Drum won’t install over new brakes

[Tom_S]

I just got my RR drum back from being turned at the machine shop. I was excited thinking that I was on the home stretch. New brakes and cylinder installed, but the drum won’t slide over the brakes. I have the adjusters retracted (arrows pointing toward each other). What else can I do? The rear only has a major adjuster on the heel of the brake, no minor one that I can see.

There is a spring loaded 3/4” nut that appears to hold the shoe retaining clip. Is that somehow a minor adjuster?

[Ivan_B]

Did you compress the wheel cylinder all the way in? Did you also install the new shoes? I, once, had to grind the metal shoe tip, a bit, to make it fit, because it was an after-market part and a bit too large.

[joecoozie]

Sometimes the new shoes (lining) are a little too thick and need to be "shaved".

Others may call it "arced" to fit the drums

 

[Plymouthy Adams]

did you change the cylinders.....the profiles of the pistons (cup depth) in the cylinders s are often not the same as stock either so this is where majority of the mismatch occurs...pistons and pins...they turn out to be too long 

[Tom Skinner]

Tom S.

One more idea Tom, The Cams can be released to narrow the shoes (In order to facilitate spring removal and installation).

Also the Anchors may be turned to facilitate the drum fitting. I personally just used a wood rule (Grandpa's and his wrenches) to size it up before attempting to slide the Drum back over new shoes.

If you have 11" Brakes a quick wood rule diagonal measurement check is all you need to get the drum on. I also just cleaned up my old Wheel Cylinder Pins and used them.

Answering your question: Yes the Spring Loaded Cam Adjustments are the ones to use to increase clearance of the shoe to the drum. All other adjustments should adhere to your Service Manual Instructions. Especially Torque of all pertinent Bolts. Anchors 50 - 70 FT. LBS Etc., (Anchors) Arrows Pointing toward each other on Rear Brakes ETC.

The Fronts the Arrows Point toward the adjacent Wheel Cylinders) With New Shoes you should refer to the Major Brake Adjustment Section and be certain to follow the instruction - as yours, and others, Lives depend upon it. Good Luck let us know how you did!

Tom S.

Huntersville, NC

[Ivan_B]

5 hours ago, joecoozie said:

Others may call it "arced" to fit the drums

I was under impression that arching is done to fit the shoe to the drum more precisely, not for size reduction.

[Tom Skinner]

Tom,

When done - Bleed and Adjust. Re-Bleed and Adjust. You will have got it by thorough process of elimination. I used to just eyeball shoes on now I use my home made gage on my Spindals where the Castle nut screws on. My Gauge is similar to the one shown (Shown is Don's but is a good example)

Tom

[desoto1939]

15 minutes ago, Ivan_B said:

I was under impression that arching is done to fit the shoe to the drum more precisely, not for size reduction.

Yes the arcing gets the lining of the shoe tobe more precise with the drum but in most cases the lining might be higher r thicker in certain spots. The use of the eccentric pins move the shoe lining in and up or down and out. These have to be set properly to get the shoes to make perfect contact and whe doing this with the pins is called a makor brake adjustment and just when using the big nut on the back of the backing plate is  called a minor adjustment.

 

Also measure the lining thickness and let us know how thick the lining material is on your new set of shoes I think it should be 3/16th.

 

Rich Hartung

Desoto1939@aol.com

[Tom Skinner]

My Gauge

[Tom Skinner]

Tom,

I made my Gauge with a 3/4" 16 Nut 3/8" Threaded Rod and Scrap Strapping.

I used JB Weld to Fasten the Rod to the Nut (Welding is probably better but JB Weld Works too)

Tom

[Ivan_B]

If no tool is available, a simple ruler can also be used (as already mentioned)

[Sam Buchanan]

21 minutes ago, Ivan_B said:

If no tool is available, a simple ruler can also be used (as already mentioned)

 

Please explain how the brakes are adjusted with just a simple ruler...... 

[Ivan_B]

Instead of measuring the distance from the axle nut to the shoe surface with the tool, do the same with a ruler using the axle, etc., as your base. What's the problem?

