why liquids are used as brake fluids?
Versus what, a solid? The reason is pretty obvious.
Brake fluid is a type of hydraulic fluid used in brake applications in motorcycles, automobiles, light trucks and some advanced bicycles. It is used to transfer force under pressure from where it is created through hydraulic lines to the braking mechanism near the wheels. It works because liquids are not appreciably compressible. Braking applications produce a lot of heat so brake fluid must have a high boiling point to remain effective and must also not freeze under normal temperatures. These requirements eliminate most water-based solutions. In the USA brake fluid comes in a number of forms, standardized under by the United States Department of Transportation (DOT). DOT 2 is essentially castor oil; DOT 3, DOT 4, and DOT 5.1 are composed of various mineral oils, glycol esters and ethers; some are synthetic oil based, and DOT 5 is silicone-based. As of 2006, most cars produced in the U.S. use DOT 3. Glycol based fluids are two times less compressible than silicone type fluids, even when heated. Less compressibility of brake fluid will increase pedal feel (firmness), but in either case this effect is minimal.
Liquids are not appreciably compressible. Brake fluid is a type of hydraulic fluid used in brake applications in motorcycles, automobiles, light trucks and some advanced bicycles. It is used to transfer force under pressure from where it is created through hydraulic lines to the braking mechanism near the wheels. It works because liquids are not appreciably compressible. Braking applications produce a lot of heat so brake fluid must have a high boiling point to remain effective and must also not freeze under normal temperatures. These requirements eliminate most water-based solutions.
