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Converting drum brakes to disc brakes

Started by 1956biarritz, March 15, 2023, 08:42:25 AM

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1956biarritz

I'd like to get your opinions on why it has worked for those of you that have had your drum brakes converted to disc brakes on your caddy's that had them and why it would be best to just leave them as they were with drum brakes instead of converting them. I've read that converting drum to full disc brakes including booster gives better stopping power than drums.

1956biarritz

As a supplement to my earlier message, according to Caddy Daddy's site that sells the full conversion kits, The original booster had 800 to 1000 psi stopping power with the conversion to disc brakes the conversion booster has approximately 1200 to 1400 psi with 16in. of vacuum , roughly 400 to 600 psi more than the original for better stopping power.

fishnjim

What problem are you trying to solve?
Are you just reacting to sales info?

The only safety advantage is to have a dual master system, whihc came after your car was made.  The period ones are single, so if it fails, no brakes at all - except emergency(rear). 
If you go disc, then the stock wheels won't fit.   So you have to decide what you want.
One can't just equate pressure to braking power as with any hydraulic system, a lot depends on other factors.  You need more pressure with disc because the brake pad area is much smaller.  Compare friction area of a set of brake shoes vs a pair of pads.

TJ Hopland

One thing I don't think I have ever seen brought up in these discussions is where and how these cars are driven.  I have spent time in places where you could just about daily drive without any brakes but where I live which is a top 20 metro area for population if you are going to daily drive you need all the brake you can get.  Sunday drive maybe you can get a way with less but even there you can't always stay on the slower quieter roads.

When I say daily drive here I don't literally mean its your only car.  I'm saying when you drive the car you are planning the trip based on where you need to go not the roads or traffic.  A Sunday drive would be more about the drive where you have the luxury to plan the time and route because its more about the drive. 

Those are quite different situations on their own and that is leaving out the variable of do you live in an area with a million or more people?  There are apparently 56 of those areas in the USA so lots of us are in those areas.  There are another 50 areas between a million and 500,000.  The list I looked at goes to 384 areas goes down to only 58,000.  That still leaves a lot of cities and towns.  Maybe you live in a county that only has 10,000 people in it?  Driving there is quite different than my little suburb of 70,000.  We won't even mention mountains.           
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Jeff Rosansky CLC #28373

It depends on what you are trying to accomplish. Yes discs are more modern, but are they necessary better?
Our 55 is just fine. I have driven it in traffic and it holds its own just fine; but admittedly I don't drive it as aggressively as my daily driver.
So, a disc brake conversion would be meaningless to me.
With that said, there are times where I think I should have looked into a dual system, but if I did, I certainly wouldn't go discs.
Just my opinion.
Jeff R
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

Dave Shepherd

2 obvious improvements,  no brake fade and water has no real affect on braking efficiency.

signart

As I live and travel in mountainous areas, when traveling curvy steep grades, drum brakes can heat up and fail completely, where disc perform.
 
Also a dual master cylinder brake line failure will leave you without brakes to stop if you are traveling at any speed or down any grade. Unless you are just rolling, and then you better have plenty of room.

Whatever brakes you have, wheel cylinders, master, pads/shoes, brake lines should be in top shape.
Art D. Woody

PHIL WHYTE CLC 14192

I have a 54 with the original brakes. I rebuilt them as per the manual. The crucial thing is to adjust the shoes as per the manual. I drove this car on long journeys and all round London when I lived there. The original brakes are great. I really feel it is unnecessary to change them. Phil

Lexi

Well put Phil. Same with my brakes. They seem appropriate for the age and size of the car. Clay/Lexi

Clewisiii

I converted to all wheel disk brakes with factory wheels.  I am removing the rear disks and going back to drums. I had to use 3/4 inch hub spacers for stock wheels. That made to small of a gap between tire side wall and the inside of the fender skirt. 
"My interest is in the future, because I am going to spend the rest of my life there."  Charles Kettering

Cadman-iac

The only time that you would really need a disc brake system is if you are traveling at interstate speeds and need to use them frequently, as a drum system has a tendency to fade when pressed.
But just driving more defensively can help prevent that as well.
I used to travel 700 miles round trip from Texas to Arizona at least once or twice a month in a 56 Chevrolet with drum brakes, and only experienced brake fade when I got more aggressive with my driving.
Granted, an emergency stop will cause the drum system to heat up and begin to fade if you persist in heavy braking, but the whole point of cruising our classics is to sit back and enjoy them.
If you're going to be road racing it, then definitely convert it to discs, but for occasional cruising or even more frequent use, the stock drum brakes are more than adequate, and a lot cheaper than a conversion.
I went through the same thing when I was considering whether or not to convert my 56 Coupe Deville to discs, and after much thought, decided that if I just drive conservatively, it's not really necessary. After all, it's a Cadillac, not a Corvette, so if I want to race, I'll use my wife's Corvette, (if she'll let me) lol!!
Besides, even with disc brakes, this Cadillac will still handle like the Queen Mary in rough seas when driven aggressively.

On another note, I did update the drum brakes to a dual master cylinder, and newer, wider shoes with self adjusting hardware, and drums with more cooling Fins. I'm going to find some shoes with semi-metalic linings to replace the normal linings as well. With all that, I believe that it will be just as responsive as a disc system.

 And just to add another point, if I had gone through with converting it to disc, my original wheels would not have worked with them, and therefore neither would the hubcaps, and I really want to keep the original hubcaps at all costs. I even considered having wheels made that would fit over the discs that were able to use the original hubcaps, but this was just another large expense for not much benefit.

