Steel Brake Drums

[Guest]

When I worked in a GM parts department I sold hundreds of brake drums. I have had to peplace five or six drums on modern cars that I have owned. My 1930 Pontiac (daily drive) that now has 470,000 miles on it has steel brake drums (pressed steel?). I have relined my shoes about 10 times. Each time I have had my drums checked for roundness. They are always okay, they have no scores in them and the brake shops say if there were scores they could not turn them as they are steel. How come these drums have lasted so well? Any ideas guys.<BR>Happy hobbying<BR>ps What would happen if you rivited linings on with "pop rivets" rather than brass ones?

[Guest]

Originally my drums were 10.75 in diameter. Now they are 10.769. <BR>Happy hobbying

[Peter J.Heizmann]

Reid, how are you?<P>PackardV8 made some good points.<P>I am in the foundry business. We used to make brake rotors by the thousands, just for a case example. We lost "all" the work to China. Gets down to price. (My company: <BR>$ .38 per pound. China: $ .26 per pound "DELIVERED TO YOUR COMPANY".) We testified in D.C. before a Senate Sub-Committee some years ago about the dumping of inferior, price driven replacement parts (the parts you buy at your local discount parts "Chain Stores" AND at the "Dealership" where your modern day driver was purchased.) All to no avail...<P>Steel certainly has a higher Brinnell & Rockwell hardness & wear characteristics Vs. Cast Iron. However, the cost of Steel is considerably higher than cast iron. Price, again.<P>Brass Vs. Pop-Rivets: I am not in the non-ferrous industry, but, my best guess is brass has better spark resistance than aluminum pop rivets, though negligibe as PackardV8 proved. Do not know if my theory on spark resistance has much to do with this.<BR>Aluminum will score quicker than brass, but, again, PackardV8 proved it is a mute opinion.<P>Pop Rivets sure are cheaper than brass and if they work, try it.<BR><B>"Delivered"</B><P>Regards, Peter J. <p>[ 08-19-2002: Message edited by: Peter J Heizmann ]

[Peter J.Heizmann]

Reid, I rambled on the previous response, forgetting to mention your drums are down only .019". Again, as PackardV8 mentioned, I would not panic at this point. Depending on the wall thickness of the drum and it gets down to (-) .025 "a side" then make a decision. (Don't know how thick the section size is, so, I am making conjecture.)<P>Regards, Peter J.

[Guest]

i use Al. pop-rivets on my 48 indian motorcycle brake shoes. WHY NOT!!! They seem no softer than brass and should not score the drum any worse either. They have lasted about 20K miles and do need relining now. The pop rivets have held very well. In fact, the front brake shoes r Al.<P>as for your Drums i'm not sure. If they r not severely scored nor severely out of round then WHY turn them??????<P>What does your service manual say.???? <P>In many cases, brake shops do not want to deal with anything out of the ordinary. This is one the major reasons alot of companies like studebaker, nash and hudson had service problems and hence sales problems during the 50's and 60's.

[Guest]

take the drums to a regular machine shop. They CAN be turned on a lathe. Most of these automotive machine shops these days r just high priced hobby shops anyway.

[Guest]

something else to keep in mind is that your '30 brake drum is A REAL BRAKE DRUM!!!!<BR>Thats why it has lasted.<P>Drum brakes have gotten a bad rap over the years NOT because it is an inferior design but rather because the auto companies cheapened them up so much in the post war years.

[Guest]

what diameter does it measure???

[Guest boettger]

My 1930 DeSoto also has steel brake drums. They are quite worn and a bit out of round.<BR>Does anyone have any solutions for restoring said drums? I'm afraid they are getting a bit thin. Spray Welding, source for replacements...?

[Restorer32]

Talk about desperation...restored a brass car with severely worn and warped brake drums, no luck finding anything remotely close for replacement. As the show date loomed we chucked a 14" diameter steel slug in the lathe and made those suckers...ended up with 2 extremely nice brake drums as well as two 55 gallon drums of turnings...desperate times call for desperate measures

[Guest]

Peter Heizmann: What will become of Bethlehem Steel????? Can u cast Aluminum in your foundry???

[Guest]

If you have junk drums I believe there are three options: Make new ones from steel, cast new in iron, or sleeve with cast iron.

