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Drum brakes versus disc brakes
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wizard
Posted 2018-11-11 3:03 PM (#573327)
Subject: Drum brakes versus disc brakes



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As I had a very interesting discussion with a dear friend of mine, I found it interesting to share this with you guys as well.

As many knows, I own a '60 Saratoga and I'm driving it a lot during long road trips during the summer season. These old cars doesn't necessarly have to follow the traffic ryth, they can also set it.

On the biannual inspections I had Always a very good result as for the brake tests, but it's actually only now that I realise how good.

2012, with the Total Contact 3-platform drum brakes, new Wheel brake cylinders, fresh DOT 3, fine adjusted, bleed and fresh wheel bearings, I got these values;


Front left 4.1 kN (921.7 Pounds)
Front right 4.0 kN (899.2 Pounds)

Rear left 3.0 kN (674.4 Pounds)

Rear right 3.2 kN (719.4 Pounds)


This is far higher values than ANY of our 3 modern cars can reach with disc brakes, which amazes me.

Naturally, this is the initial brake force, that will fade much faster upon hard braking than a disc brake set-up will do.


Still, mind that the brake shoes AND the drums are the original ones, 58 years of service, perhaps due to the asbetos brake shoes.

Of course the disk brake set-up requires less service, if the car is not driven in the Winter salt-slush.

I have never been able to compare the unsprung weight of drum brakes versus disc brakes, but I don't expect the difference to be high in weight.


I would be very interested in to learn about your inspection brake tests with disc brakes.

Below, please find a scan of the report (in Swedish, sorry)




Attachments
----------------
Attachments Inspection report drum brakes.PDF (298KB - 19 downloads)
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1960fury
Posted 2018-11-11 3:49 PM (#573329 - in reply to #573327)
Subject: RE: Drum brakes versus disc brakes



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wizard - 2018-11-11 3:03 PM


I have never been able to compare the unsprung weight of drum brakes versus disc brakes, but I don't expect the difference to be high in weight.





The Wilwoods I use are noticeable lighter than the small 2"x11" OE brakes, but the other disc kits I've seen are probably even heavier than the OE brakes (which used ribbed aluminum pistons, btw).

However, the rotating mass of discs is always lower due to the design difference of drums/discs. Drums have to be build extra heavy because they do not receive a counter-force for the expanding pistons, unlike discs AND most of the weight of drums is in the circumference, which affects performance even more. Another big minus for drums.

That said, the OE brakes are perefectly adequate for normal everyday driving, today just like 60 years ago.
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mikes2nd
Posted 2018-11-11 8:34 PM (#573344 - in reply to #573327)
Subject: RE: Drum brakes versus disc brakes


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wizard - 2018-11-11 3:03 PM On the biannual inspections I had Always a very good result as for the brake tests, but it's actually only now that I realise how good. 2012, with the Total Contact 3-platform drum brakes, new Wheel brake cylinders, fresh DOT 3, fine adjusted, bleed and fresh wheel bearings, I got these values; Front left 4.1 kN (921.7 Pounds) Front right 4.0 kN (899.2 Pounds) Rear left 3.0 kN (674.4 Pounds) Rear right 3.2 kN (719.4 Pounds

 

what did they use to test your brakes?   a roller type?

We dont get brake tested over here in the states... they assume your good over here if it stops

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wizard
Posted 2018-11-12 12:51 AM (#573355 - in reply to #573329)
Subject: RE: Drum brakes versus disc brakes



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1960fury - 2018-11-11 9:49 PM

wizard - 2018-11-11 3:03 PM


I have never been able to compare the unsprung weight of drum brakes versus disc brakes, but I don't expect the difference to be high in weight.





The Wilwoods I use are noticeable lighter than the small 2"x11" OE brakes, but the other disc kits I've seen are probably even heavier than the OE brakes (which used ribbed aluminum pistons, btw).

However, the rotating mass of discs is always lower due to the design difference of drums/discs. Drums have to be build extra heavy because they do not receive a counter-force for the expanding pistons, unlike discs AND most of the weight of drums is in the circumference, which affects performance even more. Another big minus for drums.

