Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

Oil/grease/grime on disc brakes?

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

Oil/grease/grime on disc brakes?

Old 03-10-15, 06:22 PM
  #1  
AcornMan
Senior Member
Thread Starter
 
AcornMan's Avatar
 
Join Date: Sep 2009
Location: Denver, CO
Posts: 143
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Oil/grease/grime on disc brakes?

I've owned my mountain bike for less than a year, but I've already had to have the rear brake pads replaced, and the caliper professionally cleaned, twice because grease, grime, or oil have caused horrible screeching when I brake. I've never used any kind of oil or grease anywhere near that part of the bike, and it has only been a problem on the rear brake, never the front. But there was clearly some kind of oil or grease in that area because it has attracted a lot of dust and dirt that sticks to it. I was convinced that there must be some kind of a fluid leak, either brake fluid from the rear brake line, or grease from the rear hub. But my LBS mechanic says he checked it thoroughly and found no leak. So what the heck is going on? I store my bike by hanging it upside down from the ceiling. Could that possible be allowing fluid from the brake line to leak out that might not otherwise if it were upright? That's all I can think of.
AcornMan is offline  
Old 03-10-15, 06:42 PM
  #2  
FlashBazbo
Chases Dogs for Sport
 
FlashBazbo's Avatar
 
Join Date: Feb 2007
Location: Middle Tennessee
Posts: 4,019

Bikes: BMC SLR01 TeamMachine Disk Di2; OPEN new U.P. Di2

Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 798 Post(s)
Liked 17 Times in 13 Posts
The rear of a mountain bike (or gravel bike) is a much dirtier place than the front. For that reason, on my gravel bike, I notice that there are certain conditions that will cause the rear brake to squeal while the front doesn't. (And when I get especially wet/muddy, they both squeal until I clean them.) It could be as simple as the rear brake disk catching dirt, moisture, goop on the ride while the front disk rides high and dry.

Does the squeal go away after a good cleaning using rubbing alcohol or acetone? Even a good water bath with vigorous drying seems to make my rear brake squeal go away. Just a thought.
FlashBazbo is offline  
Old 03-10-15, 06:43 PM
  #3  
AcornMan
Senior Member
Thread Starter
 
AcornMan's Avatar
 
Join Date: Sep 2009
Location: Denver, CO
Posts: 143
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by FlashBazbo View Post
The rear of a mountain bike (or gravel bike) is a much dirtier place than the front. For that reason, on my gravel bike, I notice that there are certain conditions that will cause the rear brake to squeal while the front doesn't. (And when I get especially wet/muddy, they both squeal until I clean them.) It could be as simple as the rear brake disk catching dirt, moisture, goop on the ride while the front disk rides high and dry.

Does the squeal go away after a good cleaning using rubbing alcohol or acetone? Even a good water bath with vigorous drying seems to make my rear brake squeal go away. Just a thought.
Unfortunately cleaning it with rubbing alcohol and/or water doesn't help, or only helps a tiny bit for a very short time.
AcornMan is offline  
Old 03-10-15, 06:56 PM
  #4  
dsbrantjr
Senior Member
 
dsbrantjr's Avatar
 
Join Date: Sep 2010
Location: Roswell, GA
Posts: 6,224

Bikes: '93 Trek 750, '92 Schwinn Crisscross, '93 Mongoose Alta

Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 654 Post(s)
Likes: 0
Liked 47 Times in 43 Posts
Water or alcohol will do little to remove grease. Real (not "green") mineral spirits or brake cleaner (be careful of plastic and paint) will do a better job. Or a solution of Dawn liquid and a VERY thorough rinse with hot water. Never use gasoline as a cleaner.

If the pads are badly contaminated replace them. If this is not done the pads will re-contaminate the rotors and the squeal will return shortly.
dsbrantjr is offline  
Old 03-10-15, 07:37 PM
  #5  
mtbikerinpa
Shimano Certified
 
mtbikerinpa's Avatar
 
Join Date: Dec 2004
Location: PA
Posts: 1,840

Bikes: 92 Giant Sedona ATX Custom

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 37 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
What sort of chain oil do you use? How much? When using wet lube I have found trouble with cross-mounted car racks if the brake rotor is placed on the rear facing side of the bike. The wind from the car will blow occasional slaps toward the rotor. Likewise if the bike is laid in a car or truck bed, leave the rotor up. Mind you that was even with consistent ragging off of any accessible extra. Not a problem with a dry or wax lube, but depending on the conditions it may not be feasible. One indicator if that is a related issue is that the hub will also have some filming. The most effective way to clean the caliper assembly would be to spray it with brake-cleaner, but don't go crazy. The surface would then be about as clean as possible. Same treatment to the pads, and rotor, front and back. Once cleaned, sand them with 180 or so sand paper and clean again. The pad will sand a clean color, not black when it is clean. Repeat until it is. Yes that wears the pad down, but the other option would be to throw them away, so whats to lose.
mtbikerinpa is offline  
Old 03-10-15, 10:28 PM
  #6  
gsa103
Senior Member
 
Join Date: May 2013
Location: SF Bay Area
Posts: 4,153

Bikes: Bianchi Infinito (Celeste, of course)

Mentioned: 19 Post(s)
Tagged: 0 Thread(s)
Quoted: 629 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
The most common source of this is a leak around the hydraulic piston. Very throughly clean the brake and piston area. Install, ride a little in relatively clean conditions, then remove the pads. If you have a ring of deposits on the back the pads, you most likely have a leaking piston. Unfortunately, the solution is usually a re-build or a new caliper.

What brand/model brakes?
gsa103 is offline  
Old 03-10-15, 11:37 PM
  #7  
Bandrada
Bandolero
 
Bandrada's Avatar
 
Join Date: Dec 2013
Location: Land of Enhancement
Posts: 402

Bikes: ...

Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 2921 Post(s)
Liked 4 Times in 4 Posts
Some rotors are prone to squealing. If you are not losing braking power, your pads/rotor are probably not contaminated. Often times I've found that vibrations from the frame will ping heavily into said "prone" rotors. Try a different style of rotor, preferably borrow one if you can so as to eliminate that variable.
Bandrada is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Metal Man
Advocacy & Safety
52
08-25-14 05:05 PM
sykerocker
Classic & Vintage
15
12-08-12 01:48 AM
George
Fifty Plus (50+)
17
09-28-07 06:21 PM

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.