Go Back  Bike Forums > Bike Forums > Classic & Vintage
Reload this Page >

Single Pivot Brake Squeal

Classic & Vintage This forum is to discuss the many aspects of classic and vintage bicycles, including musclebikes, lightweights, middleweights, hi-wheelers, bone-shakers, safety bikes and much more.

Single Pivot Brake Squeal

Old 03-16-19, 02:04 PM
  #26  
Dfrost 
Senior Member
 
Dfrost's Avatar
 
Join Date: May 2013
Location: Pacific Northwest
Posts: 1,331

Bikes: ‘87 Marinoni SLX Sports Tourer, ‘79 Miyata 912 by Gugificazione

Mentioned: 112 Post(s)
Tagged: 0 Thread(s)
Quoted: 262 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I put a rubber band around the back end of each pad when adjusting them to achieve toe-in. I use Kool-stop salmon pads in their holders that allow enough motion for toe-in and rim surface matching.

When I had a front dual pivot brake that resisted these methods and still squealed occasionally, several wraps of Teflon pipe sealing tape around the brake attachment “nut” solved the problem.
Dfrost is offline  
Old 03-16-19, 02:28 PM
  #27  
P!N20
Senior Member
Thread Starter
 
P!N20's Avatar
 
Join Date: Aug 2010
Posts: 296
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 118 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Dfrost View Post
I put a rubber band around the back end of each pad when adjusting them to achieve toe-in.
Yes, that’s what I do with my bikes that have the concave/convex washers that allow for toe in adjustment. The ‘problem’ with the old holders is they bolt straight onto the caliper arm.
P!N20 is offline  
Old 03-16-19, 09:27 PM
  #28  
dddd
Ride, Wrench, Swap, Race
 
dddd's Avatar
 
Join Date: Jan 2010
Location: Northern California
Posts: 6,370

Bikes: Cheltenham-Pederson racer, Boulder F/S Paris-Roubaix, Varsity racer, '52 Christophe, '62 Continental, '92 Merckx, '75 Limongi, '76 Presto, '72 Gitane SC, '71 Schwinn SS, etc.

Mentioned: 66 Post(s)
Tagged: 0 Thread(s)
Quoted: 470 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
My standard for accelerating the mating of the pads to the rim is to force some heavy beltsander belt cloth past the brake pad surface under the exact alignment and direction as when using the brakes while riding. This simulates the first hundred miles of riding in just seconds.

Applying the brake while rotating the wheel forward with the belt moving with the wheel:




Note that Kool-Stop's black compound is their grippiest, so most likely to squeal.
The pink compound is all-weather, with iron oxide and less grippy.

Loose pivots don't actually move with the squeal frequency, since the elasticity of the arms, cable and pads keeps the pivot loaded uni-directionally under braking force. Nearly all of the squeal motion thus occurs in the pad itself and the flexing arm.
Sloppy pivots can affect the effective pad toe however, since the pad will change angle in three dimensions as the pad first hits the rim and all freeplay is taken up by the constant braking force. As such, note that the accelerated bedding-in process pictured above has all slack preloaded out of the pivots in the exact direction as when braking, so the leveling of the toe under force is indeed level with the rim surface.

Additional toe can be quickly applied to the pad surfaces with a stone in a high-speed Dremel tool once the wheel is removed. I would not bend a Campy caliper.

One first thing to check for is whether the toe is equal on both pads, and if not the caliper may need aligning at it's mounting point.

The most common cause of squeal is too much friction, as when the air is humid.
dddd is offline  
Old 03-20-19, 05:06 AM
  #29  
P!N20
Senior Member
Thread Starter
 
P!N20's Avatar
 
Join Date: Aug 2010
Posts: 296
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 118 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
OK, so I gave the pads a heavy sand with a 60 grit paper and gave the rims a light sand with a 600 grit wet and dry paper...because that was the roughest I had save the 60 which I thought was too rough.

I’ve only ridden around the block, but early signs are good. The rear is silent and the front only squeals under heavy braking, which I can live with, but I might get a rougher wet and dry and give the rims another go.

Stoked! Thanks everyone for your help.


P!N20 is offline  
Old 03-20-19, 02:09 PM
  #30  
Erzulis Boat
3rd Grade Dropout
 
Erzulis Boat's Avatar
 
Join Date: Oct 2005
Location: Santa Barbara Calif.
Posts: 1,166
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 89 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by BigChief View Post
For folks like me riding old bikes with steel calipers, toe in, no matter how you achieve it, won't wear in as the pads wear. What happens is the front of the pad contacts the rim first and then the brake calipers flex with more pressure so the pads contact the rim evenly. The toe in adjustment doesn't change.
This is how it was explained to me in my youth.
Erzulis Boat is offline  
Old 03-20-19, 02:41 PM
  #31  
Salamandrine 
Senior Member
 
Join Date: Oct 2015
Location: Los Angeles
Posts: 4,697

Bikes: 78 Masi Criterium, 68 PX10, 2016 Mercian King of Mercia, Rivendell Clem Smith Jr

Mentioned: 100 Post(s)
Tagged: 0 Thread(s)
Quoted: 1628 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by BigChief View Post
For folks like me riding old bikes with steel calipers, toe in, no matter how you achieve it, won't wear in as the pads wear. What happens is the front of the pad contacts the rim first and then the brake calipers flex with more pressure so the pads contact the rim evenly. The toe in adjustment doesn't change.
Good point. I'm sure this effect also happens to some degree with the more flexible aluminum caliper brakes, like the formerly ubiquitous Dia Compe 750, for example. The toe in on those will disappear as the pads wear in, but it takes longer than it would on a stiff campy caliper. I was attributing it entirely to less use, but that's not correct, or at least not the whole story.

At any rate I'm glad the OP has solved the issue. Yeah, 80 grit is too coarse for sanding rims. My preference is for 220 or 320P, but it's not super critical.
Salamandrine is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.