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TR4/4A TR4A Solid Axle Rear Brake Backing Plates

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J

Jerry_Oliver

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Hello All,
I'm restoring a 66 TR4A solid axle car. Since the car had a TR4 rear end in it, I obtained a TR4A unit and had a Seattle machine shop rebuild it. However, they incorrectly mounted the brake backing plates, and I am now unsure of their orientation. I searched any number of manuals, looked at a number of cars (none 4A Solid Axle) and haven't come up with a definite answer. It has to do with the location of the hand brake lever, the bracket for that cable, and the two different slots in the backing plate for the wheel cylinder. That combination determines left and right backing plate and the "clock" orientation of the hand brake lever and wheel cylinder. If anyone has a photo of the rear brakes on a solid axle 4A, it sure would help me out now that I am reassembling the chassis.
Jerry Oliver
Olympia WA
 
Jerry, here are a couple of shots. The brake cylinder is on top which I believe is correct.

Left_Rear.JPG


Left_Rear2.JPG
 
Sorry Jerry, didn't intend to mislead. Aaron's photos jive more with the with diagrams in the TR4A spare parts catalogue.
IMGP1744.jpg
 
Thanks to all for the reply. Aaron, could you take a photo of the other side wheel? One factor that confused me is the placement of the bleed screw. If you look at Jay's photos, in that arrangement with the wheel cylinder at 3 o'clock, the bleed screw is on the bottom. Since Triumph had only one bleed screw in the rear for the solid axle car, that doesnt make sense. However, it looks like Aaron's car has a rod for the hand brake lever, while Jay's car has a cable, which is like my car and like the IRS cars. Thanks again to all that responded.
Jerry Oliver
Olympia WA
 
Jerry_Oliver said:
Thanks to all for the reply. Aaron, could you take a photo of the other side wheel? Since Triumph had only one bleed
Click to expand...

Yep! One bleed nipple for the solid axle 4A guys. Crazy Brits. :nonono: The nipple is at the top at least so those air bubbles that don't make a wrong turn (to the left side) will be forced out the one and only rear nipple.

Also, my car is very original and does have the cables (just like the IRS cars but unlike the rods on the 4). The end of the cable just looks like a rod because it's "all-thread". I believe this is the same cable arrangement as a TR6. Hope this helps.

Right_Rear.JPG
 
Hello All,
Well, a little more information on the 4A solid axle backing plate orientation. Today, I took off both plates, making sure to keep the shims in place. In that process, I found a part number stamped on that back of each plate 8124 R and 8124L, so that identified the right and left plate. Now, as to the orientation, in the parts diagram (why isn't that one in my manual?) the wheel cylinder is at 12 o'clock. I tried that on the LH wheel, and it seems to me it wouldn't work at all, as the bracket for the handbrake cable is at 9 o'clock (front, parallel to the ground). Also, there is a retaining bracket for the flex hose on the frame. Placing the flex hose in the bracket, and passing it up to the 12 o'clock position would place it right over the buffer pad on the top of the axle housing. So, as I see it, the option is to rotate the plate to one of two positions; about 11:30 or about 3 o'clock. I choose the 3 o'clock as that allows the brake cable to line up better. It does make the crossover brake line make a tight loop into the LH wheel cylinder, and it does place the opposite side wheel cylinder with the bleed screw on the bottom. I assume that was just a Triumph oddity. Note, that the cross over line has a bubble fitting on one end (into the empty bleed screw hole on the LH side) and a double flare fitting on the RH side. I do have the original line, so I'm pretty sure of the routing. So, my final position is the same as Jay Barnhardt's car. It may or may not be original, but it seems to work the best. I would say that on both Jay's car and Aaron's car, there are no lock tabs on the backing plate retaining bolts. I am positive that there were on my rear end I sent into the machine shop. Anyway, this process has been again a test of will, but today for the first time in over a year, the chassis sat on all 4 wheels, with the rebuild engine (long block), rebuilt transmission, rebuilt rear end, and new rear brakes in place. Yeah!
Jerry Oliver
Olympia WA
 
Jerry, It was good to read your reply, because since this started, I was considering what changes I might make to mine. I came up with the conclusion: Nothing. Even if wrong, it works with no compromise.
Particularly because of the flex hose routing, and that the parking brake cable routing wasn't unattractive to my eyes. By the way, I replaced that cross over brake line, and remember it as you describe (bubble fitting into bleed screw hole in left hand side). When I went to bleed the brakes, I simply "gravity" bled and it could not have been easier. That (gravity bleed) wasn't my intent, it just kept running out when I opened the nipple.
 
Found this old thread from a search. I'm going thru the same issue with the orientation of the rear brake backing plates on a solid axle TR4A. Unfortunately, all the reference pics from the posts here are gone. Can anyone help me out? Thanks!


Brian
 
Not certain this shot is any help, Brian - It's one that I submitted back then of the RR backing plate as viewed from in front of the axle. Can't be sure this is correct, my solid axle 4A has a storied past - I just don't know the story.

 
Thanks ... that's exactly what I was looking for! I thought that might have been the proper orientation due to the position of the hand brake support on the axle but sure couldn't find any diagrams from the many TR books that I have. Thanks a million!
 
Hey Jay

Saw this old post of yours and since I just blew out my back brakes I'm researching what others have gone through.

You have some photos on your photo bucket which I could not access. Do I have to have a Facebook account to view them?
Thanks
John
 
John, here are 4 shots the 4A's solid axle backing plate. Hope these help.







 
It was missing Mike...and was corrected shortly after these photos were taken.
 
Thanks Jay - just want to confirm I am doing the right thin in my rear axle rebuild. After putting in the final piece the actuator was pretty tight - it slid back and forth, but with a lot of resistance. When I saw these pictures, I thought maybe the final piece should not be there, perhaps explaining the tightness...

Thanks for confirming I am doing something right! :wink-new:
 
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