 I will also admit that even with my modifications to the drum brakes, I still have to use the stock spindles and hubs with the ball bearings, the weak link in the whole thing.
 I would love to find a way to convert the ball bearings to roller bearings, but like I said before, it's a Cadillac, not a Corvette.
 Just food for thought. It's your car and your choice. I wish you the best of luck with whichever way you go.

  Rick
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

Cadman-iac

Quote from: Clewisiii on March 18, 2023, 12:18:09 PMI converted to all wheel disk brakes with factory wheels.  I am removing the rear disks and going back to drums. I had to use 3/4 inch hub spacers for stock wheels. That made to small of a gap between tire side wall and the inside of the fender skirt. 

 What year is your car, and which vehicle did your disc brakes come from?  Just curious how that worked out.

 Rick
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

Clewisiii

Quote from: Cadman-iac on March 18, 2023, 01:00:40 PMWhat year is your car, and which vehicle did your disc brakes come from?  Just curious how that worked out.

 Rick

Mine is a 61. I bought a kit from Classic Disk Brakes.
"My interest is in the future, because I am going to spend the rest of my life there."  Charles Kettering

bcroe

My drum brakes worked very well on a sunny day. 
THE PROBLEM was when they got wet, esp from a
pot hole one one side, hard braking could throw
the car sideways. 

Discs up front cure the problem.  I see no need
to convert rear drums, experience has been rear
discs are a lot of trouble.  I will not have a
car with single circuit or front drums. Bruce Roe

Cadman-iac

Quote from: bcroe on March 20, 2023, 11:31:32 AMMy drum brakes worked very well on a sunny day. 
THE PROBLEM was when they got wet, esp from a
pot hole one one side, hard braking could throw
the car sideways. 

Discs up front cure the problem.  I see no need
to convert rear drums, experience has been rear
discs are a lot of trouble.  I will not have a
car with single circuit or front drums. Bruce Roe

 Bruce,
 Thanks for the reminder about wet drums. I had forgotten that part, as I've converted all of my old trucks to discs because of hauling heavy loads.
 The last full drum vehicle I had driven was my 56 Chevy back in the early 80's, and I sold it without ever converting it.
 I remember now how scary it was the first time I hit water and had to use the brakes. It scared the crap out of me!
 Since I'm not converting my 56 Cadillac to discs, I'll have to remember that bit of information.
  Thanks, Rick
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

Chopper1942

Water also affects disc brakes.  The diac pads drag slightly on the rotors which quickly dry them off.  The biggest problem with wet drum brakes is the dust inside the drums adsorb the moisture and cause the brake application to either pull, grab, or fade.  If thers is not a lot of dust inside of the drums, if you run through water or puddles is to slightly apply the brakes and dry them out.

The best drum brakes were on Buicks.  Several years had finned aluminum drums front and rear with cast rings for the shoe contact area.  We used the riveted premiun linings for the shoes. When we used these on street rods and for circle track racing, they worked very well. 

Any brake will fade on long down hill braking in the mountains if you keep them lightly applied.  They can not disappate the heat being generated.

OK, now the discussion about wheel bearings.  Ball bearings work great if they are lubricated and "properly adjusted".  Ball bearings must set with preload.  Any free play will quickly destroy the bearing.  To make is simple, you tighten the nut while turning the wheel/drum until it is tight and still turns. Line up the castellation in the nut with a hole in the spindle and insert the cotter key.  You may have to slightly tighten or loosen the nut to install the cotter key.  Do not back off very much.  You do not want any end play.

Follow OE specs and procedure when adjusting.

With tapered roller bearings, you torque the nut, while turning the wheel/drum or rotor, to specs.  Then you back off the nut and install the cotter key.  Again, follow OE specs and procedure.

The main reason for the change from ball to tapered roller bearings is cost.  Ball bearings are much more costly to manufacture. Front inner and outer ball bearings for a '57 Cad Deville = $100.00.  Front inner and outer for a '64 Cad Deville = $15.00.  These are Rock Auto pricing.

wheikkila

You can also purchase a better compound for your brake shows. They use them on vintage race cars. I checked into it for my LaSalle. But to my surprise, it had new shoes on it. If I recall it was not that bad. I defiantly agree on a duel master cylinder. The biggest problem with drum brakes. People don't maintenance them as they should.
                        Thanks Wayne   

signart

How would a dual master cylinder improve braking on drum brakes?
Art D. Woody

TJ Hopland

Quote from: signart on March 22, 2023, 10:38:08 AMHow would a dual master cylinder improve braking on drum brakes?

Dual is about safety / redundancy.  With a single system if you start to boil the fluid in one wheel or have some sort of a line failure you loose the whole system.  Dual at least you have half the system that should still work which is a lot better than nothing working.  I think the Feds made dual a requirement in 67 ish.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

signart

A dual master with a line failure is a false sense of security. A line rupture will leave you without brakes if traveling at speed or down a hill. The peddle will go very near to the floor with only enough braking to stop while rolling, then you better have plenty of room in front of obstacles.
A safer bet would be to upgrade hoses, lines, and wheel cylinders, then maintain and adjust the emergency braking system and depend on that in combination of grabbing a lower gear. Otherwise, I don't see the point in going to a dual master unless converting to disc brakes, where there is an advantage in braking. However the same results apply to disc brakes when a rupture occurs.
 
Unfortunately, I speak from a lot of experience, just a word of caution.
Art D. Woody