Another brake system question

[Whaler]

Hi ..I am laying out my brake system and I am wondering if I should be looking at residual valves and a proportioning valve?
My builder tells me neither are necessary unless the car was to be raced. He also says that I do not have the type of disc brakes that require it.

I quote .

" External proportioning and residual line pressure valves are generally not required. We use these only when going to 4-piston calipers and a racing application."

He is a skilled guy and I trust him but thought I would throw it out to seek a second opinion. If I need them I would like to do it at this stage.

I thought elevation of the master in relation to the brake calipers elevation was the deciding factor??
FYI I have floor mounted assemblieswith the remote reservoirs
The master is easily lower than the calipers at each wheel. Therefore, do I need the residuals or not?
They would act as check valves acting against the head and drainage back to to the master ....correct??

Tim

[Bob Putnam]

Whaler,

It's not the height of the master cylinder per se - it's the tendency for fluid to flow back into the master. Because your reservoirs are above the calipers, it maintains slight pressure in your system all the time. You don't need RPVs.

[Whaler]

Thanks for the quick reply Bob. Planning the layout without the residual valves will make the work a little easier and cleaner looking. A couple tees here and there...
it makes sense that the remote reservoirs should actually have a cancelling effect on any head effect created by the height of each wheel caliper. The tendency to "backflow" is likely very little as you said.....

Tim

[Jack21]

Proportioning valve is going to be specific to your front/rear brake setup and car it's used on.

If you're buying a set, follow the manufacturers recommendations. If you're cobbling a set together, put prop valve in, then dial it in when you put the car on the street.

If your front and rear brakes are evenly balanced, the worst that could happen is that you'll open the prop valve all the way. If you have too much - too little, the prop valve is how you adjust it.

Every car is different. The same brakes on a Mustang (front heavy, same size tires front/rear) won't balance the same way on a Cobra (50/50, larger tire on rear) e.g. rear brakes can do more work.

Your master cylinder needs to be the right type for your brake system. Verify application through system vendor if not part of kit vendor.

Mixing & matching brake systems is like mixing and matching engine components (Ford block, Chevy pistons, Mopar rods), it'll work if you're certain it all fits, and someone has tried this before.

[justa6]

I thought I'd just add a comment to this thread.

I just finished (last year) my car and was told by several people including a tech at Wilwood that you don't want to use proportioning valve which is mainly a way to decrease pressure to one system but that you want a balance rod type system that lets you simply adjust the amount of pressure to either set of brakes. Now that assumes that you have two master cylinders. One for the front and one for the rear brakes. I took their advice and the system works very well.

Just an opinion...

Regards,

[bad_sss]

I'm using Wilwoods on front and rear. I have Tilton pedals with a balance bar, and am using 2 psi in line valves. I would definatly use a proporting valve if you do not have a balance bar; you can't expect the brakes to 'fire' perfectly; you will have to adjust them.

Also, don't forget to fit an in-line pressure brake switch, unless you have another way to signal the brake lights.

Good luck...

[bad_sss]

I just received a new Painless Wiring catalog; they also have an in-line pressure brake switch (along with Ron Francis).

[justa6]

I think you can get a in line pressure switch at any NAPA or other parts store a lot of cars use them... Probably save some money also.

Regards,

[Whaler]

Thanks for the considerations and suggestions guys....laying on my cold concrete floor tonight drilling and tapping,
drilling and tapping,drilling and tapping
LOL
.....will look into the brake switch ..forgot all about that puppy.

Tim

[Jack21]

Another option would be to put the brake light switch right on the brake pedal, and leave your brake line hydraulics alone. Most OEM's today use pedal switch and they're easy to find. Take a look at your "Other" car, and see how it's connected.

Admittedly, the balance bar is preferred with all aftermarket brake system, two master cylinders, etc. But with a single master cylinder made for 4 wheel disk brakes, Corvette, Ford T-Bird, Lincoln, Cad; use a proportioning valve in the rear brake circuit to balance the front/rear brake effort. You dial this in when you put the car on the street.

That being said, I have 11" rotors/4 piston calipers in front, 10" rotors/single piston calipers in rear. Master cyl is T-Bird. Weight distribution and tire size on this specific car, my dial in was all the way open. So I didn't need one. Had I used a different engine, different tires, it may have worked out differently.

[Whaler]

Hi Again,
I have run my front brakes lines to the master and now about to do the back brake cct. My builder suugest using a Volkswagen brake switch (SLS-34 switch )
I need to source something so I can proceed the run fairly soon. ( my flaring tool is on loan from my mechanic buddy)

Wondered what you guys have used and can I find a generic switch?
I would guess its a 2 pin style thats normally open and closes on pressure..what kind of pressure we looking at for activation and reset??

I have the wildwood master floor mounted pedals and remore reservoirs. An electrical switch off the pedal would be more of a pain that the hydraulic tie in.

This info will help should I have to describe the operation to a counter guy.

Are these puppies a single input port in a 1/8 or 1/4 NPT thread??


Thanks
Tim

[jeff_taylor]

Tim,

I have a Pegasus Racing catalog that lists a hydraulic brake light switch with a 1/8 NPT male thread. The part number is #3601, the cost is $10.08 US. You can reach Pegasus at 1-800-688-6946, or on the web at
http://www.pegasusautoracing.com/

The switch has 2 pins for wiring connection and is normally open.
Good Luck!

[Whaler]

Jeff Thanks for the response.....I will follow up on your find.

Tim