65 brake pedal travel.

[JoeVac]

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

[simplyconnected]

How did you adjust the new booster to the new M/C? What is your clearance? - Dave

[JoeVac]

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.

[JoeVac]

P.S. pinched off front and rear flex lines,,pedal went to 3 inches off floor,,better, but not where I want it.

[simplyconnected]

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

[scumdog]

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!

[JoeVac]

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?

[simplyconnected]

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

[JoeVac]

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.

[simplyconnected]

...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

[JoeVac]

Using prestone DOT 3,, rear brakes and drums all new,,and all new hardware. adjusted fairly tight, slight drag. Hardly any miles on them, you're right, they may get better with use.

I rebuilt the proportioning valve a while back, but didn't trust it so I bought a Summit adjustable proportioning valve,,may reinstall original and see what happens.

How are the brakes on your bird? Minimal travel?

[simplyconnected]

I forgot to ask... what size piston is your M/C? I hope it's a one inch bore.

I have a '59 Galaxie Fordor w/two-stage 8" booster and dual-piston 1" M/C. My front calipers have 2.5" diameter pistons and my rear drums are stock 11". My emergency brake is stock as well.

This car is a huge grocery-getter but the brakes are right up there with most modern cars. The pedal is high and it will put everyone through the windshield if I jump on it (and I have, on I-75).

When the car had drums up front, it would pull one way when cold, then the other way when warmed up. Disk brakes with a prop valve straightened all that out. (I prefer the GM-style comb. prop. valve.) I can let go of the wheel, step on the brakes and the car stops straight as an arrow. My cousin has a '57 Chevy. I drove him to the airport when a little Asian car squirted in front of us. I had to slam on the brakes. Johnny was pinned to the dash when he said, "G'D@mn! I didn't think your car could do that!"

If you're using DOT-3 and a tiny bit of air is in the system, it will absorb out. Once your pads and shoes bed-in, they will work much better as well. So give your system a chance before passing judgement.

I see no problem with an adjustable prop valve EXCEPT, most of them are really 'flow control' valves. They don't adjust the proportioning feature at all. That means, they simply close down the size of the hole on the rear circuit. That's great but it won't work the same with different pedal pressures. - Dave

[JoeVac]

I'm "assuming" it's a 1 inch bore MC, ordered it for the 65 bird. I may put the original proportioning valve back in as there was little change with the aftermarket one. Seems to me it does more than limit pressure to the rear brakes with all the parts and orifices in it. Does it also hold a small amount of pressure to the rears? Learning more about brakes than I ever thought. I always thought that the early cars had pretty sensitive brakes.

[simplyconnected]

... Seems to me it does more than limit pressure to the rear brakes with all the parts and orifices in it. Does it also hold a small amount of pressure to the rears?..

There's a big difference between controlling flow and controlling pressure. Disk brakes hardly use any flow. Rear brakes are the same when the shoes contact the drums. Getting the shoes to the drums is where flow control comes in.

Modern aftermarket M/Cs normally don't include a rear residual valve (to hold the shoes close to the drums). Old M/Cs did include the residual valve. I don't like them because that 'system' gives you a false sense of brake adjustment. In other words in the old days, when the pedal went to the floor it was time for a brake adjustment. Springs did a good job of retracting the shoes.

With the residual valve, wheel cylinders simply extended farther and farther. Sometimes the piston would come out of the wheel cylinder. A better choice is a self-adjuster that actually ratchets the star wheel out. By expanding the bottom of the shoes, the pistons don't need much stroke (or flow) to contact the drum.

I only use residual valves in brake systems where the M/C is below the wheel cylinders. - Dave