OH LORDY! SHE WON'T STOP!

[Dave Burke]

Hiya Folks!

Well here I am, 4 days away from trying to get my recently-acquired '57 Sedan Deville to Amelia Island (if I can fix this pesky fuel-delivery problem).  The issue du jour is the drum brakes: I did a full rebuild on them, including new shoes, and bled them good and I have a good, hard pedal.  But danged if she wants to stop!  I figured that I would follow the usual bed-in policy, but I expected that with power-assisted brakes, she should stop on a dime, and at present I am afraid that dime might be in some poor citizen's pocket!  I took all of the drums back off and blasted them with brake cleaner and the shoes as well, but still she just slows down and takes her time.  I figure that it is because I am not getting a good contact surface, so I wonder: if I but a bit of grinding/lapping compound on each shoe, might that round the shoe surface so that I get better contact?  Any experience with this?  Pros/Cons? 

Thanks for the info!

Dave Burke
CLC# 27968

[Jay Friedman]

I have 3 suggestions.

1. If you feel you are not getting good contact surface, you may want to take off the shoes and bring them with the drums to a brake shop and have the shoes "arced" to the drums.  This is a procedure that is necessary when the drums have been previously cut on a brake lathe to a larger diameter than the diameter of the circle described by your new shoes, which decreases the contact surface.    The brake shop will grind the shoes to the larger diameter, making the lining contact the drums for its entire length. 

2. Also, if you bought new shoes you may want to make sure the linings on these shoes are the same dimensions as called for in the specs in the shop manual.

3.  Make sure the brakes are adjusted correctly as per the shop manual.  This includes the "major" adjustment which comprises adjusting the eccentric anchor pin which is the part in the middle of the top of the 2 shoes that the springs attach to.  You adjust this by loosening the lock nut for the pin at the rear of the backing plate and then centering the pin using a feeler gauge through the slot on the outer perimeter of the front face of the brake drums.  The shop manual explains it. 

[txturbo]

That happens if the drums have been turned a lot. Shoes have to be re-arched to match the new radius of the drums.

[russ austin]

Did you put the smaller shoe in the front?

[Dave Burke]

smaller shoe? 

They looked the same size when I took them out of the box...

Hmmm...

Maybe a trip to the brake shop might not be a bad idea too.

Dave

[waterzap]

New wheel cylinders too?
Brake shoes usually pivot at the top. So when you stop, they swing out from their pivot point. Because of the rotation of the drum, the rear shoes will try and pivot up, and grab tighter to the drum. They call this self energizing, or self applying. The front shoes on the other hand wants to pivot away from the drum, but the brake pressure keeps them against the drum. So most of your braking would be done with the rear shoes. If you change them around, that could be the reason for the bad braking.

[txturbo]

The metal part of the shoe is the same size....it's the friction material that is different sizes. The rear shoes will be almost completely covered and the front shoe will have less surface area covered.

[Walter Youshock]

What, if anything, did you do with the brake booster?  The Hydro-Vac boosters are strange animals.  When you did the bleeding procedure, did you also bleed the booster?

[Dave Burke]

I rebuilt the brake booster and all pistons cylinders (some pistons were jammed).  I bled the system already, starting with the booster, puked all of the lines until they were clear, and I'm probably going to do it again but I know the feeling of air in a brake system, and I have a pretty firm pedal.  So I will take a look at the brake pads and see if I switched the "long" and "short" shoes before risking the embarrassment at the brake shop ("hey Hank, look at the doofus who has his shoes on backwards!"). 

I reckon that eventually I am going to convert the front brakes to disc since the old girl is a driver.  Now I just have to work on fuel delivery: she keeps acting like she is vapor-locking but I have a feeling that this new fuel pump, coupled with my looking at the fuel tank to fuel line hose will solve this (fingers crossed).  I have sunk gobs of time, money, and money, not to mention money and also some money into getting her primed for Amelia Island.  I ain't ready to quit - no Sirree! 

My other problem is that my students, and the University, are making unreasonable demands that I grade and hand back a stack of exams so that they will know whether to drop the class or not.  If not for this, I wouldn't feel pressed for time!  Focus - I must focus!

Best,

Dave 

[J. Gomez]

Dave,

On the ’56 Shop manual there is a procedure to adjust the front brakes; I would assume the same applies to the 1957. It may be listed under major brake adjustment in your manual.  Remember that the higher percentage of stopping power comes from the front brakes.

Re-arcing brake shoes was an old technique seldom used anymore with new brake linings. If I recalled truck brake shops may still have and use the re-arcing equipment. Don’t be surprised if you received a blank face from your local brake shop techs if you asked about re-arcing the shoes. 

Good luck..!

[Gene Beaird]

^^ What Mr. Gomez says.  When I was in college, I worked weekends and between semesters at a parts house that turned rotors and drums.  I _never_ re-arced any shoes, and it's sometimes quite an effort around here these days to just find someone who will turn a rotor or drum. 

