Just call me .... Howard Jr.

[Mike]

Alex,

It would have been near 50:50, not binding, but not bias adjustable.

I beg to differ.

Put the system together the way it is in the first picture on an operating car that has been brake system tuned, and see what happens to the bias bar. It WILL bind.

Again, I thought maybe it was set up that way for mock up purposes or something, but I guess not. Whatever the case, Alex now knows of the possible issue and can address it.

(potential) Problem fixed via forum. It did it's job.

 

[Alex]

I don't know how far along you are but there really isn't much point in trying to finalize the peddle box position and brake bias until the car is running. Brake bias adjustment is the first thing to do once the car will move under it's own power but you will need to drive the car to do so.

I have put together the entire brake system but will leave it dry and as new until I am ready to begin driving the car. Filling up the brakes with fluid and letting it set for a year isn't a very good idea. You may need to remove something like a master cylinder and the fluid will just create a mess. Brake oil will become contaminated with water over time and you might just as well wait until you need it in the system to fill it.

The bias bar does look wrong until you fill the masters with fluid and bleed the system. The travel of the masters is way to much dry to get any idea how the bias system works.

I have no intention of putting any fluid in until it's ready to roll

The nice thing about the adjustable idea is that I can set where I think it's going to be sitting there and playing with the pedals, then have around 2.5'' of forward/back travel available if I need to change it down the road. The side-to-side travel of the assembly isn't really a concern because on one side you have the LCA box, and on the other I need to keep it clear to figure out how to run a gas pedal cable, so that pretty much eliminates any side-to-side potential adjustment.

but I will undo what I did with the balance bar.

I beg to differ.

Put the system together the way it is in the first picture on an operating car that has been brake system tuned, and see what happens to the bias bar. It WILL bind.

Again, I thought maybe it was set up that way for mock up purposes or something, but I guess not. Whatever the case, Alex now knows of the possible issue and can address it.

(potential) Problem fixed via forum. It did it's job.

I still don't get though how it can bind - if both rods are even, and both rods start and stop at the same position, how can a bind occur?

 

[Cam]

Huh, this looks like the standard Wilwood balance bar with some flat washers added. Here's more form Wil Wood:
BALANCE BAR ADJUSTMENT
The balance bar is an adjustable lever (usually a threaded rod), that pivots on a spherical bearing and uses two separate
master cylinders for the front and rear brakes. Most balance bars are part of a pedal assembly that also provides a mounting
for the master cylinders. When the balance bar is centered, it pushes equally on both master cylinders creating equal pressure,
given that the master cylinders are the same size bore. When adjusted as far as possible toward one master cylinder it
will push approximately twice as hard on that cylinder as the other, Figure 2.
Thread the master cylinder pushrods through their respective clevises to obtain the desired position. Threading one
pushrod into its respective clevis means threading the other one out the same amount. Sometimes this will lead to a
“cocked” balance bar when the pedal is in the relaxed position, see Figure 2, “no pedal effort”. This is perfectly acceptable
as long as each master cylinder pushrod is completely free of pressure when the pedal is relaxed.
Notes:
To obtain maximum performance from your brake system you should utilize Wilwoods quick check gauge, P/N 260-0966.
This gauge allows for quick brake line pressure checks from 0 - 1,500 psi for assisting brake bias set-up.
A flexible hose or cable connecting the balance bar (threaded rod) to an accessible knob or crank (similar to a drill auger) is
a popular way of adjusting brake bias to accommodate changes in track conditions and vehicle handling.
FRONT M/C
REAR M/C
FRONT M/C
REAR M/C
FRONT M/C
REAR M/C
NO PEDAL EFFORT
NOTE:
THE PUSHROD ADJUSTMENT DEPICTED IN THIS FIGURE IS REPRESENTATIVE OF A TYPICAL ASPHALT APPLICATION.
THAT IS, LARGE CALIPER PISTONS IN FRONT, SMALL CALIPER PISTONS IN THE REAR.

 

[Wayne]

Alex,
Fran designed the pedal assembly correctly. Balance bar is adjustable for pushrod travel for each mc. No binding. Howard and Cam got it right.
Regarding pedal placement: Because you have 2.5" travel front to back, center your plate. I mounted mine 12.5" from the 2" crossmember by the seat and 4" from the left side foot well. I drilled/tapped the 1/4" floor pan , so moving pedals 2" for/aft is easy.

