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Hi all , I've been doing some experimenting with L and 1st Gen Liberty front brakes to See what interchanges on the Liberty hub type assembly .

What I want to do is retain the L's front hand brake because it makes Gareth's conversion simpler not having to change the HB handle or re route cables .
The early Liberty "strut feet" and hubs all seem to be the same so std and turbo Liberty RS calipers and rotors are interchangeable .
Some clever person worked out that The L front calipers bridge or floating section is interchangeable with the RS's twin piston floating section - as long as you use the L calipers slide bolt fittings which fit the RS calipers mounting bracket .
There some important differences with brake pads - mainly a new or full thickness L pad is much thicker than any of the Liberty ones so they won't work . To be confirmed but it looks like L series front rotors are 18mm thick (new) and Liberty ones I believe 24mm thick new .
So it appears that to get the thicker rotors inside the caliper Subaru used thinner pads with Liberty's and ended up with the same total distance from one pads backing plate to the other .
Another thing with pads is that the Liberty ones don't have the little short stub like L series ones do to stop the mechanically actuated piston revolving when the front hand brake is applied and released . An easy mod on Lib pads can correct this .

More Later .

Thoughts ? Cheers A .

Keep the info coming. You are making good progress on the front of 'Subaru LEGOness'

LOL yes Subaru seem to have that Mechano set interchangeability like Nissan in the same era .


Hokay ... now the thing I really wanted to find out was that would the L's floating or bridge section of the caliper work with the std or non turbo Liberty bracket and disc rotor . The news is mostly good because physicaly it all fits and lines up but some little bugga at FHI threw a spanner in the works by changing the thread pitch on the slide pin fittings . The bolt shanks look like being the same diameter but the non turbo threads are finer pitch .
The fitter and machinist in me went away and spoke to someone who's been a car and motorcycle mechanic (ex rally cured petrol head) to see what he thought about helicoils . He reckons yep no prob so long as the inserts are fitted squarely to the bracket and the hole centers the same as original . He said and I tend to agree that a properly fitted helicoil or nutsert like Worth makes would be superior to the std tapped hole in the cast iron bracket .

In case you wondered why anyone would want to use the non turbo Lib sized rotors just remember that early RS calipers don't grow on trees and they weight more because the rotors and brackets have more material in them . Unsprung weight is something you don't want on a lightweight car like an L and its debatable if you really need RS sized brakes on a car thats at least a couple of hundred kilos lighter than an RS Liberty . Maybe if using huge Lancruiser wheels .
Someone may correct me but I think you need at least 15" wheels to fit over Lib RS turbo brakes where 14" GX wheels (remember cheap/common) go over std 1G Lib brakes .
I have to check this but off the top of my head L series rotors measure 242mm diameter by 18mm thick . I think the base Lib ones are 260mm by 24mm which is a substantial increase over the L series fronts .

If I can prove this combination works it sort of looks surprisingly like what a Vortex XT6 used on the front though the rotors may have been 250 or 260mm - checking that very soon .

Lastly fitting that peg to a Liberty pad is as easy as drilling a small hole in the appropriate pads back plate and drifting in a small pin .

Long story short , I believe (so far) that you can fit 5 stud stuff to you L with only the Crossbred type rear hubs , a plain rear backing plate/caliper mount (won't need the internal expanding shoe drum brake bits) and the front control arms modified to suit the Lib lower ball joints .
All the rest can be easy to find mostly second hand factory parts .

So ... let me know what you all think and if you can see any holes in the plan sound off .

Cheers Adrian .

A little more info from the 92 Liberty manual .

The front pad dimensions are slightly different between the std and turbo 90-92 Libertys . The std type is 112.4 x 44.3 x 11 mm .
The RS turbo ones are 112.3 x 50 x 11 mm .

The change is the height of the pad by 5.7mm , I suspected something like this because the spring clips are slightly different - though interchangeable .
These spring clips that fit over the square shaped slider section of the mounting bracket have two "legs" which bear up under the pad and probably supress vibration and squeel . The turbo ones have these legs a little lower and don't touch under the ends of L or std Lib pads . They are obviously designed to work with the 5.7mm taller RS disc pads .
Since the pads are the same thickness you would obviously use the turbo pads with the turbo brackets and rotors and the normal ones with the normal brakes .

