Brakes: 11" Drum Swap, Front To Rear

[JoeHall]

I need to replace the 11" factory rear drums on the 63GT, which I am installing Fairborn flanged axles in. Since the car originally came with disc brakes, it has Avanti style 11" rear drums, instead of 10". I have several good, 11" finned front drums and would like to avoid buying new rear drums if possible.

MY QUESTION: once the hubs are removed from front drums, are the drums themselves (minus their hubs) interchangeable, front to rear? In other words, can I remove the hub from an 11" front drum, then use that drum on the rear? Either way, with flanged axles, the drum will have to be hub-less, so removal of the hub is a non-issue. Question is, front to rear interchange of bare drums.

Thanks in advance.

Joe H

[jclary]

My "backyard tinkerer" mind thinks it is "do-able," but, like any mechanical rotating part, I'm wary about concentric repeat-ability, and balance? Even if the measurements allow it without additional machining, are the tolerances close enough that will allow the drums to be removed & put back on without balance/vibration issues?

[rkapteyn]

Yes you can use them.
The 11"rear finned brake drums are the same as front 11" drums .
Check the size of the center hole.
Robert Kapteyn

[thunderations]

With that question being answered, let me ask another. Can the 11" front backing plates with all the hardware be bolted to the rear axle to replace 10 or 9 inch rear brakes? I'm putting Turner discs on the front of a 64 Daytona 113" wheelbase chassis that will be the frame for my 50 Champion convertible and it would be nice to update the rears to 11" if that would work. Thanks in advance for any advice, Ken.
This whole project is to build a retro Studebaker using the most modern Studebaker mechanical parts available under one of the most iconic Studebaker bodies ever made.

Yes you can use them.
The 11"rear finned brake drums are the same as front 11" drums .
Check the size of the center hole.
Robert Kapteyn

[41 Frank]

The one problem I see with doing that Ken is the front backing plates have no provision for the rear emergency brake cables to mount to them.

With that question being answered, let me ask another. Can the 11" front backing plates with all the hardware be bolted to the rear axle to replace 10 or 9 inch rear brakes? I'm putting Turner discs on the front of a 64 Daytona 113" wheelbase chassis that will be the frame for my 50 Champion convertible and it would be nice to update the rears to 11" if that would work. Thanks in advance for any advice, Ken.
This whole project is to build a retro Studebaker using the most modern Studebaker mechanical parts available under one of the most iconic Studebaker bodies ever made.

[thunderations]

Very true, Frank. Guess I might compare the front and back plates real close and see if the front can be modified to accept the EB cables. I'm not sure how much better 11" rear brakes are then the 10" when you consider adding the front discs that will be doing the majority of the braking. Might be smarter to just leave well enough alone and concentrate on the rest of the build. The 11" front drums could be a big improvement for someone wanting to upgrade their drum brake system from 9's or 10's.

The one problem I see with doing that Ken is the front backing plates have no provision for the rear emergency brake cables to mount to them.

[WCP]

Joe, the 11" castings are identical, front and rear, but the machining is not. I had a set of NOS 11" front drums and considered them for the rear of my Daytona, but realized the re-machining would be less doable than modifying Dodge truck drums from Napa. On the front drums the braking surface needs to be narrowed and the relief for the backing plate "labyrinth seal" needs to be machined deeper. I didn't like the idea of trimming the backing plate lip.

[StudeRich]

And Then there is the aforementioned Center Hole Size issue!

[wdills]

WCP, please tell us more about the dodge truck drums and their modifications.

[bensherb]

The center hole is a non issue since nothing on the Stude is hubcentric anyway.

Beyond the e-brake cable the spindle and rear axle flanges are different sizes and bolt patterns. You might be able to fudge the mounting holes, but welding them up and driling new holes would be the way to go. There might also be a difference between the backing plate mounting surface to wheel mounting surface measurement front to rear that would need to be addressed. It could be done but you'd need to swap the e brake parts over and probably graft the cable mount from the rear backing plate into the front backing plate.

If having the drums/wheels hubcentric instead of lugcentric is important to you it can be done relitively easily with some simple machining if you have the capabilities, probably not cost effectve if you have to pay a shop. Here are some hubs I did for mine.

[WCP]

Wayne, the drums used are Napa 440-1169. The modification required removing 1/8" from the brake surface inner edge. These drums are supplied balanced and fairly inexpensive. I removed the centering rings from the Fairborn axles and new rings machined to suit the smaller drum bores. The dimensions used for the rings as follows:OD 2.840+/-.002" and ID 2.580+/-.002" and depth or length of 0.25". Radius inside bore edge 1/16D". I later noted that an OD of 2.838" would be better, as I had to tweak the drum bores to slip over the installed rings. I heated the rings with a propane torch and slip them onto the axle bosses. If you go this route, be sue to check the bore diameters. Mine measured 2.833 & 2.840".
The stud holes are 0.653" vs 0.634" for the NOS 1558903 Stude drums. The backing plate relief is 11/16" deep vs. 7/16' for the Stude front drums so no problem removing the 1/8" from the brake surface edge.
As posted above, the brake surface of the 1558903 is 2.5" and needs to be trimmed to 2 3/8" and not 1/4" (bad memory). This results in a relief of only 5/16" and contact with the backing plates

[rkapteyn]

Ask Phil Harris!
He is an expert on this and gives good customer service.

[JoeHall]

Thanks much for the above info. My flanged axles came from Ted H., and he had ran them in a car on the track. They may be earlier or later, because the flange that centers the drum is stepped, at 2.605" then 2.750. It has an adapter ring fit over the inboard, 2.750", and the adapter's OD is 3.105". So with my axles, to use the NAPA drums, I'd need an adapter ring with an ID of about 2.753 and an OD of 2.833 to 2.840". That is a very thin adapter ring, and not sure if it can even be made. Will ask the local machinist.

[bensherb]

A ring with a .040" wall thickness, no sweat. Is this ring to resize the hub to fit the wheel/drum to make them hubcentric?

You could also replace the existing ring wth one of the size you need, or turn it smaller so the extra resizing one would be thicker. With tight tolerences or thin resize rings, fitting the ring then turning the entire assembly to the desired size as a unit works best for me.

2.840" is big, the bore of both my front and rear disk rotors, and my wheels is only 2.700", and it's way bigger than my stock Stude wheels; I had to leave .005" clearance in order to get the wheels and rotors to fit over the hub without pounding them on, so they are 2.695"

[WCP]

Joe, the bosses on mine measured 2.580" and 2.583" and the rings were for 3 1/8" drum bores.