24 replies to this topic

[salamiman]

Hi All,

 

Wanting to fix or upgrade a tired PBR 235 brake booster.

 

All other components of the system have been replaced or repaired.

 

Old dual boosters are hard to come by, or very expensive.

 

So do I repair the original or go for something like in the links below, any other suggestions, I don't necessarily care for original look, function is more my thing, and not break the bank.

 

I can weld, so brackets/rods can be modified if necessary.

 

Any other reasonable booster options out there?

 

Any help/feedback appreciated.

 

 

 

https://performancew...r-brake-booster

 

https://www.rolan.co...UcaAqatEALw_wcB

 

 

[Shiney005]

You might need to re drill your firewall to bolt them up.  Pushrod to the pedal would also need modification I reckon.

[Shiney005]

Do the Commodore ones fit in LJ?

https://www.gmh-tora...-master-on-lhx/

[salamiman]

You might need to re drill your firewall to bolt them up.  Pushrod to the pedal would also need modification I reckon.

Pretty sure Bolt patterns are the same, pushrod mods no probs.

Has anyone had experience with these boosters or is there a better option.

[salamiman]

Do the Commodore ones fit in LJ?

https://www.gmh-tora...-master-on-lhx/

Could be onto something I reckon!

[yel327]

Just get it rebuilt.

[salamiman]

Just get it rebuilt.

Was wondering is there any benefit to rebuilt vs 8'' dual diaphragm 8'', which would apply more pressure(stopping power)

[yel327]

Last time I did an LX I got a HG disc brake one and got it rebuilt with the Torana’s pushrod. Bolted straight in. The same should apply to a VH235 in an LJ. You should be able to use any of the following using the VH235 rear rod (Datto will probably confirm if you ask):

VH300
VH304-306.
VH308
VH311-317.
VH320-322.
VH324.
VH329-334
VH345.

Some of those are Holden, some are Torana, some off Ford trucks, Acco trucks, Rambler and other applications.

[RallyRed]

Happy to be corrected.. but was of the view that the dual diaphram boosters were more about masking low vacuhm from tripples/ aggresive cam, than actually providing more stopping power...could be wrong...

Edited by RallyRed, 26 September 2025 - 06:43 PM.

[yel327]

Every HK-HG with front discs had one and none of those could really be accused of having big carbs or aggressive camshafts. Nor 4 wheel drum HQ with booster. Or V8 Torana. I thought it was all about improved braking power and less pedal effort? Also useful on heavy vehicles hence why some of those big double diaphragm boosters were on stuff like Acco trucks and F350 etc.

[rexy]

As above, get it rebuilt and if you are worried about having enough vacuum add a vac pump.

 

I had Hydroboost make me a custom dual diaphragm smaller diameter booster to clear the tall rocker covers on the 383 in my yellow LJ. It bolted straight up to the standard mount and master cylinder. I run a vac pump from a Volvo with the Volvo pressure switch. Works fab.

[gtrboyy]

Easiest option probably having yours rebuilt then vacuum reservoir or pump if it needs help.

Don't mind the electric m/cyl but they're 3k just for the kit.

[salamiman]

Last time I did an LX I got a HG disc brake one and got it rebuilt with the Torana’s pushrod. Bolted straight in. The same should apply to a VH235 in an LJ. You should be able to use any of the following using the VH235 rear rod (Datto will probably confirm if you ask):

VH300
VH304-306.
VH308
VH311-317.
VH320-322.
VH324.
VH329-334
VH345.

Some of those are Holden, some are Torana, some off Ford trucks, Acco trucks, Rambler and other applications.

 

Thanks for the input fellas, was thinking that one of those replacement repro ones may be the way to go, seeing the old ones listed are now very hard to come by.

[yel327]

People ask stupid $ for them but plenty around. Look at a few swap meets or FB.

[salamiman]

People ask stupid $ for them but plenty around. Look at a few swap meets or FB.

Will keep an eye out, Thanks.

 

Im guessing the ones I posted links for are either junk or a prick to fit, any input on that front?

[yel327]

Will keep an eye out, Thanks.

Im guessing the ones I posted links for are either junk or a prick to fit, any input on that front?

No idea. I wouldn’t use any non standard (or identical to standard) for a Series components in brakes, unless I was Engineering other stuff at the same time. Brake Engineering is way too expensive. And if you don’t do it and have an issue you may have no insurance.

[salamiman]

No idea. I wouldn’t use any non standard (or identical to standard) for a Series components in brakes, unless I was Engineering other stuff at the same time. Brake Engineering is way too expensive. And if you don’t do it and have an issue you may have no insurance.

