Balance bar adjustment

[samier]

Having spoken to a few people I am getting different answers... some say set the rods coming out of the master cylinder as equal, others says they should only be equal when the pedal is pressed.

I am now confused as to how to set this up. The rod coming out of the front master cylinder s longer than the rear master cylinder. I belive that due to the greater volume of the front MC the rod should be longer than the rear.

Initially setup like this:


On someones advise I added a nut, so when fully screwed into the clevis the angle is level.

[tristancliffe]

This is how I set them up. Easier to post a link than to try and describe, so I Googled for a page that shows my method.

http://www.stockcarproducts.com/tech1k.htm

AP also have some info, but I didn't really understand the middle two options. What are the extra dotted lines representing? http://www.apracing.com/drawings/Balanc ... ttings.pdf

[phuston]

I am writing this so that those with greater skill in these matters can add their comments later.

The balance bar should be adjusted so that the front wheels generate a greater braking force than the rears.

This can be adjusted empirically by jacking the car so that all four wheels are off the ground, and exerting a small/moderate force on the brake pedal.

Adjust the balance bar so that it takes appreciably greater force to rotate the front wheels than the rears. This gives a reasonable starting point. Refining the brake balance is then done on the track.

Any lateral imbalance between the wheels on an axle means that you have a problem with your braking system.

The closer the balance bar is to operating at a right angle when under load the better but by its nature it is designed to operate through an angular range.

[samier]

As I understand there are 2 stages to the setup process. First is to get the initial setup regards to the MC rods and the adjuster bar central as well as making sure there is some slack so that the clevis does not bind against the cylinder.

I am getting conflicting views on that initial setup and dont know what the base position should be and what the position should be when the pedal is pressed.

Do I also need to bleed the system as part of the process? for it to be setup properly?

[schomosport]

[quote="samier"]As I understand there are 2 stages to the setup process. First is to get the initial setup regards to the MC rods and the adjuster bar central as well as making sure there is some slack so that the clevis does not bind against the cylinder.quote]

Yes you do need to get the mechanical arangement correct before worrying about how much bias you have either way. I had a similar problem where although both my cylinder rods were same length they were so unequally adjusted that one was only two turns into the clevis while the other was sticking all the way through the clevis. That amount of maladjustment potentially causes all sorts of mechanical problems through binding and mis-operation and needs sorting. I think this was the cause of some front end lock-up on my car because whatever I did with the bias adjuster made no difference. Taking it all apart and setting things up equally seems to have fixed it. Make sure you don't screw the adjusters in so far that they bind on the clevis pivot pins as that will also cause mis-operation. Doesn't look too far out in your pictures.

Yes you need to do it all with the brakes properly bled becasue the next step is to adjust it all so the pedal is in the correct position when you are seated. If the pedal pads are individually adjustable you might not have that problem.

Then initially set up bias as per Patrick's recommendation. It will be within a turn or two of corrrect.

Given the limited access can easily take half a day..................

[samier]

Ok so how should I do this?

2 rods coming out of the master cylinders, front is 5mm approx longer than the rear.

Should I remove that 5mm nut from the rear bar?

Fully screw both MC rods into the clevis? ( the front MC clevis will be higher than the rear.

Then depress the pedal fully and set the both clevis so they are level?

While all this is done, the Balance bar is dead centre. This will be adjusted to fine tune the balance.

Please correct me and point out anything I may be about to do wrong...

http://www.apracing.com/drawings/Balanc ... ttings.pdf

AP guide contradicts this

http://www.bgcmotorsport.co.uk/faq.html

[tristancliffe]

My method would be

1. Connect it all up however (and remove the spacer nut for the time being) and bleed the brakes. Get all the air out. If possible do a front and rear caliper at the same time so that you get full travel on both master cylinders with the bias bar binding.

2. Set rough brake balance by turning front wheels until they just lock and making sure the rears are similar or a little easier to turn. The bias bar will be vaguely close to where it'll be once you're done.

3. Set your throttle pedal so that any stops work where they need to (zero and full throttle) and that you actually get this on the engine end too.

4. Screw push rods of m'cyls so that the brake pedal is a bit higher than the throttle when you're not pressing either of them.

5. Adjust angle of bias bar using push rod lengths, keeping pedal in same position relative to throttle pedal. Get it so that the bias bar is at a slight angle.

6. Press the pedal with all your might and see (get a friend) if the bias bar goes past 90° and starts to angle in the other direction. Tweak pushrods until this occurs AND keeps the pedal positions correct for heel&toe. This should mean that at moderate pressure the bias bar is not inclined.

7. Check that the front and rear brakes are coming on at the same time as per step 2, that the pedal up position allows heel&toe, and that the bias bar isn't binding up at any point.

8. Check that you have enough threads of the pushrod into the clevis. At LEAST 5, but ideally 8 or more.

9. Fit lock nuts and tighten up.

10. Refine bias on the track to suit what you want. As a novice you'll need more front bias in the dry, and gradually add rear bias as your experience, ability and comfort increases. In the wet you'll want more rear bias as well, but not so much that the rears lock first (obviously).


I'd also be tempted to say that as long as you have enough threads in the clevis, that you bleed the brakes properly, and if the bar isn't running out of angular travel then you will be fine. Everything else can be sorted on the bias bar and/or when you've worked out how you use the brake pedal in real life situations. It's hard to emulate how hard you press the pedal whilst in a workshop!