Oh, and if they're considering dropping the class, they should probably just go ahead and do it.     Now get back to fixing your Cadillac!!

[Dave Burke]

First off - guys, I sure do appreciate the info on the brake shoes and that is where I will start - with looking to see if I put them on backwards.  I may throw a shmear of grinding compound on the shoes too to help round them if needed, but it is just more likely that I have them in the wrong way around.  I figure that the worst that could happen is that the compound will wear the shoes faster, but eventually it should disappear along with the rest of the brake dust.  The fronts are easy: I can get that car on the jacks and the wheel and drum off in a jiffy, but I hate doing the rear, especially the adjustment because I have a natural phobia of working on a couple of tons of metal elevated above me by jacks and jack-stands, and I have to have both rear wheels off and they are a bugger even in the best of circumstances.  But I reckon a couple of hours' work and I should be OK. 

"Labor of love," I keep telling myself, "Labor of love." 

Dave

[Walter Youshock]

I'll agree that the shoe installation could be causing your issue but:  when you did the brake job, did you change the hoses?  Also, did you rebuild the booster yourself or have it done?  The power piston leather has to be lubricated in order for the booster to work properly.  Even with no or little power boost, you should be able to stop the car.  Then again, even I'll admit with a fully working HydroVac, the '57's can be a chore to stop.

[Jon S]

Did you play with or re-adjust the push rod?  Do you hear a nice "hiss" sound when you depress the pedal in Neutral?  Does the pedal return to the full upright position when released?

[D.Yaros]

Is grinding compound petroleum based?  I sure would not be putting petroleum based anything on the linings of my brake shoes!

[Jay Friedman]

I don't know where you are located, but I'm in the Atlanta area where we have the Atlanta Safety Brake Company.  I've had brake shoes for my '49 Cad relined there a couple of times over the years and each time they re-arced the linings to the drums.  This firm's shop is in an industrial area with a neat old time look about it that I like.  They mostly deal with brakes for large trucks and considered it routine to re-arc my 49's brake lining.  I'm not suggesting you ship your shoes and drums to them but, as J. Gomez wrote, you may want to find a firm like that in your area.  As Gene Beaird wrote, an ordinary brake shop may not be able to do it.

Like Gene, when I was in college I worked on brakes, in my case doing brake jobs in the late '50s and early '60s at an Oldsmobile dealer  belonging to a friend of my Dad.  I do remember having drums turned by a nearby machine shop but don't remember re-arcing brake lining.  On the other hand, the dealership only worked on relatively new cars whose drums usually had not been turned that much.

I don't know about grinding new shoes with compound, but sometimes after many miles lining that is worn but still usable can become too smooth to stop the car well.  In that case, roughing the lining up by lightly sanding it can help.  You might want to try that. 

I agree with Walter that your hoses can be an issue.  Frequently when brake hoses go bad, they look fine on the outside but have collapsed on the inside, thereby impeding the flow of the fluid. 

BTW: I haven't seen a '57 shop manual, but my '49 manual refers to the front shoe on each wheel with the shorter lining as the "primary" shoe and the rear shoe with the longer lining as the "secondary" shoe. 

[Rod Dahlgren #19496]

Clues: #1 - Dave says he recently acquired the Cadillac (past history unclear)  #2 It is a 1957 (remote hydro-vac unit)  #3 - Some of the wheel cylinder were STUCK (system has been inactive) --  #4 - He bled the system (lines and hoses probably are clear) #5 - "firm pedal" (hmm--he rebuilt the hydro-vac unit, is this a key statement?)

Hey Gang, This is a 1957--- think 1957 ONLY! -------  Shoes backwards? Maybe-- But just how much will that change the total brake effectiveness? Some, but not to the point that they are ineffective.. Arc of the shoes. maybe--- A close look at them to see the scuff pattern will tell the tale here.. Oversize drums, yep, could be--- But if the arc and contact pattern of the shoes looks OK, the brakes will work, but with downhill braking heat will build and the brakes will fade.. OK-- I am getting ahead here---  So I will  STOP  !

I don't have the answer, but I think it is time to revisit the hydro-vac unit.

[Jon S]

Rod -

I repeat . . . Did you play with or re-adjust the push rod?  Do you hear a nice "hiss" sound when you depress the pedal in Neutral?  Does the pedal return to the full upright position when released?

[Walter Youshock]

Me, too.  I've tackled A LOT on the '57 and went so far as to order the HydroVac rebuild kit.  NO WAY was I going to rebuild that booster myself.

Exactly what push rod are you referring to???

[Jon S]

The adjustable push rod behind the brake pedal that affects brake pedal travel.  If adjusted too long (high pedal) the booster will not work properly and provide the hard pedal Dave is referring to.  If adjusted too low, the brakes will be grabby.