More in a sec , A .

Ah kay more facts and figures - is anyone still awake ?

Waiver - see the note towards the end of this post . The golden rule with automotive brakes is that if you don't understand the things then leave them well alone . If they act up seek the help of a qualified mechanic or brake specialist .


Some interesting specs from a Vortex XT4/6 manual that someone here kindly linked me to some time back , thanks for that .

By the looks of things XT4's use most if not all the same bits as our RX turbo sedans though there is mention of an optional 15/16 master cylinder vs the usual L and XT4's 13/16 one .

XT6 front , the discs on these measure 262mm diameter by 22mm thick so 2mm up on the diameter and 2mm down on the thickness of the basic 1G Lib rotor .

XT6 rear , these are unique discs and measure 256mm dia by 10 thick . They would only be of any use to you if you had the also unique XT6 backplate because it mounts the usual L type rear caliper further out to fit over this 256mm disc , L series and XT4 rotors are 226 x 10mm and use a slightly smaller diameter backplate to move the caliper in for the 226mm disc .

Front pads , these are the same as L series at 118 x 45.5 x 12mm . The 1mm extra new thickness I can understand but not the 118 vs 112.3/112.4 length . I'll measure up L and Lib pads tomorrow with a Vernier caliper .

Something I forgot to mention earlier is that all the L series front calipers I've seen don't have anti squeal shims over the outsides of their pads backplates , the Lib pads have two on each pad so there may be allowances made for pad thickness if L's dont have them std .


One last VERY seriuos message .

Be very - very careful if you mix and match brake parts because it can all go horribly wrong if not done properly .

One literal killer is that if there is room for the worn down pad/backplate to slide inside the mounting bracket ( between the bracket and the rotor) it has been known to get wedged and lock the disc to the caliper . If the wheel locks up at an inoportune moment lives can be lost .

Another issue is front to back brake bias and probably much of the reason why Gee use disc size wise and hydraulic set wise a manufacturers complete set of parts off one model car . If you get this wrong and over brake the rears the vehicle will swap ends if it locks the rear wheels going around a corner .
If anyone knows the tight loop road just south of Waterfall to get from the southbound old princes Hwy to the north bound lanes just picture this .
Being young and silly goes into very tight 180 deg bend too quickly , realises a little late that we're not going to get round and tries to slow down . The car had unbeknownst to me master cylinder bias valve probs and locked the rears up . The tail came round and I wound up mounting the curb (nose to the apex) and hit the sandstone wall - out of sight blocking the road around a blind corner . Survival relay clicked in and I hoofed it back around the corner to stop the traffic . I'm still here but only because no one followed me round that bend and T boned me .
The fix was to replace the faeces quality Australian made Girlock master cylinder every 18 months because they can't be repaired . The REAL fix was to get a Japanese home market BMC from an imported front cut (same model/era car) , rebuild it and also use its booster and external bias valve .
Great wrap from a bog std Australian manufactured Japanese car .

Anyway I refuse to be held liable for anyone elses alterations so do this at your own risk . I somehow cheated the angel of death and I don't aim to try it again .

On a lighter note if the calipers mounting bracket is the right width for its native disc then there won't be room for the pads to wedge in , particularly if you renew the pads when the tell tales start scratching and you don't use less than the minimum specified thickness if the rotors have been machined .

Adjustable bias valves can be fitted if something factory doesn't get the job done .

Cheers Adrian .

LOL some of us are attempting to hang in there however i think that the golden rule is if it isn’t broke don’t F with it (but then we would not learn anything sometimes now would we).

I agree that there are some wise words in this thread, like

discopotato03 wrote: brakes is that if you don't understand the things then leave them well alone . If they act up seek the help of a qualified mechanic or brake specialist .

On a final note (and I was unsure from you thread so sorry) however you are aware that the Subaru does not have front/rear master cylinder bias adjust flow valve thing-e in the RX, so you should have nil issues with locking the rear's like in your story.

