New brakes = Worse brakes ???

[JFBrink]

Hi, gang,

I just replaced more than half my brake system with new, and the end result is noticeably worse than what I started with. And, yes, it's bled.

When I bought the car, the rotors were thin, the pads thin, the drums thin and the shoes thin. I replaced the rotors, calipers and pads with new.

There was some improvement, but not stunning. The car stopped okay by my standards, but scared others. You certainly couldn't lock the brakes.

This past month I spent evenings replacing the following:

-Master cylinder (it was leaking slightly down the firewall)
-Drums (with adapter & finned aluminum Z drums, per Tech section)
-Shoes (with '71 510, per Tech section)
-Slave cylinders (they were solid, but old)
-Rear steel lines (scary rusty, and the nuts were stripped)
-Front pads

Everything seemed pretty normal going together. I did have to slack the e-brake cable about 1" to get the rods to reach the new levers.

Also, the shims for the slave cylinders seemed really tight. The legs of the last one sort of splay out to the sides a little, which can't be factory spec.

After I bled them, then drove them to a trusted garage to have them pressure bled, the car stops worse than it did before.

Pumping the pedal makes no significant difference. Also, I can now feel an oscillation throught the pedal: an in-out-in-out that wasn't there before.

Any ideas / questions / suggestions? I'm very sad.

Jesse.

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[JFBrink]

Mark,

The master cylinder shims are still in place.

Wouldn't the pressure bleed have effectively bled the MC as well?

Pedal travel is an inch or so before I feel resistance, which seems odd, but I think that it was that way before, too.

Funny how quickly memory fades over a few weeks of disassembly.

Jesse.

[spyder]

Is it possible the master cylinder is not the correct one? If you don't have the firewall brake brace get one. Removes stress on the firewall and gives a stiffer pedal feel. Are the rear shoes mated to the drums, the correct arc? Original diameter tires and rims?

[nomadtrash]

The master cylinder on the roadster is horribly difficult to get bled properly. The problem I've had is that the end of the cylinder points up and that is where all the bubbles go. You can pressure bleed or vacuum bleed and all you get is fluid from the reservoir. The bubbles stay in the cylinder because they are at a higher level than the hole that draws fluid from the reservior. To get mine bled properly I had to jack the rear of the car about 3 feet off the ground which made the reservoir level. The bubbles made their way out while tapping on the cylinder and pumping the brakes. It took a good deal of time but I finally got a stiff brake pedal.

[JFBrink]

Andy,

If the MC is as tipped on my '66 as it is on later cars, it really could have air still trapped in there, huh? That's interesting. I'll have to take a look at it tonight. Have any of the rest of you had the same experience, with a low-windshielf car?


Spyder,

As for the MC being the right one, I'm almost certain that it is: 3/4" bore for a 65-67. I don't think that I *can* put a brake brace on a '66. I know that lots of people are running these shoes with these drums, so I have to assume that the arcs match.

Thanks,

Jesse.

[S Allen]

You are correct--the brake brace is for the 67.5 and later cars. There is no firewall brace for the earlier cars. None that I know of anyways. I vote for air in the master. Bench bleeding a new master is highly recommended.

Steve

[JFBrink]

Okay, so that's 3 votes so far for air in the master. Does that jibe with the fact that pumping the pedal seems to have no effect?

But what about the other curious, and perhaps spurious, "symptom" -- the new in-out-in-out feeling that I get through the pedal?

[Ted928]

I am no expert but I have heard that it takes a while for new pads to break-in. Until that occurs, they won't work as well. I suspect that the rear drums are even more in need of break-in since the shoe/drum contact area is very localized which spreads with wear.

I also think that people are no longer familiar with brakes that lack power assist (35 years). Every spring I relearn the lesson that they do work once you push hard enough.

[JFBrink]

Okay, so the MC is definitely tipped in such a way that I could imagine air getting trapped in the front of it. But, shouldn't the bleeder on the top of it take care of this? If not, what use is this bleeder?

Jesse.

[deliver]

What is the condition of your rubber brake lines??

[JFBrink]

The three rubber lines are just barely a year old. Everything is a year old or a month old, except for the main steel lines, which are solid.

I looked at the MC last night & it is certainly tippy, but it really seems like the MC bleeder could bleed that front portion. Can it not?

Jesse.

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[ppeters914]

You are correct--the brake brace is for the 67.5 and later cars. There is no firewall brace for the earlier cars. None that I know of anyways. Steve

Hmmmmm, wonder what I bought last year from Vendor X for my '66. Guess I better pull that out of the box plus check the packing slip.

[dbrick]

Couple things, maybe way off base, but you never know.

1 Rear wheel cylinders should slide tightly but freely in the slot, if they don't, only one shoe will make contact. Are they 13/16 wheel cylinders?

2 If the front pads were hard to slide into the calipers, they may be binding on the sides of the pads to the caliper bracket. Also, are they street or race compound brake pads? Any improvment when the brakes are hot?

3 The air bubble everyone else mentioned. With the bleder on the end, what Mark said should work on the master. Tapping it will help as Andy mentioned. Was it any better after the power bleeder than the ride to the shop to get them bled?

4 Front rotors and or drums are machined too smooth, not enough "bite"

5 Do the parking brakes work?

6 Take it for a ride, don't tailgate Get the brakes hot. Carefully without burning your finger see if both fronts get equally as hot, and if the rears get hot equally.

7 Do you run out of travel on the brake pedal, hit the floor at all? New master may not need the shims the old one needed. Also, does the cylinder fully retract when the pedal is up?