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LJ Standard disc Brake Improvements

LJ Brakes LC Disc

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#1 salamiman

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Posted 05 December 2023 - 07:40 AM

Hi all,

Calling on the Brake gurus.

 

 I know this has been thrown around a million times but once again calling on people's experience if I can.

 

 I would like to improve the braking on my LJ Torana, as it wont lock up at the front ATM, not that you really want that, but guessing they should? Did these old systems have enough breaking power to lock the front brakes in a straight line?

 

It has a standard disc front end at the moment-12.7mm disc in good condition, pads are old.

 

The brake booster seems to be working well, replaced the master cylinder in the last two years and reconditioned the calipers.

 

Im not racing, or trying to improve brake fade, just looking for good hard braking when needed.

 

What improvements have been made by a certain disc types or pads?, bigger booster? or am I wasting my time?

 

 

 

 

 



#2 RallyRed

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Posted 05 December 2023 - 07:54 AM

I'm not a brake guru.

However, my experience with these cars.......

 

Assuming the actual braking system is working, and not some bitsa put together by a previous owner etc.

 

Put some decent new pads in, you'll be surprised at the improvement.

Next level would be some track spec pads, you'll really be surprised at the improvement. However, can be a lottle flakey until they get warmed up . i.e. first set of traffic lights can be interesting.

Next level, swap to a full track set up like BMW vented rotors and Volvo twin spot caliper with race pads, you'll really really be amazed at the  improvement.

We have two cars, one with standard xU1 discs and track pads, normal booster - very good braking

The other with the BMW/Volvo/race pads and normal booster - excellent braking.

 

p.s. used to have a road GTR that suffered poor brakes, found the front hoses were all part blocked, and the rear body to diff hose was completely blocked.  Fixed those and hey presto.



#3 yel327

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Posted 05 December 2023 - 08:16 AM

I was always amazed on my LX the difference it made when I replaced the pads and bled the brakes with fresh good quality fluid.

#4 salamiman

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Posted 05 December 2023 - 08:29 AM

Thanks Fellas.

 

So New pads for sure, Brand??-for street use or where I live hard braking to avoid a Roo, so no brake pad warm up period.

 

Any suggestions on Rotor type, as there are many versions available, Slotted, J type, drilled?

 

Would it be worth going to the XU1 thickness rotor?

 

Cheers



#5 RallyRed

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Posted 05 December 2023 - 08:55 AM

Good road pads?... There are real brake gurus on here who work in the trade, they could prob. answer that best...

#6 salamiman

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Posted 05 December 2023 - 10:06 AM

What was the idea of the thicker XU1 rotor?

 

I can imagine it took longer to heat up & cool down because of its mass.(dont see the advantage here, depending on how long it takes to cool)

 

Was it distortion prevention?



#7 salamiman

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Posted 06 December 2023 - 09:43 AM

Can you use a turned down HQ rotor, with std LC LJ girlock caliper  with larger Caliper spacers to allow for the 25mm ventilated disc?, or do we have to go the hole hog & change calipers, steering arms ect.

 

Otherwise XU1 rotors & caliper spacers might be the easiest best bang for buck.

 

Bendix ?



#8 RallyRed

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Posted 06 December 2023 - 09:54 AM

Not sure, tried turned down HQ and HQ calipers on a car once and it fouled on full lock...not sure of the details..to long ago.
Brake gurus...

#9 salamiman

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Posted 06 December 2023 - 10:07 AM

Thanks for the help Col.

 

What were the drilled rotors you were talking about, the BMW ones?

 

Are they a direct fit & can they be used with the Std caliper.



#10 RallyRed

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Posted 06 December 2023 - 11:15 AM

The BMW/ Volvo combo is an approved for use package on Group Nc type track car LJs.
The BMW vented ( not drilled) rotors are available from competition brake supply places.
The Volvo calipers are from a paricular series of Volvos ( 240's??) and are twin spot type.
I think there is a bit of drilling/ tapping reqd to mount them. Not 100% sure.
The was a engineer guy in Sydney who did a complete packagevfor around 2k ( some years back), but I think he passed away.
You may may need engineering sign off to do this on a road car?.
From back in the day, the GTRs/ XU1'setc had ok brakes as standard, maybe just be 100% sure what you already have is working correctly first?.

#11 S pack

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Posted 06 December 2023 - 01:27 PM

Hi all,

Calling on the Brake gurus.

 

 I know this has been thrown around a million times but once again calling on people's experience if I can.

 

 I would like to improve the braking on my LJ Torana, as it wont lock up at the front ATM, not that you really want that, but guessing they should? Did these old systems have enough breaking power to lock the front brakes in a straight line?

 

It has a standard disc front end at the moment-12.7mm disc in good condition, pads are old.

 

The brake booster seems to be working well, replaced the master cylinder in the last two years and reconditioned the calipers.

 

Im not racing, or trying to improve brake fade, just looking for good hard braking when needed.

 

What improvements have been made by a certain disc types or pads?, bigger booster? or am I wasting my time?

Unless you are going to be driving like Fangio all the time the 15.6mm XU1 rotors and calipers will be more than adequate. I dare say the std 12.7mm rotors will suffice for street use.

The fact your front brakes will not lock up says there is something wrong with your existing braking system that needs to be investigated & rectified.



#12 salamiman

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Posted 06 December 2023 - 01:54 PM

Thanks for the help fellas.

