21 replies to this topic

[marko1au]

        ive tried to find the answer myself with no luck ........ 1976 lx torana aftermarket master / proportioning valve and disk / disk setup ..... master is 1inch .......i  supposably have a disk / disk prop valve but have a low pedal great braking but i hate the free travel ....... my question is what is the internal differences between disk / drum and disk / disk ....... i have both but one has a removable front plug .....( supposed to be disk / drum ) and the disk / disk only has removeable fitting for rear brake line. ive searched online and have two trains of thought and both relate to the disk / drum prop valve ...... one theory is to increase the spring pressure in the front ..... theory no 2 is to take out the piston in the rear part of the prop valve ...... im confused to what the correct answer is ...... any help would be appreciated 

[claysummers]

May sound funny but make sure your front wheel bearings don't have any excess play in them. This can contribute to low pedal.

Sent from my SM-G781B using Tapatalk

[marko1au]

claysummers ........ all of the driveline is less than 500 kms old, thankyou for your suggestion ........

[marko1au]

i have removed the master to bench bleed, ive re lubricated all of the caliper slides ...... i dont remember how many times over the last 6 months that i have bled the brakes. but i cant solve the issue of the free travel ....... have vt front disk and vs rear disks .... so im back to the prop valve as its the only part trhat im not sure about ...... all suggestions greatly appreciated 

 

                                   mark

Edited by marko1au, 07 January 2024 - 07:31 AM.

[claysummers]

Still worth checking wheel bearing play. Specially if new. Inspector found excess play in my freshly built car after bed in. Another of my cars the brakes would go to the floor first application as the play in the pads was taken up due to loose wheel bearing. Don't discount it, eliminate it.

Sent from my SM-G781B using Tapatalk

[yel327]

Make sure the reaction disc hasn't fallen off inside the booster. Having it missing creates a long pedal.

[Indy Orange]

Certainly got a reaction out of me! Had to take the brake booster off and shake it out of the booster ,hours of fun!

[marko1au]

booster is less than 6 weeks old ....... i had it rebuilt incase it was the issue .......

claysummers ...... i will check the wheel bearings ....... thankyou

[LJ RB30]

If you have VT calipers on the front then you will need a VT master cylinder as they are a "Fast fill" unit.

 

The VT master are not just a 1" master cylinder but a 1" that supplies the rears AND a 1 1/4" to supply the fronts.

 

This is due to the  VT having 2 spot calipers requiring more volume of fluid.

 

The VT calipers will take more of the fluid and pedal travel before you get any effective braking.

 

Hope this makes sense

[marko1au]

LJ RB30.......... i had the feeling that would be the issue, food for thought then ......... so its either the calipers or master i have to change

claysummers ........ bearings are good ........ but again thankyou

[marko1au]

LJ RB30 .....in my excitement i forgot to thank you for that information

Edited by marko1au, 07 January 2024 - 04:38 PM.

[LJ RB30]

No worries mate.

[dattoman]

Ok lets go back a step

 

What master is on the car ?... replaced when fitting the disc rear ?... is its to suit 4wdisc ?

What valve are you using... as its unlikely to be a thing.. .what what did it come off ?

 

Are you sure they are VT calipers ?... any casting #'s on them ?

Got any pics of setup ?

 

Yes check the booster to make sure the reaction discs has not fallen out

 

It is possible to adapt a VT style master... but lets check some other things first

[marko1au]

dattoman........ 

master is an aftermarket 1 in bore to suit 4 wheel disks ........ prop/ combination valve also aftermarket to suit 4 wheel disk ..... booster recently re built using commodoe booster to suit torana bolt pattern .... pics to follow and the vt calipers i will take pics of this afternoon and send them to you.

 

                      Mark

[marko1au]

dattoman ....... email sent

[dattoman]

dattoman ....... email sent

 

 

First thing I'd do is check the booster pushrod to master clearance

But it may be a displacement issue with that master as mentioned

You can buy a spacer bracket to bolt to H series/Torana booster to take the VT master

https://www.ebay.com...6kAAOSw8HpgSK2u

This may be an option if its a displacement issue... but will need to repipe car (metric fittings)

 

Have you tried clamping the rubber hoses (all 5 ) to determine you have a good high pedal to start with.... and dropping a clamp at a time to see if the issue points to a particular wheel ?

[marko1au]

dattoman

 

push rod on booster was setup by the booster repairer, i gave him the master to setup correctly. ......... if we are sure we need the vt master ive already been quoted for the re pipeing ......... havnt clamped the rubber hoses yet but will do to confirm the issue ....... thankyou for your assistance ....... will check out the adapter you suggested

[marko1au]

dattoman

 

clamp off all 5 ......... i only count four .......

[dattoman]

dattoman

 

clamp off all 5 ......... i only count four .......

 

1 to each caliper

1 body to diff

[marko1au]

dattoman

 

i forgot that one ......... thankyou

[marko1au]

dattoman

 

will test the displacement theroy on sunday

 

                    Mark

[marko1au]

LJ RB30

 

 

dattoman

 

thanks for the information and i feel it is a distibution issue ....... if i have the rear calipers and body hoses clamped i still have the excessive free play ........ if i clamp both front calipers the free play is noticebly less ...... there is approx 8-10 mm difference between clamped and un - clamped front calipers ..... this measurement is taken between the brake light switch bracket and the pedal it self .......im not sure what the difference is at the pedal pad but ill assume probably 50 mm or more 

 

                             Mark