One or Two Brake reservoirs

[Caddy Dad]

I'm almost at the point in my build where I'll need to run the hard brake lines and mount the brake reservoir. The kit came with one reservoir. Is that sufficient for both front and rear or should I purchase a second and run them separate?
Thanks!

[KenWilkinson]

I'm almost at the point in my build where I'll need to run the hard brake lines and mount the brake reservoir. The kit came with one reservoir. Is that sufficient for both front and rear or should I purchase a second and run them separate?
Thanks!
No question, two . One for front, one for back. This is for safety.

[GoDadGo]

No question, two . One for front, one for back. This is for safety.

Ditto, but in my case it's a triple reservoir since I'm running a hydraulic clutch.

[chrisarella]

Ditto, but in my case it's a triple reservoir since I'm running a hydraulic clutch.
Agreed on going with one in the front and one for the back for safety. And I also went with a Triple reservoir for my hydraulic clutch setup.

So basically: Ditto Ditto. 😂

[frankb]

Ditto, Ditto, Ditto! Keep the front and rear brake systems separate...if one fails, the other will stop the car!

[edwardb]

This was talked about in another thread a couple years ago. Including a response from Jim Schenck at Factory Five. Check it out. https://thefactoryfiveforum.com/showthread.php?27202-Two-or-Three-Reservoirs. Based on responses on this and the other thread, many likely won't agree. But the single reservoir from Factory Five works and does provide safe stops in case of a failure. They would not sell it that way if not the case. Having said that, there are reasons to have more capacity and also when adding a hydraulic clutch.

[FFinisher]

Ditto, Ditto, Ditto! Keep the front and rear brake systems separate...if one fails, the other will stop the car!

Not true.

With one reservoir or two, if a line fails or there is no pressure in one of the systems, the pedal box (balance bar)will depress the one with the least resistance (the one with no pressure) and you won't have any brakes. The one with fluid will have high resistance and the balance bar will offset to the one with no pressure.

Once you bleed the brakes you will see what I mean.

Also an answer no one will like.

Extra capacity is ok, but you only need enough to function the brakes , any more is wasted.

[Jeff Kleiner]

Not true.

With one reservoir or two, if a line fails or there is no pressure in one of the systems, the pedal box (balance bar)will depress the one with the least resistance (the one with no pressure) and you won't have any brakes. The one with fluid will have high resistance and the balance bar will offset to the one with no pressure.

Once you bleed the brakes you will see what I mean.

Also an answer no one will like.

Extra capacity is ok, but you only need enough to function the brakes , any more is wasted.

I’m glad you stepped up to say it because I didn’t want to have to be the one to start the $hitstorm with all the guys who think they know better. It’s all yours now Brother ;)

Jeff

[GoDadGo]

Jeff & FF,

Thanks for the enlightenment!

Steve

[edwardb]

Jeff & FF,

Thanks for the enlightenment!

Steve

Same thing Factory Five said in the link I posted in #6. But hey, who's counting? ;)

[chrisarella]

I always thought the "safety" aspect was the added insurance of having plenty of fluid supplied in the reservoir(s) going to each master cylinder separately, so if you ran too low and/or sucked in air you still had a working pair of brakes. No? Asking for a friend. lol

[frankb]

Jeff: My eyes are now open! Thanks for that!

[Avalanche325]

OK I'll bite. But more with a question.

Yes the balance bar will push the M/C with the least resistance......until it bottoms out. Then it will start to push on the one with pressure. Is there not enough pedal travel for that? I don't remember hitting the floor when I was doing my initial bleed, but that was a long time ago.

[NAZ]

If the balance bar style pedal assembly is not adjusted correctly and if the installation does not allow full travel of both M/Cs -- then yes, you could have a situation where a failure of front or rear could result in loss of both systems. Knowing that these cars are built by amateurs I'd bet there are some out there that have that failure potential built into their rides.

However, if the balance bar side gap is set according to Wilwood's directions AND you have installed the pedal assembly so you have full travel, you will still have one system operational if the other should fail.

The original question of one reservoir or two -- the reservoir included in my kit was sufficient (yes I did the math) but I elected to run two separate reservoirs for more fluid capacity. I also made sure I had plenty of hose from the reservoirs to the M/C -- hose = fluid capacity.

BTW, I've had system failures so I'm maybe a bit more cautious about how I set-up my brake systems. A failure can be a slight leak (best case) where the pedal slowly drops to the limit and provides some breaking force on its way down or can be a instant large leak where the pedal drops to the limit quickly with no braking action on the failed system. In the case of a slow leak the reserve fluid will come in handy as you can still pump on the pedal and get some breaking. In the case of the second failure mode you better have a good backup system or you will eventually will stop when you run out of energy or hit something.

[lance corsi]

I’m quite sure that a single reservoir would not pass inspection in Ohio. I totally agree with Naz.

[AdamIsAdam]

I always thought that modern brakes used two systems diagonal, so if you lost one, you still have 1 front and 1 rear wheel braking. Is that not the case?

[NAZ]

I always thought that modern brakes used two systems diagonal, so if you lost one, you still have 1 front and 1 rear wheel braking. Is that not the case?

Adam, the typical set-up has the front and rears independent of each other. Should one end fail the other would provide breaking, of course at a reduced amount since only two tires & rotors (or drums) are effective. This was a Federal mandate sometime around 1967 so all cars sold in the US were required to have dual braking systems. Up until then it was common to have one M/C operate all four corners.