Just curious: do you always get the fancy tools to block the crank and camshafts when doing a timing belt change on a modern car, instead of just counting teeth on the belt? 🤭 The tools make some things easier, true. But unless you are doing them daily, you can easily work with substitutes as well.

Edited September 29 by Ivan_B

[bacelaw]

8 hours ago, Plymouthy Adams said:

did you change the cylinders.....the profiles of the pistons (cup depth) in the cylinders s are often not the same as stock either so this is where majority of the mismatch occurs...pistons and pins...they turn out to be too long 

 

THIS!  I changed master cylinder and couldn't ever get brakes properly adjusted.  Turns out, the depth of the piston cupboard different, and brakes never fully released.  Pushrod adjustment did the trick.  If your pushrod length is not correct, you'll never get shoes to fully release.

[Plymouthy Adams]

14 minutes ago, bacelaw said:

 

THIS!  I changed master cylinder and couldn't ever get brakes properly adjusted.  Turns out, the depth of the piston cupboard different, and brakes never fully released.  Pushrod adjustment did the trick.  If your pushrod length is not correct, you'll never get shoes to fully release.

that is true, but in this case, he is not even to the point of adding fluid to the system...his base circle of the shoes is even larger than his now larger cut base circle of the drums on resurfacing.  The manner of repop cylinders, the cups often will NOT match the cups of original stock in depth...thus it holds the base circle of the shoes to even greater distance.  You have to work the magic of mix and match of cups and pin to correct this error.  

[Sam Buchanan]

1 hour ago, Ivan_B said:

Instead of measuring the distance from the axle nut to the shoe surface with the tool, do the same with a ruler using the axle, etc., as your base. What's the problem?

Just curious: do you always get the fancy tools to block the crank and camshafts when doing a timing belt change on a modern car, instead of just counting teeth on the belt? 🤭 The tools make some things easier, true. But unless you are doing them daily, you can easily work with substitutes as well.

 

There's no problem, if using a ruler works for someone, fine. The reason for using the tool is try to get the measurement within the 0.006" tolerance called for in the manual. I'm not good enough to get that fine an adjustment with a ruler.......

 

No need to attempt to deflect the discussion with timing belt changes on a modern car, I was just commenting on adjusting brakes on an old Mopar.

 

Edited September 29 by Sam Buchanan

[Tom_S]

I got the drum on!

It was a combination of issues. The biggest being that I didn't understand the minor adjustors. But, and this is a big one, the springs that came with my brake kit seem to be too weak to fully retract the shoes. I opened the cylinder bleader and manually squeezed the toes of the shoes together to force the cups in- and they went! I closed the bleeder and was able to slide the drum on, but I guess the shoes eeked back out a little and I had a struggle removing it. I took the new spring off and put the old one back on. I was able to the brake adjustment procedure a couple of times to get an approximation of good.

Now Ill work on the other 3 wheels then bleed and adjust again. I feel so much better

Thanks all for your help and suggestions🙂

[Ivan_B]

3 hours ago, Sam Buchanan said:

The reason for using the tool is try to get the measurement within the 0.006" tolerance called for in the manual.

That's a good start. Do you also check the drum with a dial indicator?

[Sam Buchanan]

20 minutes ago, Ivan_B said:

That's a good start. Do you also check the drum with a dial indicator?

 

No. However, the diameter of the drum is derived per the following procedure. The drum is installed and one minor adjustment is made so a shoe lightly contacts the drum. The drum is removed, the tool installed and set to the diameter of the drum indicated by the high point (maximum diameter) of the minor adjustment. Then the concentricity of all shoes are adjusted so they match the dimension derived from the first minor adjustment. This is a work-around that is necessary because we don't have the old tool (Armstrong?) that measures the drum and directly transfers it to the shoes. But our simple tool is a good work-around that yields excellent results.

 

This procedure is detailed in my old thread when I built the tool:

 

https://p15-d24.com/topic/50182-brake-adjustment-tool-updated/

Edited September 30 by Sam Buchanan