Retrofitting rear wheel disc brakes

[James Peck]

Neill Maken, the octogenarian editor of the former publication "Skinned Knuckles", had a 50 Ford convertible he used as a daily driver. He advocated for 4-wheel disc brakes for cars driven in traffic. I agree with him. This means segregating antique vehicles into two categories: Those that are used for transportation and those used for show. 25-year-old vehicles sold new with no options are likely to have front discs and rear drums. Converting to rear discs is likely a not very visible modification. 

[Pfeil]

3 hours ago, James Peck said:

Neill Maken, the octogenarian editor of the former publication "Skinned Knuckles", had a 50 Ford convertible he used as a daily driver. He advocated for 4-wheel disc brakes for cars driven in traffic. I agree with him. This means segregating antique vehicles into two categories: Those that are used for transportation and those used for show. 25-year-old vehicles sold new with no options are likely to have front discs and rear drums. Converting to rear discs is likely a not very visible modification. 

This means calling one an antique vehicle, and the other a modified vehicle-and no longer antique status.

[1912Staver]

Rear disk brakes seems rather unnecessary on a mostly stock 1950's car. Are you really going to using a vintage car in a way that would require 4 wheel disks ? If you live in an area of heavy traffic and drive your vintage car as a regular driver, then a swap to front disks may make sense. But rear disks are probably a extra expense and not a small amount of re - engineering for little if any benefit.

[alsancle]

Why?

[1912Staver]

There were a few times when I sure wished my 1969 Buick GS 400 had the optional front disks.  The big finned drums worked fine the first couple of times, but after that things got very dicey. Around town it was never a problem , but as soon as you leave the Vancouver B.C. urban area you are in some serious mountain terain.  I used to drive the G.S. a fair bit out of town. If there was one shortcoming with that car it was the brakes in the mountains. Gas milage wasn't anything to write home about either.

 I believe 1969 was the last year disks were an option on a GS. Even the factory knew disks really were necessary.

Edited June 11, 2023 by 1912Staver (see edit history)

[3macboys]

19 hours ago, James Peck said:

Neill Maken, the octogenarian editor of the former publication "Skinned Knuckles", had a 50 Ford convertible he used as a daily driver. He advocated for 4-wheel disc brakes for cars driven in traffic. I agree with him. This means segregating antique vehicles into two categories: Those that are used for transportation and those used for show. 25-year-old vehicles sold new with no options are likely to have front discs and rear drums. Converting to rear discs is likely a not very visible modification. 

Sticking to the 25 year old mark, you are in the realm of anti-lock brake systems, that is not going to be a simple hardware conversion.  

[George K]

5 minutes ago, alsancle said:

Why?

Proportional brake valving. Many modern 1/2 ton pickup trucks have drum rear / disk fronts.

[alsancle]

1 hour ago, George K said:

Proportional brake valving. Many modern 1/2 ton pickup trucks have drum rear / disk fronts.

I should’ve been more clear with my post. I wanted to know why he wanted to add disk brakes. Personally, antilock is a much bigger safety feature.

 

Generally, I think if you are worried about braking, you probably should not be driving an old car.

Edited June 11, 2023 by alsancle (see edit history)

[DonMicheletti]

alsuncle hit the nail on the head about driving an old car.

[TAKerry]

I have been under the impression that properly set up the front brakes take the brunt of the work. I have the factory settup on my 1977 Trans Am. The 400 motor is built like it should have been not the way it was, LOL. A bit more hp than stock. I have disc br. on the front and drum br. on the rear. I am pretty sure that everything is set up properly as I have never had a problem stopping the car and although it does not stop like my 2013 f150, the brakes on the ole TA do the job just fine as is. I often wonder why people go through the trouble of a rear brake swap?

