brakes II

[old-tank]

I have been driving a few months and few thousand miles after rebuilding the brakes on my 55 Century ( previous thread ).

Anyhow the car is a bear to stop when the brakes are cold. Even backing out of the garage on fast idle or forward after that I have to stand on the pedal before it literaly groans to a stop. After use and heating the brakes up it stops better than any of my other ones with no fade and always straight stops. The pedal has normal firmness, the power brakes are working normally. I even bled the system again and inspected the shoes. The shoes showed no glazing and good contact pattern. The shoes are RAYBESTOS Part # 197PG. It seems that the friction material is too hard.

Any suggestions other than carrying an anchor until the brakes heat up...

Willie

[JohnD1956]

Just taking a wild shot in the dark. If everything else is wearing normally, I'd say you have a low vacuum condition at start up, and that is impacting the vacuum available for the power brakes.

Now this is really a wild theory, but... when driving the 56, and using the wipers, they work slower when stepping on the gas. I think the same thing is at play here. At fast idle the vacuum ought to be lower anyway, and maybe with a small leak or on start up there is little or no reserve available for the power brakes? It may pay to look into that angle before tearing anything else apart.

I know the 56 has the vacuum reservoir on the drivers side fender, tucked into the alcove behind the wheel. The vacuum tank is hooked to a "y" at the power brake booster. There is vacuum hose here, but not sure the 55 is the same. Where-ever it is, perhaps yours has dry-rotted?

JD

[NTX5467]

The way you describe things, it kind of sounds like the classic "metallic" brake lining situation from the 1960s. For example, the '62 Impala SS cars came with semi-metallic drum brake linings to go with their increased (especially with the 2x4bbl 409!) straight line performance (factory equipment front disc brakes were still about 5 years off for those cars, at that time). When they got hot, the brakes worked great, but if you had an automatic and were staging for a drag race, they took much higher pedal pressure to not roll out and red-light. Therefore, the metallics went in the dumper in favor of normal brake linings (that would allow for normal staging of the vehicle, not worrying about stopping at the other end of the track).

On fast idle with a first-started engine, manifold vac might be a little lower than when the motor is fully warmed, but typically not that much lower (especially on a new motor/new car back then). Still, on fast idle I would suspect the manifold vacuum to be a little higher (spark advance is operational at that rpm, too) than at base idle.

In the "high effort" mode, what kind of pedal travel does it take to stop the vehicle? More or less than when the engine's warmed up and at base idle? How does that pedal travel compare to when the brakes are warmed up? More or less?

Is there a check valve in the vac reservoir (mentioned) for the brakes? That might be an issue, too, if there is one in the system and it's not holding vacuum as it should.

Also, in "servo" brakes, there is no "servo" action in reverse as there is when moving forward. If everything else is working correctly, this should not be a problem, but it might be with compromised boost issues.

Now, for the brake linings . . . starting in the later 1960s, Federal specs arrived for the max pressure exerted on the brake pedal for a particular intensity of stopping situation. This tended to result in brake shoe linings becoming "softer" while still retaining sufficient heat non-fade characteristics for one panic stop. I believe this was operational for OEM production vehicles and also suspect it would also apply to replacement parts later on.

Not sure how much of this might apply to your '55, but

Just some thoughts,

NTX5467

[old-tank]

Seems that I am adding confusion when talking about fast idle. I meant the increased ground speed of fast idle made more difficult stops.

I did not change anything is the master cylinder/power assist portion of the system. The power assist seems to be working as it should. Yesterday I disconnected and plugged the vacuum line to the booster and the brakes were a little worse with a very hard pedal that did not have the normal "feel" of power brakes.

I could easily change to different shoes, but without a diagnosis it might be an exercise in futility.

These were new shoes, not relined in an old shelf worn box...one suggestion is this is one of the leftover first examples of non-asbestos shoes. Another reason to be suspicious of this is the first shoes that the parts store ordered were relined (same raybestos) in new boxes and the shoes in the 2 sets were visibly different colored linings (the reason I did not take these).

I guess this is what I get for 'doing it right'...in earlier times I never checked or turn drums; just replaced shoes and let them adjust to the grooves in the drums...the brakes were a little squirrely at first but were better than this later.

Willie

[Bhigdog]

When I restored my 57 I put new shoes on. They came with the car so were an unknown quantity. They would not stop the car. Everything looked good they just would not stop the car. I checked and adjusted/readjusted everything and all looked normal. Still would not stop the damn car. I finally put a new set of NAPA shoes on and it was an instant fix........Bob

[old-tank]

Bob

When did you get your shoes from NAPA? I checked today and their part number is a variation of the Raybestos number and made by United. I know they used to have Raybestos products such as wheel cylinders. Maybe Willis knows who what brands are available.

Willie

[Bhigdog]

Willie, It's prob 3 years now since I got them. I just asked for a set of shoes for a 57 Buick Special, they looked in the book and said they would be in the next day. There was a core deposit so I'm sure they were rebuilts not NOS. They fit and worked perfectly. As I remember the set (4 wheels) was under $60....Bob.

[old-tank]

Well I finally replaced the shoes and braking is normal! I had some old shoes relined at San Antonio Brake and Clutch after explaining my problem which they say is common with Raybestos linings. Next project is to return the Raybestos linings for a refund.

Willie

[Bhigdog]

Glad to hear it, Willie. I could not beleive that the linings could make such a difference. Before I changed the linings I actually sent the power booster back to the rebuilder because I was sure that was the problem. He bench checked it and returned it as working fine. He was correct.......Bob

[old-tank]

Bob wins with the correct solution to the problem.

I took the shoes back to CarQuest and they said they did not know if they can be returned for a refund. I said nothing and just stared...in a few minutes they asked me if it would be alright the put the refund on the credit card. By the way did I mention that these were Raybestos shoes?

Willie

[Guest kevinshea]

Willie - What did the shop use?

Did anyone tell you what the difference was between the material used in the shoes. I used NOS asbestos shoes for my 35 Ford and they work way better than the "new" stuff. Is it better to get a "good" set out of a old junker and use them instead of buying new stuff?

[old-tank]

Kevin

I don't know what brand or grade they used...I just asked for something that would solve the problem and it did. The shoes ended up costing twice as much as the parts store shoes. I tried to find some NOS/NORS asbestos shoes but could not find two sets of the same brand. Stay away from shoes with old bonded linings...riveted are OK.

Willie

[NTX5467]

Willie, I know you're up in Salado this weekend, but did you happen to notice any "stamp codes" on the side of the shoes you took back (Raybestos), the new linings, and the original linings you replaced?

I know this is something that many people don't look at, but the stamped codes on the side of the lining are supposed to include, not only the compliance with Federal codes on that subject, but also some co-efficient rating numbers (i.e., cold stop, hot stop) performance numbers, er letters. Somewhere, I remember seeing what those codes meant, other than the FMVSS compliance, but that's been several years ago. That might be a key to the whole situation, not to mention "shelf life" issues (as many hard-part items were actually produced a good while back, whereas something from a reliner might be much more fresh).

It seems interesting that this was not the first time the operative at the "reliners" had heard of a problem similar to yours.

Just some thoughts . . .

NTX5467

[old-tank]

I noticed the codes but did not record them before returning. I asked Carquest if I could get an update on the disposition or diagnosis and all I got from them was a bunch of crying about how they were going to have to eat the cost of my refund. I am just glad they are gone and never again...

Willie

[Bill Stoneberg]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> Willie, I know you're up in Salado this weekend, </div></div>

And where were you ? We saw a lot of your chapter members and we missed you. You missed a good show Saturday nite at the banquet (talk to any of your members about that).