That said, the OE brakes are perefectly adequate for normal everyday driving, today just like 60 years ago.


Thanks' Sid, yes, the rotating mass is higher for drum brakes. If you think of the Pontiac 8 lug drums and wheels, those would surely have the highest rotating mass (but the drum brakes was very good on those).
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wizard
Posted 2018-11-12 1:19 AM (#573358 - in reply to #573344)
Subject: RE: Drum brakes versus disc brakes



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mikes2nd - 2018-11-12 2:34 AM

wizard - 2018-11-11 3:03 PM On the biannual inspections I had Always a very good result as for the brake tests, but it's actually only now that I realise how good. 2012, with the Total Contact 3-platform drum brakes, new Wheel brake cylinders, fresh DOT 3, fine adjusted, bleed and fresh wheel bearings, I got these values; Front left 4.1 kN (921.7 Pounds) Front right 4.0 kN (899.2 Pounds) Rear left 3.0 kN (674.4 Pounds) Rear right 3.2 kN (719.4 Pounds

 

what did they use to test your brakes?   a roller type?

We dont get brake tested over here in the states... they assume your good over here if it stops



Thanks' Mike, now that's strange news for us from Europe?!


I asumed that every country in the world test the cars for uneven brake force and too low brake force.


Yes, the brakes are tested on a rollers here in Sweden, two sets of rollers with 2 brake force gauges. The technician drives the car up on the rollers and start to apply the brakes - the rollers will sense when the brakes closes up to locking and the value is checked exactly before lock-up.

As for uneven brake force, the limit is 30% difference (left/right front and left/right rear).

The lowest acceptable brake force has a formula based on the pressure in the brake system, but to cut it short, a brake system must have over 58% of it's performance for to be accepted. Practically, this will rarely be tested, since that uneven brake force will be the first tell tale.


The fact that the brakes are not tested in USA (?) means that you don't have any real insight of the brake force values - therefore, for your conveniancy, as a comparision, our Chrysler 300C Touring 2007 have the following values;

Chrysler 300C Touring 2007
disc/disc

Front left 2.5 kN (562 Pounds)
Front right 2.6 kN (584.5 Pounds)
Rear left 1.8 kN (404.65 Pounds)
Rear right 1.8 kN (404.65 Pounds) )

Chrysler Saratoga 1960
drum/drum

Front left 4.1 kN (921.7 Pounds)
Front right 4.0 kN (899.2 Pounds)
Rear left 3.0 kN (674.4 Pounds)
Rear right 3.2 kN (719.4 Pounds
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BigBlockMopar
Posted 2018-11-12 6:20 AM (#573364 - in reply to #573327)
Subject: Re: Drum brakes versus disc brakes



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We have the same system and rules here too, only here, cars built before 1960 are except from bi-annual checkups.

My '57 Windsor was checked once for the license application.
They used a roller brake-force bench at the time, but I didn't write down any numbers.

'Normal' check-up garages and stations here usually have 2 simple plates on the ground where the brake tests are done on.

The car had Wilwood discs when I bought it but still the stock drums at the rear.


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BigBlockMopar
Posted 2018-11-12 6:24 AM (#573365 - in reply to #573327)
Subject: Re: Drum brakes versus disc brakes



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Comparing brake forces is one thing, but it's really about 'brake control'.
Disc brakes are easier to control than drums.
Also, a discbrake system has way fewer parts which would be a big plus for the factories. Quicker assembly and less costs.
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wizard
Posted 2018-11-12 6:42 AM (#573367 - in reply to #573365)
Subject: Re: Drum brakes versus disc brakes



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BigBlockMopar - 2018-11-12 12:24 PM

Comparing brake forces is one thing, but it's really about 'brake control'.
Disc brakes are easier to control than drums.
Also, a discbrake system has way fewer parts which would be a big plus for the factories. Quicker assembly and less costs.


Yes, that's correct Herman, the real reason for implementing disc brakes was less expencive, less service AND, practically no fading during normal conditions.

To adjust the drum brakes requires knowledge and some tweeking for to get it right.

