on a freshly ground disc. You normally will not see this line unless you have your disc ground, it doesn't show on discs that are not ground fresh. It does not affect braking at all as far as I can tell.

 

[andy750]

Everyone who has owned a Honda SOHC has an opinion on brake squeal so Ill give mine . I have two CB750s and have had them for over 20 years. Fixed that nasty squeal two ways: drilled disks, stock pads and Corning High Temp silicone grease behind the pads (with the white o-ring present). This worked, and continues to work for me -the silicone grease has to be reapplied about once a year and it solves the squeal everytime - at least for me. I tried cutting the pads, new brake lines etc but it was the Corning silicone grease that worked for me -when you get it right you will enjoy the bike so much more!!

Good luck!
Andy

[Deltarider]

Everyone who has owned a Honda SOHC has an opinion on brake squeal so Ill give mine . I have two CB750s and have had them for over 20 years. Fixed that nasty squeal two ways: drilled disks, stock pads and Corning High Temp silicone grease behind the pads (with the white o-ring present). This worked, and continues to work for me -the silicone grease has to be reapplied about once a year and it solves the squeal everytime - at least for me. I tried cutting the pads, new brake lines etc but it was the Corning silicone grease

I'm with you, but I fail to see what drilled disks have to do with it.

[RAFster122s]

The Corning Silicone grease is High Vacuum Silicone grease referred to as Petcock grease (chemistry). It works well and does not move or migrate to other areas at high temp.