I'll have to double check the manual but I think you'll find that they have a four pipe hydraulic gadget under the back that acts as a bias valve and splits the system . Yes the BMC has no bias valve in it .

Cheers A .

Yes L series cars have such a valve only in the factory WSM they call it a proportioning valve .
It also has a complicated means of shutting off brake fluid flow if either rear side develops leaks .

I reckon I may loose the hill holder if I can't get it to work , are they worth having ?

discopotato03 wrote:I reckon I may loose the hill holder if I can't get it to work , are they worth having ?

I think its really personal opinion, I love my hill holder, but you can live with out it -the old heal toe method still works a treat.

I find the hill holder great when 4wdin too. Only it seems to hold the front brakes and not the rears so much.

Cheers

Bennie

PS - very interesting read Adrian, your good at your research for things that your passionate about...

Thanks for your thoughts Benny .

It is frustrating at times - particularly when the truth is that all many really need is a set of XT6 bits but they're virtually unobtaenium .

I also feel muzzled about what its healthy to suggest or not because of litigation reasons . All it takles is some mechanical ignoramus to take the ball and run badly with it and the sugestee ends up in the slammer .

There really is only one seen to be 100% watertight option that keeps the authorities happy and thats Gareths one because he went to the trouble of having it type approved by a mechanical engineer .
I have worked with mechanical engineers over the years and having been a Fitter Machinist I can see why they generally think the way they do .

I think between myself and people I know there are several different ways to solve the L 5 stud hub/brake issues but I doubt its an economic reality in very small numbers or even one car . The approval costs are probably more than the result is worth .

I swear I must wake up every morning for the rest of my life stating I will never again attempt to drag an 80's Sputnik into the 90's or beyond .
More modern cars left these dinosaurs behind because the factories solved their shortcomings and moved on .

discopotato03 wrote:I swear I must wake up every morning for the rest of my life stating I will never again attempt to drag an 80's Sputnik into the 90's or beyond .
More modern cars left these dinosaurs behind because the factories solved their shortcomings and moved on .

Maybe you should look into 4wd'n a Sputnik, I am

And XT6 hubs/discs would be sweet. As much as I like the ocean and distance between Aust and the US, sometimes its a pain the arse...

Bennie

Currently on the beg for bits from the US .

We'll see what happens , cheers A .

Maybe not as impossible as I thought . I've bounced some of my ideas off my engine builder rally person and he can't see any problems getting engineering approval provided the brake bias is acceptable .
With a choice of Sube factory bias valves and two rear caliper piston sizes to experiment with it could be pretty straightforward .
I'll be speaking to Gareth about it tomorrow , he or someone else may or may not be interested in getting type aproval because it has the potential to make his original kit simpler/cheaper/easier to fit . All it would lack is the L type rear caliper .

A .

Did we come to a conclusion on whether there is a difference between drum and disc bias valves? I know its been asked numerous times.

If i have converted to discs, which obviously have more stopping power than a drum, are they gonna be too sensitive with the drum brake bias valve still in the car?

more likely to be the other way, as discs require more line pressure than drums.

The L type rear disc brakes are quite small at ~ 226mm/8.9" , also the cars are pretty light so they don't need much braking effort . The advantage of having them over drums is their self adjusting characteristic and ease of changing pads when they wear out .
Truthfully for the first hard stop when cool the drum is the better brake , their problem is that they have less exposure to air and can't cool as easily . So between ease of manufacture/servicing/bragging rights upmarket cars got rear discs in that era .

According to the genuine 86 and 87 workshop manuals (Aus ones) the proportioning valve is the same for disc/drum - 569 psi front wheel drive and 640 psi 4wd - in an L series sedan anyway .

Latest research leads me to believe that non ABS 1st gen Liberty's use the same type 4 hydraulic line proportioning valve as L series sedans but their line pressure limit is set at 533 psi .
So it looks like Subaru gave themselves a choice of 3 pressure limits - 640 , 569 , 533 psi - to cover all eventualities .

Interesting eh ?

Cheers A .

See , it wasn't an epic ....