ivan
09-03-07, 03:39 PM
Brake Fluid Selection
This leads one to contemplate the type of liquid that is used as brake fluid. In theory, even simple water would work – since, being a liquid, water cannot be compressed. However, it is important to remember that the fundamental function of the braking system is to convert kinetic energy into heat energy through friction. And the reality of this process is that certain parts of the braking system will be exposed to very high temperatures. Since the boiling point of water is 100degC, it is easy to see that water within the brake system could boil easily – and therefore release gases into the brake pipes – which would reduce the efficiency of the system. (Water would also present a big problem in cold weather if it froze to ice!)
The "obvious" solution to this problem is to utilize a fluid that is less sensitive to temperature extremes, hence the development of "brake fluid". However, there unfortunately is no such thing as a "perfect" brake fluid. And like most things in the world, the addition of certain beneficial characteristics usually brings tradeoffs in other areas. In the case of brake fluid, we generally must balance the fluid’s sensitivity to temperature against its cost and its impact upon other components within the system.
Stated more bluntly, it is possible to reduce a fluid’s sensitivity to temperature by varying the ingredients of the fluid. However, certain combinations of ingredients can significantly increase the cost of the fluid and may react with OEM materials to damage seals and induce corrosion throughout the braking system.
The chemical composition and minimum performance requirements of the fluid are generally indicated through a rating such as "DOT3," DOT4," or "DOT5." The DOT-rating itself is assigned after a series of government tests. However, this rating is NOT intended to indicate boiling points, even though higher DOT ratings generally do correspond with higher boiling points. Perhaps more importantly, the DOT rating does indicate the base compound of the brake fluid - which allows manufacturers to specify fluid types which are less likely to react negatively to known materials used within a particular braking system.
The greatest irony about brake fluid, however, is the fact that the chemical compositions that tend to be less sensitive to temperature extremes also tend to attract and absorb water! So even though the fluid itself is unlikely to boil (most glycol-based DOT3 fluids have a "dry boiling point" around 400 degrees Fahrenheit,) the water that it absorbs over time tends to boil easily (at 212 degrees Fahrenheit.) It is this characteristic of absorbing moisture that leads to the measure known as the "wet boiling point." The wet boiling point is the equilibrium boiling point of the fluid after it has absorbed moisture under specified conditions. Because brake fluid will absorb moisture through the brake system’s hoses and reservoir, evaluation of the wet boiling point is employed to test the performance of used brake fluid and the degradation in it’s performance. Do NOT expect to avoid bleeding your brakes just because you bought expensive brake fluid.
As one might guess, "racing" fluids will use relatively "aggressive" chemical compositions which will tend to have higher wet boiling points and higher costs, while the average street fluids will use more conservative compositions which will have lower wet boiling points and lower costs. In some cases – such as a purpose-built racecar – the tradeoffs of using the expensive racing fluid is outweighed by the competitive advantages. But for the average driver – whose driving style is less likely to induce brake temps as high as those seen on the track – the costs of the fluids and potential wear-and-tear factors upon system components may justify the use of a more conservative fluid with a lower wet boiling point.
Down to the Brands
So what brands are good to use? Well there are a lot of brands out there and the price varies quite a lot. Also to note, the below will be classed in two categories. Spirited Driving, being the fluids aimed at the race cars and people who take their cars to track events, and Normal Driving for the car owners who would like to run a good quality fluid for piece of mind.
Brake fluids for Spirited Driving:
Motul RBF600
Brake fuids for Normal Driving:
Castrol ???
Regards,
Ivan
Note: This article may have been copied from another website and revised to better suit the Starlet community. If you are the owner of the original article and would like us to remove it, please contact me via email with the subject "Remove Article" and i will remove it from this website as soon as possible.
This leads one to contemplate the type of liquid that is used as brake fluid. In theory, even simple water would work – since, being a liquid, water cannot be compressed. However, it is important to remember that the fundamental function of the braking system is to convert kinetic energy into heat energy through friction. And the reality of this process is that certain parts of the braking system will be exposed to very high temperatures. Since the boiling point of water is 100degC, it is easy to see that water within the brake system could boil easily – and therefore release gases into the brake pipes – which would reduce the efficiency of the system. (Water would also present a big problem in cold weather if it froze to ice!)
The "obvious" solution to this problem is to utilize a fluid that is less sensitive to temperature extremes, hence the development of "brake fluid". However, there unfortunately is no such thing as a "perfect" brake fluid. And like most things in the world, the addition of certain beneficial characteristics usually brings tradeoffs in other areas. In the case of brake fluid, we generally must balance the fluid’s sensitivity to temperature against its cost and its impact upon other components within the system.
Stated more bluntly, it is possible to reduce a fluid’s sensitivity to temperature by varying the ingredients of the fluid. However, certain combinations of ingredients can significantly increase the cost of the fluid and may react with OEM materials to damage seals and induce corrosion throughout the braking system.
The chemical composition and minimum performance requirements of the fluid are generally indicated through a rating such as "DOT3," DOT4," or "DOT5." The DOT-rating itself is assigned after a series of government tests. However, this rating is NOT intended to indicate boiling points, even though higher DOT ratings generally do correspond with higher boiling points. Perhaps more importantly, the DOT rating does indicate the base compound of the brake fluid - which allows manufacturers to specify fluid types which are less likely to react negatively to known materials used within a particular braking system.
The greatest irony about brake fluid, however, is the fact that the chemical compositions that tend to be less sensitive to temperature extremes also tend to attract and absorb water! So even though the fluid itself is unlikely to boil (most glycol-based DOT3 fluids have a "dry boiling point" around 400 degrees Fahrenheit,) the water that it absorbs over time tends to boil easily (at 212 degrees Fahrenheit.) It is this characteristic of absorbing moisture that leads to the measure known as the "wet boiling point." The wet boiling point is the equilibrium boiling point of the fluid after it has absorbed moisture under specified conditions. Because brake fluid will absorb moisture through the brake system’s hoses and reservoir, evaluation of the wet boiling point is employed to test the performance of used brake fluid and the degradation in it’s performance. Do NOT expect to avoid bleeding your brakes just because you bought expensive brake fluid.
As one might guess, "racing" fluids will use relatively "aggressive" chemical compositions which will tend to have higher wet boiling points and higher costs, while the average street fluids will use more conservative compositions which will have lower wet boiling points and lower costs. In some cases – such as a purpose-built racecar – the tradeoffs of using the expensive racing fluid is outweighed by the competitive advantages. But for the average driver – whose driving style is less likely to induce brake temps as high as those seen on the track – the costs of the fluids and potential wear-and-tear factors upon system components may justify the use of a more conservative fluid with a lower wet boiling point.
Down to the Brands
So what brands are good to use? Well there are a lot of brands out there and the price varies quite a lot. Also to note, the below will be classed in two categories. Spirited Driving, being the fluids aimed at the race cars and people who take their cars to track events, and Normal Driving for the car owners who would like to run a good quality fluid for piece of mind.
Brake fluids for Spirited Driving:
Motul RBF600
Brake fuids for Normal Driving:
Castrol ???
Regards,
Ivan
Note: This article may have been copied from another website and revised to better suit the Starlet community. If you are the owner of the original article and would like us to remove it, please contact me via email with the subject "Remove Article" and i will remove it from this website as soon as possible.