Re: {Chrysler 300} Remote Brake Booster

On Aug 16, 2024, at 4:05 AM, 'Hugh Boultbee' via Chrysler 300 Club International <chrysler-300-club-international@xxxxxxxxxxxxxxxx> wrote:

My first post - I hope it ends up in the right place(s).

Remote brake servos for cars and light to medium commercial vehicles were specified for many UK built vehicles from the mid to late fifties onwards and the same underlying designs remained in use until maybe the late seventies for some model ranges. The pipe fittings probably remained UNF/SAE, throughout, usually 3/8” thread for 3/16” bore pipe, whereas the master cylinder based vacuum servos that started to appear in I suppose about the late sixties (in the UK) will have eventually been altered to have metric pipe fittings.

In the present collector vehicle spare parts market, the two primary choices available (even if that’s a tautology) will be as follows:

1. Girling design (various names could be searched for alongside ‘remote brake servo’, but particularly Powerstop, Mark 2A or Mark 2B

2. Lockheed design (just ‘Lockheed remote brake servo’ will find plenty of examples online)

One particular practical difference applies (plus probably also some special variations for certain applications) –

1. Girling remote servo – bracket location via the right-hand side of the cylinder casting (when viewed from behind the vacuum chamber)

2. Lockheed remote servo – bracket or direct to bodyshell location via studs attached to the outer half of the vacuum chamber (early small units two studs, later units all three studs)

These servos were also offered as dealer or amateur installed upgrades via either ‘universal’ or model specific accessory kits. Via my own experience and some research, for either factory fit or accessory, they seem to have varied upwards in size all the way from 5 inches (e.g. Mini Cooper) to maybe 8 or 9 inches (Jaguar, Alvis, Bristol, Jensen, commercial vehicles, etc.; possibly also used on some contemporary Ferrari/Lamborghini/Alfa Romeo models where Dunlop disc brakes would have applied)

Cylinder size and output pressure related data is probably quite easily findable, but I have nothing to offer there myself at present. In many cases the original build specified units will have been in association with either disc front/drum rear or discs at both front and rear (Dunlop or Girling). However, some drum/drum applications also applied, particularly for commercial vehicles.

Practical note 2 – many UK or USA based collector vehicle parts suppliers will be competing with each other to supply modern (maybe replica) versions of both of the above described remote servos, so shopping around and gauging the likely levels of experience and goodwill involved in each case will be a worthwhile venture. As ever, old stock will possibly turn out to provide the best engineering quality but complete disassembly of such a unit followed by reassembly with new seals on the hydraulic side might be advised (repair kits are probably available). Note, however, that the Girling vacuum chamber piston seal sometimes has to be installed by attaching its two ends together with adhesive (or at least I think so).

Final note – just remembered – for larger vehicles, this type of remote servo would be supported by a vacuum reservoir (and an associated vacuum gauge in the case of the relevant medium payload commercial vehicles)

I hope some of that may help.

Hugh

On Friday 16 August 2024 at 05:49:10 BST, Nick Taylor <nicksgaragesd@xxxxxxxxx> wrote:

Yes, I've been looking at the Australian ones. The VH40 is the 9 inch version. Same size as the one I need. But there still seems to be a lot of variations.

On Thu, Aug 15, 2024, 9:33 PM Henry Schleimer <henry.schleimer@xxxxxxxxxxxxxxx> wrote:
I don’t know if this helps at all but the VH44 boosters used as an option on all Australian built cars in the sixties are available over here. For example https://www.hemiperformance.com.au/shop/universal-vh44j-remote-brake-booster-kit-suit-disc-brakes-front-drum-brake-rear.html

But they typically were for 9 or 10 drums. My parent’s 67 Valiant had one from new with 9 inch drums and a master cylinder that looked the same as a typical 300 single, but I don’t know its bore diameter. Those brakes were over-boosted in my opinion and would lock all four crossplies if you stabbed the pedal. However, my father chose that option as he had an artificial leg.

But without knowing the diameter and stoke of each to compare, I can’t give any advice about compatibility. Maybe someone would like to delve deeper into this or just buy one to “suck it and see” as we say.

Hemi Performance also list a 9 inch version with higher psi output for disc braked cars but it isn’t cheap.

Cheers

Henry.

From: 'James Douglas' via Chrysler 300 Club International [mailto:chrysler-300-club-international@xxxxxxxxxxxxxxxx]
Sent: Friday, 16 August 2024 1:36 PM
To: Chrysler 300 List Server (chrysler-300-club-international@xxxxxxxxxxxxxxxx)
Subject: {Chrysler 300} Remote Brake Booster

About 10 years ago, when I “restored” my 1949 Desoto Convertible, I made one change to the car that was not stock. I rebuilt the car with a four-wheel disc brake system. The car stops too good!

I used the stock master cylinder, and I used a remote power brake booster like the one I had on my RAM 300K convertible in High School.

Midland Ross was sold a long time ago, but around 2013 the factory that made the boosters was still operating under another name. I managed to talk with the manufacturing manager who had started there in the 1970’s. We had a long talk. They were still making these boosters. The big issue was the special rubber parts were made now in Turkey. They are essentially he told me the same as the ones used in the 1950’s Ford Thunderbird.

I asked him if he had any of the pressure curves and he was kind enough to send me the two attached drawings. One with the pressures.

I found out that a couple of years later that the Turkey plant burned down and they had stopped making any of these remote units anymore.

One can try to see if the Ford Thunderbird suppliers are still sitting on any.

Best, James
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