Brakes: Dual Circuit Hydrovacs

[Dan White]

I know that MP Brakes in NC has advertised these dual circuit hydrovacs, but the price is almost $800. This place in the UK has them for far less and also a compact unit that looks like it would fit most of the Studes that have hydrovac and provide a dual MC solution at a reasonable price!

https://www.carbuilder.com/us/medium...um-brake-servo

https://www.carbuilder.com/us/compac...te-brake-servo

youtube video: https://youtu.be/fW0VXo7iqEs

[E. Davis]

Very interesting . Wonder if its made in China.

[Dan White]

No they are made by Iruna in Spain. Reviews look very good. I found another place that is less expensive. I am planning to buy one for my C cab and would like to find anyone else that would be interested to get a break on shipping. Let me know if you are interested.

https://creative-engineering.com/pro...ect-servo-kit/

That is $382.16 plus shipping.

[StudeNewby]

What would it take to retrofit one of these beauties to a non-Hydro-Vac car or truck? I just installed Turner discs on my 8E7 and love them, but some power assist would be really nice!

[Dan White]

Not too hard at all. C cabs had Hydrovac was an option from '55 on. They mount on the drver's outside frame rail behind the cab. Not sure all of them were there but most I have seen that is where they are.

[StudeRich]

Since Studebaker used a Dual Diaphragm SINGLE Hydrovac on Disc Brake Setups, I don't see how Two separate Single ones would produce the correct amount of boost especially for the Front.

A DUAL Circuit is not the same as a Dual Diaphragm.

[Dan White]

Rich I am not sure of the point you are making? These units have two diaphragms, one for each circuit. The original hydrovacs powered all 4 brakes with a single hydrovac so I don't see the issue. No doubt if you are running disk/drum setup you would need to use a proportioning valve on the rear brakes as you do with any resto brake setup. For drum drum or disk disk this would most likely not be necessary. The whole concept here is to answer the problem of using a dual MC with a single hydrovac.

[64V-K7]

Why not just add this to your existing Hydrovac. Same idea for a lot less money

[r1lark]

Why not just add this to your existing Hydrovac. Same idea for a lot less money

That won't work with a dual master cylinder, which is what I believe Dan based this thread on - how to use some sort of hydrovac with an underfloor dual master cylinder. Dan, please correct me if I have mis-stated.

[StudeRich]

I guess you would need to know the OUTPUT Pressure on EACH of the 2 Halves.
Two Units running separately, is NOT the same as Two Units running TOGETHER!

[Dan White]

Yes that is correct. Using a splitter is not the same thing. There are two independent brake lines that are driven by each connection to a dual MC. The Studebaker setup used a single chamber MC and drove a single diaphram Hydrovac. Rich as noted before you would probably want to use a proportioning valve on the rear/drum brakes. This would be no different than what you use on a firewall setup if switching to disk drum from drum drum. If you have drum drum or disk disk you would not need to use a proportioning valve. I do not know why you would assume the pressure in each side is different. The vacuum and atmospheric pressure will be the same in both sides of the unit. as there is only one vacuum connection and only one regulator. These have been used in Europe from what I can find out for about 8 to 10 years and I cannot find any complaints or problems with them.