[Pfeil]

3 hours ago, TAKerry said:

I have been under the impression that properly set up the front brakes take the brunt of the work. I have the factory settup on my 1977 Trans Am. The 400 motor is built like it should have been not the way it was, LOL. A bit more hp than stock. I have disc br. on the front and drum br. on the rear. I am pretty sure that everything is set up properly as I have never had a problem stopping the car and although it does not stop like my 2013 f150, the brakes on the ole TA do the job just fine as is. I often wonder why people go through the trouble of a rear brake swap?

You are correct that the front brakes do most of the work, and the more aggressive the braking the more work they perform, the proportioning valve sees to that. Seeing is proof, and if you look at a car with four-wheel disc brakes you will see that the front brakes are much larger than the rear brakes.

Why do people add rear disc brakes. I have a 69 Pontiac LeMans that serves double duty as a car for car shows, cruise nights and as a track car as in grand touring. Drum brakes, with the exception of the giant finned Buick brakes or Pontiac's Eight lug aluminum drum/steel wheel brakes are not able to dissipate heat fast enough like disc brakes do. If I didn't have them, I wouldn't have any braking at all in the rear after one lap on certain tracks. On the other side of the coin when I go to a cruise night, I see cars with disc brakes that I know have never been on a road course it seems they were just for bragging rights.

I would like to see a comparison braking test between two late 70's T/A's rear drum/rear disc. I think 78 has rear drums and 79 has rear disc, or whatever year they switched. I'll bet in standard 60-0 test that the drum brakes work just as well. Earlier SD455's had rear drum, so I don't even know why the factory decided to put disc on a 79 or 80 wheezer - low hp T/A.

Edited June 13, 2023 by Pfeil (see edit history)

[TAKerry]

Pfeil, agree completely. If the car will see any extra activity I can understand a dual disc settup. No doubt in my mind they are better and def. easier to maintain. 

Rear disc was an option on the 79 TA, standard on 80 and up. I have rear disc on my 79 I am restoring. One of the things that is different than my 77 that I am looking forward to as a comparison.

[EmTee]

Living in the Northeast, I wish my '04 Silverado had rear drum brakes...

[nat]

     The front brakes do the bulk, (60%?), of the work whether  they are drum or disc.  The drum/disc diameter and wheel cylinder/caliper piston diameter ratio between front and rear determine how the braking force is proportioned.  

     Disc brakes are in some ways superior to drums but probably became common because they require fewer parts and less assembly.  Rear drums were, (and still are), in common use for the simplicity of working in harmony with the parking brake 

     Disc brakes will out perform drums in extreme conditions.  Money might be better spent on a life insurance policy than on a disc brake conversion if one is planning to drive their antique auto in extreme conditions.

[pfloro]

My 1984 Oldsmobile Toronado, which I bought new and owned for 28 years (200,000 miles) came equipped from the factory with standard 4 wheel disk brakes.

 

Background:  The rear calipers never self adjusted properly and the service & parking brake pedals would sink lower and lower as the rear pads wore.  Eventually, the calipers leaked

                         from the parking brake actuating shafts.  Even with new calipers & pads, I always thought that braking performance was not the best.   Other folks I knew who had

                        Toronados or Eldorados from the same era also complained about the rear disk brakes and poor braking performance.

 

After about 15 years, I learned that Buick Rivieras from the same era had rear drum brakes as standard equipment (bone yard touring is a good thing!).  This got me me thinking

and I decided to convert the rear disks to drums.  I added/replaced all necessary components:  backing plates, hubs & bearings, parking brake cables, etc. The master cylinder

was also replaced for one designed for a disk/drum system.

 

There was a significant improvement in braking performance after the conversion.  This was especially apparent during the last part of a rapid stop when the car slowed to

about 20mph.  The deceleration from 20 -> 0 mph was now impressive for such a heavy car.  I determined that this was due to the "self energizing" affect which drum brakes possess.  

I never had any brake concerns for the next 13 years.  The service brake pedal was always high and the parking brake finally worked as intended.

 

As others have stated, a disk/drum setup is perfectly fine for a daily driver or an older car driven with common sense.  4 wheel drums are generally fine and 4 wheel disk

brakes have their respected place too.

