Rear brake adjustment

[nkaminar]

My suggestion is to have a second set of eyes look at your brakes. Or maybe several more sets of eyes. In my Model T club we would have Tech Sessions where the club members would be invited to a members house to work out a technical problem. The member with the problem would supply lunch. This worked well and we all learned from these sessions.

Mad Mac, That is a really good video, thanks.

[Jim/GA]

Make a brake adjusting board with the steps in it, like in Les Andrews' book, if you don't already have one, so that you can place the brake pedal in the same 3 reproducible spots time after time. A lot of guys poo-poo this board, but its reproducibility helps when sorting out problems.

One of the unfortunate characteristics of mechanical brakes is that 1 or 2 or 3 brakes that are adjusted too tightly can prevent that amount of brake rod movement from engaging the other wheel(s) properly.

The 4 brake rods are all mechanically bound to each other. They are all forced to move together, and if one wheel stops that movement prematurely, the other rods can't move as far as they need to for proper braking.

The solution, once you identify which wheel(s) are too tight, is to actually loosen the tight wheel(s) a bit. This allows the other brake rods to move a bit further and actuate their brakes more.

With all 4 wheels off the floor, see what amount of braking you have at the 3 "good wheels" when on just the first step of the board. We know there will be none on the 4th wheel. Then do the same at the 2nd and 3rd step of the board. It should be getting progressively tighter. You should not have a wheel lock up on the first step (that's too tight).

If the above does not point you to a wheel that is too tight... After noting the braking force at each wheel for each step on the board, start applying the board in steps with each one of the 3 "good brakes" disconnected. See if that helps get better progressive braking action on the other 3 wheels (including the one that is not braking now). Do this for each of the 3 good wheels, one at a time. This may help you identify which wheel(s) need loosening of braking adjustment. It might be more than one.

The loosening of a tight wheel might be done one of two ways: 1) by lengthening the brake rod a bit at the tight wheel. Make very small changes each time (like 1/2 turn of a clevis) and test again. See if directionally it seems to help. Keep a record of your changes, in case you need to go back.

Or 2) the loosening can be done at the brake adjuster screw at the tight wheel.

Since you have 2 things that you can change at each of the 4 wheels, it can get a bit complicated fast. Take your time, make small changes, and record exactly what you are doing on each wheel at each change. An assistant note-taker helps there.

With the brakes not applied, the shoes should not rub inside the drum. A light brushing touch in one or two spots as the wheel goes around is OK, especially on a wheel with new shoes, but they should not rub all the way around.

Changes to the clevis by 1/2 turn are much finer than changing the adjuster screw. So if you find yourself where one adjuster screw click is too much, go back and take 1/2 clevis turn on that wheel instead.

Good luck. Keep us posted on what you find.

[Mad Mac]

Thanks Jim, - some good suggestions there. If one or more of the other 3 brakes are too tight, would they not heat the drum even when disengaged?

[rotorwrench]

One more thing to contemplate would be how much play might there be due to worn rear hub bearing components. I've seen some badly worn journals on the axle housings that allow excessive movement of the hub & drum. Combine that with wear on the other parts and it might rub the drum when the wheel is on the ground but not with the wheel off ground.

[Jim/GA]

Originally Posted by Mad Mac

Thanks Jim, - some good suggestions there. If one or more of the other 3 brakes are too tight, would they not heat the drum even when disengaged?

No, not unless they were adjusted out to rub against the drum when disengaged.

When I say "too tight", I really mean "adjusted too close". So the shoes get firmly against the drum right away, but are not touching at rest.

I would also recommend you pull the drum off of the "bad wheel" and inspect how the parts were all put together. It is possible that something has been accidentally assembled incorrectly. I can't predict what off the top of my head. A photo of everything with the drum off might help us spot it. (My apologies if you have already done that, posted a picture; I don't remember seeing it.)

[J Franklin]

Sponsored Links (Register now to hide all advertisements)

A photo might solve it all right.

[bobbader]

The fact that only the left rear brakes "didn't work" before you relined them begs the question ................... "Why is that the only one that didn't work?"

The other question is, if you run out of adjustment on the L/R brake rod, has that brake rod been shortened (CUT).

Your check list doesn't appear to have any holes in it. You've checked off and seemed to eliminate anything to do with how you did your repair and re-assembly. That suggests there was something wrong aside from a need to reline the shoes on that wheel while none of the others needed attention. As others have suggested, another set of eyes could be very helpful. Good luck as you continue to find a culprit.

[Dino's A]

Originally Posted by Rob Doe

I suggest that all Model A Brake mechanics, especially the DIYer types, watch this video 10 times and then revisit it often. It is clear, concise and thorough. There is no stammering, stuttering or wasted words.

https://www.youtube.com/watch?v=3GFMJ7iiWiI&t=8s

Thank you, Excellent tutorial

[Mad Mac]

Thanks everyone, especially Jim/GA whose suggestions demonstrate considerable experience with Model A brake issues.

In answer to Bobbader: No the brake rod has not been shortened. The only reason why I re-lined the service brakes on that wheel was because it was the only one with grease on the brake linings. All the others are OK.

Attached are two photos, taken after assembling everything onto the backing plate but before attaching the brake drum. I don't want to remove the brake drum to check it again, as I am sure that everything was assembled correctly on the backing plate, as per Les Andrews' book. Please note that I temporarily disconnected the "C" from the e-brake shaft to more easily attach its return-spring (this is not relevant to the service brake issue).

