Modification of Faulty New Made Rear Brake Shoes
As part of a recent ‘refresh’ of a 1924 (ish) T one of the many things needing attention was the rear brakes.
Removing the wheel exposed one shoe on one side and 2 on the other, all three were well worn. Drums were also well used.
A look in the catalogues and 2 new rear drums and 2 sets of rear shoes – complete with linings – were ordered.
The parts arrived and looked good. The first we noticed about the shoes was that the pair for each side was cast together. Hmm, that is different. We were assured “this is the latest thing and it works very well, better than original.
OK, lets give it a go, but as the shoes can hardly be separated they will put a lot of strain on the brake rods, clevises and driver’s arm.
Inspecting the “one piece” casting we noted that the outside diameter of the linings (outside edge) was about the same as the outside diameter of the ‘original’ steel shoes. Some thought has gone into this to cast the shoes smaller to compensate for the lining so that they fit in the drum.
We put one set up on the rear backing plate, and noticed the flats were about ½ inch too far to the rear when sitting on the cam – the new shoes are ‘shorter’ as a consequence of making them smaller.
Worse, the little tabs (for hooking the springs over) on the front (cam side) of the shoes are now interfering with the radius arm bolts. Shrinking the castings to keep the lining diameter in the drum has had an unintended consequence here.
As they came from the packing the new shoes will not fit, will not operate safely or fully and may prove to be dangerous if they bind to the radius rod bolts.
Also, we wondered, why are the shoes too small for the drum when mounted? The answer is that the castings are in a tighter radius than the drum. There is too much clearance between the linings and the drums.
After some pondering we figured that the shoe castings are malleable iron, and then a light went on. “back in the day” before repro shoes were made my friend Brian had made his own shoes by welding flat iron together, then having linings attached. Disaster followed as the newly lined shoes were too small. Comparing them to his jig, it was found that the shoes had been ‘squashed’ when the linings were clamped to the shoe while gluing. Brian spread the shoes out on the jig and they fitted again. It seems this is also what has happened with the new castings, when the linings are clamped on to the shoes to glue the pressure on the clamp has compressed the linings into the smaller radius we noticed.
How Did We Sort This Out?
Cut the single casting into 2 shoes. There is no way around this step.
Following ‘shade tree’ tradition we put each shoe in a vice and ‘opened’ it with about 2 turns each. This spread the shoes to a radius that matched the drum.
Cut off the two ‘front’ tabs for clearance on the radius arm bolts.
Drilled holes for the springs to fit into.
Tried the shoes with the drum. We had to “close up” one shoe just a bit as we had over spread it, but otherwise the shoes (and linings) now line up with the drums and work very well.
It took a bit to figure out what had happened, and I wonder how many folk just install the shoes as they come, resulting in ineffective (and possibly dangerous) rear brake installation.
If you have bought the new shoes and they just don’t seem to fit or work, I hope this post will point you in the direction to fit them properly and safely.
Cheers all Adrian
Adrian, the cutting of the tabs wasn't necessary - it's this particular T that has the radius rod bolts the wrong way around
Here's what it looks like originally:
I wonder how the original brake shoes was fitted?
And usually, this new Snyder's design of one piece lined shoes from c:a 2012 is better than what was offered before. Maybe something has changed in the production recently?
Didn't have any circular fit issues in my installs, have done 3 now of the newest Snyder one piece shoes with lining. They are superior to the earlier 2 piece cast parts.
My only issue was the longer cam, as you noted. That longer cam on the outer edge caught on several hub bolt nuts as the wheel revolved. Solved that by grinding away a 45 degree angle of the longer tab....thereby eliminating any impingement. The shoes fit the drum well, didn't need or want to split them, and they work!
Ground off the leading edge of the cam for relief.
Brakes for the Ford, new lined shoes for emergency, and RM brakes for service, with Ford transmission brake as final go to.
This all proves if you want good parts, get stuff that was made when the Model T was new. I wonder how many manufacturers of new T parts bother to test their parts before marketing them?
Adrian, I believe the shoes should be split into two halves. Otherwise they can break in unfortunate places. You have noted that this reduces load on the cams, arms, brake rods etc.
