39 P8 Rear Brake Drum

[Racerstev]

Hey all, need a little help. Seems my spare tire is wrong for my car. Bolted it on in the dark and didn’t notice it hit the rivets  in the drum. This flexed the drum and caused it to fail. The drum itself is now not attached to the hub. 
 

Besides Mopar Pro ($425!) is there a source for these? 
 

Steve

[FarmerJon]

 

Looks like '39-42 dodge are the same. Maybe check french lake auto or one of the other vintage mopar junkyards.

[Ivan_B]

Is the old drum still repairable? It could be cheaper to redo the rivets 🙄

Do you have a picture of your spare tire? I am very curious about how it managed to break the rivets... 🤨

[Racerstev]

I’ll take some pics. The rivets didn’t break, they came in contact with the inner part of the wheel holding it from fully seating. Tightening the bolts made the drum flex. The flex made the  welds break on the drum. Yeah SO strange, hell the spare was painted the right color so I had no idea it was wrong.  
 

pics tomorrow…

Steve

[joecoozie]

What is the drum diameter?

Sent you a PM

[Racerstev]

Closer inspection revels at least one problem. The spare that caused all this dosn't have clearance holes for the rivets. There are 4 rivets and a guide pin. 

[Racerstev]

[Racerstev]

[Racerstev]

The result. 

[Racerstev]

Just a note, this drum was overheated because of a seized wheel cylinder. It was not round, it did pulsate a bit.  So that, the age and the wrong wheel all contributed to the failure. 
 

This live and learn stuff isn’t fun! Lol 

[Ivan_B]

I don't think that pushing on the rivets would brake the welds on the drum like this. Was your wheel actually too small for this drum? Was it pushing onto the outer edge of the drum when you tightened the bolts? This is the only way I can see the wheel braking the drum off the hub like this.

Edited April 22, 2024 by Ivan_B

[Racerstev]

I will look closer but the only thing I saw was the rivets hitting the drum. Someone did drill a hole in the wheel to clear the alignment stud. The wheel does have about 1/8” more clearance between the wheel and drum, assume from the rivets holding it up. 
 

Maybe it was just ready to let go… when it popped it sure made me think about that single master cylinder.. It was “POP” and the pedal fell a good bit. Car did stop and the pedal came back. Made a awful racket, grinding..

 

Steve

[Racerstev]

I received a used drum today, it’s in pretty bad shape. Don’t think it’s useable.

[Racerstev]

Going to see if it will fit on my brake lathe but I don’t think it will center with the adapters I have. 
 

Next option, can the old drum be welded? The hub and drum were swedged (spell??) from the factory, not welded. Wonder if I weld to the existing ears if it will hold??? 
 

Also played with the wheel a bit, drilled clearance holes for the rivets. The wheel stands off over .100” more then the stock wheel. The offset is 1/2” different as well. 

[Ivan_B]

Did you figure out how it broke off? Seriously, no way that pushing on the rivets (essentially the hub) would break the cylinder off. Maybe it was just a coincident?

The new drum looks bad... Probably out of specs if you resurface it to a reasonable degree...

I was thinking, maybe there is a way to adapt some modern drums to the hub? Or, sleeve the old drum? Some "modern" cars use an aluminum alloy drum with a steel/iron sleeve inside. I was very skeptical of this, when I first saw it, but it works. So I suspect that sleeving the old iron drum might work too 🤔

 

Later: this guy did a motorcycle hub:

Do you have an industrial lathe around? 😅

Edited May 1, 2024 by Ivan_B
More info

[Racerstev]

No clue if it was just old age, all I know is when the spare was put on it failed 2 miles later. 
 

Found a reliner J&G brake drum, around $300 if the old drum is thick enough… for a few dollars more you can get a machined stock drum. Has anyone worked with the “ Mopar Mall” 

they have OE machined drums in stock. $337.69

 

Steve

[Ivan_B]

Yep, I figured that with the expense of "small production" labor, getting a new/re-manufactured one would cost very comparatively

I am still using the stock ones, with 50k on them. Hopefully, these will last a while.

[9 foot box]

   Several years ago a guy had a post “Found a brake drum solution”. You can still find it in a Google search, just add p15. If you go into RockAuto in 66 Fairlane with a V8, depending on your brake shoe size, there is a 10”x1 3/4” or a 10”x2” brake drum. 2623R and 2637R. Same bolt pattern. You would have to machine the center hole to make it hub centric. It might be a solution for a lot of us, when a new brake drum is needed. I was lucky enough to find a good drum, when a brake return spring broke and ruined my drum. This is an opinion, but for $30, I will probably buy a drum and see if it will work for my cars, unless you do it first.  Rick D.

[Racerstev]

That is just a perfect solution! Rock has one on the way..,  I’ll stay in touch.

 

Steve

[FarmerJon]

7 hours ago, 9 foot box said:

   Several years ago a guy had a post “Found a brake drum solution”. You can still find it in a Google search, just add p15. If you go into RockAuto in 66 Fairlane with a V8, depending on your brake shoe size, there is a 10”x1 3/4” or a 10”x2” brake drum. 2623R and 2637R. Same bolt pattern. You would have to machine the center hole to make it hub centric. It might be a solution for a lot of us, when a new brake drum is needed. I was lucky enough to find a good drum, when a brake return spring broke and ruined my drum. This is an opinion, but for $30, I will probably buy a drum and see if it will work for my cars, unless you do it first.  Rick D.

Nice option for us plymouth guys, but dont the dodge cars have 11" drums?

[Racerstev]

From what I found 2955R is the 11” drum.

 

I ordered 2637R hopefully fits the 10” drum. 
 

Steve

 

 

[Racerstev]

This is a no go. The Ford drum is .48” too deep. So the shoes hit the edge of the drum .5” before the face hits the hub.

 

Spacers maybe, but would need one that is hub centric for the wheel and hub. Plus long lug bolts…

 

 

Back to Rock with this…

 

bummed out…

 

Steve

 

 

[9 foot box]

   I’m sorry for the bad references for a brake drum replacement. I think there is a brake drum replacement for less than $400. I haven’t found it yet. Call Then and Now Automotive, 781 335-8860. 

[Racerstev]

It was worth a shot, I’d bet there is a drum out there that would fit. Rock doesn’t list enough info to be absolutely sure. 

 

Ok, plan C… Mopar Barn has machined  used for $300ish, I’ll try then and now as well. 
 

thanks for the help! 
 

Steve

[Racerstev]

I tryed a list of place’s. Kanter, Mopar Mall, Arizona Parts, Rocky Mountain Parts,  Then and Now, and the winner is Mopar Pro. The free shipping made his new part competitive with the used stuff.   
 

So $450 (with tax) plus wasted money on the other attempt's. 
 

Bottom line, I can drive my baby again!

 

Steve