Should I switch to a dual master?

July 1, 2010 | By Richard Prince


I am restoring my 1950 Buick Special, and would like to change the original single reservoir master cylinder to a dual reservoir master cylinder. Do you know which dual reservoir master cylinder would possibly fit it for a replacement? I was told three years ago that a single reservoir master cylinder is not as safe as a dual reservoir unit would be. Could you please advise me on this subject?


As the name implies, a single reservoir master cylinder has all of the brake fluid in one reservoir. This single reservoir provides the fluid that actuates the wheel cylinders at all four wheels. The problem with this is that all of the fluid in the car’s brake system is affected by a problem anywhere in the system. So if there’s a loss of pressure at any hose, any connection, any cylinder or anywhere else, all pressure and all braking action is lost.

Beginning in 1967, all cars sold for street use in America had to have a dual reservoir master cylinder. With this setup the brake system was effectively bifurcated with one chamber in the master providing fluid to the two front wheels and the other chamber delivering fluid to the two rear wheels. With this arrangement a vehicle is very unlikely to simultaneously lose braking action to all four wheels. And that, in summation, is why a dual reservoir master cylinder is generally safer than a single reservoir unit.

I don’t know offhand what OEM dual reservoir master cylinder would fit your Buick with little or no modification work. If your local auto parts retailer is sympathetic, he can help you to visually match your original with something they have in stock. In the alternative, you can buy a dual reservoir suited for your vehicle from a specialist brake company, such as Master Power Brakes (