Topic: Front brake rebuild and upgrades, squeals worse than ever

[Dunk]

CB750 K5 I've owned since 2015. The brake has always squealed a bit. Over the years sometimes more and sometimes less as I tried various things. What always seemed to work best for a brief time is disassembly, cleaning, and smearing some brake grease on the back of the pads. That would only quiet it for a tank or two of gas though.

My latest attempt is rebuilding the caliper again, but using a phenolic piston from Godfrey along with his anti-squeal shims behind the pads. No more domed spacer between the piston and pad, no grease, pads installed dry, New drilled rotor from 4into1 installed as well. It was pretty quiet for about 50 miles, but now squeals worse than ever before. Super loud and annoying as this is my daily rider rain shine or snow.

I used Vesrah VD-102 pads this time. They have a chamfer already around the perimeter. I notice if I get some heat in the brake it will stay quiet until it cools. Squeal is at light to moderate stop effort, or hard effort when cold but quickly goes silent when stopping hard. After a hard stop or two it will be quiet for a couple light brake applications. But give it a minute or few and it's back to horribly loud.

The squeal is driving me nuts, and loud enough it is uncomfortable without ear plugs even just walking the bike around and using the brake. Oddly my K1 has a virtually silent front brake using EBC pads. Worst I had from that is a rattle that I resolved by shimming the slop in the caliper bracket. What do I try next?

[grcamna2]

Hi Dunk,sorry to hear the brake screeching at you 
I'm just going to ask if you think the pads get 'heat glazed' from a rapid heat-up with very hard brake applications:going from cold brakes,then intense hard braking?
I could almost bet that when you remove the pads you would probably see the pad surfaces shiny/heat glazed:sand the pads to remove the shiny glaze.
I had that a few times and since then I would progressively/gradual build-up the heat on the pads before making a hard 'panic stop'. I think the organic pads will glaze more than sintered or semi-metallic pads.
Have you tried using semi-metallic or sintered brake pads ?

[BenelliSEI]

I share your pain.... despite many efforts, on multiple occasions, making all kinds of adjustments and changes, my K1 does the same. I also ride a K3 and K4 and they never squeal. Why is that?

I’m going to swap in a cast iron disc over the winter. I suspect these regular complaints are tied to our rust free disc.....? I’ve noticed none of the bikes I ride with iron discs make these horrible noises.

[dave500]

have a look at how sloppy that swing pivot arm might be?theyll vibrate up n down!make up some shim if you can move it up n down.

[MauiK3]

I found a pad that got sticky in the bore, had to chamfer edges and smooth the side.

[Dunk]

Indeed there is some slop in the pivot that allows the caliper to move up and down. Probably about like my K1 had before I shimmed it, though that bike rattled over bumps and this one doesn't. I'll try to tighten up that vertical slop, maybe it will help.

Interesting bit I tried this morning for my commute, I removed the caliper adjuster nut, screw, and spring. It is less loud than when improperly adjusted, but similar or slightly more noisy than when I get it adjusted for quietest braking. The interesting part is that after about 15 miles of stop and go the brake started dragging a bit. Stopped at a light for a minute temps around freezing it dragged less afterward. I tried pushing on the caliper to get the piston back in the bore, it wouldn't retract at all. Drag was just enough that I could still move the caliper up and down on the sloppy bracket. After it sat for an hour or two to totally cool to frigid temps I tried again and there was a slight free play between the pads and rotor but I couldn't retract the piston when pressing the caliper hard into the disk. Pads are definitely glazed now, need inspection and roughing up.

I'm wondering if it could be a plugged up master cylinder bleed hole (when bleeding last time I observes bubbles and flow through both holes). Alternatively, maybe a collapsing inside of a brake hose. I don't think I ever replaced the hoses, probably original 70s parts. New lines maybe stainless might be in order. I'm tempted to try one of those new original-ish ribbed master cylinders. Felt really nice on one bike I used one on, though I'd prefer a round original appearing master cylinder. Not sure if bore size is different than originals. That or I could just rebuild the original.

[grcamna2]

Indeed there is some slop in the pivot that allows the caliper to move up and down. Probably about like my K1 had before I shimmed it, though that bike rattled over bumps and this one doesn't. I'll try to tighten up that vertical slop, maybe it will help.

