Brake drums

[BTFD 3227]

Greetings all and thanks for letting me in. New here but have been reading along as a guest for a while but can’t find the information I’m in need of.

I’m working on a 55 B85F for our local Firefighters Union and need some help locating rear hydraulic brake drums. At some point the rear brakes have gotten really hot and the pass rear drum broke. The driver side is intact and can hopefully be turned out.  
Does anyone out there have or know of a source for these drums? Or an aftermarket alternative. I just need to find drums to get this old girl stopping again.

Any help would be appreciated.

[Geoff Weeks]

whoo-boy, that is going to be difficult is my guess. Look for some casting numbers on the old drum.

If one got that hot, it is likely you'll need two. Once a drum get hot, it gets hard and will not grab the lining, requiring more pressure to stop, which leads to what you see in that picture.

What is the brake size? Hopefully it is a common size.

[Geoff Weeks]

1st measure the ID of the drum, along with how wide the shoes are

Next measure the pilot diameter (red) and the bolt circle diameter (blue) and start looking for a match

Ideally you'll have a Mack # or a casting # to try and cross.

[BTFD 3227]

Yeah, I’m finding out that the hydraulic brakes on these older Mack’s are rare and rather unique. Especially the rear brakes. I’ve got a casting number off of the good drum but nothing crosses over. 
The rear shoes are 15x5 and are rare as well. 
I’m wondering if I source a set of drums without the concaved bowl, which I’m guessing is by design in case of a seal failure to stop oil from entering the drums, will there be any issues. Unless there’s a seal failure. 
which brings me to another question,,, is the inner bearing a grease bearing or oil bath? If it’s oil bath like the outer, then why is there a seal in the middle of the hub? Another topic for another day I guess.

[Geoff Weeks]

15x5 sounds small for a B85? IIRC that size may be used by wedge brakes.

I have some that have a stamped steel piece that is like your concave bowl.

I don't have a lot of Mack axle experience.

I would 1st try and get some numbers

2nd I would grab a catalog and start looking for drums that match those measurements.

[Geoff Weeks]

here is Webb's offerings, you can look up by brake diameter, you need inboard with 6 or 5/6 mounting holes, and with the pilot measured from your old drum.

https://www.webbwheel.com/webbipad/pdf_files/SD 090 - 2019 Catalog.pdf

[Geoff Weeks]

Gunite's offerings

https://www.accuridecorp.com/sites/default/files/resources/2023-08/WE1.011 Rev. 4 Gunite Brake Drum Product Catalog 8-7-23.pdf

[BTFD 3227]

Thanks Geoff 

Aftermarket seems like it may be my best option. I’ve talked to a couple of individuals up north that may or may not have drums laying around somewhere in their collection. 
 

The stamped steel piece you mentioned, is it separate from the drum and hub? How does it attach? Just wondering if something like that would solve my concern in case a seal fails. 
I need to figure out if it’s even needed. 

[Geoff Weeks]

The stamped steel mounts inside the drum, and is held in place by the same bolts that hold the drum to the hub.

It seams to be left off newer set-ups, My guess the improvement in seal tech made them obsolete.

[h67st]

16 hours ago, BTFD 3227 said:

which brings me to another question,,, is the inner bearing a grease bearing or oil bath? If it’s oil bath like the outer, then why is there a seal in the middle of the hub? Another topic for another day I guess.

The inner bearings were greased. When I built mine I omitted the center seal and made them both oil bath. As GW said, wheel seals have come a long way over the years.

[BTFD 3227]

Thanks guys.

Makes sense. I appreciate the information. 
Hopefully I can find drums now and get this old girl back on the road soon.

[BTFD 3227]

No luck on aftermarket drums. Gunite went out of the drum business and Webb wheels doesn’t have anything that match these specs. 
Back to square one. Surely someone out there has a couple drums, knows where some might be or knows of a solution to get this old girl back out on the road. 
Without rear brakes this project is pretty much done for.

[mrsmackpaul]

I doubt you'll buy something off the shelf

However, that isn't a drama

Find a 15 inch drum machine it to suit 

Something like this 

So it's 180 mm deep, 5 inches is roughly 125 mm

Machine it down to suit that width drum

ThenI dunno about the center, but it can be re drilled and machined to suit what you need 

You will not buy what you need new, all the secondhand ones will most likely be worn out

Gotta adapt something to suit 

And if this is no good, then assuming the truck has 20inch wheels or bigger then adapt the truck to a more common brake combo

This really isnt to bigger issue, just saying

 

Paul

[Joseph Cummings]

Just go see Mustafa the brake drum maker. Take him the old one and he'll hook you right up.