Dan's mod with the angles ground on the cam faces to clear the wheel bolt nuts is the only problem I have encountered with these new shoes. They are far superior to the previous offering which needed hours of fettling to get them to sit and work properly.
Roger picked the bolts fitted wrong way round. Nuts go on the outside. In his photo the brake shoe spring shown is fitted in reverse to how I like to fit them. If the open end of the hook is towards the outside rather than to the backing plate, the springs will tend to pull the shoes towards the backing plate, thus keeping them out of harms way.
Hope this helps.
Allan from down under.
Thanks for the post, Adrian. Another thing to check while doing my restoration.
Larry, do you run original bare cast iron shoes on your cars, or some period lined shoes?
If lined, which period shoes do you recommend?
Yes, the nut was wrong way around, however, the original shoes missed the bolts completely with no interference, (and right way round was still going to just catch the head on this T).
Dan, it looks like there is a lot of clearance between the linings and the drum in your picture. I think if you put the pivot bolt in you would have much more clearance at the cam end of the shoe than the pivot end as well. This means the cam must strain hard to spread the one piece shoe to get proper contact on the drum.
If you sat the shoe in the drum like in my picture with the pivot end in against the drum you would see the same issue we found.
We had to make no adjustment to the cam, nor champher the shoes on our install.
In any case, each T is "its own machine" so I would think your install may vary, but in this case please be wary too!
Thanks for the comments :-)
Adrian, have you tries the action of the hand brake connected to the rear wheels with your shoes in place?
If the hand brake lever is fully forward in the off position the shoes have to be away from the drum, pull the lever back to the vertical position and you are in neutral (and the car can roll without the brake shoes touching the drums) its only when you pull the lever back past the neutral position that the shoes clamp the drums.
There has to be a gap between the shoes and the brake drum so the cam can move the shoes apart, if the shoes are against the drums in the fully forward position it won't be possible to pull back the lever and get neutral and then the park position.
You posted: This means the cam must strain hard to spread the one piece shoe to get proper contact on the drum.
But, the Model T emergency brake (parking brake) is rather rudimentary. Only resembles the modern 2 piece shoes in an internal expanding brake setup.
With modern, the design is maximized for the force vectors of forward rolling wheel.
Note the best systems use an anchor point for the two-piece shoes. The primary shoe is driven out by the piston to contact the forward portion of the drum. The trailing shoe is normally called the secondary shoe, is also driven out.
Now the Model T is much different, just a very simple expanding shoe. The anchor point is at the rear, bolt holding the shoe to the backing plate. The force of the cam opens the shoe, and contact is mostly at the top and bottom.
This photo was on the forum, isn't mine, but shows the wear pattern of the original cast iron shoe. The wear isn't on the cam portions, but on top and bottom. In this one, there is no rear spring, just the bolt holding the one-piece shoe in place. The cam forces open the shoe, you need the bolt firm there for the anchor, or the shoe shifts and contact is lost.
Also, the later Improved Car featured similar emergency brake or parking brake, but lined the one-piece shoe. The shoe is now steel, but note, no anchor bolt. The steel shoe can expand a bit, but really the front top and bottom sections of the shoe do the stopping and holding. Tabs on the backing plate keep the shoe from shifting.
Peter has indicated there needs to be some clearance between the shoes and the drum. Put another way, for the best neutral position the handbrake is just on the cross shaft cam. At the same time, the brake shoe cam should be absolutely level.
When the handbrake lever is set forward to engage high gear, the brake shoe cam is rotated a bit, spreading the shoes somewhat. So this does not make the shoes drag on the drums, there needs to be some clearance between the shoes and the drum.
Applying the handbrake the same amount as when the lever is set forward will give the same result. It is not until the lever is pulled further back that the shoes should start engaging on the drum.
I learned this when making sleeves to go over worn brake shoe cams in the backing plate.
Hope this helps.
Allan from down under.
I run old stock lined brake shoes. I like the reinforced type, but I have the non reinforced type in one of my T's too. I only use them for parking.