 

Paul

 

Edited June 15, 2023 by pfloro (see edit history)

[60FlatTop]

 

A person designed this tool back around 1980:

 

"It will live in infamy".

[James Peck]

Neil Maken has dropped out of sight almost a year ago. I have never found out the circumstances. Did he really have a fifty ford that had 4 wheel disc brakes? I may never know. With the transitioning of much manufacture of aftermarket auto parts to the PRC, the difficulty of a PRC based manufacturer doing a project like this increase, 

 

Posted June 11

Rear disk brakes seems rather unnecessary on a mostly stock 1950's car. Are you really going to using a vintage car in a way that would require 4 wheel disks ? If you live in an area of heavy traffic and drive your vintage car as a regular driver, then a swap to front disks may make sense. But rear disks are probably a extra expense and not a small amount of re - engineering for little if any benefit.

[rocketraider]

Re pfloro's experience with GM 4-wheel disc brakes:

 

Back in early 90s I located a 78 Eldorado junker with them, and thought "they'll be an improvement on my 69 Toronado". Those familiar with 1st generation Toronado know that those cars have a whole lot more go than they have stop, even with the optional 67-70 front discs.

 

I ran it by a good friend who was an Oldsmobile Zone Service Manager and after a half hour conversation I figured it probably wasn't worth the time and expense. He told me the only thing they ever had more trouble with at Zone level  than rear disc brakes was Comfortron automatic temperature control. That was all I needed to hear.

[Ed Luddy]

On 6/13/2023 at 8:08 AM, TAKerry said:

Pfeil, agree completely. If the car will see any extra activity I can understand a dual disc settup. No doubt in my mind they are better and def. easier to maintain. 

Rear disc was an option on the 79 TA, standard on 80 and up. I have rear disc on my 79 I am restoring. One of the things that is different than my 77 that I am looking forward to as a comparison.

I've been considering doing a rear disc swap out on my recently purchased 1976 Trans Am as the rear diff in it is toast. Think I'll just stick with a drum brake 10 bolt Post Trac unit after reading all this thread. It will never see any track duty or likely any high speed hard driving. 

[zepher]

I am surprised to hear of so many issues with GM rear disc brakes from the 70's and 80's.

I owned a '78 Silver Anniversary Corvette with the L82 / 4 speed combo.

Shortly after I purchased the car back in the late 80's, I went through all 4 calipers since the car had been sitting for about a year before I bought it.

All 4 calipers were machined to accept stainless sleeves to help prevent any future corrosion since there was some very minor pitting upon disassembly. 

The 4 piston front calipers coupled with the 2 piston rear calipers were very stout brakes and would throw you through the windshield if you stomped on the pedal.

I don't recall ever having an issue with the parking brake or pedal travel as the pads wore down.

[TAKerry]

11 hours ago, Ed Luddy said:

I've been considering doing a rear disc swap out on my recently purchased 1976 Trans Am as the rear diff in it is toast. Think I'll just stick with a drum brake 10 bolt Post Trac unit after reading all this thread. It will never see any track duty or likely any high speed hard driving. 

If you want to do a rear swap with disc, see if you can find a third gen firebird/trans am rear end complete. I have been told they will bolt right in. Havent done so myself but a friend did so with no problem.

[Guest]

From a trans brake with cast rear shoes for the parking (model t) to modern 4 wheel power disc antilock self braking there have been numerous advancements in braking.  However, if one notices the most common accident on the road today is "inadequate" braking. . .

 

The common factor resulting in accidents today isn't from lack of braking it's as simple as who is behind the wheel.  

 

My personal opinion, disc brakes look horrible when placed on a car that is out of period.  Of course this means they are "visible" which is about anything that doesn't have everything covered by a wheel and hubcap.  An argument for "safety" seems a little absurd when one looks at the rest of the car.  The truth is most people I have found (model t world) just want to be able to stop faster.  One could argue that increasing the speed of the car is a safety issue as well as it creates less of an obstacle on the road for other drivers.

