Hydraulic Handbrake Setup

[TJR32GTS-T]

G'day guys, finished putting in my hydraulic handbrake today and I'm having issues, there is pressure in the handbrake but it's not locking the rear wheels.

I have bled the whole brake system and still no go.

It's not running a separate booster just taped into the rear brake line.

My next plan of attack is to machine the rotors and fit new pads and see if that helps.

Any other ideas would be greatly appreciated.

Cheers - Trent

[GTSBoy]

Have you thought about what happens when you push brake fluid into the rear brake line? ie, is it venting through the master cylinder into the brake reservior in the engine bay?

[TJR32GTS-T]

I don't know is it?

[GTSBoy]

I'm not sure if there's a valve at the main MC that will stop it from happening. The thing is, you have to close your eyes and imagine the insides of the main MC. In the back half of it there is a piston. In front of the piston in the cylinder itself, there is brake fluid. At the top of the cylinder there is a hole connected to the back half of the fluid reservior. At the bottom of the cylinder (and further forward than the hole in the top) there is a hole that leads to your rear brake line.

So when you push the brake pedal, the piston moves forwards and blocks off the hole at the top (stopping fluid from being pushed up into the reservoir) and the resulting displacement of fluid gets pushed out the brake line to work your brakes. The pads move to take up the knock off, then the pressure in the line rises (with no further displacement). When you let off the pedal, the reverse happens. The pressure is relaxed and pad knock off pushes the little bit of displaced fluid back into the cylinder. If there is ever any leakage, the loss is made up from the reservior.

But what if you jam fluid into the same brake line at some point half way along with another, separate master cylinder? (Sound familiar?) You squeeze fluid into the line, and you expect it to raise the pressure, this pushing the pads onto the disk, as if you were using the normal MC. But I reckon that what happens is that the fluid takes the easy path up into the main MC's reserviour, because that is all open to flow.

I don't know about hydraulic handbrakes real well, because I've never had need or want to play with them, but I expect that if they get put on the normal main rear brake line then you have to pull some shenanigans with check valves or something to make them work.

[blind_elk]

Usually, a hydraulic handbrake "master" is not like a normal master. The fluid can only be pushed in one direction. The problems that can arise is if you plumb the master in the wrong way. My experience is that the fluid comes in the rear fitting and out the front fitting - so the fluid does a sort of "loop-the-loop" on its path from the MC to the rear brake.

Also, make sure the HB master has been bled properly before bleeding the rear brakes.

Q. - what is the reason for the hydraulic HB? Does it replace the existing HB, or is it additional to it? If it replaces the existing HB, make sure the car is ALWAYS parked in gear, because a hydraulic HB will gradually lose pressure and slowly release the handbrake. (been there, done that! car ended up across the road, and reportedly just missed another car that drove past the driveway)

[TJR32GTS-T]

It's for my drift car. And it is replacing my existing one.

Thanks for the heads up blind elk haha

Yeah we have it plumbed in with the fluid going into the rear fitting and out the top/front.

I'll give the hydraulic hb another bleed and see what happens.

I'm sure there is some very useful infomation in what you've written gtsboy but to me it's all jibberish

[bluey33]

So many people have issues bleeding these correctly.

How Are you bleeding it?

What size master or you using on it?

GTSboy is talking about the compensation ports that allow fluid to go back into reservoir. These are blocked when you hit your foot pedal so fluid can't go back into reservoir.

Hydraulic handbrakes run a one way valve to compensate for what he is talking about. Hence If you put the lines back to front it would not work at all.

[TJR32GTS-T]

Standard master, any recommendations in what master to run? Maybe a r33 one?

To bleed it I'm undoing a fitting at the handbrake , giving it a few pumps then holding it engaged and tightening fitting, and repeating that process and then the same at the rear brakes with the foot brake.

I need to know now what a good master Replacment will be.

Thanks for the advice guys - Trent

[TJR32GTS-T]

Just did abit of reading my current master is 15/16" bore size, can anyone confirm if 33 masters are 1"?

[bluey33]

I meant what size master on the HHB? Standard brake master won't be an issue.

I found best way to bleed it up is to bleed HHB master using the HHB lever as you were but also push foot pedal. Then do the same for rear calipers. (using both)

This is how I found get a better bleed and feel.

It's also important to get your free play right on the lever.

[TJR32GTS-T]

Thanks for that mate, I was at the workshop 2night and we took the brake booster out of my 180b and are now running that with the hydro. Final touches 2moro and we'll see how we go