Brakes: M5 - how to adjust brakes?

[tedtaylor]

just acquired my '46 M5 pickup and rebuilt the wheel cylinders, but my question is HOW DO I ADJUST THE BRAKES, and i mean this because there are four (4) adjustment screws, one top and bottom for each shoe!!!!
What is the proper procedures to get it right. There must be a right way, rather than guess work on my part.
thanks for your help!

[nvonada]

You are trying to accomplish two things here. The first is to center the shoes in the brake drum. The second is to position the shoes close to the drum so the brakes work quickly and evenly. I am not sure how different your brakes are from my 41 Champion but on mine there are three adjustment points. The bottom anchor pin for the shoes is an eccentric bolt with a lock nut and does the gross centering. Then there are two eccentrics about 2/3 of the way up each shoe that are just held in place with a stiff spring under the adjuster. They essentially move the shoe in and out. Here is what that looks like:

And from the back side you can see the lock nut and adjuster at the bottom and one of the spring loaded adjusters at the top


So how do you do this? The "correct" tool is a brake gauge like the Ammco 1750. It looks like this:

It fits over the hub and you adjust the brakes until the gap between the end of the gauge and the brake shoes is even all the way around. Then your brakes are centered. Of course they have not made this tool in decades. They show up on e-Bay regularly but sell for pretty big $$$. But this is the gold standard. So what are the alternatives for a CASO? Well any decent machinist could probably rig something up that works the same way but if you are paying a machinist buying a 1750 might be cheaper. Or you can find an old hub and brake drum and cut "windows" in the drum so you can see the shoe gap. Or you can do what I do and spend a ton of time on it.

My "technique" is simple but time consuming. I use the "fine" upper adjustments and try and get both shoes to drag evenly on the drum. Then I move the bottom "centering" adjustment to try and reduce or eliminate that drag. That will make the shoes "more centered". I repeat the process until I can't get it to be any better then adjust both shoes with the fine adjuster until they just brush the drum and call it good. If the car pulls under heavy braking I do it again. It is a pain in the butt but the good news is that once the bottom centering adjuster is close it seems to stay where it should be. Every year or so I re-adjust and usually only have to mess with the fine adjusters.

The good news is that the brakes work pretty well once adjusted. Not up to modern standards but I can lock all four wheels up no problem. Good luck!

Nathan

[tedtaylor]

Nathan, excellent information, thank you!!!
Wow, i would have never thought you adjust brakes without the drum in place. An interesting tool.
My situation with the M5 is that i have what you have WITH AN ADDITIONAL bottom centering pin. Each shoe has a top and bottom adjuster, times two equals four points of adjustment. I don't have that tool and will probably play/experiment with adjusting it with the drum in place, as you said, snugging it up, backing off and going around. I just wasn't sure if there was a set rule to do one (top or bottom) first then the other end second, and so on.
I used to think older vehicles were more simple, but that is always not the case. Over the years, they have streamlined and simplified the mechanism and serviceability.

[RadioRoy]

MoTors manuals generally have great information on things like this. You might try to find a truck manual that covers your year.

[Ross]

Whilst you have the drum off, drill a 1/4" hole through the side right at the friction surface. Then with a flashlight you can see the gap between the shoe and the drum. I have often done this on older Chrysler products that had 4 eccentrics. Packards came with such a hole for adjusting their top eccentric. Makes the job manageable w/o a special tool.