Front Brake Drums Not Fitting over Shoes

[1941_Saratoga]

I recently overhauled the front brakes on my  '41 Saratoga. The front brakes have two cylinders on each side (top and bottom), which I sent out to be rebuilt and resleeved. Had the drums turned and while I was at it, media blasted the backing plates to make everything look pretty. 

 

Everything went back together pretty easily, but for some reason the drums aren't even close to fitting over the new brake shoes. Used my Ammco 1750 to adjust the shoes up and down (the adjusters at 6 & 12 O'Clock)  and set the width adjusters to that the gauge barely scraped the brake linings. Drums won't go over the shoes. I compared the shoes and linings to the old pair of  shoes I took off  - which fit - and there really isn't any difference. 

 

I know the new linings should be contoured a bit, but I can't get anywhere close to getting these drums over the shoes. Adjusted the shoes so that they were all the way in, and still no luck. The only way I could get the drum over (and pretty tightly) was to take the pins out of the cylinders and put the return springs back on, so that the shoes were pulled far in. Never had drums fight me like this, and was wondering if there's something obvious I'm overlooking.

 

Any thoughts are welcome. Thanks!

Dave

[c49er]

These are your possibilities...

1) New linings are thicker than new OE .180"

2) Anchor cam bolts are not rotated to let shoe retract

3) Wheel cylinder replacement push rods too long...some are longer than others.. 

4) New replacement wheel cylinder pistons too tall....there are three different wheel cylinder piston styles..

****When the drums have been turned usually .040" or more generally there is no trouble getting the drums on after retracting the shoes.

This by retracting the cam and anchor bolts fully.

Brake linings should be no thicker than 3/16".....180".

[1941_Saratoga]

Hi Bob,

 

Appreciate the quick reply! Let me address each point below:

 

1) New linings are thicker than new OE .180"

I've laid the new shoes on top of the old ones and there is virtually no difference in thickness or contour. I replaced the old shoes not because they were worn, but because they had gotten pretty well soaked in brake fluid, so there was a lot of lining left, and I had no problem taking the drums on and off when they were in place.

 

2) Anchor cam bolts are not rotated to let shoe retract

I have the cam rotated all the way in, so there's no way to go but up

 

3) Wheel cylinder replacement push rods too long...some are longer than others.

I'm re-using the old push pins, but it is strange that the shoes don't seem to close as much as they did before they were rebuilt, and the only way to get the drum on at all is to remove them...

 

4) New replacement wheel cylinder pistons too tall....there are three different wheel cylinder piston styles..

This is an interesting possibility. I don't believe Chrysler used the two single wheel cylinders for more than a couple of years, so perhaps the replacement cylinders are not standard? You have me wondering if the pistons are too tall. Not even sure how to remedy this if it's the issue, other than contact the rebuilder...

 

Dave

 

 

 

Edited March 14, 2020 by 1941_Saratoga (see edit history)

[c49er]

Well then....

All that is left...taller different design pistons...

* Re-use your old pistons

* Use shorter push rods ( yours have a tiny hole at the open end slot?

* Have the lining ground down on a lining arcer

Edited March 14, 2020 by c49er (see edit history)

[1941_Saratoga]

You, sir, are an amazing resource! Those pictures are very helpful. Yes, my push rods have a tiny hole on the shoe side - they look exactly like the middle one  in the line-up. Let me ask you - is the size of the piston typically denoted by the color? What is the silver one on the right typically used on?

 

Unfortunately, using the old pistons isn't an option, as they went out to White Post with the cylinders. I may have some others, so I'll root around and if not, I'll check with Bernbaum. I can also see if they might have shorter push rods too. I'd rather explore these first, before grinding a substantial amount of the lining off. 

 

Thanks Bob, I appreciate your help!

 

Dave

Edited March 14, 2020 by 1941_Saratoga (see edit history)

[c49er]

You should hunt up the shorter push rods.....easiest solution looks like.

Your problem is very common.

I can measure one if you need. 

[1941_Saratoga]

Hi Bob,

 

Just came back from the garage and I did a couple things...

 

Measured the push rods with my micrometer and got 1.11 and 1.08. Mine were more pitted than your picture and I had cleaned them under a wire wheel, so I may have taken some material off.

 

Also, in reference to my question above about color-coding, I took the boots off and the pistons are yellow. I haven't removed the pistons to measure height, but I'm pretty sure these cylinders left with red pistons. If I leave these pistons in and get my drum on with a shorter push rod, does that affect performance at all?

 

Thanks,

Dave

[c49er]

I forgot to tell you I cannot answer if piston color means anything as to size.

I have seen gold ones like yours.

I guess for future reference I should gather them all up and measure piston heights.

Won't matter as to which push rods you use. Rods sometimes are at a very slight angle. Make sure they are seated as you know.