Interesting bit I tried this morning for my commute, I removed the caliper adjuster nut, screw, and spring. It is less loud than when improperly adjusted, but similar or slightly more noisy than when I get it adjusted for quietest braking. The interesting part is that after about 15 miles of stop and go the brake started dragging a bit. Stopped at a light for a minute temps around freezing it dragged less afterward. I tried pushing on the caliper to get the piston back in the bore, it wouldn't retract at all. Drag was just enough that I could still move the caliper up and down on the sloppy bracket. After it sat for an hour or two to totally cool to frigid temps I tried again and there was a slight free play between the pads and rotor but I couldn't retract the piston when pressing the caliper hard into the disk. Pads are definitely glazed now, need inspection and roughing up.

I'm wondering if it could be a plugged up master cylinder bleed hole (when bleeding last time I observes bubbles and flow through both holes). Alternatively, maybe a collapsing inside of a brake hose. I don't think I ever replaced the hoses, probably original 70s parts. New lines maybe stainless might be in order. I'm tempted to try one of those new original-ish ribbed master cylinders. Felt really nice on one bike I used one on, though I'd prefer a round original appearing master cylinder. Not sure if bore size is different than originals. That or I could just rebuild the original.

Replace the hoses then try again.

[Dunk]

The ride home sucked, brake started sticking. Slight squeak-sueak-sueak. Lightly and rapidly pulled front lever a few times, it stuck harder dragging noticeably. Stopped and let it cool a minute, pushed in hard on caliper against disc. No noticeably freeplay in brake but the bike moved easily again so not more than a slight touching the rotor.

Carried on avoiding front brake but had to stop hard for a selfish driver ignoring stop sign, front seemed hard to pull and low on stopping power... Or maybe my fingers were losing feeling and usefulness since it's 35* outside and I didn't grab the heated gloves this morning. Brake stuck again, gave caliper a push/jiggle at the next red light just up the street and it freed up for most of the rest of the way home but stuck later even hardly touching the front and I had to stop let it cool and push the caliper again. The rotor is now very discolored from heat. No free play in the caliper and I wasn't able to get any when pushing on it. Even cracking the bleeder open once I got home. Just a slight seeping of fluid like what gravity will do.

I'm wondering about the phenolic piston OD vs caliper ID. I did not check clearance or compare dimensions to the old piston. The marketing of this material is no pitting along with less heat transfer to the caliper and brake fluid. I believe it since every time I touched the caliper today it was either cold or barely warm, while the rotor was quite hot. If the brake was dragging at all, slowly heating up the rotor and pads, and to some extent the piston... I wonder how stable the size of the piston is with whatever heat it was getting and the rotor growing closing up that few thousandths clearance vs the brake fluid staying fairly cool and aluminum finned caliper just hanging out there in a 40-50 MPH 35* breeze. Might the easy enough clearance to install the piston and move freely initially have closed up and started sticking? I don't know, just a thought.

I did not pull it apart yet, I'm thinking I'll order braided lines, new Kawaski style repop master cylinder, rebuild kit for the original, new orings for the caliper and a new chromed steel piston along with a variety of pads. I'd like to have options on hand to try. This is my daily rider, I want the brake to just work on not be obnoxiously loud while looking reasonably original or period correct. Trying without the adjuster screw was a bad idea, given the other issues going on with this brake.

[BenelliSEI]

How well did you clean out the groove in the caliber where the seal sits?  I have a very strong dental pick that works well for this job. It takes forever to really get the solid crap out of that groove, then I use a small brass wire wheel on my Dremel to polish it out. ANY crap or scale left in that groove will cause the seal to fit too tightly on the piston and the brakes WILL drag.

Also.... really look at the hoses. They will rot from the inside and I’ve had a set act as a check valve! Pressure from the master will force fluid down the hose, but they are so blocked that pressure will not release!

[Dunk]

I thought I cleaned it pretty darn well. I used a pick to get into the corners where the seal sits but did not think to use a dremel. I'll do that this next time around when the parts come in. I have an ultrasonic that works great on carbs, maybe I should use that as well. Granted this caliper is powder coated by PO, I'm not sure waht the ultrasonic will do to that but I can always blast and paint it.