A disc brake set-up has more even brake force and does not normally tend to give uneven brake force, which practically means better brake Control.

That said, I clean up, check and adjust the drum brakes twice per driving season and I've got a decent brake control as well as very high brake force.

With a quality disc brake set-up (no floating calipers) and some good brake pads, it's not likely to have to do anything during the expected life cycle (apart from changing fluid/bleeding the brakes once every two years. This is of course only valid for cars not driven during the winter season in our type of salt slush.
Typically, disc and brakes needs to be exchanged in the worst case every 2 years on the new cars here in Southern Sweden
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wizard
Posted 2018-11-13 12:28 AM (#573425 - in reply to #573364)
Subject: Re: Drum brakes versus disc brakes



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BigBlockMopar - 2018-11-12 12:20 PM

We have the same system and rules here too, only here, cars built before 1960 are except from bi-annual checkups.

My '57 Windsor was checked once for the license application.
They used a roller brake-force bench at the time, but I didn't write down any numbers.

'Normal' check-up garages and stations here usually have 2 simple plates on the ground where the brake tests are done on.

The car had Wilwood discs when I bought it but still the stock drums at the rear.


Here in Sweden, cars over 50 years doesn't need to do any inpections any more (for good and bad). We can do volantary inspections, but there will not be any legal remarks.

This is good for the guys that love and care about their cars, but I'm somewhat worried for the beer barges used by younger guys just for heavy revelry .


I'm curious to know how the brake testing plates works Herman.



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wizard
Posted 2018-11-13 3:44 AM (#573429 - in reply to #573327)
Subject: Re: Drum brakes versus disc brakes



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I just talked to our local Opus inspection manager about this subject.
The brake force is checked at locking brakes actually, if the technician feels that there's a risk of damaging the tires, then the brake force gauge has an indicator for just before brake locking.

As for the lowest acceptable brake force, this is more complicated;

Let's assume that a vehicle has perfectly even brakes, but the technician get the information from the brake force gauge that the force is low, then the bring a retardation gauge and make a practical test, by driving the vehicle up to 40 kilometers per hour and apply full brake.
The retardation gauge then gives a value that makes part of a complicated formula that includes the vehicle weight and age - practically a brake force <58% of the brake system performance is not acceptable.

These tests are very seldom performed, as it's more common that a vehicle has uneven brakes.


The most common brake force values for a modern car is;

Front brakes 2.5 kN (562 Pounds)
Rear brakes 1.5 kN (337.2 Pounds)


The manager informed that the values I have with drum brakes are seldom reached anymore, but in the old days, it was a normal thing after a complete brake service.

The manager also informed me that Opus also have inspection stations in America but he said that the proceedures and tests vary a lot from state to state.


This thread has been created for to inform you that a classic car, with drum brakes, serviced properly can be driven with safety and has no real need to be upgraded to disc brakes.


Naturally, the disc brakes will out perform drum brakes, especially as for brake control. If the classic car is driven active in higher speeds and/or in mountainous landscapes, then the disc brakes are a clear advantage.


Mind that many of our members are good experienced mechanics and do the disc brake conversion by them self with various kits and components.


For a layman, a disk brake conversion diy can end up in a real sourdough

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BigBlockMopar
Posted 2018-11-14 2:31 PM (#573511 - in reply to #573327)
Subject: Re: Drum brakes versus disc brakes



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The brake testing plates works with simple electronic load-cells mounted inside/under the plates, which register the braking force applied to them.

Here's a clip of how they are operated;
https://www.youtube.com/watch?v=0dtVgL8uv1I&t=90


My previously owned '64 Newport had drums all around too, and it also easily achieved above 4K values everytime.


Edited by BigBlockMopar 2018-11-14 2:33 PM
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1960fury
Posted 2018-11-14 3:20 PM (#573515 - in reply to #573327)
Subject: Re: Drum brakes versus disc brakes



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I know that the OE drum parking brake in my car really scared the guys on the test machine. They apply it like on a new car and the Fury locks immediatly and jumbs out away from the rollers! I heard it several time. "I never checked a car with a better working parking brake before!" And of course, uneven braking is impossible.