[Rusty_OToole]

The most any brakes can do is skid the tires. Any good drum brake system will do that. If they are in good shape and adjusted properly drum brakes are good for all practical purposes. If you drive in real meat axey traffic or in mountainous country, discs would be a good idea but in that case I would rethink driving a 50+ year old car regularly.

[Mark Gregush]

2 hours ago, swab said:

The truth is most people I have found (model t world) just want to be able to stop faster.  One could argue that increasing the speed of the car is a safety issue as well as it creates less of an obstacle on the road for other drivers.

Off topic.

RE Model T's.

Or that they want more controlled stopping without skidding. Skidding is not stopping, been there done that more than a few times! Also, if installing any type of inline transmission, such as a Warford, that does or can have a neutral, adding some type of extra brakes to the car, such as disk or Rocky Mountain, is needed. 

Edited July 5, 2023 by Mark Gregush (see edit history)

[pfloro]

14 hours ago, zepher said:

I am surprised to hear of so many issues with GM rear disc brakes from the 70's and 80's.

I owned a '78 Silver Anniversary Corvette with the L82 / 4 speed combo.

Shortly after I purchased the car back in the late 80's, I went through all 4 calipers since the car had been sitting for about a year before I bought it.

All 4 calipers were machined to accept stainless sleeves to help prevent any future corrosion since there was some very minor pitting upon disassembly. 

The 4 piston front calipers coupled with the 2 piston rear calipers were very stout brakes and would throw you through the windshield if you stomped on the pedal.

I don't recall ever having an issue with the parking brake or pedal travel as the pads wore down.

The rear calipers used on the '79 -85 GM "E" bodies (probably also on the high end mid-70s GM cars) were of the single piston floating design...  The pistons were 

supposed to self adjust but didn't.  The 2 piston rear calipers used on your '78 Corvette were a very different design and they obviously worked properly.  Your 4

piston front calipers were also quite different than the front single piston floating calipers used on so, so many GM models of the 70s and beyond.

 

I'm glad that you missed the aggravation of those stinky rear calipers...!  It wasn't fun...

 

Paul

Edited July 5, 2023 by pfloro (see edit history)

[Frank DuVal]

1. I read Skinned Knuckles from the early 80s to when Neil took over and then to the end of publication. I do not recall Neil mentioning converting his 50 Ford to disc brakes. The magazine was about keeping vehicles STOCK.

 

2. I drove an 81 ElDorado Diesel from 110K miles when I bought it (1991) to 270k miles when I parked it (2004). Never had an issue with the rear disc brakes. Front and rear were single piston calipers.  

[alsancle]

2 hours ago, Frank DuVal said:

1. I read Skinned Knuckles from the early 80s to when Neil took over and then to the end of publication. I do not recall Neil mentioning converting his 50 Ford to disc brakes. The magazine was about keeping vehicles STOCK.

 

2. I drove an 81 ElDorado Diesel from 110K miles when I bought it (1991) to 270k miles when I parked it (2004). Never had an issue with the rear disc brakes. Front and rear were single piston calipers.  

Color me impressed with that diesel El Dorado mileage.

[Larry Schramm]

7 hours ago, Mark Gregush said:

Off topic.

RE Model T's.

Or that they want more controlled stopping without skidding. Skidding is not stopping, been there done that more than a few times! Also, if installing any type of inline transmission, such as a Warford, that does or can have a neutral, adding some type of extra brakes to the car, such as disk or Rocky Mountain, is needed. 

 

Agree with this statement. I put disc brakes on our T because I want to stop.  With a Warford transmission or a Ruckstell differential if by chance it goes into neutral, there are no real brakes.  Then if you drive/tour in the mountains the extra brakes are of great value.  That is why Rocky Mountain Brakes were developed in the after market in the day.   Here is one article on them.

