J Franklin
Well-known member
Are the rods the same length? Do they move the same distance when the pedal is depressed? Are the levers on the back plates at the same angle? And move the same distance to fully activate the brakes?
Rear brake adjustment
- Thread starter Mad Mac
- Start date
Thanks JFranklin, I will respond to those questions when I get a chance.
In the meantime I have prepared a chart to record the situation at each wheel before and after, I start using the " brake adjustment board" and make any changes to the brake adjusting screw on each wheel. This is following Jim/GA's earlier recommendations. The car is now up on 4 jack-stands.
The first chart (see below) shows the current situation before I start using the "board" or making any changes. I will up-date the chart over the next day or so, each time I change anything. By this process I hope to discover whether the "tightness" of some brakes is restricting the amount of clevis adjustment available on the troublesome LHS rear wheel.
Thanks Jim,
But if the brake rod is adjusted too short, that wheel should have better braking action (it hardly has any). My next move is to disconnect the e-brake rod in case that is causing the slight drag.
Y-Blockhead
Well-known member
Mac, I'm gonna go back to your ebrake for a moment. You seem to suggest that, even with the adjusting wedge being fully retracted, you still have drag on this wheel. Since your focus has been replacing the grease soaked service linings, are you sure the same drag wasn't present before .............. but from the ebrake rather than what you assume NOW to be the service brake. You might try removing the ebrake band and reinstalling the drum to see if the drag still exists.
Then again, the new linings have not been arced to fit the drum. If it's an original steel drum, chances are good it's fairly worn oversize. In this case, you could probably take a file to both ends of each lining and chamfer the lining down from full thickness at about 1 inch in from the end to about 1/8 inch thickness at the end of the shoe. This would go a long way to seating the shoes against the drum better. Just a thought.
Then again, the new linings have not been arced to fit the drum. If it's an original steel drum, chances are good it's fairly worn oversize. In this case, you could probably take a file to both ends of each lining and chamfer the lining down from full thickness at about 1 inch in from the end to about 1/8 inch thickness at the end of the shoe. This would go a long way to seating the shoes against the drum better. Just a thought.
Reply to Blockhead:
It was just temporary - Please refer back to post #29
Reply to Bobbader:
Thanks Bob, This morning I temporarily disconnected the e-brake rod and found that the drag on that wheel is still there. I don't know whether it was there previously.
Yes its an original steel drum and is probably worn (I have not measured it). Its starting to look more and more like I should remove the drum, especially if chamfering will help seat the new shoes onto the drum.
Another problem: Despite my best intentions, I have not kept a careful enough record of what happens to drag and tightness when I change the adjuster screw settings on each wheel. So this is starting to turn into a bit of a nightmare - I am almost at the stage of locking it in the shed and throwing away the X@#*$ key!
It was just temporary - Please refer back to post #29
Reply to Bobbader:
Thanks Bob, This morning I temporarily disconnected the e-brake rod and found that the drag on that wheel is still there. I don't know whether it was there previously.
Yes its an original steel drum and is probably worn (I have not measured it). Its starting to look more and more like I should remove the drum, especially if chamfering will help seat the new shoes onto the drum.
Another problem: Despite my best intentions, I have not kept a careful enough record of what happens to drag and tightness when I change the adjuster screw settings on each wheel. So this is starting to turn into a bit of a nightmare - I am almost at the stage of locking it in the shed and throwing away the X@#*$ key!
J Franklin
Well-known member
You are worrying about 2 different things. I would first address the inability to apply braking force, then see about the inability to release the drag. You may find they are related. Answers to my posts #33 & #41 are important to solve things.
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Jim/GA
Well-known member
Your experience is why mechanical brakes have a bad rep. When they are adjusted right, they are great. But they can be frustrating to get adjusted properly.
Start from scratch on all 4 wheels.
Start out by adjusting the rod lengths to each wheel to just take up the slack in the levers when you are not stepping on the brake.
Then screw the adjuster in at each wheel until you get some drag, then back out 3 to 5 clicks to get rid the drag.