[Caddy Dad]

Adam, the typical set-up has the front and rears independent of each other. Should one end fail the other would provide breaking, of course at a reduced amount since only two tires & rotors (or drums) are effective. This was a Federal mandate sometime around 1967 so all cars sold in the US were required to have dual braking systems. Up until then it was common to have one M/C operate all four corners.

Yes, I can recall the time my 66 mustang MC failed on me with no warning. Fortunately, it happened just as I turned into a parking lot. I coasted to a stop with a little bit of help from my E-brake. Fun times!

[Murd]

Not true.

With one reservoir or two, if a line fails or there is no pressure in one of the systems, the pedal box (balance bar)will depress the one with the least resistance (the one with no pressure) and you won't have any brakes. The one with fluid will have high resistance and the balance bar will offset to the one with no pressure.

Once you bleed the brakes you will see what I mean.

Also an answer no one will like.

Extra capacity is ok, but you only need enough to function the brakes , any more is wasted.

I can confirm this is the case as it happened to me. Lost the front MC, pedal to the floor produced just enough drag on the rears to stop very slowly, engine braking slowed the car more than the brakes. Actually freaks me out more the more I think about it.
This is the reason everyone says you have to bleed front and rear at the same time, you run out of pedal travel before the MC bottoms out.
Now that I think about it, is this a FFR problem as opposed to a wilwood pedal box problem? The crossbar on the frame limits how high you can adjust the pedal, if the pedal could come up further you’d have more travel to completely bottom out the MCs.

[NAZ]

If you have two separate systems that are codependent you do not have a redundant braking system. If one system fails and the other also fails to provide braking capability, for whatever reason, that is a safety issue.



First, let me say that I respect FFinisher’s opinion and it’s important to consider opinions from those with subject matter experience. While our opinions differ, it is not a matter of one is right and the other is mistaken – divergent experiences do not necessarily invalidate. Most here are dealing with what FFR gave you. If there is a chassis component that stops the pedal before the M/C piston has bottomed in the bore, unless you’re willing and able to make design changes you will end up living with a less than ideal braking system. If you failed to adjust the side gap properly that may result in loss of redundancy as that side gap limits the independent travel of the balance bar and the amount of stroke of the failed M/C before the functioning M/C piston moves.

The information I provided in Post #14 is not just theory, but practical hands-on working with braking systems in general and the Wilwood balance bar systems in particular. The system in my car uses a Wilwood balance bar pedal assembly, Wilwood M/Cs, and Wilwood calipers. I sized the M/Cs for the calipers I’m using and the pedal assembly is installed so that I get full travel of the M/C pistons. I have adjusted the balance bar side gap per Wilwoods instructions and I have verified that if either the rear or front brake system fails the other will supply the same breaking force as when both systems are operating. While I have made significant modifications (improvements) to the FFR chassis, no modifications were made to the Wilwood, only changes in sizing of components to fit my needs.


Regardless of how you manage it, you really should have a redundant braking system so that if one end fails the other will provide some back-up stopping performance. And I am confident the Wilwood balance bar system can provide that redundancy.

[Tony_G]

Not true.

With one reservoir or two, if a line fails or there is no pressure in one of the systems, the pedal box (balance bar)will depress the one with the least resistance (the one with no pressure) and you won't have any brakes. The one with fluid will have high resistance and the balance bar will offset to the one with no pressure.

Once you bleed the brakes you will see what I mean.

Also an answer no one will like.

Extra capacity is ok, but you only need enough to function the brakes , any more is wasted.

Exactly what FFinisher said happened to me. I had the rear master cylinder fail with only about 1000 miles on it. I have dual reservoirs on a wilwood set up and when this happened I had almost no brakes.

[KenWilkinson]

Exactly what FFinisher said happened to me. I had the rear master cylinder fail with only about 1000 miles on it. I have dual reservoirs on a wilwood set up and when this happened I had almost no brakes.

Would love to hear what wilwood has to say on this! Since you experienced this, would you mine calling tech support on this?

[lance corsi]

I have learned a lot by reading Naz’s posts. From what I know about the Wildwood system, I can fully agree with Naz. Looks like I’ll need some fine tuning to get my system fully capable. Redundancy is very important to me. Redundancy is very important to me.

[MisterAdam]

NAZ......excellent response.

[AdamIsAdam]

I'm about to take delivery of my new-to-me Cobra. According to the builder/seller, it's got 13" Cobra R brakes up front and FFR 11.65 rear brakes. The master cylinder looks like some sort of OEM unit, not the FFR, right? So how do I know if I have properly working redundancy?


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[NAZ]

I'm about to take delivery of my new-to-me Cobra. According to the builder/seller, it's got 13" Cobra R brakes up front and FFR 11.65 rear brakes. The master cylinder looks like some sort of OEM unit, not the FFR, right? So how do I know if I have properly working redundancy?

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Here's how I check the systems. I have pressure transducers on the front and the rear so I can see what pressure I'm getting at each end (but a cheaper way is buying a gauge that adapts to a single caliper). Have a helper crack open a bleeder valve to simulate a failure on the front or rear while I maintain pedal pressure and watch the gauges. The failed end will go to zero and if the other end maintains pressure you know that failure mode will still have redundant breaking. Do the same on the other end. Remember to have your helper close the bleeder before you release pedal pressure so you don't suck air into the system. Top off the reservoirs when done. Takes me about 10-minutes total including set-up and topping off the fluid after the test.

[AdamIsAdam]

I asked and my setup is OEM 1993 Mustang cobra front brakes and master. Hopefully that means properly set up with redundancies.