Handbrake plumbing

Pete, Volvos bolt pattern is 5 on 4.25", I stink the later Maz-dog stuff is sumpin else. Not sure but sumpin.

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

D'oh! I thought it was 5 on 4.5, like the Mazdas and half of the (American) RWD Fords.

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.

Bringing this back.

If applying the foot brake, and then pulling the hydro hand brake (plumbed the way you guys mention), would the foot brake pedal not sink deeper since fluid is being displaced within the same system?

Why not plumb directly from the handbrake lever to the rear most brake calipers/drums lines with a master that has a reservoir? Something like this? This way, a minimal amount of fluid in the original brake system moves? In my head, this makes the most sense. But please, do tell me why it doesn't.

Need to plumb my handbrake soon .

Cheers,

Carthik

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Carthik S
1999 Honda Civic 2DR



Edited 2 time(s). Last edit at 01/23/2015 02:52PM by Carthik.

Quote
Carthik
If applying the foot brake, and then pulling the hydro hand brake (plumbed the way you guys mention), would the foot brake pedal not sink deeper since fluid is being displaced within the same system?

Why not plumb directly from the handbrake lever to the rear most brake calipers/drums lines with a master that has a reservoir? Something like this? This way, a minimal amount of fluid in the original brake system moves? In my head, this makes the most sense. But please, do tell me why it doesn't.

Q1 answer - Marginally and not enough to matter in slightest.

Q2 answer - the pressure would be applied to the caliper and the back side of your main master cylinder. Everytime you pushed the brakes you would be applying pressure to the back of the handbrake master. Not to mention double the lines and complexity for trying to solve a non-existant issue.

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Grant Hughes

You can use that if you use a shuttle valve, otherwise you will need another set of calipers out back.

AP Racing shuttle valves are ~$300. Hydraulic ones are ~$70, but I'm not sure if they will work with DOT brake fluid.

As far as the pedal changing while having both applied, there is a slight change. It's very minimal, but it's there. Others may have more experience, but I never had much of an issue with it.

I guess I didn't really think that through now did I, it goes both ways...

The idea of the pedal moving when the hydro brake is used bothers me, but I guess the only way to eliminate that would be to add an additional caliper to each side on the rear like they do on drift cars. Well, I'm not doing that.

Thanks for the input.


Cheers,

Carthik

*EDIT*
Just saw your post Robert, looking into these "shuttle valves".

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Carthik S
1999 Honda Civic 2DR



Edited 1 time(s). Last edit at 01/23/2015 03:07PM by Carthik.

Quote
Carthik
The idea of the pedal moving when the hydro brake is used bothers me

Get over it. It hasn't been a problem for the last like five thousand generations of rally drivers.

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Grant Hughes

Aha, so this isn't a problem that only bothers me but also the folks over at AP Racing. On their product page they specify that typical usage is for separating the hydraulic foot brake from the hydraulic hand brake.



Product page:
http://www.apracing.com/product_details/race_car/pedal_boxes/hand_brake_assemblies/cp5088-1-shuttle_valve.aspx

Plumbing pdf:
http://www.apracing.com/drawings/CP5088-1CD.pdf

Only thing is it seems the fancy AP Racing machining costs about $500 USD. There has to be a similar valve out the that can handle brake fluid for significantly less money. Like 10 times less money.

Now we just have to find it...

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Carthik S
1999 Honda Civic 2DR



Edited 3 time(s). Last edit at 01/23/2015 03:26PM by Carthik.

Oh no, what have I done! Most people just use a CNC staging brake, $150 and the fluid passes through.

Report back if you find a cheaper solution that can handle brake fluid. The benefit of the shuttle valve is that is you can an independent fluid supply, and if you have a failing MC... well it's less of a problem.

Downsides: Expensive as all get-out! The shuttle valve also has to move, so you will have increased pedal travel by adding it into the system.

Yeah Robert this is all your fault now!

Let's say your hard on the brakes, but not locking up, and want to lock up the rear. Will the gentle tug of the hydro handbrake be enough to open the valve? I'm guessing the pressure would have to be greater than than of your foot in combination with the size of the foot brake master cylinder.

Is this one of the downsides to a shuttle valve or am I not processing how it functions properly?

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Carthik S
1999 Honda Civic 2DR



Edited 1 time(s). Last edit at 01/23/2015 03:45PM by Carthik.

Quote
Carthik
If applying the foot brake, and then pulling the hydro hand brake (plumbed the way you guys mention), would the foot brake pedal not sink deeper since fluid is being displaced within the same system?

No, by pulling the handbrake the piston will close off the feed port (on the HB master) and the pressure coming from the foot pedal, so it wont do a thing to the pedal because it effectively blocks the rear system.

Quote

Why not plumb directly from the handbrake lever to the rear most brake calipers/drums lines with a master that has a reservoir? Something like this? This way, a minimal amount of fluid in the original brake system moves? In my head, this makes the most sense. But please, do tell me why it doesn't.

Reinventing the wheel never produced a round result. Just stick to what works because adding complexity to the system will not only make it less effective but add certain failure.

Quote
Carthik
Yeah Robert this is all your fault now!

Let's say your hard on the brakes, but not locking up, and want to lock up the rear. Will the gentle tug of the hydro handbrake be enough to open the valve? I'm guessing the pressure would have to be greater than than of your foot in combination with the size of the foot brake master cylinder.

Is this one of the downsides to a shuttle valve or am I not processing how it functions properly?

Nevermind

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.



Edited 1 time(s). Last edit at 01/26/2015 02:24PM by john vanlandingham.