TR4/4A Wheel Cylinder Backing Springs

[dgaldrich]

I'm doing a frame off resto on my 63 TR4 (CT21405) and purchased all new hydraulics since the car has been sitting for quite some time. It's time to replace the rear wheel cylinders. The parts books and vendors all show 3 pieces on the inside of the backing plate that hold the cylinder in place -- 2 "springs" and one "plate". The previous owner managed to put them on with one spring (different on each side) and one plate. It sort of looks like I might have one complete set plus one plate. One of the springs has 2 tabs that seem to fit 2 notches in the plate. The other spring just has a bent over lip and it's shorter than the other 2 pieces.

By now, you've guessed that I have no idea which way the springs go and what order to put them in. The emergency brake arm is smack dab in the way just to irritate mechanics. The service manual indicates that the plate is the first out/last in of the pieces but provides little more information about how the springs go. I'm guessing that the long spring with the tabs mates with the plate (concave in) with the plate is against the flange part of the wheel cylinder. Because of the e-brake lever, it looks like the plate must be put in from the opposite side. What's with that 2nd short spring?

There HAS to be some logic to it all. Thanks in advance.

Dave Aldrich

 

[TR3driver]

The smaller piece goes against the wheel cylinder, and acts like kind of a flat washer.

Leave the handbrake lever out at first. Install the smaller piece with the tabs away from the backplate and the opening away from the handbrake lever. Then the large piece with the tabs goes between it and the back plate, same orientation. That should leave just enough play to pop the handbrake lever into it's place under the end of the cylinder. Then slide the other large piece in from the other side (opening towards the lever) between the first two plates. Use a punch or screwdriver to tap it into place, until the two tabs on the other large plate engage with the notches.

 

[trrdster2000]

Dave, Randall is spot on. Before you get it all together, use a bit of brake lub on both sides of the backing plate. It doesn't slide much but you would be surprised how much the lub will help center the brakes during operation. Don't use much on the inside but a 1/4 inch around the hole on the outer surface is about right. Crazy system but it's worked for a long time.

Wayne

 

[charleyf]

If you think this system is crazy try doing the rear brake cylinders for a Sunbeam Alpine. At least this system leaves one feeling the parts are securely on the car. Can't say as much for the Alpine. The British seem to have come up with a variety of ways to put the wheel cylinders on.
Charley

 

[Foura]

Dave, Randall's advice is excellent. I posted some time ago about a vibration in the 4A caused by a sticking wheel cylinder in the right hand drum. New return springs plus new wheel cylinder retaining springs plus lube have eliminated the vibration, improved the brakes in general and the hand brake in particular. Well worth doing. I managed to get the springs into place with the handbrake levers in place but disconnected from the cable. It seems like a weird system but actually works quite well. Probably worth buying two new sets of plates from the usual suppliers rather than using old rusty ones.

Buckeye Triumphs also has a excellent set of pictures showing how the plates mount around the wheel cylinder. https://www.buckeyetriumphs.org/technical/Brakes/Rear/Rear.htm

Good luck!

 

[TR3driver]

Buckeye Triumphs also has a excellent set of pictures showing how the plates mount around the wheel cylinder. https://www.buckeyetriumphs.org/technical/Brakes/Rear/Rear.htm

Nice pictures, but wrong.

 

[Foura]

Randall, you are absolutely correct. In fact, I used your instructions to reassemble my brakes.

One does not become a Great Pumpkin just by being up after midnight!

 

[Foura]

This pic probably gives a better idea of how the plates are assembled.

 

[Tybalt]

If you think this system is crazy try doing the rear brake cylinders for a Sunbeam Alpine. At least this system leaves one feeling the parts are securely on the car. Can't say as much for the Alpine. The British seem to have come up with a variety of ways to put the wheel cylinders on.
Charley

I've got to ask which series Alpine were you working on? The first couple of series used a cylinder that shares the same base casting with the Triumph cylinders but was final bored to .875" instead of the .700" of the cylinders used on the TR4 through most of the TR6 models. That cylinder assy, 64673804, will drop right into the Triumph backing plate and uses the same "plates and spring" retainer system. It works very well in conjunction with the four piston Toyota front caliper conversion. That cylinder was also used on just about every four wheel Morgan ever produced until they went "modern."

The Series III and IV Alpines and Tigers used a different casting and the bore was reduced to .750". Series V used yet another cylinder and the final series after Rootes Group went under Chrysler control used yet another. That last one was probably set up for self adjusting brakes since they list specific LH and RH cylinders.

 

[charleyf]

I've got to ask which series Alpine were you working on? The first couple of series used a cylinder that shares the same base casting with the Triumph cylinders but was final bored to .875" instead of the .700" of the cylinders used on the TR4 through most of the TR6 models. That cylinder assy, 64673804, will drop right into the Triumph backing plate and uses the same "plates and spring" retainer system. It works very well in conjunction with the four piston Toyota front caliper conversion. That cylinder was also used on just about every four wheel Morgan ever produced until they went "modern."

The Series III and IV Alpines and Tigers used a different casting and the bore was reduced to .750". Series V used yet another cylinder and the final series after Rootes Group went under Chrysler control used yet another. That last one was probably set up for self adjusting brakes since they list specific LH and RH cylinders.

sorry I can quote which series it was. The owner passed away and his wife ordered the parts and two of us installed them for her. I Just know that the retainer pieces seemed less than reliable. Our TRs may be hard to get on and off but I have never been concerned that they looked like they could just fall off the car.
Charley

 

[dgaldrich]

Thank you all. I have the idea now. Gotta love the BCF.

 

[Tybalt]

Charley, thanks for responding back. I figure any time we have a chance to learn some of the details of any of these cars, it's worth taking a shot at it.