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Sun Jul 17, 2005 5:53 pm

Got a rail setup with front and rear disc brakes. Pedal setup is per picture. 3/4 master brake cylinder. Tee'd off front and rear lines. Bled the brakes, no air, leaks. Brakes work but are mushy and do not stop well at higher speeds. How should I have this setup? Do I need a proportioning valve set up somewhere in this setup? Bigger master cylinder? Thanks in advance.

Sun Jul 17, 2005 6:14 pm

A proportioning valve would be to balance front to rear braking. You may need a residual pressure valve ... helps with discs

http://www.cbperformance.com/catalog.asp?ProductID=1130

Sun Jul 17, 2005 6:17 pm

Where would I isntall the residual valve? Right into the master before the tee's?

Sun Jul 17, 2005 6:28 pm

Depending on how you've tee'd it ... it can be installed "in line" to the line that goes to the rear brakes only. Install it as close to the master cylinder as possible. If you install it into the master cylinder it will affect the front brakes as well (if your master cylinder is tee'd to feed both front and rear). A 4 pounder is fine for rear discs. Be aware of the threads on your current setup.

Mon Jul 18, 2005 6:55 am

Thanks for help! So are you saying that I am better off having the valve only on the rear brakes or I could have it come off the master and affect both front and rear. If I can go both front and rear will 4lb work or do I need more or less?

Mon Jul 18, 2005 8:00 am

You might want to take a look at this thread:
http://www.thesamba.com/vw/forum/viewtopic.php?t=116491&highlight=

There are a couple pics that may help. You may want to go ahead and plumb in a proportioning valve so you can control the brake bias and make sure you put in the residual disc brake valves for both the front as well as the rears. This will give you as much brake performance and tuning as you will ever get out of your setup.

Hope this helps. Good luck.

Mon Jul 18, 2005 9:50 am

Thanks Thing. Sounds liek the way to go. Should I go 4psi both front and back? Do you also recommend a larger master cylinder like a 7/8"?

Mon Jul 18, 2005 10:11 am

If it were me, I'd go with the 2# residual valves. 3/4" masters should be plenty for discs. FYI, they normally use 5/8" masters for drums with a 10# residual and 3/4" master with a 2# for discs.

I'd get the parts and plumb it up, bleed them and you should be just fine without having to spend much more money on it. Good luck with it.

Tue Jul 19, 2005 7:29 am

One question about the proportioning valve. Do I want to run this on the front or rear line? Since this a sand rail and I have read that with rails braking geometry is different then with most cars where front brakes do most of the work. Do I want to control the rear pressure or front pressure from lock up?

Tue Jul 19, 2005 8:02 am

You will run from your master cylinder into the proportioning valve. You will then have the front as well as the rear brake lines extend from the valve to your brakes. You can then simply turn the valve knob to adjust how much pressure is split to your F/R brake systems. You will find it really easy to get them the way you want them.

My car is something of a dual sport setup and I find I have different settings between street driving and offroad. I have dual 3/4" brake master cylinders and I noticed after looking at your pic again more closely you only have a single brake master. You may want to check with the brake supplier you are using to ensure that single master will do it for you, given your application.

Again, good luck with your car. I hope this helps you.

Tue Jul 19, 2005 12:14 pm

Sorry to keep kicking this around but in doing some research on master cyclinders I have found a dual circuit Wilwod brand master that would work with my setup.

I like the idea of dual circuit as it isolates the front and rear brakes to run on seperate channels but are controled with one pedal. I like the idea that if one end fails from leaks etc I still have the other end braking.

With this in mind I would now be running a seperate line to front and rear. Would I want to drop the prop valve on the rear line to control the rear brakes since they have all the weight etc or better on the front? Any suggestions?

Thanks again for the help.

Tue Jul 19, 2005 12:17 pm

If you get a dual circuit master setup, they are available with a balance bar that allows you to tune the brake bias there versus needing a separate bias valve. I have the CNC setup in mine and the balance bar setup works great...

What is the Wilwood p/n you are looking at?

Tue Jul 19, 2005 1:21 pm

Here is the link to the one I am looking at:

http://wilwood.com/Products/006-MasterCylinders/008-CRTMC/index.asp

It mentions if you click into the p/n in the PDF file that if I have a caliper higher then the mster that I will need to install a 2psi residual pressure valve. This is true for the rear brakes but eh front calipers are below or right at teh same height as the master. I do not see anything mentioned about adjusting bias front to back though, unless some of the screws located on teh unit adjust the bias. Check it out and let me know. I am also going to look at the unit you use. DO you have a link? Thanks again.

Tue Jul 19, 2005 2:25 pm

I bought all my parts over at Kar Tek in Corona, CA. I believe the link is www.cncbrakes.com but can't be sure. Let me check. The residual valves are really inexpensive and you may want to put it in in case you have any question about it being borderline. All these brakes aftermarket guys know their stuff...

I put hanging CNC pedals in mine with three separate remote reservoirs mounted up high. That may be an option for you if you are concerned about res height.

Fri Jul 22, 2005 12:45 am

clearsurf2001 wrote: You may need a residual pressure valve ... helps with discs

I am about to fit a residual pressure valve - but - I currently have a pressure activated brake light switch fitted. Thr pressure from the valve won't be high enough to activate the switch constantly and keep the lights on all the time, will it?

Fri Jul 22, 2005 6:59 am