Yes brake lines are suspect. New braided lines are ordered. I'll cut the old ones apart for curiosity sake. Rotor looks pretty cooked. I'll hit it with the line sander to break the glaze and help the new pads seat.

I ordered typical cheap organic pads as well as ceramic pads. Any thought on which is better?

[grcamna2]

I thought I cleaned it pretty darn well. I used a pick to get into the corners where the seal sits but did not think to use a dremel. I'll do that this next time around when the parts come in. I have an ultrasonic that works great on carbs, maybe I should use that as well. Granted this caliper is powder coated by PO, I'm not sure waht the ultrasonic will do to that but I can always blast and paint it.

Yes brake lines are suspect. New braided lines are ordered. I'll cut the old ones apart for curiosity sake. Rotor looks pretty cooked. I'll hit it with the line sander to break the glaze and help the new pads seat.

I ordered typical cheap organic pads as well as ceramic pads. Any thought on which is better?

Ceramic pads need a lot of heat to work efficiently/at their best,so for the street  organics? but the organics aren't too aggressive;I like sintered or semi-metallic.

[Tim2005]

How much of the caliper is powder coated? Just the outside?

[BenelliSEI]

For regular street use, the organic should be fine (and quieter too).

[scunny]

How much of the caliper is powder coated? Just the outside?
this is an important question.

[Dunk]

Just the outside of the caliper of powdercoater, nothing anywhere near the bore and none of the inner surfaces. Now that it's apart again I'll clean it in the ultrasonic. If it looks rough or takes the powdercoating off I'll just use caliper paint on it.

In any event, mystery solved... New parts came in today so I pulled the caliper off. The piston side pad locating screw backed out until it jammed in the groove in the caliper so it could not retract without significant force. I'm reasonably certain I checked the screw on the pad was snug, but maybe I didn't. I'll be using loctite on that screw this time around.

The fluid came out looking very clean as expected, but had black particles in it. The brake hoses are breaking down and shedding bits into the fluid. New lines were a good idea.

[grcamna2]

Just the outside of the caliper of powdercoater, nothing anywhere near the bore and none of the inner surfaces. Now that it's apart again I'll clean it in the ultrasonic. If it looks rough or takes the powdercoating off I'll just use caliper paint on it.

In any event, mystery solved... New parts came in today so I pulled the caliper off. The piston side pad locating screw backed out until it jammed in the groove in the caliper so it could not retract without significant force. I'm reasonably certain I checked the screw on the pad was snug, but maybe I didn't. I'll be using loctite on that screw this time around.

The fluid came out looking very clean as expected, but had black particles in it. The brake hoses are breaking down and shedding bits into the fluid. New lines were a good idea.

The problem was the caliper adj. screw ?

[BenelliSEI]

Just the outside of the caliper of powdercoater, nothing anywhere near the bore and none of the inner surfaces. Now that it's apart again I'll clean it in the ultrasonic. If it looks rough or takes the powdercoating off I'll just use caliper paint on it.

In any event, mystery solved... New parts came in today so I pulled the caliper off. The piston side pad locating screw backed out until it jammed in the groove in the caliper so it could not retract without significant force. I'm reasonably certain I checked the screw on the pad was snug, but maybe I didn't. I'll be using loctite on that screw this time around.

The fluid came out looking very clean as expected, but had black particles in it. The brake hoses are breaking down and shedding bits into the fluid. New lines were a good idea.

The problem was the caliper adj. screw ?

No.... 8 think it was the round head screw in some pads that keeps the orientation and slides in a groove. Jams when it backs out too far?

[MauiK3]

Good call to also do the lines.

[Don R]

 Thanks for the cure report. We can all learn from it. 

[grcamna2]

Just the outside of the caliper of powdercoater, nothing anywhere near the bore and none of the inner surfaces. Now that it's apart again I'll clean it in the ultrasonic. If it looks rough or takes the powdercoating off I'll just use caliper paint on it.

