LocostUSA.com

Learning how to build Lotus Seven replicas...together!
It is currently Tue Sep 02, 2014 7:33 am

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 3 posts ] 
Author Message
PostPosted: Fri Aug 22, 2014 5:39 pm 
Offline

Joined: Tue Feb 12, 2008 2:08 am
Posts: 247
Location: Olympia WA
Hello,
I have a completely stock me on a break system, with the addition of half pound residual valves for the both front and rear brake lines. At this point, The reservoir is below the calipers. (I have had remote reservoirs, yet they seemed to leak a lot. ) My challenge is, both front and rear pads hang up a bit at the end of an autocross run.

If I take the residual valves out, how long will it take for the brake fluid to bleed back? I am thinking that I'll just get in the car pump the brakes once or twice the pressure would be back in little be just like normal.

Do you run residual valves in your car?
Thanks for your time _ JEB

_________________
● Aerodynamics are for people who can't build engines. ~ Enzo Ferrari
● I have a dream: My car has a new type of engine: a half-turbine half-reciprocated engine. I invented it! ~ Dr. Felix Wankel
● It has occurred to me, amateurs built the ark and professionals built the titanic.


Top
 Profile  
 
PostPosted: Fri Aug 22, 2014 6:49 pm 
Offline
The voice of reason
User avatar

Joined: Thu Jan 10, 2008 4:47 pm
Posts: 5609
Location: Massachusetts
I don't think you need those valves. The fluid won't bleed back unless you have leaks in your calipers.

Atmospheric pressure should keep the fluid up for at least 30 feet. I don't know how good the seals are supposed to be though.

_________________
Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.


Top
 Profile  
 
PostPosted: Fri Aug 22, 2014 9:46 pm 
Offline
User avatar

Joined: Mon Apr 12, 2010 5:40 pm
Posts: 1831
Location: san francisco bay area
First off, I'm a lot more forgiving of residual pressure valves than I used to be.
That 37 Olds I worked on with a manual single master driving a boosted single master driving 4w drum brakes did it to me. :ack: :BH:
Effectively the only thing that a residual pressure valve does in a disc system is eliminate any "take up" before the brakes begin to function but you know that, siphon drawdown is one problem but you know all about that too based on your post. ..
If you have a slightly out of true rotor (very common, especially on vehicles driven "spiritedly") and no valve it will knock each side back separately resulting in a wider gap, with a valve in place it will push fluid back and forth between the pistons (or back and forth on the sliders for a single piston) only releasing the pressure above 1/2 psi back to the master.
Hot or cold it shouldn't make a difference on pressure settings.
I'm having a hard time blaming the residual valve for dragging when the brakes are heated unless it's in a location that gets the valve itself hot. .. I suppose it could be because of the friction material itself getting more ornery when it's hot?
Still, 1/2 psi ain't very much applied pressure. ..
I'm interested in how much free play you have in the pedal when the system is heated up compared to when it's cold.

_________________
"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 3 posts ] 

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: Bing [Bot], wrightcomputing and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
POWERED_BY