Opinion: Do you feel that two brake reservoirs are preferrable to one?

[jeskam]

Just wondering if I should buy two more in addition to the one included with the kit (for the clutch and two have one for front brakes/1 for rear brakes).

[CaptB]

YES. To me its a safety issue.

[narly1]

I'm going the double route for my build. It's a cheap measure to take in order to ensure that you at least have braking on 1 axle (instead of NONE) in the event of a failure, IMO.

Earl

[jeskam]

Good point Earl.. thanks!

[narly1]

The possibility of a complete brake fluid leak-out before you get the car slowed down enough are pretty slim, but for the cost of an extra reservoir why take the chance?

Earl

[Mike.Bray]

Yes for safety.

Also makes it easier to power bleed.

[F500guy]

When I hit the track, I would prefer 2. Street only I probably would have done just 1.

[gbranham]

For those who run two reservoirs for safety, what do you do in your daily driver vehicles? Aren't they all single reservoir? I get it...building a car from scratch, not a lot of extra money, so why not, but do you ever worry about the lack of redundancy in your daily driver?

I'm just running the single kit-supplied reservoir. I figure I've never had a brake failure in 50+ cars and likely millions of miles in my daily drivers, so I'm not going to worry about it here, for a weekend cruiser that won't see track time. Not criticizing...just curious.

[Mike.Bray]

For those who run two reservoirs for safety, what do you do in your daily driver vehicles? Aren't they all single reservoir? I get it...building a car from scratch, not a lot of extra money, so why not, but do you ever worry about the lack of redundancy in your daily driver?

I'm just running the single kit-supplied reservoir. I figure I've never had a brake failure in 50+ cars and likely millions of miles in my daily drivers, so I'm not going to worry about it here, for a weekend cruiser that won't see track time. Not criticizing...just curious.

A lot of OEM cars & trucks have separate reservoirs. They may be in the same MC but they are there. And OEMs invest millions and millions of dollars plus endless testing of their systems. An FFR kit car has not had anywhere close to this level of R&D not to mention the difference in performance from your wife's grocery getter. I'll spend the extra for another reservoir for my FFR car.

[RoadRacer]

If one fails, and you have a balance bar, then all(most) the pedal effort goes to the failed side.. just saying it's not the safety plus that most people think it is.

But the only failure I've heard of is the MC seals, not reservoir related.

[CaptB]

Single res' in today's cars is very rare. Many cars from the 60's and before were "mason jar" single res'.

[gbranham]

Single res' in today's cars is very rare. Many cars from the 60's and before were "mason jar" single res'.


So now I'm curious. I have a 2018 Cayenne Turbo and a 2024 RAM 1500...I need to go look at their reservoir setups!

[Norm B]

All modern vehicles are dual compartment reservoirs. The master cylinder has an inlets for each of the front and rear circuits. They also have a proportioning valve that is supposed to isolate each front wheel and the front from the rear in case of a wheel cylinder failure. The reservoir also has a sensor that warns of low fluid level. All these components are required to pass inspection where I live.
I used the red dash light, through a relay, to indicate if the fluid is low or the park brake on.

At the very least, dual reservoirs aren’t going to hurt anything.

Norm

[Papa]

If one fails, and you have a balance bar, then all(most) the pedal effort goes to the failed side.. just saying it's not the safety plus that most people think it is.

But the only failure I've heard of is the MC seals, not reservoir related.

I was going to say the same thing. There are several old threads that mention this same consideration with the balance bar. I'd be interested in any real data/testing that shows what would happen in a total loss of fluid from one reservoir in a balance bar brake system. I wonder if a larger single reservoir would be a more effective safety measure?

[RoadRacer]

I was going to say the same thing. There are several old threads that mention this same consideration with the balance bar. I'd be interested in any real data/testing that shows what would happen in a total loss of fluid from one reservoir in a balance bar brake system. I wonder if a larger single reservoir would be a more effective safety measure?

My thoughts on testing this is to simply open a front bleed valve and depress the pedal - and see if the rear brakes work at all. Easy to do with the car in the air. And then try it reversed. I expect that the balance bar will still have some pressure on the good side but how much will be interesting to test.

[CraigS]

To check a modern reservoir be sure to remove the cap. That way you may be able to see the divider wall inside.

[Jeff Kleiner]

If one fails, and you have a balance bar, then all(most) the pedal effort goes to the failed side.. just saying it's not the safety plus that most people think it is.



James,
You are one of the few here who actually get it! I've had this very conversation with Jim Schenck and you are exactly right...open one end and the balance bar is going to pivot to that end and do nothing to the other. One reservoir or two won't change that.

Jeff

[rthomas98]

I run two reservoirs and it has nothing to do with safety. It is strickly to allow me to more quickly diagnose where a brake leak might develop. If I feel the pedal getting mushy I can open the reservoir and see if it is the front or the back brakes where the issue is based on the amount fluid in it. The one with the lower fluid is the area of the car to look first.