[Al Smeraldo]

If a steel drum is scored or bell mouthed or out of round but still in tolerance for turning it can be ground. When I taught auto mechanics I had an AAMCO brake lathe that had a grinding attachment. We usually used it if the drums had hard spots that couldn't be cut with the regular cutter. Al

[Peter J.Heizmann]

Hello, gents. <P>Some interesting queries. I'll do my best to get back with some facts after consulting our metallurgical gurus tomorrow.<P>Steve and Terry: I made note to check out the spray welding, though, I am not a big fan of this for longevity, heat atmosphere, etc. Sleeving, that Terry mentioned sounds better, but, I still want to investigate to the best of my resources.<P>Restorer32: I'll tell you what, my hat is off to you for determination, not to mention the success of turning that 14" slug.<P>PackardV8: As for Bethlehem Steel - sorry. It is dead. The huge Bethlehem, PA Comlex is part of a rehabilitation project. Most recently, there was an effort to retain a few of the huge stacks for historical purposes. The rest of the complex will become, I believe, shops/restaurants/etc.<P>Aluminum: We pour Fe (grey iron & ductile iron) castings. We have cross-business relations with Aluminum/Non-Ferrous foundries, so, let me know what, if any help, I can lend.<P>Al: Know where you are coming from hitting the hard spots. Many castings, "New", are machined perfectly and sold. This is relative to any commercial casting. A BIG however, is when one mills down the original machined surface deeper, then deeper, then deeper, it is inherent with Ferrous Castings that you probably, or, eventually will hit carbides, even porosity pockets that were not evident when the part was new.<P>Going through it big time now with an industrial account's Bevel Gears for valve actuators. They did not tell us up front that they would take an as-cast 6" diameter, and, depending on special orders, turn it down a full 2.76" a side. That's a hell of a lot of material.<P>Remember: Cast Iron parts and Porosity/Carbitic Pockets are part of the beast. Section Size dictates the severity.<P>--I'll get back to you folks shortly with any advise. Must get to the plant tomorrow and discuss with the "gurus".<P>Regards, Peter J.

[Guest]

When I was a kid,I had several 1936 Chevrolets,The Master had GM "Centrifuse" drums.They had a steel web with an iron ring cast onto the web. The Standard had steel stampings.The Master had VERY good brakes.The brakes on the Standard were marginal at best,plus they "Squeeked".To all of you who have studied science, you know that energy cannot be destroyed,it can only be moved around.A moving car has lots of kinetic energy. The brakes,because of friction,turn this kinetic energy into heat,then dissipate the neat.A lightweight steel drum.wont absorb much heat,so fading is a problem.A large cast drum will absorb much more heat,but they too will fade if used for a prolonged period.Disc brakes are superior because they will dissipate heat more readily. Buick had aluminum drums which were very good,but very expensive.Aluminum dissipates heat at a seven times better rate than ferrous material.

[Restorer32]

Also had a pair of extremely rare brake drums for a '20 Kissel spray welded...incresaed the diameter by almost 1/2 inch then turned them back to standard...worked well except only spray weld I could have done locally was stainless steel which is of course a very poor dissipator of heat but the brakes seemed to work well...again...done out of desperation...drums were so thin you could flex them with your fingers, literally, dual externally contracting so I think we would have some warning before complete failure, at least I hope so

[Guest]

Pop Riveted Linings: Keep in mind that most linings are drilled for a riviet and then COUNTER SUNK with a kind of bevel or funnel like cut at the bottom of the hole. IN this case u will need to use an appropriate type pop rivet with a head that accomodates a counter sink. Also, u mite have to drill out the holes in the shoes to accomodate the pop rivet diameter u r using. Dont just throw a pop rivet in there. Analyze the parts first to determine what needs to be done. Mite be easier to just go ahead get brass rivets it requires and put them in. Special peening punch and bucking drift can be made from common punch and chisel. I used pop rivets because the rivets supplied were not correct and i could not find any that small (motorcycle). They do just fine tho.

[Al Smeraldo]

Peter, we would encounter these hard spots while taking the first cuts on a drum. we never cut drums more than .060 oversize. I am curious. Could these hard spots have been caused by the heat of braking? This seems unlikely as the heat generated probably never exceeded 700-800 deg. Al

[Peter J.Heizmann]

Al...Sorry. I did not comment on the wear causing the hard spots.<P>My opinion is "Possible". Depending on where carbides were when the casting chilled, the wearing of the casting, it is within the realm of possibility that you could hit a hard spot/carbitic area.<P>You are correct concerning the .060. That equates to .030 "A SIDE" on a round part. On a flat casting, .030 is the norm up to 4" in length, .045 progressively to 6" in length, and so on. If you have a 1 foot long casting, the A.S.T.M. recognized machining flatness tolerance is over .120.<P>Regards, Peter J.

