8 replies to this topic

[biga064]

Hi i have an Eh holden running p76 rotors torana callipers vh 40 booster only boosting front brakes on hr frontend , rear is BW vn commodore rear discs . My question is what master cylinder should I be running ?? and should I have removed some sort of little valve in the master cylinder side that feeds the rear discs ?? Thanks any help much appreciated !! PS current M/C is 1 inch .

[Balfizar]

Hi i have an Eh holden running p76 rotors torana callipers vh 40 booster only boosting front brakes on hr frontend , rear is BW vn commodore rear discs . My question is what master cylinder should I be running ?? and should I have removed some sort of little valve in the master cylinder side that feeds the rear discs ?? Thanks any help much appreciated !! PS current M/C is 1 inch .

There is something about engineering,  something that takes a while to learn and understand,  something about the mechanical calculations that make a brake system balanced and efficient and appropriate.

Something that most modifiers don't understand.  Just because it can be made to fit doesn't made it right and just because you think it works doesn't make it right.   With such a "collection" of parts thrown together its going to be hard and certainly a compromise to get any master cylinder that "Works"   You will find out at that first high speed crash stop.   Even if you don't anticipate doing these speeds if it works and is stable you might have it right.   200 kph to 60 kph in the dry and 200 kph to 140 kph in the wet.  When you have done 150 laps and braked for 11 corners per lap wet and dry and nothing get out of shape on you then you may have an brake upgrade that can be relied on.  Racers have an adjustable front/rear brake bias (for weather and fuel load), road cars are a static/crack point system based on weight distribution / rotor size/ piston size and pad size.  That's what determines booster and master cylinder and crack point and its a compromise for tyres and weather.   Good luck with anyone who will volunteer a M/C size with all your variables.

Edited by Balfizar, 19 November 2018 - 09:02 PM.

[Ice]

Dattoman will be the one to know that info

[dattoman]

Hi i have an Eh holden running p76 rotors torana callipers vh 40 booster only boosting front brakes on hr frontend , rear is BW vn commodore rear discs . My question is what master cylinder should I be running ?? and should I have removed some sort of little valve in the master cylinder side that feeds the rear discs ?? Thanks any help much appreciated !! PS current M/C is 1 inch .

 

 

Wow what a soup your in

 

1. P76 rotors are vented... Torana calipers only suit solid discs... so first thing we need to figure out is what actual caliper you have.

2. Boosting front only with a disc rear is not the best method... not enough pressure to the rears and overpowering the fronts... all wheels should be booster with discs

3. Which VH40 do you really have... there's varying piston diameters and poppet sizes... so while it may be a VH40... its likely a VH40 (something)

4. What's the actual current master... besides being 1"... is it the original single piston EH one ?

 

https://cache.gmh-to...ke-Parts/vh.jpg

http://www.gmh-toran...rviki-calipers/

[biga064]

Hi Datto,

 

1. LX-UC alloy pbr cradle has Holden embossed on it .

2. I know this is not a good method but im trying to rectify and sort it out .

3.Only details I can see on booster say PBR Made in Australia 580220.

4.No not original EH .Protex brake master P7470 ?? if I remember correctly .  

 

Hope this helps ?? Thanks 

[dattoman]

Only way to identify booster if it has no tag on it is by pulling it apart

 

OK so you have a HZ master for 4w discs already... no valves to remove

 

It'll work... but I think you'll find the lack of rear brakes abit underwhelming with no boost

[biga064]

Hi Datto , sorry for the lenghty delay but i had a fall and fractured my scapula !!   

 

I have since fitted a 7inch dual diaphram booster to my firewall which now boosts front and rear still with same master cylinder ! 

 

Just a couple of quick questions if i may ??  Brake pedal is a little soft when brakes are applied ??  I cannot get the brakes to lock up no matter how much leg I use ?? 

 

Would a 15/16 M/C help or maybe a pedal ratio change ?? currently 6:1 . 

 

Brakes have been bleed correctly !!! but im reckon I could have a low vacuum problem as I run a 250 @50 cam and only seeing 8 to 12 inches of vacuum at idle ? 

 

Thanks again any help much appreciated Adam 

[dattoman]

Adam

Usually low vac would give you a harder feel and less boost

I'd be looking at the calipers first

Check the bleeders are to the top

Also those calipers can be tricky to bleed if theres a big depression in the back of the piston... tricky air stays behind them

[biga064]

Thanks Datto 

 

Bleeders at the top !

 

Ill bleed them again but i dont reckon theres air ? Also i think my pistons are flat not like that one ?? But not  100% sure ?

Edited by biga064, 30 December 2018 - 03:15 PM.