 

I think the weakest link in my chain will be the 35 Yr old brake pads(car has been off the road 32 of those yrs).

Everything else in the system except the booster has been has been replaced in the last 2yrs & bled again recently.

 

The booster is working(but how well) & so is the one way vac valve.

 

Is there a easy method of checking the boosters working capacity/efficiency?

 

For the little extra in cost, will prob go with drilled XU1 thickness drilled DBA rotors, or after reading this below, the 12.7mm may be enough.(as I can still keep the rotor cover, but loose it with the XU1 rotor, correct?)

 

From Brembro

 

For those, on the other hand, who do not expect to subject their brake discs to extreme operating conditions, the “drilled disc” option is preferable because one of the benefits of this version is that it provides greater cooling capacity. ​

 

​Any recommendation's on Pad type & brand?

 

Cheers



#13 claysummers

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Posted 06 December 2023 - 01:58 PM

Pretty sure you can retain the backing plates. A mate fitted XU-1 spec brakes on HR spindles to the front of his EK ute and used Torana backing plates.


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#14 salamiman

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Posted 06 December 2023 - 03:25 PM

Even better thanks Clay.

 

did you sort your hyd throwout, read your thread a bit late, just fitted one of those myself.



Can anyone else confirm the rotor/disc cover fitting with the XU1 Disc rotor?


Edited by salamiman, 06 December 2023 - 03:26 PM.


#15 S pack

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Posted 06 December 2023 - 05:36 PM

Even better thanks Clay.

 

did you sort your hyd throwout, read your thread a bit late, just fitted one of those myself.



Can anyone else confirm the rotor/disc cover fitting with the XU1 Disc rotor?

Yes the XU1 rotor will fit with the backing plate in place however the idea behind removing the backing plate is to improve cooling of the rotor.

 

Are you sure DBA are still producing the 15.6mm XU1 rotors? I had read, possibly on this forum, that RDA are the only brand that still make XU1 rotors and they are not cross drilled or slotted?
 



#16 Statler

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Posted 06 December 2023 - 06:44 PM

I don't know if it helped , but i sold a lot of box torana front stub assemblys to the baby torana guys over the years. 



#17 S pack

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Posted 06 December 2023 - 06:47 PM

I don't know if it helped , but i sold a lot of box torana front stub assemblys to the baby torana guys over the years. 

LH/LX/UC disc brake rotors fit straight onto LC/LJ stubs.
 



#18 S pack

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Posted 06 December 2023 - 06:53 PM

These guys could be worth a call

https://www.vmaxbrak...-xu-1-1972-1973

 

https://wolfracingpr...-1-my70-74.html


Edited by S pack, 06 December 2023 - 06:57 PM.


#19 claysummers

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Posted 06 December 2023 - 06:54 PM

Just need to paint firewall, fit new 5/8” master, complete engine rebuild, install pressure plate, shim slave to spec, install box, install driveline, flare and plumb hard line, bleed, and should be good to go.


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#20 salamiman

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Posted 06 December 2023 - 09:12 PM

Thanks fellas, I'll do a bit of checking around and see what I can find and if they're still made.

I reckon you're on the right track Clay with the 5/8 master. I'll report back on your thread. Thought you might have already had it done. I'll add a bit to your thread now and see if I can help.

#21 salamiman

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Posted 07 December 2023 - 11:33 AM

Thanks for the input Dave.

 

Any hacks for checking booster performance? besides unhooking the vac line.(huge difference, but unsafe)



#22 salamiman

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Posted 07 December 2023 - 11:37 AM

Also looks as if I can still get My hands on 12.7mm DBA Drilled discs or Vmax slotted 15.9mm, any thoughts on which may fair better under a NSW V8 compliance braking test or would both fail.



#23 S pack

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Posted 07 December 2023 - 12:58 PM

You may have a chance with the thicker XU1 rotors with a V8 but ultimately you would need to consult an engineer for such mods.

#24 ChrisLC

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Posted 07 December 2023 - 04:17 PM

Good road pads?... There are real brake gurus on here who work in the trade, they could prob. answer that best...

What is a good set of grippy pads for LC/LJ? Anyone know?



#25 S pack

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Posted 07 December 2023 - 05:44 PM

Thanks for the input Dave.

 

Any hacks for checking booster performance? besides unhooking the vac line.(huge difference, but unsafe)

Start the engine and let it idle to create vacuum in the booster. Turn off the engine and wait a minute, then pull the hose and check valve from the booster. You should hear the booster take a gulp of air as soon as the check valve dislodges from the grommet. This indicates the booster and check valve are holding vacuum. Refit the check valve and hose to the booster, start the engine and let it idle to replenish the vacuum. Turn the engine off and depress the brake pedal, release and depress again, by the time you release and depress the pedal a third time you should notice the brake pedal become harder to depress as the booster runs out of vacuum.

With the engine idling, depress and release the brake pedal rapidly. You should notice the engine idle quality will deteriorate as the manifold vacuum tries to keep up with the demands of the booster.

To my knowledge if your brake booster behaves as described in the aforementioned tests it is OK.

 

Finally, with the engine idling, have an assistant depress and hold the brake pedal whilst you listen to the rear of the booster. You should momentarily hear air being sucked into the rear of the booster as the pedal is depressed. If the sound stops the booster is good, if the sucking sound is continuous until the brake pedal is released or does not stop even after the pedal is released then the rear seal has failed in the booster.


 


Edited by S pack, 07 December 2023 - 05:47 PM.






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