I have now made the brake-adjusting board as suggested, and my next move will be to use it to try to solve the service-brake problem.

[Rob Doe]

Mac,

I've one more idea for you. I've had this issue bite me more than once and learned to be careful about falling victim to it.

The video "How to Stop on a Dime" shows the narrator installing the rear shoes and springs in a specific order. He installs them by hand and it looks easy. It is not so easy for a 74 year old with skinny, bony hands.

When I use the $22.00??? pistol grip leveraging tool, it is fairly easy, but you have to be absolutely certain that you get the head of the roller pin seated on the roller track, and pushed all the way back, (toward the backing plate) else your shoes will not be in position to function correctly. They can look right to the non professional as we work on the brakes infrequently, but still not be fully seated in the correct position.

This leaves the shoes off center for sure.

[bobbader]

Thanks for clarification on why you relined just one wheel. Assuming you have hooked up the "C" horseshoe link for the emergency brake since you're not anxious to pull the drum again. If so, is it possible the ebrake lining is too thick? It's hard o tell from the pictures, but it looks to be the same 3/16" thickness as the service brake linings. It's supposed to be 5/32". Perhaps this is causing the drum to heat up as opposed to the service brake adjustment?

Otherwise, Rob Doe's supposition about the roller pins not being properly seated is definitely worthy of inspection.

[CT Jack]

I think you might have a bad wheel bearing that is seized or ready to seize.

[J Franklin]

I will predict you will pull that drum. When you do, remove the rod and work the lever by hand and see what is not working.

[Bob Johnson]

Did you arch the shoes to the drum? If the new lining is thicker or thinner than the old lining it is possible that the shoe will contact the drum in only one spot. If you adjust the shoes to contact the drum they will rub on that one spot and heat up the drum. But you will not have much stopping power because there will not be full contact.


Bob

[Jim/GA]

Originally Posted by Rob Doe

Mac,

I've one more idea for you. I've had this issue bite me more than once and learned to be careful about falling victim to it.

The video "How to Stop on a Dime" shows the narrator installing the rear shoes and springs in a specific order. He installs them by hand and it looks easy. It is not so easy for a 74 year old with skinny, bony hands.

When I use the $22.00??? pistol grip leveraging tool, it is fairly easy, but you have to be absolutely certain that you get the head of the roller pin seated on the roller track, and pushed all the way back, (toward the backing plate) else your shoes will not be in position to function correctly. They can look right to the non professional as we work on the brakes infrequently, but still not be fully seated in the correct position.



This leaves the shoes off center for sure.

This is very true. I have had this problem several times.

Here is the tool that Rob Doe references. It is $19 from Bratton's.

You hook up all of the brake springs without having the rollers engaged yet, pull the shoe away at the bottom/front, stretching the smaller brake spring out, and get the head of the roller clevis pin up on the track. Then let the spring pull the rollers back in against the wedge (front) or cam (rear) to fully seat.

[Mad Mac]

Originally Posted by bobbader

Is it possible the ebrake lining is too thick? It's hard o tell from the pictures, but it looks to be the same 3/16" thickness as the service brake linings. It's supposed to be 5/32". Perhaps this is causing the drum to heat up as opposed to the service brake adjustment?

Thanks Bob: The e-brake was not re-lined - it still has the old lining, which didn't need replacing.

[Mad Mac]

Originally Posted by Rob Doe

Mac, You have to be absolutely certain that you get the head of the roller pin seated on the roller track, and pushed all the way back, (toward the backing plate) else your shoes will not be in position to function correctly. They can look right to the non professional as we work on the brakes infrequently, but still not be fully seated in the correct position. This leaves the shoes off center for sure.

Thanks Rob,
I hope you are wrong about that, as I want to avoid removing the drum again if possible. I used a jack to lift the upper shoe onto the roller after the springs were installed. An unusual method, but it gave precise and effortless control as the spring-loaded shoe was lifted up and over. I saw and heard the shoe click into place and it was not off-center.

[Mad Mac]

Originally Posted by CT Jack

I think you might have a bad wheel bearing that is seized or ready to seize.

The bearing was removed, checked and replaced. It is perfect.

[Mad Mac]

Originally Posted by J Franklin

I will predict you will pull that drum. When you do, remove the rod and work the lever by hand and see what is not working.

Thanks J Franklin,
During assembly I worked the service brake lever back and forth several times to confirm that the cam was expanding and contracting the shoes properly (it was). And after installing the drum I temporarily disconnected the brake rod and worked the lever again. This got excellent brake action with the lever pulled forward. But the clevis has insufficient adjustment to achieve the same result when the brake rod is re-connected. That is my problem in a nutshell.

[Mad Mac]

Originally Posted by Bob Johnson

Did you arch the shoes to the drum? If the new lining is thicker or thinner than the old lining it is possible that the shoe will contact the drum in only one spot. If you adjust the shoes to contact the drum they will rub on that one spot and heat up the drum. But you will not have much stopping power because there will not be full contact. Bob

Thanks Bob,
You might have a point. The shoes were not arced to the drum and also I did not taper off the ends of the new linings as recommended by some. But I find it hard to believe that my problem (as described in the above posts) can be attributed solely to those two omissions (especially if you read post#39 above).