In your case the shortest push rod is the only choice.

Use them if you have them....

I will check to see what is the shortest rods later today just to see.

I think 1-1/8" is it.

I arc the linings which I always do to to accurately pre-fit each shoe to each

drum.

Does not take too much over size lining to create drums from slipping over the shoes.

[1941_Saratoga]

Thanks Bob, I really appreciate the response and the time you took to take the pictures. Just out of curiosity, do you know the heights of the 3 pistons you showed? I was thinking of asking White Post what size they used in the rebuild, but I think the quickest solution is for me to give BernBaum a call Monday and see if they have any of the shorter rods. Then I'll have the linings arced to fit the drums.

 

Dave

[ply33]

One thing I don't see in the above replies: The anchor for the shoe is on an eccentric bolt (the “major adjustment”). If those had been adjusted out as the old shoes wore then they may not be correct for your new shoes.

 

But I am confused as you said you used an Ammco 1750 to adjust the shoes. The 1750 also has the ability to measure your drums and if used properly should have set the clearance between drum and shoes correctly. Or, if the shoes are not arc'd for the drums, it would show you that it was not possible to get the heal and toe clearances specified. I am wondering how you used the tool. . .

[mobileparts]

Too late now for you now ----- but maybe not too late for the next guy.....

 

I have ++ NEW ++ Asbestos ++ Brake shoes ++.      &

++ NEW ++ Made in U.S.A. made wheel cylinders --- less expensive than having ones reserved.....

 

And.... Always best to simply call me -- Craig -- 516 - 485 - 1935..... 

 

(1941 Saratoga -- too bad you didn't ask for quality sources here -- I would have responded.  I have a whoooooooole lot more for your car.)

[c49er]

Types of Lockheed push rods, length and piston design and general piston height/length ..

Piston length/height measured with Starrett ball micrometer from piston push rod radius socket to rear backside of piston.

This measurement plus either return spring, piston stop button or bottom piston rubber cup determine how far the pistons can be bottomed out in front single cylinder lockheed front MoPar brake systems.

Which also can be a factor if the new brake shoes can be retracted enough.for drums to be installed.

There are also different length's of push rods that were available...generally short rods on dual cylinder front brakes... longer  push rods on single cylinder rear brakes.

Over the years piston styles and push rods.... changed and got mixed up causing difficulties of drums not being able to be installed no matter how you adjusted all cams...especially if shoes are too thick..over .180" factory max spec.

 

 

Edited March 15, 2020 by c49er (see edit history)

[c49er]

Arcing linings to fit drum....Misc adjusting shoes

[1941_Saratoga]

Thanks Bob, I'm going to bookmark this page, as those pictures are invaluable. I found a few other pistons and will measure in the morning. 

 

Ply33, I used the Ammco gauge initially to get a measurement across the 12" drum. The eccentrics I set with the arrows facing their adjacent cylinders, then put the gauge on the axle and set the cams until there was a consistent light drag around both shoes. I expected the drum to slip right on, but it did not fit. Even with the cams set all the way in, the drum wasn't close to fitting.

[ply33]

2 hours ago, 1941_Saratoga said:

Thanks Bob, I'm going to bookmark this page, as those pictures are invaluable. I found a few other pistons and will measure in the morning. 

 

Ply33, I used the Ammco gauge initially to get a measurement across the 12" drum. The eccentrics I set with the arrows facing their adjacent cylinders, then put the gauge on the axle and set the cams until there was a consistent light drag around both shoes. I expected the drum to slip right on, but it did not fit. Even with the cams set all the way in, the drum wasn't close to fitting.

FWIW, the way I use my Ammco 1750 is to lock the measurement at the drum size. Then I use feeler gauges to verify the correct clearance between the tool and the shoe at the toe and heal, finally I swing the tool along the shoe to verify it is not touching anywhere. There is some back and forth between the major and minor adjustors because at the same time you are getting the clearances correct you are also centering the shoe to be concentric with the axle.

 

I've had better luck getting things lined up using feeler gauges to check the clearance between the shoe and the tool set to drum diameter rather than changing the tool's settings for the desired clearance and then having the tool just touch the shoe.

[1941_Saratoga]

Thanks Ply33, I'll try the feeler gauge method. I've always gone with the "feel" of the shoe against the gauge, then adjust the cams accordingly. But the gauge should give me the consistent clearance to get the drum on.

 

Dave

[1941_Saratoga]

Just wanted to pop back in and thank everyone for the great advice. Got the new cylinder pins and everything fits together like it's supposed to. Put a new line in  between the upper and lower cylinder as long as I had it open.  New bearings, seals, shocks, shoes, tie rod ends, steering arm bushings, rebuilt cylinders. I may need a new project to get me through this pandemic...

 

Thanks again!

Dave