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  #1  
Old 04-04-2018, 09:35 PM
JoeVac JoeVac is offline
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Default 65 brake pedal travel.

Still trying to get brake pedal feel and travel to where I think it should be, but may be chasing my tail on this one.

Brake pedal is 4 inches off the floor, 1/2 inch of free play. Front discs start to engage at 3 inches off floor, and rears start to engage at 2 inches off floor.

Is this normal for 65 birds or am I missing something?

New booster, MC, all hard and flex lines, new rear brakes and hardware, new wheel cylinders, rears adjusted fairly tight, and bled till doomsday. Booster pushrod moves MC piston at 1/2 inch travel.

How sensitive are these power brakes supposed to be? Any help will be really appreciated,,,Thanks,,,Joe
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Old 04-04-2018, 10:05 PM
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How did you adjust the new booster to the new M/C? What is your clearance? - Dave
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Old 04-04-2018, 10:10 PM
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Dave, made a guage as in shop manual,,used that to set clearance. had my wife sit in car as I watched master cylinder piston. She just took up free play in pedal and MC piston moves with slight touch of brake pedal.
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Old 04-04-2018, 10:30 PM
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P.S. pinched off front and rear flex lines,,pedal went to 3 inches off floor,,better, but not where I want it.
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Old 04-05-2018, 01:49 AM
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Quote:
Originally Posted by JoeVac View Post
Dave, made a guage as in shop manual,,used that to set clearance. had my wife sit in car as I watched master cylinder piston. She just took up free play in pedal and MC piston moves with slight touch of brake pedal.
Every new booster and master combination that I've ever worked on has their own unique setting. Most people never know this because it's already set when you get the car and rarely does the M/C require replacement.

My 'special tool' for a crush-gauge is really food. Don't laugh but I use a piece of American cheese, still in the wrapper. I cut a square of it and stick it in the M/C input hole.

The output shaft of your booster has an adjustment 'jack screw'. Only press the brake pedal to expose this screw for your adjustments, then leave the pedal alone until done.

'Marry' the M/C and booster w/cheese, then disassemble and look at the cheese. Keep adjusting the screw out until the cheese is squeezed out at the point of contact. Then, remove the cheese and adjust the screw out a tiny bit more so the booster actually moves the M/C piston.

If you adjust too far out fluid from the lines and pistons will be trapped and will not return to the reservoir(s). Typically, the lines heat up, the fluid expands and the brakes will apply themselves. If this happens, back off on the jack screw just a little.

We've used DOT-3 ever since the 1940's and I hear horror stories about how it removes paint. DOT-3 is glycol-based (like antifreeze) and it instantly washes off with plain water.

Keep water and petroleum products away from your exposed M/C. I got buddies that won't open the reservoir cap if it's raining outside. That's how much DOT-3 sucks in water. - Dave
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Old 04-05-2018, 03:11 PM
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My 2-cents worth: The pedal on my ‘66 is about 2” off the carpet when the brakes are hard on - but that’s with barely enough pressure on the pedal to squeeze a lemon.

And at that level of pressure the wheels are locked up and you’re kissing the steering wheel!
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Old 04-05-2018, 11:16 PM
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Ok,,going to start from ground zero ,, going to totally remove MC from car so its easier to check booster pushrod clearance. should I set pushrod to just touch MC piston, and then a tiny bit more to just move The MC piston, or just touching?
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Old 04-05-2018, 11:51 PM
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You don't need to disconnect the brake line during this adjustment but you do need to unbolt the M/C from the booster.

If space is cramped, I use a small mirror to 'look around'.

I use the American cheese to determine when the output shaft of the booster just touches the M/C piston. The cheese will squish out of the way leaving a witness mark.

Then, I remove the cheese and adjust a tiny bit more so that the M/C piston just starts to move. Done.

This will take out any mechanical 'lash' between the booster and master but still allow the piston to fully retract. At the same time, brake line fluid will freely return to the reservoir. - Dave
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Old 04-08-2018, 08:18 PM
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Readjusted booster pushrod to .996,, master cylinder bore is .995 deep. Not much change in pedal feel. maybe 1/2 inch better. Brakes rebled. Not sure if that's just the way it is,,no experience with Birds of this era.

Going to make a power bleeder and do that and call it good. thanks for all the help and info.
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Old 04-08-2018, 10:52 PM
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Quote:
Originally Posted by JoeVac View Post
...Brake pedal is 4 inches off the floor, 1/2 inch of free play. Front discs start to engage at 3 inches off floor, and rears start to engage at 2 inches off floor.

...Booster pushrod moves MC piston at 1/2 inch travel...
Ok, now that your M/C is correctly adjusted, I have to ask, what type of brake fluid are you using?

DOT-3 won't compress. DOT-5 gives a spongy-feel because of the silicone in it. I always suggest using DOT-3 but that's another discussion. We'll get into it if you like but later.

Are your rear brakes adjusted correctly? I usually tighten up the star wheel, then back it off. Simply adjusting until you hear the shoes 'scuff' can change if someone applies the brakes, then lets off of the pedal. BTW, do you have working self-adjusters in the rear?

A combination proportioning valve applies the rear brakes first, then it holds back pressure in the rear circuit in proportion to the front circuit. So, rears should come in first for better control of the car, especially on wet leaves or loose gravel. Then, the front disks do 80% of the stopping power.

If you have new pads and shoes that aren't 'bedded-in' yet, your brakes will improve as you use them. Stay on top of rear shoe adjustments for a while. - Dave
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