Better Brake Power?

[kenmatthews]

This weekend my dad and I bled brakes on my 55 Super (orig. brake system- no PB). The reason is most of the power to stop the sled is the last few inches of travel close to the floorboard. If I let off and pump a little, I get better breaking higher up.

So I bled each cylinder in this order (FL, FR, LR, RR). I tested and didn't get any improvements. Could it be a matter of adjusting the brake clearance on the pads rather than bleeding? At least I can knock bleeding off my TO DO list.

[Guest sixpack2639]

Ken, I adjusted the brakes on my 51 Special (noPB) 2 weeks ago and my pedal came way up. I would suggest adjusting yours too. You want to bring them up until you hear a very slight drag while rotating the tire. Also, I have always been told that you should bleed brakes starting from the furthest away from the master cylinder and working twords the master cylinder ie. RR,LR,RF,LF. Hope that helps, Carl

[kenmatthews]

Hey there SIXPACK,

AT this point, I'm willing to try bleeding in the order you mention. You know, I went by the shop manual which says to bleed starting closest to master cylinder to get the air out there first and then work towards the back. My master cylinder happens to be under my foot accessible through the floorboard.

In the next couple of days I'll do the adjustment. I seem to remember there's a star nut that you turn to move the brakes in or out...right? We probably have the same setup btwn 51 and 55.

[Guest sixpack2639]

Yes, it is the same. They haven't changed drum brakes very much over the years. Carl

[Gene Brink]

Ken,

As the pedal pumps up I'd say you must have air in the lines someplace. Shop manual gives three possible causes for a "spongy" pedal. They are: 1) low fluid in master cylinder so air is sucked into system (this is probably not your problem); 2) clogged filler cap vent that permits air to be pulled past the piston secondary cup on the return stroke; 3) leaking check valve causing loss of static pressure in the system permitting air to be pulled into the system past a wheel cylinder. Fix by cleaning/replacing as needed.

Bleed order is left front, right front, left rear, right rear.

Good luck

[old-tank]

Hey Ken

Try adjusting the shoes first. But unless the system is nearly new consider replacing the wheel cylinders (NAPA and Raybestos should have life-time cylinders), the hoses (2 front and one rear) and replace the master cylinder or have it rebuilt after resleeving. Turn the drums and replace the shoes if more then half worn (thin shoes will not dissipate heat and will fade more quickly). This also is a good time to check bearings and seals. Change the fluid every 2 years and drive it regularly. Marginal brakes will have your butt biting big donut holes out of the seat....

Willie

[NTX5467]

After you get the brakes adjusted to specs, THEN and only then can you finish things up by then tweaking the cable/linkage adjustment on the parking brake.

It is possible to cheat on the rear brake adjustment by first adjusting the linkage for the parking brakes to where it only takes a couple of clicks to get them to hold. When you then get the foot brake adjustments done, the parking brake adjustment could well be too tight and lead to a false adjustment on the rear brakes.

I suspect that when you get the brakes adjusted, then the pedal travel will be "right". If you don't want to do the "turn and feel" method, you can go "high tech" and get one of the caliper tools to measure the inside diameter of the drum (off the car) and then use the same caliper to adjust the brake shoes. When you put the drums back on, there should be equal and optimum space between the brake shoes and the brake drums friction surface. Of course, to make this method work correctly there would have to be little to no "lip" on the outside of the drum's friction surface. You can probably find the caliper tool from NAPA or similar's tool catalog. Not much call for them in a "disc brake world" . . . They work pretty slick.

As Willie mentioned, by-passing at the wheel/master cylinder and flex in the brake lines might give the false impression of a "low" pedal under brake pressure. Usually, a brake hose will let go internally and basically form a "one-way valve" internally that can keep the brake applied when there is no pressure from the master cylinder or do just the opposite and keep the fluid from getting through to the wheel cylinder. They can look good on the outside and be flaky on the inside.

Enjoy!

NTX5467

[NTX5467]

On the brake bleeding issue, if you keep getting solid fluid out of the bleeder screw and still have a low or spongy pedal--after adjusting the brakes--you might consider getting one of the brake bleeder pump kits from an auto supply. Rather than use it at the bleeder screw end, you can fashion a seal for the master cylinder (kind of like a power bleeder would use) and apply vacuum to the brake master cylinder reservoir. If there might be some air bubbles hiding somewhere, putting a vacuum on the reservoir could force them out of hiding. That's how they do it at the assembly plants, rather than laboriously bleed each wheel from under the car (they first pull a vacuum on the system and then add the fluid to the vacuumed system). Don't get too carried away, though, in applying the vacuum as it might point up something else that needs replacement.

Just some thoughts,

NTX5467

[Guest brh]

If there is no air coming out when you bleed the lines and there is no leaking, I'd say you have a bad master, that is in need of a rebuild. I have had the pedal go straight to the floor no warning, yet luckily, I had the sense to pump it up and get my brakes back. Its not an experience I would want anyone else to share in. Sounds like she's telling you something is wrong. Just my two cents.

[kenmatthews]

Thanks Bruce.

No problems with the master cylinder. There was air in the lines and I got it out...with only marginal improvements. Got wheel cylinders and brake hoses on order. It's high time I changed them out anyway.

K

[Guest imported_NikeAjax]

I would agree with Bruce; if your brakes are anything at all like the '56, which are a joke, then you should look into a rebuild on the master cylinder. I bled mine till I was blue in the face, and it still wouldn't stop. I finally put an after market power brake system in it and now it will stop, I couldn't justify $400+ to have someone rebuild it for me, your's won't cost that much, it's ONLY the cursed 1956. Most, if not all of the cars from that period are very under braked. Did you check to see if it's your shoes that are glazed? You can do a simple test by scuffing the shoes with some sand paper, wear a respirator so you don't breath the crap into your lungs; it the car stops a lot faster, then your shoes are in question.

Just a though,

Jaybird