[Peter J.Heizmann]

Hi, Ken. Were all family here. There is no dumb question.<P>Without going into a littany, here's my best shot.<P>--Pretend each of your drums is a 1/2 piece of "pine" wood you just bought at a lumber yard.<P>--You do not like the smoothness. Taking a hand-held wood plane, you successfully smooth 3 of the pieces, however, piece #4 you banged with a hammer, causing a dent.<P>Your goal is to have all pieces equally smooth, AND, retain the same thickness. <P>Well, you plane, plane, plane #4 for 10 strocks until you get the hammer dent out.<P>Unfortunately, #4's thickness is now down to 3/8" thickness. That means you must take #1-#3, and, plane them down to 3/8" so all are equal.<P>--As for metals, we could go on forever. Uneven wear caused your #4 to look good with the eye, however, if there is a "scored", "uneven" area, a machinist would "turn" (plane) until the uneven area is smooth. Unfortunately, he would be reducing the thickness of the part to the point it would be too thin "overall". It would fail in functional atmosphere.<P>--Denial: After awhile, there are parts that lend themselves "shot". You cannot keep repairing, planing, milling forever. After awhile there is no more material to take away. In time, you will be milling "air" on the low spots, material on the thicker spots.<P>--Material of your drum: Hopefully, someone on the forum with more experience in the older cars will chime in.<P>Regards, Peter J.

[Guest Ken G]

Please forgive me if this is a silly question. One at least of the drums on my Rover is significantly worn. Looking at it with a totally ignorant eye, there appears to be lots of thickness, allowing it to be turned. However, I have seen several messages making distinctions between pressed steel and cast drums, and possible objections to turning one or the other. Why does the material affect whether a drum can be turned, and most importantly, how do I tell which I have?<P>Ken G, 1925 Rover 16/50

[Al Smeraldo]

Ken the thickness may appear to tolerate turning and in fact it may be able to be turned to a smooth surface. However if the material gets too thin it cannot dissipate the heat properly. This causes the drum to expand away from the shoes causing a condition known as "brake fade". The pedal pressure needed is greatly increased under this condition. I can remember going down a long, steep hill on a hot day standing on the brake with both feet in a car experienceing brake fade. Al

[ply33]

Hmmm.... I had never really thought about the actual mechanism that leads to brake fade (other than it was heat related).<P>I think the concept you are putting forward here is that when cool the shoe "outside" diameter matches the drum inside diameter and you have a full contact area for your friction. As the drums heat up they expand to a slightly larger diameter but the shoe "diameter" remains the same. Now the contact area between the shoe and the drum is reduced (because of the mismatched diameters) leading to reduced braking.<P>I guess that sounds reasonable. I wonder if that is what is really happening....<P>It would also mean that disc brakes need not disipate heat any better than drums to still achieve fade resistance: Any expansion in the rotor would not change the contact area with the pads....<P>It would also suggest that the old externally contracting band brakes would not have the same fade problems as internal expanding shoe brakes. I have no experience with driving a car with external band brakes. Does anyone out there know how they deal with prolonged hard braking?<P>I have to think about this some more... Thanks for the thought provoking post.

[Guest]

I drove a 27 pontiac with just 2 wheel external contracting brakes and a 28 pontiac that had external contracting on the rear and internal expanding on the front. The one with front brakes was a tad more stable in high speed panic stopping. The rear external contracting brakes never faded when I was driving of course my 30 with the steel drums has never faded either. However I have experienced sever fade on every vehicle with cast drums that I have ever driven.

[Guest]

I am building a fuel-injected 455 (with a blower) Where can I get a set of 1928 Pontiac brakes for it ?

[Peter J.Heizmann]

Unregistered.<P>Try <A HREF="http://www.amalgamated1928brakeshoescorp.com." TARGET=_blank>www.amalgamated1928brakeshoescorp.com.</A> <P>If no success, try <A HREF="http://www.funeraldirectors.com." TARGET=_blank>www.funeraldirectors.com.</A> <P>The latter will probably be of more use based on the game plan.<P>Regards, Peter J.

[Guest]

Shouldn't all tales about how wonderful steel brake drums are start out with "Once upon a time"?

[Guest]

Only if you can say they lived happily ever after, and I can. I am still driving with my steel drums, and they still lock up all four wheels with three-quarters of a pedal on dry pavement anytime. By the way Peter I am one. (re your last comment on your last post)<BR>Happy hobbying

[Guest]

Tod, Disc brakes and externally contracting brakes tend to lock up if overheated as the disc/drum will expand towards the braking surface. I had this happen a few years ago while driving down Bear Mtn. N.Y. on a 105deg. day. Al

[Guest]

My '27 Buick had what appeared to be pressed steel external contracting drums and there was no discernible wear in 60,000.00 miles of hard driving plus my '15 Stellite {cast iron drums} showed no discerible wear in approx 17,000 miles of hard use.

much depends upon driving skill and knowing when and where to apply the brakes, make damn sure you have woven semi metallic linings though, as original, as a friend with a '27 Lincoln used cast linings and had cause to regret it!

[Guest Ken G]

I'm feeling a bit sore because I prepared and sent a reply yesterday, and it was visible in the thread, but in the change to the new regime it seems to have been discarded.