 

[Mike]

Alex,
Fran designed the pedal assembly correctly. Balance bar is adjustable for pushrod travel for each mc. No binding. Howard and Cam got it right.

Did you even LOOK at the pictures?

I never said that Fran got anything wrong. What I said was that the way the pedal assembly was setup IN THAT PICTURE with the added spacers and tightened down so that no rotation could occur, WILL CAUSE A BINDING AND NO BIAS ADJUSTABILITY.

Alex just needs to see how one works in application and all will be well. He will understand it and be able to set it up properly. I'm 100% confident in that.

 

[Mike]

I still don't get though how it can bind - if both rods are even, and both rods start and stop at the same position, how can a bind occur?

They start in the same position, but the do not end up in the same position, which is why there needs to be space between the clevises and the pedal, and why the crossbar needs to be able to rotate.

 

[Alex]

The balance bar has defeated me for today.

i removed the washers except for 1 and ended up with this - it's similar to the photo of the car Craig built, so I'm on the right track

the problem is the outer balance bar is very crooked - but before you say it's right when it looks wrong, i almost need vice grips in order to spin the rod forwards/backwards. That can't be right.

I put my washers back and I can freely spin both bars by hand .... according to the Wilwood manual, it's acceptable for the balance bar to be crooked; it is NOT acceptable for the push rods to be crooked, so be definition I need to use the washers to make sure the rods are going straight into the master cylinders?

But on another note I got my pedal box mounted in today. Dave's velcro trick did the job and kept it held solid while I tested out the clutch pedal to find the right place for the assembly (I'm kind of surprised it worked - i would have expected the force of pushing the clutch pedal to cause it to move around, but it didn't) ... thanks Dave. :thumbsup:

 

[Alex]

edit: Cam, do you have any problems braking? I've noticed you've shimmed yours as well to ensure cylinder rods are perfectly straight

http://www.gt40s.com/forum/282017-post81.html

 

[Jac Mac]

The balance bar has defeated me for today.

i removed the washers except for 1 and ended up with this - it's similar to the photo of the car Craig built, so I'm on the right track

the problem is the outer balance bar is very crooked - but before you say it's right when it looks wrong, i almost need vice grips in order to spin the rod forwards/backwards. That can't be right.

I put my washers back and I can freely spin both bars by hand .... according to the Wilwood manual, it's acceptable for the balance bar to be crooked; it is NOT acceptable for the push rods to be crooked, so be definition I need to use the washers to make sure the rods are going straight into the master cylinders?

But on another note I got my pedal box mounted in today. Dave's velcro trick did the job and kept it held solid while I tested out the clutch pedal to find the right place for the assembly (I'm kind of surprised it worked - i would have expected the force of pushing the clutch pedal to cause it to move around, but it didn't) ... thanks Dave. :thumbsup:

You sure do make an easy task seem difficult Alex. All that you have done wrong this time is screw the threaded part of the pushrod clevis a few too many turns onto the balance bar. The distance from center of one of these to the center of the other should be the same as the two brake master cyls are apart, ie when viewed from above the two pushrods for the two brake cyls should be parallel--- in the pic you posted they converge toward the pedal/balance bar end...

 

[Howard Jones]

Like this. It's OK if it seams to flop about a bit. It's meant to work like that. When the system is full of fluid and properly bled peddle travel will be restricted and it will all be revealed. It's OK for now. Work on something else.

 

[Alex]

ie when viewed from above the two pushrods for the two brake cyls should be parallel--- in the pic you posted they converge toward the pedal/balance bar end...

But that's why I used those thin washers as shims initially. Without shims I end up with the above (one rod almost straight, another crooked; no way of making them parallel). If I add in 3 shims, then the clevis is moved away from center, the rod becomes straight and thus both are parallel.

That's what making this so difficult for me to follow- if I use the shims I end up looking like the acceptable Wilwood picture (rods straight and parallel). if I don't use them I end up like the picture with a big x through it (rods crooked and not parallel)

Like this. It's OK if it seams to flop about a bit. It's meant to work like that. When the system is full of fluid and properly bled peddle travel will be restricted and it will all be revealed. It's OK for now. Work on something else.

Okay, I see what you've done - essentially the same thing I did except instead of using shims and keeping the balance bar equi-distant you spun the balance bar to the outer side and have a gap between the outer clevis and the brake pedal in order to achieve good rod alignment.

But that then leads to another question - why do you even have the washer in there, since it can vibrate back and forth (between the clevis and the brake pedal) on the balance bar? it seems like it's useless to have it there?