 

https://www.fordmodelt.net/m/rocky-mountain-brakes.htm

[Glen Andrews]

The rear disc brakes on GM vehicles of the 80's into the 90's typically wore out the front pads way before the rear pads, often times the rear pads never wore out. The GM calipers were supposed to self adjust by use of the parking brake pedal, and many drivers did not use the parking brake, just put it into park; so the brake pedal would drop after  many miles of driving and since the rear pads were not adjusting out enough to do much work toward stopping the car then the parking brake pedal would drop because the pads were not adjusting outward. The pistons in the rear calipers were a "ratcheting" type, the picture of the square block tool a few posts before this post was the tool used to ratchet or screw the piston back in when rebuilding the caliper or replacing the rear pads. The pistons did tend to leak.

Corvettes from 1965-1982 used fixed mounted calipers front and rear and each had four pistons, the front pistons were slightly larger diameter than the rear, and the same brake pad was used front and rear. The parking brake system consists of two small brake shoes on each side that fit inside the rear rotor, it's a miniature brake drum within the rotor. Jay Leno used this Corvette Caliper set up on one of his early Teens? very heavy vehicle because he wanted it to stop.

It's personal preference as to putting on rear disc brakes as someone said, maybe for bragging rights, or it's a car that's going on some type of race track and disc brakes will perform better in spirited driving. Once again, it's personal preference and spend your money the way you want, as long as it works and you're satisfied!!!!

[Rivguy]

I never had problems with the stock drum brakes back in the 70's with my old Cadillacs. I felt that I could stop safely in traffic. Back then in Driver's Training we were taught to allow on car lengths distance per 10 mph. on the highway. Modern drivers and traffic will not allow you to do that. I often see cars following less than 20 ft. behind at over 70 mph! In the '80s i drove a '66 Riviera and the brakes were fine in traffic. It wasn't until the mid 2000's driving my '70 Mustang with 10 inch manual drums that I felt uneasy. I think that it's traffic and drivers that have changed. I never tailgate, but you see the favorite tactic of modern drivers is to dive into the lane in front of you, just before traffic slows suddenly, then slam on their brakes. A very scary, common situation that makes driving an old car quite stressful. 

In the 2000's Car Craft magazine did some testing on a 70's Dodge Dart before they switched to front discs. There was an appreciable reduction of the stopping distance coupled with less fade with the disc brakes. On the initial stops with the stock drums they actually stopped better and were easier to modulate once they had heated up a bit. 

If you want to improve the braking of your vintage car and can install front disc brakes, I think that's a good idea. If you're going to take your old muscle car to the track then it should be upgraded appropriately. If you have an old car you have to be constantly vigilant, and that can be hard to do in heavy modern traffic.  I suppose this is why most people don't often drive their really old cars. 

[Guest]

3 hours ago, Larry Schramm said:

 

Agree with this statement. I put disc brakes on our T because I want to stop.  With a Warford transmission or a Ruckstell differential if by chance it goes into neutral, there are no real brakes.  Then if you drive/tour in the mountains the extra brakes are of great value.  That is why Rocky Mountain Brakes were developed in the after market in the day.   Here is one article on them.

 

https://www.fordmodelt.net/m/rocky-mountain-brakes.htm

Not much braking is required to stop the wheels on a T.  I often wonder how "hard" disc brakes are on T spokes.  It seemed if memory serves Howard had metropolitan brakes on the front of his speedster.  In my opinion much more attractive than the giant discs being sold these days and very adequate for a T.

[76 Caddy]

That is the reason I got a '76 Seville, because they used rear drums.  1977 and newer had all discs and I was told they gave trouble, especially with the E-brake cable.

My 1999 Silverado (172,000) has all discs and I have already had to replace the rear calipers.

 

Tim

[Mark Gregush]

On 7/5/2023 at 7:47 PM, swab said:

Not much braking is required to stop the wheels on a T.  I often wonder how "hard" disc brakes are on T spokes.  It seemed if memory serves Howard had metropolitan brakes on the front of his speedster.  In my opinion much more attractive than the giant discs being sold these days and very adequate for a T.

No harder them any of the outside brakes that people install.