Wow, Bigblock, even with painted bumpers and those rims and that color, that machine is a feast for the eyes!

Edited by 1960fury 2018-11-14 3:39 PM
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1960fury
Posted 2018-11-14 3:34 PM (#573518 - in reply to #573327)
Subject: Re: Drum brakes versus disc brakes



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The ****** EU (or just ****** Germany) made a big fuzz about the brake testing devices recently. As of this, or last? year, all shops had to change to a new computer integrated system. Even newly purchased, perfectly fine working devices had to be scrapped. This is a major financial problem for the smaller shops. The MOT-stations of course simply charge the "customer". A freaking bi-annual check, that takes 10 minutes and no work at all, is over €100 now! Unfortunately old cars here are not excepted, like in Sweden.

Edited by 1960fury 2018-11-14 3:36 PM
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wizard
Posted 2018-11-14 4:06 PM (#573521 - in reply to #573511)
Subject: Re: Drum brakes versus disc brakes



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BigBlockMopar - 2018-11-14 8:31 PM

The brake testing plates works with simple electronic load-cells mounted inside/under the plates, which register the braking force applied to them.

Here's a clip of how they are operated;
https://www.youtube.com/watch?v=0dtVgL8uv1I&t=90


My previously owned '64 Newport had drums all around too, and it also easily achieved above 4K values everytime.


Thanks' Herman, that test seems to be very smooth with less risks for damaging the tires, especially for spiked Winter tires.
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wizard
Posted 2018-11-14 4:10 PM (#573522 - in reply to #573515)
Subject: Re: Drum brakes versus disc brakes



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1960fury - 2018-11-14 9:20 PM

I know that the OE drum parking brake in my car really scared the guys on the test machine. They apply it like on a new car and the Fury locks immediatly and jumbs out away from the rollers! I heard it several time. "I never checked a car with a better working parking brake before!" And of course, uneven braking is impossible.


Wow, Bigblock, even with painted bumpers and those rims and that color, that machine is a feast for the eyes!


Sid, the technicians at the inspection stations here are not allowed to test the propeller shaft brakes on the rollers, due to high risk of damaging the car, the rollers and even personal.

That said, I always inform the technicians that my car has this type of parking brake - then they don't test it on the rollers, they do a mild brake test in low speed on their test run instead.
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wizard
Posted 2018-11-14 4:15 PM (#573523 - in reply to #573518)
Subject: Re: Drum brakes versus disc brakes



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1960fury - 2018-11-14 9:34 PM

The ****** EU (or just ****** Germany) made a big fuzz about the brake testing devices recently. As of this, or last? year, all shops had to change to a new computer integrated system. Even newly purchased, perfectly fine working devices had to be scrapped. This is a major financial problem for the smaller shops. The MOT-stations of course simply charge the "customer". A freaking bi-annual check, that takes 10 minutes and no work at all, is over €100 now! Unfortunately old cars here are not excepted, like in Sweden.



Agreed, this is the jack-in-offices at their worst. A test here goes for roundabout €40, but since they opened the market for more actors than the former state controlled monopoly stations, the prices has started to point upwards.

WE have more stations to chose from and higher availability for inspection booking, but…...
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1960fury
Posted 2018-11-14 4:20 PM (#573524 - in reply to #573327)
Subject: Re: Drum brakes versus disc brakes



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How can they damage the car? If you make an emergency stop, you will have to use the E-brake too and my propeller shaft sees more brutal action regularly. Yes the rollers provide more friction but you usualy brake at a higher speed, with more weight on the front axle. They always test all the brakes until the brakes lock up.
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wizard
Posted 2018-11-15 12:52 AM (#573555 - in reply to #573327)
Subject: Re: Drum brakes versus disc brakes



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It has happened here in the past, that the testing of propeller shaft brakes snapped off universal joints or U-bolts Sid.

I do beleive that the risk is higher with brakes that has the brake shoes external on the drum.