Thanks Yel, didn't even think of the insurance aspect, better stick with a std option!

[yel327]

Thanks Yel, didn't even think of the insurance aspect, better stick with a std option!

That’s the way I look at it. Hence why I’d copy XU1.

[4dabush]

As above, get it rebuilt and if you are worried about having enough vacuum add a vac pump.

 

I had Hydroboost make me a custom dual diaphragm smaller diameter booster to clear the tall rocker covers on the 383 in my yellow LJ. It bolted straight up to the standard mount and master cylinder. I run a vac pump from a Volvo with the Volvo pressure switch. Works fab.

Terry did mine very similar but no vacuum pump. Wasn’t very expensive either and from memory, arrived the same week I ordered it. Terry at Hydroboost is awesome to deal with. 

[dattoman]

Its all about less effort... apparently some people let their wives drive... who would have thought

 

The STD booster would be fine... if working correctly and your not being asked to change it for rego

 

Those aftermarket units are generally poo... I'd say 60+% of the ones we see don't work out of the box and can't be repaired (no parts avail)

 

Big cams mean no vacuum... so if you fit a bigger booster... it makes it worse... would need a pump (again... not cheap US garbage).. VE V6 pump , switch,wiring will do the bizs.

[salamiman]

Its all about less effort... apparently some people let their wives drive... who would have thought

 

The STD booster would be fine... if working correctly and your not being asked to change it for rego

 

Those aftermarket units are generally poo... I'd say 60+% of the ones we see don't work out of the box and can't be repaired (no parts avail)

 

Big cams mean no vacuum... so if you fit a bigger booster... it makes it worse... would need a pump (again... not cheap US garbage).. VE V6 pump , switch,wiring will do the bizs.

Thanks Dattoman.

[salamiman]

Due to impatience & cost($120 on fleabay deliverd)I went with an aeroflow dual 8'' GM booster.

Made a input clevis(you can also buy them) & modified a hi tensile bolt to extend the master push rod.

 

After a bit of test & tune, this thing worked a treat, pulls up on a dime & with a crow 35803 cam as well.

 

But, & there's always a but, as Yel warned me it may not be compliant, I should have googled this before jumping the gun.

 

It looks like it will have to be engineered in NSW to be compliant

 

So the conundrum.... do I refurb the old one & comply(breaking was hopeless, but obviously worn out) or hope the constabulary aren't too smart in spotting the fake mmm?

[yel327]

Don't be concerned about Police, that is a nothing issue. Its the "what if" you have an accident and modifications are questioned. Like if you run into and write off a $150,000 car, or hit a house. Let alone being in a Coroner's Court. Its the way my brain works, being an Engineer and understanding compliance and the consequences of not complying with Standards and Regulations. The easiest path is to demonstrate compliance, ie copy what was standard or optional. As soon as you modify brakes it becomes a very expensive exercise to demonstrate compliance as you cannot do it yourself - it requires an Engineer's Report which will include brake tests. Not a deal breaker if you are doing a whole heap of other mods together, but to spend $5000 on Engineering simply to avoiding fitting an original and rebuilt GMH booster seems folly to me! Plus the GMH one once rebuilt should last you 30 years. The cheap Chinese one will be stuffed inside 2 years.

[salamiman]

Don't be concerned about Police, that is a nothing issue. Its the "what if" you have an accident and modifications are questioned. Like if you run into and write off a $150,000 car, or hit a house. Let alone being in a Coroner's Court. Its the way my brain works, being an Engineer and understanding compliance and the consequences of not complying with Standards and Regulations. The easiest path is to demonstrate compliance, ie copy what was standard or optional. As soon as you modify brakes it becomes a very expensive exercise to demonstrate compliance as you cannot do it yourself - it requires an Engineer's Report which will include brake tests. Not a deal breaker if you are doing a whole heap of other mods together, but to spend $5000 on Engineering simply to avoiding fitting an original and rebuilt GMH booster seems folly to me! Plus the GMH one once rebuilt should last you 30 years. The cheap Chinese one will be stuffed inside 2 years.

Understood, didn't realize the importance of staying original or OEM with the booster would be such a issue.

 

Will get the original sent to Hydroboost to save any Dramas, luckily didnt change anything original to fit the aftermarket unit.

 

Thanks Again to the wealth of knowledge on this site.

[gtrboyy]

Yeah some rego blokes want engineers if not stock or a period mod just to pass a pinkslip...starting to get crazy.