Why Residual Valve Needed??? - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Suspension - Brakes - Steering
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 05-17-2007, 11:35 AM
Registered User
 
Join Date: Mar 2007
Location: Salem Oregon
Posts: 81
Wiki Edits: 0

Thanks: 1
Thanked 0 Times in 0 Posts
Why Residual Valve Needed???

When going from a disc drum Master Cylinder to a drum drum braking system, why is a residual valve needed on the disc side of the MC. If the MC is a disc disc, is a residual valve needed on both front and rear to go to a drum drum brake system?? Does the valve install into the brake lines, if not where is it installed.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 05-17-2007, 11:50 AM
Member
 

Last journal entry: Body work
Last photo:
Join Date: Jul 2004
Location: phoenix Az
Age: 59
Posts: 244
Wiki Edits: 0

Thanks: 0
Thanked 11 Times in 10 Posts
From Willwood's site.

--------------------------------------------------------------------------------

WILWOOD RESIDUAL PRESSURE VALVES:
These in-line pressure valves retain a minimum brake line pressure to help eliminate excessive pedal travel in both disc and drum brake systems.

The two pound valve is used in disc brake applications where the master cylinder is mounted below the horizontal plane of the calipers and fluid drain back occurs from gravity and vibration, thereby causing excessive caliper piston retraction and a longer brake pedal stroke. The minimal two pound residual pressure prevents fluid from flowing back without causing the brakes to drag. With drum brakes, a ten pound valve is used to compensate for return spring tension in the drums. Residual Pressure Valves are made from billet aluminum and color coded for easy identification. Ideal for drag racing, street rod and many off road applications.
lower than the wheel cylinders or calipers.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 05-18-2007, 10:35 AM
Registered User
 
Join Date: Mar 2007
Location: Salem Oregon
Posts: 81
Wiki Edits: 0

Thanks: 1
Thanked 0 Times in 0 Posts
Residual valve

So if a MC is mounted on the firewall, then you do not need to install a residual valve???
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 05-18-2007, 12:00 PM
Member
 

Last journal entry: Body work
Last photo:
Join Date: Jul 2004
Location: phoenix Az
Age: 59
Posts: 244
Wiki Edits: 0

Thanks: 0
Thanked 11 Times in 10 Posts
Right, If the master is higher than the wheel cylinders or calipers the valve isn't necessary.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 05-18-2007, 08:21 PM
Will I ever get it done?
 

Last journal entry: Rear Armrests
Last photo:
Join Date: Oct 2004
Location: Tulsa, OK
Age: 57
Posts: 1,049
Wiki Edits: 0

Thanks: 1
Thanked 3 Times in 3 Posts
The residual pressure valve is necessary for drum brakes. The seal lips on the wheel cylinder cups only seal one way. The hold the pressure in the system. They will allow air to pass them into the system if the air pressure exceeds the line pressure (absolute not gauge). It can happen. If it does, you will have air in the system and a spongy pedal. A 10 psi residual pressure valve is the commonly used for firewall or under floor MC's on the drum brake circuits only.

The square cut o-rings which seal the caliper pistons on disc brakes seal both directions. So, provided the calipers are below the MC, you don't need a residual pressure valve. If the calipers are above the MC, the liquid head can cause the fluid to go back into the master cylinder, retracting the pistons, causing a low pedal the next time you hit the brakes. A 2 psi residual pressure valve is commonly used for under floor MC's on the disc circuit only.

Most MC's made for drum/drum or disc/drum have residual pressure valves built into the drum circuits in the MC, right behind the flare seal. If you are using a disc/disc MC (or a disc/drum MC on a drum/drum system), you will have to put an external residual pressure valve on the circuit which was intended to be disc but is now drum.
Reply With Quote Quick reply to this message

Recent Suspension - Brakes - Steering posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may 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
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Valve Stem Angles, Do they Matter? Truth or Fiction? QuenchPiston Engine 35 12-28-2006 10:11 AM
desktop dyno needed!!! bobbypantera Engine 8 06-19-2005 01:27 AM
Residual Pressure Valve useful? cboy Suspension - Brakes - Steering 3 03-12-2005 07:10 AM
When is a proportioning valve needed? jpd37 Suspension - Brakes - Steering 2 03-25-2003 09:42 AM
valvetrain gurus: need help identifying mysterious valve noise blndweasel Engine 10 03-04-2003 07:59 PM


All times are GMT -6. The time now is 07:25 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.