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

Hydraulic brake question. Flipping your bike upside down for maintenance.

Notices
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.

Hydraulic brake question. Flipping your bike upside down for maintenance.

Old 01-05-18, 11:15 PM
  #1  
boomhauer
Senior Member
Thread Starter
 
boomhauer's Avatar
 
Join Date: Apr 2011
Posts: 774
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 224 Post(s)
Liked 43 Times in 30 Posts
Hydraulic brake question. Flipping your bike upside down for maintenance.

I've been maintaining my hydraulic brake bike by flipping it upside down to service the drive train, change a tire, etc...
When I do this my hydraulic brake brake acts as though there is an air pocket. I have to pump it to make it work.
This only lasts a day and then it disappears. Everything is back to normal.

Question...
Should I not continue to service my bike it the upside down position?
Am I slowly draining fluid somehow? I don't see any. How does the air get in there? Has it always been in there?

I purchased these Shimano Saint Hydro brakes on the internet. They came pre assembled and bled and have performed flawlessly for 18 months.
boomhauer is offline  
Old 01-05-18, 11:48 PM
  #2  
xenologer
Senior Member
 
Join Date: Aug 2008
Posts: 2,589
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 239 Post(s)
Likes: 0
Liked 7 Times in 7 Posts
air bubble in the reservoir
that migrates into the piston when brakes are squeezed while upside down
Then floats back out after a few pumps rightside up

So,
bleed the brakes so there's no big bubble in the reservoir
and/or
just don't touch the brakes at all when the bike is upside down
xenologer is offline  
Old 01-06-18, 12:46 AM
  #3  
bogydave
Senior Member
 
bogydave's Avatar
 
Join Date: Dec 2015
Location: ALASKA , SoCal
Posts: 914

Bikes: /Skye/ Torker mt, Sirrus flat bar

Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 188 Post(s)
Liked 24 Times in 10 Posts
I have the same on a mt bike.
New bike , First time I
Fixed a flat , took off no front brake .
“PANICK” time!!
Few pumps
& it worked, whew !

Now I pump it after upside down.
Fixable , yes
but haven’t taken the time to yet.
4 years now.
bogydave is offline  
Old 01-06-18, 04:00 AM
  #4  
cpach
Senior Member
 
Join Date: Oct 2009
Location: Mt Shasta, CA, USA
Posts: 2,062

Bikes: Too many. Cannondale SuperSix, Trek Remedy 8, Trek Crossrip+ get the most ride time.

Mentioned: 26 Post(s)
Tagged: 0 Thread(s)
Quoted: 497 Post(s)
Liked 275 Times in 209 Posts
Hydraulic brakes are not closed systems because one of their features is that the pistons automatically advance with pad wear, which ends up storing more fluid in the caliper in the space that the pistons previously occupied. In the lever, there's a reservoir of fluid and air. When you depress the lever, the master cylinder moves past the inlet from the reservoir and temporarily closes the system, but when you release the lever fluid and air can move between the master cylinder and the reservoir. When the bike is inverted, air can move from the reservoir into the rest of the braking system. As air is compressible, this means the brakes don't really work. Thankfully, gravity moves the air to the top of the system, so with a few lever pulls things are typically well again.

This behavior will be drastically lessoned if you bleed your brakes. While Shimano brakes truly require bleeding less frequently than many, they still formally recommend annual bleeds. At 18 months, you should probably bleed your brakes, or at least top bleed them.

Flipping your bike for brief work should be OK for your brakes, although I personally hate working on flipped bikes. Its really rough on the grips and saddle and is an awkward way to work. For flat changes, I remove the wheel upright and lay the bike gently on the non drive side if I don't have a stand. All drivetrain work is easier with the bike upright, even without a stand. Also get a stand if you do much work on your bike (if you can).
cpach is offline  
Old 01-06-18, 07:36 AM
  #5  
Canker
Senior Member
 
Join Date: Aug 2005
Posts: 1,605
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 274 Post(s)
Liked 134 Times in 82 Posts
It isn't a problem. With a mtn bike it is actually GOOD to turn the bike upside down every now and again to get oil on the foam rings/seals in the fork.
Canker is offline  
Old 01-06-18, 01:49 PM
  #6  
trailangel
Senior Member
 
trailangel's Avatar
 
Join Date: Feb 2014
Location: Pasadena, CA
Posts: 4,794

Bikes: Schwinn Varsity

Mentioned: 22 Post(s)
Tagged: 0 Thread(s)
Quoted: 1891 Post(s)
Liked 669 Times in 391 Posts
When will ya'lll learn.......Rule 49:
Velominati ? The Rules
trailangel is offline  
Old 01-06-18, 02:14 PM
  #7  
fietsbob
Banned
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 43,599

Bikes: 8

Mentioned: 197 Post(s)
Tagged: 0 Thread(s)
Quoted: 7607 Post(s)
Liked 1,339 Times in 847 Posts
disc brake Master cylinder/lever expansion tanks have a gasket in them.. they should allow you to do that.
fietsbob is offline  
Old 01-07-18, 11:14 AM
  #8  
skimaxpower
Senior Member
 
Join Date: Aug 2014
Location: WA
Posts: 341
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 52 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by trailangel View Post
When will ya'lll learn.......Rule 49:
Velominati ? The Rules
For real.
Won't somebody please think of the children?
skimaxpower is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
ericcc65
Bicycle Mechanics
11
06-20-17 07:37 AM
corrado33
Bicycle Mechanics
23
06-14-15 06:03 PM
dannylightning
Bicycle Mechanics
6
05-10-15 10:16 AM
Daniel 62
Bicycle Mechanics
8
12-27-14 07:17 AM
TacomaSailor
Bicycle Mechanics
3
04-25-12 03:05 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 - Do Not Sell My Personal Information -

Copyright © 2022 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.