Even in a case, let's say like you have experienced, the car jumps off the rollers and accindentally hits a custome or a technician, or damaging the car - that would be the inspection station responsability and they have excluded the test for this reason.


The propeller shaft brake is not a bad thing, but there's this risk in traffic if one locks the brake. In case of need to use the parking brake in emergency, I'm prepared to release the handle if the brake should block.
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1960fury
Posted 2018-11-15 8:53 AM (#573565 - in reply to #573327)
Subject: Re: Drum brakes versus disc brakes



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Of course standing in front of the car while testing is prohibited. Regarding emergency braking, yes, that is always the case, if only the rear brakes lock. I wanted to add a vacuum parking brake release, not only for the reason that it prevents driving with the brake applied.
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wizard
Posted 2018-11-15 12:35 PM (#573586 - in reply to #573327)
Subject: Re: Drum brakes versus disc brakes



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Good idea with vacuum controlled park brake releas Sid, perhaps an Imperial set-up would fit?
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1960fury
Posted 2018-11-15 3:17 PM (#573600 - in reply to #573586)
Subject: Re: Drum brakes versus disc brakes



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I think one could fab one pretty easily with any vacuum diaphragm hsg, like used in all 57+ FL heater systems. I have a couple of these lying around. Only thing that kept me from doing this is, it would prevent a locked parking brake with the engine running. Of course this is good in an emergency situation...
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wizard
Posted 2018-11-15 4:15 PM (#573611 - in reply to #573327)
Subject: Re: Drum brakes versus disc brakes



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No Sid, the Caddys had the brake release automatically released in any gear but neutral. Not sure, but I Think also the Imperials had the same function.

Think about it, it'll solve the problem with emergency brake as well, right?
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1960fury
Posted 2018-11-15 8:44 PM (#573630 - in reply to #573611)
Subject: Re: Drum brakes versus disc brakes



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wizard - 2018-11-15 4:15 PM

No Sid, the Caddys had the brake release automatically released in any gear but neutral. Not sure, but I Think also the Imperials had the same function.

Think about it, it'll solve the problem with emergency brake as well, right?


Yes, it would. Tempting.
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wizard
Posted 2018-11-16 3:04 AM (#573644 - in reply to #573327)
Subject: Re: Drum brakes versus disc brakes



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Came to think about the vacuum controlled parking brake Sid, there must be yet another criteria for the relese.


Let's assume that the parking brake is set and someone pushes a drive button or put the gear lever out of "Park" in for example GM-cars. If there should remain vacuum in the buffer tank, the parking brake would release.


So, at least one criteria must be ingition on or pressing down the brake pedal (vacuum switch).


Is here any Imperial owners that can explain the function and saftety measures?
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plymouth
Posted 2018-11-16 8:42 PM (#573652 - in reply to #573644)
Subject: Re: Drum brakes versus disc brakes



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The Imperial automatic parking brake release is controlled by a vacuum valve mounted to the back of the push button box. With the parking brake set and the car in neutral, the valve is closed so no vacuum can reach the diaphragm. When drive or reverse is selected the valve opens and vacuum is applied to the diaphragm causing the parking brake to release.

Edited by plymouth 2018-11-16 8:43 PM
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Stroller
Posted 2018-11-18 12:41 PM (#573710 - in reply to #573327)
Subject: Re: Drum brakes versus disc brakes


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My '77 NY had the park brake vacum release with it set and put in D or R it released. Thing about drum VS disk to me is the major brake fading issue which is prone with drum brakes. In normal day to day driving drum brakes work just fine, as long as they are working. Now to me if you have an engine producing over 500 hp in a car with crub weight of say 3,200lbs disk's would be an asset. If running something between 195-300 Hp front disk's and rear drums tend to suffice. I have done work on cars that were say oh 20 or years old with over 100k on the clock still with original rubber hoses, factory hold and return springs, wheel cylinder and calipers. They want a brake job but do not want to pay to have the rubber changed. Hard to explain to people what the black crap in the bottom of MC is the rubber from brake components. A pad slap or shoe swap is not a brake job unless your racing the thing. Also the parking brake. If you never set it, don't do it because it may not release.
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