In any event, mystery solved... New parts came in today so I pulled the caliper off. The piston side pad locating screw backed out until it jammed in the groove in the caliper so it could not retract without significant force. I'm reasonably certain I checked the screw on the pad was snug, but maybe I didn't. I'll be using loctite on that screw this time around.

The fluid came out looking very clean as expected, but had black particles in it. The brake hoses are breaking down and shedding bits into the fluid. New lines were a good idea.

The problem was the caliper adj. screw ?

No.... 8 think it was the round head screw in some pads that keeps the orientation and slides in a groove. Jams when it backs out too far?

John,I've never seen one like that as you've described; anyone have a picture ?

[Dunk]

Picture of what came out. The locating screw in the brake pad for the caliper side backed out, eventually far enough it jammed up in the caliper body preventing the pad from retracting. New pads I removed the screw entirely and reinstalled with a dab of blue loctite. I will use a dab of loctite on every brake pad locating screw in the future.

I also cleaned the caliper in the ultrasonic, and went over the groove for the pad locating screw with a file and then sandpaper as it was marred from the screw backing out. Master cylinder was ultrasonic cleaned and honed with a 14mm dingle berry brush. Distribution block on lower triple also went in ultrasonic and thoroughly flushed.

"Old" brake fluid  from recent change came out clear but with some black particulates in it. Surely from deteriorating brake lines, though they looked pretty good inside (aside from the sediment buildup which was not black).

New braided lines installed. MC rebuilt with K&L kit. MC was painted with Dupliacolor caliper paint, baked for over an hour at 200*. Disappointed in the paint durability, as I have a chip from lightly hitting it with a wrench when tightening the lever bolt. I'll touch it up with a small brush and it'll hardly be noticeable, but i suspect the paint will chip from bug impacts let alone the occasional stone or road grit. Whatever, it's a daily rider that sees rain regularly and occasional snow, but disappointing when you try to make it nice and it appears to be a wasted effort.

New brake lever and pivot bolt installed with brake grease. Brake feels very good now, smooth, easy, and progressive. Rotor was scorched to hell after the sticking. I scuffed it all around with sandpaper to break the glaze which significantly lightened the discoloration. New pads installed, cheapest pads looked softest and least metallic. New piston o-ring, same nearly new phenolic piston I used last time. Same anti-squeal shim pads. On a short test ride the brake began squealing again after a few stops, though not as loud as before when it was sticking. No hard stops, all fairly light to somewhat moderate braking effort. I did not shim the caliper for up/down movement, though comparing to my K1 with silent front brake the K1 caliper has massive up/down movement compared to this one. Because of that I am doubtful that up/down slop in the caliper arm plays any significant role in brake squeal. At least my daily rider is back on the road and the brake works good.

[grcamna2]

Looking good Dunk.
I wonder if it would help the rotor to be lightly cut on both sides?

[Don R]

 A car mag once recommended drilling the brake pad friction material and inserting a piece of similar diameter carbon rod removed from the inside of a flashlight battery. I'd think it would lubricate the contact patch.
  I did it on my 69 Firebird, it didn't squeal and still seemed to stop.

[Dunk]

I came down with coronavirus over Christmas and only just put it back together and had the short test ride that it squealed a bit, then off to travel for work for a week. Today was the first time commuting on the new front brake. It was remarkably quiet, thought had a light squeal a few times after getting some miles on it. I'll hit the disc with sandpaper a bit here and there and see how it wears in. The feel at the lever is great. Easy pull with new lever and new greased pivot bolt. Smooth progressive actuation with the new master cylinder internals and honed bore. No adjuster spring and bolt for now, seems to be working good.

[grcamna2]

I came down with coronavirus over Christmas and only just put it back together and had the short test ride that it squealed a bit, then off to travel for work for a week. Today was the first time commuting on the new front brake. It was remarkably quiet, thought had a light squeal a few times after getting some miles on it. I'll hit the disc with sandpaper a bit here and there and see how it wears in. The feel at the lever is great. Easy pull with new lever and new greased pivot bolt. Smooth progressive actuation with the new master cylinder internals and honed bore. No adjuster spring and bolt for now, seems to be working good.

Glad you were able to improve your front brake squeal;sorry to hear about the Covid 19.