Now use the notched stick to adjust the brake rod shorter at each wheel to give you the same braking at each wheel at each notch.
A small amount of adjusting at the screw may be needed, but mostly you adjust the rods, if you got the first step right.
Take your time, do one wheel at a time at each notch position.
Start from scratch on all 4 wheels.
Start out by adjusting the rod lengths to each wheel to just take up the slack in the levers when you are not stepping on the brake.
Then screw the adjuster in at each wheel until you get some drag, then back out 3 to 5 clicks to get rid the drag.
Now use the notched stick to adjust the brake rod shorter at each wheel to give you the same braking at each wheel at each notch.
A small amount of adjusting at the screw may be needed, but mostly you adjust the rods, if you got the first step right.
Take your time, do one wheel at a time at each notch position.
Mac, just another FYI, I was not suggesting that the drag would go away by undoing the ebrake rod. I WAS suggesting you remove the ebrake band altogether as, in itself, it could be the cause of the drag. You've told me the only lining you replaced was the L/R service brake because they were "grease soaked". There was no talk of whether the drag you now experience was there with the old linings because, maybe, that was never considered. You were replacing the linings only because the old ones were grease soaked. And, OK, you didn't arc the new shoes. I would think that with the adjuster all the way out, even without arcing, there should be no drag.
J Franklin
Well-known member
Hey, where did you go? have you had any insight into the problem? I was almost thinking we were conversing with an AI.
nkaminar
Well-known member
- Measure the lengths of the rods. They should be the length as specified in the Service Bulletins.
- Replace all worn clevis pins and the clevis ends.
- Measure the diameter of the drum and compare to specification, or better yet replace all stamped steel drums with a cast iron drums.
- Measure the thickness of the linings on the shoes and compare to specification.
- Check and, if necessary, replace the bearings at the cross shafts. There should be no slop and they should be properly located on the frame.
Hi again,
I am not a robot – I am someone who has a lifelong love/hate relationship with his 1929 Model A Roadster pickup (owned by me for 55 years).
Since my last post I decided to take a break and think about the problem for a few days. Recently I have done more things to identify the cause of the brake drum binding. I have:
(1) Temporarily removed the e-brake assembly from its backing plate (binding continues so that was not the cause).
(2) Confirmed that the heads of the service-brake pins are properly seated on the roller track.
(3) Chamfered the leading and trailing edges of the service-brake linings
(4) Slightly bevelled off the outer vertical edges of the service-brake linings
(5) Applied chalk to the service-brake linings to observe high spots (there was one very small one, now sanded down).
(6) Measured the thickness of the service-brake linings at 5mm (should only be 4.78mm (3/16") but that is a very small difference.
Disappointing to find that none of these actions reduced the binding of the drum sufficiently to avoid over-heating.
I wonder if the linings are contacting only a narrow part of the brake drum, because when fully tightened the drum is very close to the backing plate. And when I release the axle nut and pull the drum out by about ¼ inch, the drum is then freed up. The axle already has 2 shims, but should I apply more?
katy
Well-known member
Sounds like the hub is badly worn, suggest you measure the hub and the axle to see which is worn. Possibly use the RHS for reference dimensions?
Anyone on here have the axle shaft taper dimensions?
nkaminar
Well-known member
Apply your chalk to the sides (edges) of the shoes that are outside and then put the drum back on. You don't have to tighten it. Turn the drum while pressing in and then remove it. Observe any marks on the drum or if the chalk has rubbed off the shoe edges.
If the shoes are not concentric to the drums this can cause some drag. You can glue some 80 grit sandpaper to the drums and then rotate the drums to make the shoes concentric and take away a small thickness of the shoes.
Regarding the shims. You can make thicker shims out of shim material. Just use the old shims as patterns.
If the shoes are not concentric to the drums this can cause some drag. You can glue some 80 grit sandpaper to the drums and then rotate the drums to make the shoes concentric and take away a small thickness of the shoes.
Regarding the shims. You can make thicker shims out of shim material. Just use the old shims as patterns.