Brake fluid

By PRANAV RAM , B.E Mechanical Engg.

What is brake oil and why we use it?

It is meaning less to have a car without a brake. For the vehicles using hydraulic brake system,it is necessary to

use Brake fluid. In hydraulic braking ,the fluid required to push the pistons in

both main and wheel cylinders are nothing but brake fluids. Lets see about it ……

What is brake fluid ?..

Brake fluid is a type of hydraulic fluid used in hydraulic brake  applications in automobiles, motorcycles, light trucks, and some bicycles.

It is used to transfer force into pressure, and to amplify braking force. It works because liquids are not appreciably compressible — in their natural state

Brake fluid types

Generally,there are TWO types of fluid ,they are Petroleum based(mineral oil) Non-petroleum 99.9% of vehicle is run with non-petroleum based brake oil. It is further classified into silicone based glycol based

Glycol based brake oil like DOT 3, DOT 4 ,DOT 5.1 etc.. are preferred

Characteristics of DOT fluidsBoiling point The Brake must posses high boiling point,since it must evaporate when under going high temperature change..

BRAKE FLUID MINIMUM BOILING POINT (ERBP) SPECIFICATION

DRY WETDOT 3 205 Deg C 140 Deg CDOT 4 230 Deg C 155 Deg CDOT 5 260 Deg C 180 Deg C

Kinematic viscosity: All brake fluids (DOT 3, DOT 4, DOT 5 & DOT 5.1) must meet a

minimum viscosity test of not less than 1.5 centistokes at 100° C and must not be more than the following to meet their various classifications.

It must posses : Low compressibility Constant Viscosity High temperature Stability

DOT 3 oil

Department of transportation 3 (DOT 3) brake oil is preferred by our team, since it has more advantages from the other types.

Its dry boiling point (ERBP) is 205°C minimum and wet boiling point (Wet ERBP) is 140°C minimum.

It absorbs 1 to 2 percent of water per year depending on climate and operating conditions. It is used in most domestic cars and light trucks in normal driving.

This brake fluid does not require cleaning the system and can be mixed with DOT 4 and DOT 5.1 without damage the system.

Reason for preferring DOT3 than DOT4 DOT 3 oil absorbs less moisture from the air,than compared to DOT 4 oil More over during usage,due to absorption of water from moisture it can

drastically reduce the boiling point of the brake oil. here, after period of 2 years,the DOT 4 oil consumes lot of water and

leads to a sharp drop in boiling point that may cause to vapourise.

Do we need to change fluid?

Yes off course, we need to change the brake fluid once in 2 years .

Or else , it would cause brake failure The reason is that the oil absorbs water from moisture

and it decreases the boiling point automatically ,tends to vapourise

Percentage of water content

Brake oil must be changed when it reaches its WET BOILING point

Use of DOT 5

Even though DOT 5 type brake oil doesn’t absorb water, it is not widely used due to its cost

IT is used in some old classical cars and bikes like Davidson to avoid paint work and plastic damage.

General drawbacks

Corroded materials

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