Jump to content


Fitting UC Rear Discs On LH/X

  • Please log in to reply
4 replies to this topic

#1 enderwigginau


    Admin Wrangler

  • Moderators
  • PipPipPipPipPipPipPip
  • 2,000,527 posts
  • Name:Grant
  • Location:Brisneyland
  • Car:76 LX Sedan, 4 seater
  • Joined: 04-February 07

Posted 17 May 2011 - 09:16 PM

Article title: Fitting UC Rear Discs On LH/X
Article description: How to install a set of UC Rear Disc Brakes on an LH or LX Torana
Category: Brakes, Wheels and Tyres
Date added: Jul 24 2008, 11:01 PM
Article starter: enderwigginau
Part 1: Bits and pieces needed to install UC Torana Rear Disc Brakes on an LH/LX Torana

Torana Fine Spline axles
Posted ImagePosted Image
Twenty-three splines as opposed to twelve on coarse spline axles. Besides being stronger than coarse spline axles, these will fit straight into an LH/X fine spline diff centre.
Posted Image

The bearing on the disc axle

Resting upon the axle retaining flange is the spacer required to use disc brakes. This spacer fits into the backing plate/calliper hanger, to hold the hub far enough out for the discs to not contact the backing plate and allow the callipers to fit over.
Posted Image
Backing plate and Brake shield
The backing plates are the calliper hangers. The spacer behind the bearing fills the depth of the plate. The Shields prevent too much outside contaminants (grit, stones and even water) from coming into contact with the rotor. Water can warp the rotors if cold water comes into contact with a hot rotor, and stones and grit can become lodged between the pads and rotor. Unfortunately, these shield can also trap heat in the brakes, and cause brake-fade under hard braking conditions. The brake line retaining bracket can be seen in the lower left photo.
Posted Image
Posted ImagePosted Image

The UC Rear calliper (RIGHT HAND), with handbrake mechanism. These are shown in the "Pull from rear" UC orientation and must be removed and swapped left-calliper-to-right so as to pull from the front. These bolts also hold the retaining bracket for the handbrake cable. The brake line and bleeder are the TOP of calliper. A handbrake cable retaining bracket is held in place by three of the four bolts holding the handbrake actuator arms.
Posted Image
Posted Image

Part Two - Installing the UC rear disc

The first thing to do, if you don't already run a fine spline diff centre, is to swap them over. Pull the drums off the ends of the diff (Make sure the handbrake is off!). Using the holes in the axle hub, remove the bolts holding the backing plate of the drum brakes. Flip one drum over and place back over the wheel studs and put some wheel nuts back on a few turns. Now pull the drum out and hopefully after a couple of tries the axle will come out. Undo the brake line from the drum and gently bend out of the way. For now just place the loose drums under the car out of the way.

Mounting the backing plate
Posted Image
After removing the drum-brake backing plate, you mount the disc-brake backing plate straight onto the same points, making sure the caliper hanger holes are pointing towards the front of the car. This can be done with or with out the shield bolted onto the backing plate.
Posted Image
Now carefully insert the disc axle into the diff tube. When you feel it bump the diff centre, gently apply pressure while turning the axle. Once the splines are aligned it will slide right in. Make sure the axle flange has gone over the four axle retaining bolts. Using the holes in the axle hub, put the nuts on these bolts, preferably using locknuts so they can't vibrate loose.

Now you can push the disc rotor over the wheel studs.
Posted Image
At this point you can plumb in the calliper to the brake line, being careful not to tear the metal line as you adjust it. Push the free end of the flexible line through bracket on the rear of the shroud and then screw the main line nut into it.
Posted Image
Now mount the caliper on the hanger. Remember that the bleed valve is the top. Have you got the correct caliper for the side of the car you are on?? The nuts marked are where the handbrake cable bracket bolts on.
Posted Image
You should be complete. Hopefully it looks quite similar to this
Posted Image

In this picture you can seen the metal brake line. For a very professional job, get your hands on a flaring tool and shorten the line to a suitable, tidy length, replace the nut on the line and reflare.
Posted Image
Now you are at wheel mounting stage. Repeat on the other side of the car.
Posted Image