[gbranham]

I run two reservoirs and it has nothing to do with safety. It is strickly to allow me to more quickly diagnose where a brake leak might develop. If I feel the pedal getting mushy I can open the reservoir and see if it is the front or the back brakes where the issue is based on the amount fluid in it. The one with the lower fluid is the area of the car to look first.

That makes a lot of sense. Now I'm rethinking the single reservoir, for this reason. Thanks!

[nashuanuke]

Build school recommends two. I assume the original had one and that's why FFR only provides one. You can buy an extra from FFR off their parts catalogue, that's what I did, got it during the black friday sale. Or obviously source something elsewhere.

[Mastertech5]

Using 2 just makes things easier for a variety of reasons, all mentioned above. Personally I have a clutch so I used the one that came with the hydraulic clutch kit for the rears and bought a smaller Willwood one from Summit for the clutch.

[GoDadGo]

Because I'm running a hydraulic clutch, I'm running a triple reservoir.
I'd recommend separating each MC if possible.

[egchewy79]

2 for me, front and rear, but as mentioned before, not for safety as the brake bias will tip towards the side that has failed, also not allowing for brake pressure to the remaining side.
I found this out trying to test the brakes after only having plumbed half the system.

[Hoooper]

For those who run two reservoirs for safety, what do you do in your daily driver vehicles? Aren't they all single reservoir? I get it...building a car from scratch, not a lot of extra money, so why not, but do you ever worry about the lack of redundancy in your daily driver?

I'm just running the single kit-supplied reservoir. I figure I've never had a brake failure in 50+ cars and likely millions of miles in my daily drivers, so I'm not going to worry about it here, for a weekend cruiser that won't see track time. Not criticizing...just curious.

How new is new? New cars have split single reservoirs, so functionally its two reservoirs. Most truly new cars have ABS with individual circuit pressure sensing so not only do they have dual reservoirs feeding the system they also sense if any individual circuit has a pressure lower than expected and shuts that circuit off so you still have braking to the other wheels.

[facultyofmusic]

To me the line between "old" and "new" is whether or not the car can detect brake leak/issues and scream at you before you get into trouble. With brake-line pressure sensors the cars can go into limp mode before you get yourself into an accident. Our cars though...

[MisterAdam]

For those who run two reservoirs for safety, what do you do in your daily driver vehicles? Aren't they all single reservoir? I get it...building a car from scratch, not a lot of extra money, so why not, but do you ever worry about the lack of redundancy in your daily driver?

I'm just running the single kit-supplied reservoir. I figure I've never had a brake failure in 50+ cars and likely millions of miles in my daily drivers, so I'm not going to worry about it here, for a weekend cruiser that won't see track time. Not criticizing...just curious.

I am with you. Also, how much fluid do you think is being displaced. Single reservoirs in all my daily drivers and have never had a brake failure. Stop over thinking.

[Norm B]

I am with you. Also, how much fluid do you think is being displaced. Single reservoirs in all my daily drivers and have never had a brake failure. Stop over thinking.
Wrong! They are a split reservoir with a single fill point as already stated multiple times. They also are required to have low fluid sensor to warn you of a fluid leak. As mentioned, other safety measures are also included in OEM brake systems that aren’t readily apparent.
Not sure dual reservoirs add any safety to a dual master cylinder balance bar brake system but it won’t hurt. The experts on these cars say it won’t and for that reason, I am pretty sure that the system, as supplied, would not get DOT or MOT approval for use on a street use vehicle from any of the automakers.

[Mike.Bray]

To summarize what we've learned:

One reservoir for both front & rear brakes works fine.

Individual reservoirs for front & rear brakes works fine.

Individual reservoirs do not offer any safety benefit because of the balance bar.

Majority of OEM brake systems have individual reservoirs but cannot be compared to the FFR setup.

Individual reservoirs allow easier troubleshooting of leaks by observing fluid level for front vs. rear brakes.

FFR build school recommends dual reservoirs.

Individual reservoirs allows for pressure bleeding.

[MisterAdam]

Wrong! They are a split reservoir with a single fill point as already stated multiple times. They also are required to have low fluid sensor to warn you of a fluid leak. As mentioned, other safety measures are also included in OEM brake systems that aren’t readily apparent.
Not sure dual reservoirs add any safety to a dual master cylinder balance bar brake system but it won’t hurt. The experts on these cars say it won’t and for that reason, I am pretty sure that the system, as supplied, would not get DOT or MOT approval for use on a street use vehicle from any of the automakers.

You know what the say about opinions.
Everyone on here is an expert…..do what you feel comfortable with.

[jeskam]

In the end I decided on a single reservoir. Simplicity won the day!

[gbranham]

In the end I decided on a single reservoir. Simplicity won the day!

Ditto...I'm staying with just one.

[UKSNAKE]

Thank you all for this discussion. Im looking at the reservoir bracket on my kitchen table at the moment trying to decide. Supplied bracket only holds 2 and Im going hydraulic clutch so will whatever i do i need one for that. I went with three together look cool under the hood so going to do that and just attach them to the frame. Looks cool and safe (except of course I have a balance bar so then Im probably back to just looks cool). Always appreciate everything you all post. I just wish i could work as quickly as you guys do.