How to choose the right brake fluid?

What is brake fluid?

Essential to the good braking of your motorcycle, brake fluid is essential. It works under conditions of very high pressure and heating.

Brake fluid is an integral part of your vehicle's braking system. Indeed, it makes it possible to transmit the force braking when you press the brake pedal or pull the brake handle. Brake fluid travels through the entire hydraulic circuit and into the braking system in order to brake as it should.

Depending on the use of the motorcycle and the braking power required, there are several types of brake fluid, differentiated spar a DOT standard followed by a number that determines their compression ratio. In competition, linked to the use of braided hoses, known as "aviation hoses", its rate will be higher in order to meet extreme use.

How do you know which liquid to choose?

For motorcycles, brake fluid is most commonly synthetic, but it can be silicone. The different types of brake fluid are distinguished by par their standard DOT (American standard). As a general rule, manufacturers recommend the DOT4 index. However, check the recommendations of your manufacturer.

- DOT 3 : This is a synthetic oil which is particularly advantageous for so-called drum brakes. Boiling at 205Â ° C dry, 140Â ° C wet

â € “DOT 4 : Also synthetic, it offers a more sophisticated quality. We note, in fact, a point of dry boiling which goes up to 230 Â ° C, and 155 Â ° C once humidified. Vehicles equipped with ABS require DOT ratings greater than or equal to 4.

Be careful, however, when changing the brake fluid for vehicles fitted with an ABS car the presence of air bubbles in the ABS hydraulic unit will seriously damage the unit and require you to replace it!

â € “DOT 5.1: For the most demanding, this is an excellent alternative given its highly superior quality. It has been developed with the most recent processes, although its boiling point is no different from DOT 4. The distinction is largely based on its less viscous character. It is therefore recommended in the event that you adopt a sporty driving style or want to have powerful braking. Boiling at 265Â ° C dry, 185Â ° C wet.

In addition, DOT 5.1 is two times less viscous than DOT 4. In practice, this means that a brake system using DOT 5.1 will have faster response time, better brake modulation and faster pad retraction. During maintenance operations, the low viscosity of the liquid makes it easier to bleed and adjust the pads. DOT 5.1 is less sensitive to volume changes due to temperature rise and provides consistent braking over a wider temperature range than DOT 4.

Special feature of DOT 5: The name can be confusing, car DOT 5.1 and DOT 5 have nothing to do with it. DOT 5 brake fluid is a silicone-based oil, purple in color. Hydrophobic in quality, it is perfect for vehicles that move very little. It is not miscible with synthetic oils. So beware of mistakes, you might have to redo your braking system. It withstands very high temperatures, is more expensive, and must be changed regularly. Unlike synthetic oils, the liquid is not hygroscopic. There is a risk that water will collect in the master cylinder or the calipers will damage the entire system. Its use is reserved for American motorcycles like Harley Davidson.

Reminder: The original DOT standard was quickly superseded epar the Dot 2 standard when the disc brake became commonplace, then was replaced epar the Dot 3 standard still in use today. The evolution towards ever more efficient vehicles (ABS braking) required a more efficient and fluid liquid, DOT 4. DOT3, DOT4 and DOT5.1 are synthetic fluids based on Polyalkylene Glycol. They are generally amber in color and have the advantage of being miscible with each other. They are not corrosive for the rubber seals of brake calipers and cylinders. Unlike the others, the DOT5 is made from silicone. It is hydrophobic and therefore less susceptible to ageing. This difference between DOT5 and other fluids explains why it should never be mixed with any other brake fluid other than DOT5.