There is only one thing left to do now, and that is at the other end of the car. Be sure to place some paper or rags under the master cylinder to prevent paint damage. Unscrew the rear brake line from the rear master cylinder. Using a small drill bit, slightly smaller than the brake line, drill out the cup that holds in the drum brake line pressure valve. The cup and valve should just come out on the end of the drill bit.
Attached File  master01.jpg   31.81K   12 downloads

This one is the front circuit from a four wheel drum Torana, but is identical to removing the valve from the rear circuit - pic courtesy ls2lxhatch

Alternatively, get a self tapper and screw it into the brass cup that holds the valve in, then I wiggle it (quite tight) out and the valve should just pop out. Use the screw and a hammer to put the brass cup back in then unscrew the self tapper and you're away.

Be sure to replace the brass cup as it has a tapered end that the brake line seals on so there is no leakage! Without removing this valve, the first time you put the brakes on will be the only time the back brakes come on - and they'll stay on!

Bleed the brakes and you are ready to drive. Without the constant pressure that drum brakes use, your brake pedal may now be a lot lower when the brakes kick in, so it would be advisable to have the master cylinder plunger rod shortened to correct this.

Also, over the many years of drum brake usage, the piston has been stopping at one place. This can cause a notch to form in the bore of the master cylinder, so having it reconditioned and sleeved is a good idea if you don't have a new one lying around to replace it with.

Thanks for the able assistance of Simon Read(V6Hatch) and Sam Varcoe.
Pics part 2 - The conversion of Sam Varcoe's LH.
Article by enderwigginau

#2 Mike73


    Forum Fixture

  • Members
  • PipPipPipPipPip
  • 593 posts
  • Name:Mike
  • Location:WA
  • Car:73 XU-1
  • Joined: 31-January 08

Posted 12 June 2011 - 03:35 PM

I have a few questions, when I tried a similar conversion on my HJ Statesman I had to change my proporting valve to match the reduced pressure for the rear brakes, I tried it as you say with the standard proporting valve and the rear wheels locked up.
Can you tell me why the LX would not have the same problem?

Also if you drill out the residual pressure valve in the master cylinder wouldn't debris end up in the brake lines when bled up?

How do you get the right rear disc allignment right using a normal fine spline axle when the original rear disc ones have the axle flange machined in a much different location giving a different allignment to allow for the much thicker inner part of the discs?

How do you bolt the wheels on with the shorter wheel studs? The UC disc brake ones are much longer.

Don't the spring strenghts in the master cylinder vary between the drum brake and disc brake rear vehicles?


#3 Steve TPF

Steve TPF

    Forum Fixture

  • Members
  • PipPipPipPipPip
  • 780 posts
  • Name:Steve
  • Location:Adelaide... city of... anyone know something good about it?
  • Car:UC hatch
  • Joined: 09-June 09

Posted 12 June 2011 - 08:22 PM

Basically, if you use the Disc brakes you have to use the Disc axles, for the off-set reasons you mentioned.
Check this thread. Five posts down there's a diagram showing the differences between the disc/drum axles. If you can make it work with the drum axles without remachining them, there will be a few people interested I'm sure.

#4 Max's SS

Max's SS

    Forum Fan

  • Members
  • PipPipPipPip
  • 350 posts
  • Name:Steve
  • Location:Port Pirie SA
  • Joined: 21-May 06

Posted 13 September 2021 - 08:36 PM

Just a question on an old thread.

I refer to the photo and text about the hand brake cable and the need to swap the orientation from left to right, right to left on the caliper.

Do you just undo the single bolt and swap the lever or do you under the 4 bolts and swap the whole mechanism.

If the 4 bolts have to be removed ....is this a simple job ?

Does anyone have a diagram showing all the components.

Edited by Max's SS, 13 September 2021 - 08:37 PM.

#5 Max's SS

Max's SS

    Forum Fan

  • Members
  • PipPipPipPip
  • 350 posts
  • Name:Steve
  • Location:Port Pirie SA
  • Joined: 21-May 06

Posted 14 September 2021 - 07:41 PM

All good. I have worked it out .

0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users