Setting up a pedal box issues!!

[pdapaul]

Right, I'm getting nowhere fast with the brakes, and could really go with some input. I've taken done videos to try and show the issues.
Problems I can see:
the balance bar doesn't seem to be moving as I need. It pretty much just goes back and forwards at the same angle.
The rear m/c literally needs 5mm to be fully on. The front needs at least 20 to be fully activated.

Video 1-
Everything is connected. The balance bar is approx 45 degrees as it should be and the rear mc rod is shortened. This is with the pedal pressed as hard as possible. As you can see the rear m/c throw is so short that the front barely moves.

Video 2
This is with the rear m/c removed. As you can see it literally barely moves. But it does work the rear brake even at this small movement.

Video 3
This is with the rear m/c removed from the pedal box. As you can see the rod travel is quite long. At its fullest extension the brake pedal is nearly touching the floor and there is very little pedal pressure.

My thoughts:

I think that my issues are 2 fold. I think there is an issue with the rear m/c as I don't believe that the throw can possibly be supposed to be that short. Secondly I think that the fronts are bled properly. It was all bled with both m/c in place. This would mean that when the front calipers were being bled that the rod was hardly being moved at all, this leaving air in the system.

When the box was put together the rear calipers didn't bleed as no fluid was getting to them. I tested the m/c..seemed fine..put it on the car ..no output. Eventually it just suddenly started flowing fluid, and seemed to bleed fine.

Any help would be appreciated, otherwise I'm going back to OEM.
Cheers

 

[Eoghain]

Couple of questions,

What size are the cylinders for the front and rear and what calipers are you using?
With the cylinders disconnected from the balance bar can you freely move the balance bar for and back? what im getting at here is, is there enough clearance between the two pivot nuts the bar can pivot when you push it?

On you first video the pedal box is set up wrong, the balance bar should be level at rest and go to approx 45 degrees when the pedal is pressed. Your two cylinder rods should be the same length within a couple of millimetres of each other.

 

[Eoghain]

Also, are you sure your bias valve is open fully when bleeding?

 

[pdapaul]

Hi bud,
Thanks for the reply and I think you've hit the nail on the head the first time! Ive asked the same question in my build thread, and they also pointed out the same issues. I think that the balance bar settings are hindering it working properly. It all feels very tight, and like you say the angle being so severe at rest I think is causing it.

I can't remember the bias settings, but I don't remember setting it at all so I'll bleed them all again.

I really appreciate your replies and I'll let you know how I get on.

Cheers

 

[Eoghain]

When its at rest it should feel almost sloppy left to right along the length of the balance bar, if its all too tight when at rest you are likely to have binding of the brakes when the brake fluid gets hot. There also should be no weight from the rods of the cylinders against the piston inside the cylinder when at rest, only talking about 1mm here, just a bit of room to allow the fluid to move when everything gets hot.

I've set up a good few of that type and another trick is to redrill the hole on the pedal as high as possible to get extra leverage on the pedal box and also brace the pedal box in the engine bay as you'll see the bulkhead flexing alot and it WILL eventually crack.

 

[pdapaul]

Then it's definitely wrong, as I struggle to move the threaded balance bar at all when at rest. Putting pressure on the brake pedal loosens it up to enable me to adjust it.

I'll get a brake stopper fabbed up then if it's going to be an issue!!

Cheers bud

 

[Eoghain]

No problem!

just make sure your balance bar is level at rest, you might need to get a new rod for you back cylinder!

 

[pdapaul]

Hi guys,
Thanks for all of your help, but it has become apparent to me that I just don't know enough about this type of system to make it viable. I'm racing next weekend, and time is running short.
I'm going back to an OEM m/c and servo for the moment until I can get the time to sort the pedal box

Cheers again for your messages, everything you've said makes sense, but when I try to apply in the real world it seems that something isn't right!