However, the point was that for drum brakes, the main way in which heat from the friction between the lining and the drum is dissipated must be by conduction through the wall of the drum from the inside to the outside, and then convection from the outside surface. If that is right, then the thinner the wall the better the cooling, although in practice I don't think wall thickness would make much difference because the more significant limitation would be that convection. Anyway, this suggests that how much material you can safely remove from the inside of a drum does not depend on thermal considerations but on simple strength.

I would suppose (but I am guessing here) that steel drums have much thinner walls than cast iron ones, so removing say 30 thousandths of an inch is a much more significant proportion.

Am I way off target?

Ken G, 1925 Rover 16/50

[Peter J.Heizmann]

Hi, Ken. Don't feel bad. I lost a response last night.

Basically what I was saying in comparing planing wood with a "low" spot was just to give an idea. If by your naked eye, you think, or, suspect a round part has a "low" spot, or, out of round, you will turn (machine) the suspect part until you literally make it too thin, or, have the potential for part failure (shattering, cracking, and, so on.)

Steel "STAMPED" parts have superior strength.

Foundry "SAND CAST" Steel cannot compete with "SAND CAST IRON" concerning thickness. Cast Iron (Grey) has a fluidity rate far superiour to Steel Cast parts in order to make a thinner part.

In the business, I always use the following example:

MAPLE SYRUP:

Grey (cast iron) = Syrup heated to 100 degrees will almost like water.

Steel (cast) = Syrup at 40 degrees will flow slow and will require larger cavities to fill the mold.

Stamped or forged steel can compete with cast iron for thinner walls.

Now, I was not saying all 4 drums must be machined/turned to equal diameters.

I was only concerned about saving original parts can only go on for so long. You keep turning a drum, rotor, etc., for only so long until you will make it a dangerous part. If a round piece is worn, or, warped, you will be turning down good material until you eliminate the "low or worn spot".

The thinner the better with cast iron is not a good thing in this case...

Regards, Peter J.

[Guest]

I think the last couple of replies answered my first question. I now believe the reason my pressed steel drums have lasted so long and work so well is that they are very thin by cast standards. The edge looks to be about 8 guage? Thanks for aall the interesting comments.

Happy hobbying

[Guest]

If steel drums were good,why were they abandoned?

[JoeMarsh]

I see this is an old post but has anyone solved the problem of brake fade with pressed steel drums.

I found a shop the vents the drum surface by drilling and they claim it is very effective in reducing brake fade.

My 1930 Model S Hupmobile has scary brake fade on long hills at speed. In fact I don't think you get more

than 3 pumps on the pedal before they start to fade. It is a heavy car with small brakes, bad recipe.

I plan to have the shop do the drilling and change the brake lining to a woven Semi-Metallic of the

highest friction coefficient I can find. Does anybody have a better approach ? Dura-Brake will cast

custom drums with an eight piece minimum at about $350 a drum but the coefficient of expansion

for cast iron isn't that much better than steel. I was thinking of welding a ring around the outer edge

and some cooling fins on the outside of the active brake area. Any comments on that idea ?

[Guest]

I have never really had any problem with brake fade, however when descending a long steep hill I use second gear.

[Spinneyhill]

There is a Really Dumb Question that must be asked. Is your brake fluid less than two or three years old? If not, replace the fluid with DOT 4. Use new fluid.

 

DOT 3 and to a lesser extent DOT 4 fluid is hydrophilic and absorbs water. When the fluid gets hot (e.g. on a long downhill with the brakes on) the water vaporises. You get a spongy pedal while the steam is in there and the brakes fade.

 

Another thing is the shoe material. I understand some types are not so compatible with our old brake drums.

 

And are the shoes arced to match the drums? If the drums are worn, the shoes will only touch over a short length if they haven't been arced to fit the drum. You can do this with stick-on sand paper on the inside of the drum and then sand the shoes for that drum on it.

 

Quite frankly, IMO the brakes would not have faded when the car was new so there is a problem to fix before you start modifying them.

[HankZ]

Will stick in my 2 cents, but only for my car. I have a 1930 Model A Ford. From what I can tell, the steel brake drums on this car are not original. When I purchased this car in 2016, the brakes were kind of grabby as if the front drums were out of round. Got the drums off and took them to the local auto shop to have them turned. They both were out of round and it took about .028 to clean them up. The fellow doing the clean up had never seen steel drums before.

 

Got on a Ford message blog, and started discussing the drums, got a lot of responses. Basically steel drums were a replacement and were prone to warping as they heated up and cooled and heated and so on. Turning them to true them up, actually enhances the warping problem as the drum thickness is now thinner. So the point of this is the steel drums on my Model A Ford started warping because of heat, and cleaning them up to get them round again is nothing but temporary as a bit of braking and heat will warp them again!  I bit the bullet and bought cast iron drums! - Hank