 

[mrsmackpaul]

Some foundries in Australia will cast brake drums that are no longer available 

They need to make the pattern first and then cast exactly what you need 

The cost is 3 or 4 times what standard off the shelf drum costs 

You get a bare casting that needs machining 

Im sure this is also doable in the U.S.

 

Paul

[Geoff Weeks]

Give us the two measurements I asked for and see what can be found. we already know it is 15x 5 brake. needed are the bolt hole circle and the pilot diameter.

[Geoff Weeks]

https://www.durabrake.com/brake-drums/

In there "About us" section seam to say they make drums to order and prototypes

[BTFD 3227]

Paul, 

I didn’t really think of doing that. If I understand you correctly, I find a drum that’s 15x6 and matches all the other specs but is 1.16" more overall depth, that extra 1.16" can be machined off without affecting the drum function? 
Didn’t think of doing it that way. Makes sense though. There are a couple drums showing available but limited that match but are more overall depth. Most was about 1.36" over. I need 7" overall depth.

Joseph, 

I wish it was that easy! Can’t hardly find anybody that wants to work that hard anymore. 
 

Geoff,

The specs I’ve got are: Pilot of 11" with a stud dia of 12.5"

I’ve found a couple drums that are close as I mentioned up top. Hopefully still available or at a salvage yard close by. 

[mechohaulic]

  working on a project now for a friend  who has a unit needing brakes which similar to your situation are no longer available. a basic drum is $30=40.oo .his drums are $325.oo each. shoes per set 25.oo= 40.oo ; his shoes when found are $81.oo EACH. this case project on hold. your case instead of looking for drums ; did you consider finding a complete rearend assembly /cut off ?? having matching hyd brakes. change over to air could be involved.

[Geoff Weeks]

13 hours ago, Joseph Cummings said:

Just go see Mustafa the brake drum maker. Take him the old one and he'll hook you right up.

 

The next video you post will be another shop putting the Cummins block back together!

[Geoff Weeks]

Just looking though Webb's catalog, I find 3 numbers that match the pilot, mounting hole and brake spec's but not surprising all are being discontinued.

I found a few "hits" on those numbers, but unless you find one sitting in someones warehouse that they want to get rid of, it looks like Durabrake, is your best bet in this country.

If you are having one made, then they should be able to make an exact fit.

Problem with changing rear axles, is IIRC this truck is on juice brakes, so that would preclude swapping a more common and likely air braked axle.

I would be looking for a minimum of 2 no matter the other one you have is still in one piece.

Other than the above spec's the most important will be the hub mount to brake shoe measurement, that has to be close or be able to be machined to that spec.

[Geoff Weeks]

Another thing about "swaps" is they are never simple, yes the cut-off may not be that expensive, but then there is all the little stuff that adds up like driveshaft changes, frame splicing if not trying to bolt in.

Getting replacement drums made may be the most expensive brake job you ever do, but as long as the shoes can be re-lined (shoe table not damaged) and the wheel cyl castings are not damaged, it still may work out cheaper in the long run.

You are then left with something that is factory and not butchered, not only is it correct, but down the road it will make other repairs more straight forward.

Take time to assess what you have now, and if drums are the only hurdle on the rear of the truck, I would advise getting them made. You may be able to "hook up" with other looking for those drums to make a "group buy" to bring the cost/unit down.

[BTFD 3227]

This project is for the Firefighters Union outreach program so I’m on a fairly tight leash when it comes to modifications. Budget is pretty tight as well. 
Full rear end swaps is out of the equation. I agree that that would end up being a bigger hassle. 
The drums are the only thing that’s holding this project up. I’ve got shoes to be relined, cylinders will be rebuilt and have already obtained all new bearings and seals. 
Hopefully I can find a set new laying around or a good set in one of the repair/rebuild shops around here. 
 

I speak for the union when I say,,, we really appreciate the information and assistance from this page and its members. Thanks guys and keep up the good work in keeping these old classics rolling down the road.