1939 Hydraulic Brake Drum

[Al Corbin]

I purchased my 33 cabriolet in junk condition from a guy in Argentina about 15 years ago. Someone had made the conversion to juice brakes. A little crude, but they have worked OK.

Recently, one of my rear drums came apart. The drum portion actually broke away from the hub part. The drum surface apparently had been welded on.

Checking in Mac's catalog, I ordered a 1940-48 brake drum. I noticed too late it's a little different from the one I'm replacing. The brake shoe surface is the right diameter, but the shoe surface is 2 inches wide instead of 1 3/4, and the hole through which the hub goes is an inch too small.

Checking Mac's catalog, I find they don't list a drum for 1939, only 1940 - 1948. I had always though that group included 1939.

Can anyone give me some info on this problem, and maybe suggest a source for the part that I need.

Thanks.

[mfagan]

Al,

The 39 drum has a wide 5 pattern, different from
the 5 on 5.5 pattern for 40-48.

My understanding is the 36-38 rear drums
Are the same as the 39 drum.

Marvin Fagan

[DICK SPADARO]

Since you have a series of mix or match parts its much easier to determine ways to attack the issue if you would post pictures of the items in question. This eliminates any speculation or guessing as to a way to remedy the problem.

[Mart]

It might be worth posting a picture of the good drum on the other side.

I'd guess they retained the 33 drums, That's what they did on my 33, with 40's backplates.

Mart.

[rotorwrench]

A person also has to know if it has an inny type hub (mounted inside the drum) or an outy type hub (mounted outside the drum) on the 40 thru 48 type brake drums since both were employed and mixed. The early wide 5 drums are getting harder to find now days. The early type wire wheel drums are also getting harder to find. A person has to adapt the wire wheels to the later type drums but it's not too big a deal. It seems like the 33s had the open drums. You can't mistake those type.

A picture might answer all of these unknowns.

[Richard (EV8G)]

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Originally Posted by Al Corbin

I purchased my 33 cabriolet in junk condition from a guy in Argentina about 15 years ago. Someone had made the conversion to juice brakes. A little crude, but they have worked OK.

Recently, one of my rear drums came apart. The drum portion actually broke away from the hub part. The drum surface apparently had been welded on.

Checking in Mac's catalog, I ordered a 1940-48 brake drum. I noticed too late it's a little different from the one I'm replacing. The brake shoe surface is the right diameter, but the shoe surface is 2 inches wide instead of 1 3/4, and the hole through which the hub goes is an inch too small.

Checking Mac's catalog, I find they don't list a drum for 1939, only 1940 - 1948. I had always though that group included 1939.

Can anyone give me some info on this problem, and maybe suggest a source for the part that I need.

Thanks.

Your 33 no doubt still has the original (rear) drums and wheel cylinders have been added to the original brakes... You need to find an ORIGINAL 32-34 rear hub/drum that has not been hogged out beyond the limit (12.060" on the West coast and evidently 12.080" on the East...) As you have discovered, the new drums will not fit on the 32-34 hubs, and nobody to my knowledge makes a new drum that will.

Most hydraulic conversions for 32-34 have had all of the hubs/drums replaced with 40-style, as the 32-34 shoes are 1-1/2" wide and the shoes for hydraulic brakes (39-48) are 1-3/4" wide. As one poster discovered, if the 32-34 drums are retained, the shoes will rub, and also the offset of the front brakes usually requires replacing the front hubs/drums. This also true for 1935-36 fronts...

I have seen other cars from South America with the conversion that your 33 has. A lot of evidence suggests that things were done "a lot differently" down there!

To find a good used original 32-34 rear hub/drum, a good bet would be to contact someone who does a lot of hydraulic conversions. Even though it is a good idea to keep all the mechanical stuff for some future owner who might want the vehicle to be all original, a lot of them nonetheless "surrender" that stuff and the still-good drums often wind up on a shelf, available to those who still want or need them. Good ones are getting very difficult to find, so they are not necessarily cheap... (The bearing surface, taper and/or the key way in the hub are often damaged, so inspect carefully!)

BTW, the likely reason that the outer band became detached is that the drums had been (out of desperation?) machined WAY beyond the limit, causing the cross-section between the drum face and outer band to become extremely thin... so the shoe surface stops, but the vehicle does not... In your case, someone welded it back on???

You may contact me for more info...