As Dan mentioned above, Chevrolet had mechanical brakes until 1936 when hydraulic brakes were introduced on the new 1936 models. Prior to that all Chevrolets had mechanical brakes, including 1930. If your 1930 has hydraulic brakes then that is an upgrade that was done to the car by someone decades later.
As a suggestion, and for additional help to you when working on your car, you might want to purchase a 1930 Owner's Manual, the complete set of the 1930 Chevrolet Service News (12 issues), a 1930 Repair Manual and the 1929-32 Chevrolet parts book. All of the above are available in reprint from the Filling Station in Lebanon, Oregon.
www.fillingstation.comGood luck!