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TR2/3/3A TR3 Rear Whelel Cylinder Install

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mountainman

mountainman

Jedi Trainee
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I need help installing new rear wheel cylinders. Both Moss and Haynes show the spring plate going on first followed
by the locking plate,distance piece, and dust cover.
By looking at the pictures it shows them with the openings of
the plates going toward each other. The trouble I am having is that the hand brake cable lever prevents me from sliding the locking plate over the cylinder. What am I doing wrong?
Thanks
Greg
 
mountainman said:
I need help installing new rear wheel cylinders. Both Moss and Haynes show the spring plate going on first followed
by the locking plate,distance piece, and dust cover.
By looking at the pictures it shows them with the openings of
the plates going toward each other. The trouble I am having is that the hand brake cable lever prevents me from sliding the locking plate over the cylinder. What am I doing wrong?
Thanks
Greg
Click to expand...

I did this recently.

The spring plate goes on first with the opening towards the front of the car, (and the little "ears" up) and, therefore, away from the handbrake lever. There is enough springiness in the spring plate so that it will bend enough to fit past the lever and, at the same time, fit under the cylinder shoulder. The locking plate opening is towards the back, meaning that it is intalled from the front and away from the lever. It doesn't have any springiness, so won't go on from the lever side.

Clear as mud?
 
This is like driving through downtown Flagstaff.

I've done it many times, have always been successful, yet each time I try it I have to figure it out all over again.
 
In case it's not clear, the diagrams are wrong (as were the original factory ones). However, the instructions in the factory manual are correct and do work.
 
Andrew Mace said:
What they said...and don't forget a tiny dab of white lithium grease or similar lubricant where the cylinder fits the backing plate so that it remains free to slide!
Click to expand...

Thanks fellows,
Your posts were a great help. However I do Have one more question.
What is the purpose of the wheel cylinder moving back & forth in the slot?
Mine moves but not freely at all.
Thanks again
Greg
 
mountainman said:
Thanks fellows,
Your posts were a great help. However I do Have one more question.
What is the purpose of the wheel cylinder moving back & forth in the slot?
Mine moves but not freely at all.
Thanks again
Greg
Click to expand...

When fluid flows to the wheel cylinder, it pushes the piston out. This pushes one brake shoe against the drum. When the brake shoe hits the drum, the hydraulic force pushes the whole cylinder in the opposite direction, which pushes the other shoe against the drum. This way, both shoes share the work of braking the car.

If the cylinder is stuck (like mine was) only one shoe does the work and wears out, whilst the other shoe does nothing.
 
It's interesting that some modern cars with disc front and drum rear brakes work in just the opposite way to Triumphs! Take, for example, a Toyota Paseo my son has. The front disc caliper has only one piston, but the caliper itself moves back and forth through the motion of that piston to then pull the other pad towards the rotor. Meanwhile, the rear wheel cylinder is "double-sided"; each shoe has a piston pushing it towards the inside of the drum!
 
I've noticed the same thing, Andy. My WAG is that the double-acting rear cylinders are needed to get the automatic adjusters to work; as the Stag has both automatic adjusters and double-acting cylinders (with Girling brakes).

And the single-acting front calipers are a cost-saving measure.
 
Here's an animation of the self-adjusting mechanism for drum brakes. You'll notice that the mechanism only works when the car is in reverse. Some systems only self adjust when the E-Brake is used.

I think a dual operating cylinder is neccessary. It also has to be fixed. I think it's more because the shoes are floating where the adjusters are rather then having a floating wheel cylinder like the TRs.
 
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