Brake fluid replacement in motorcycle

Brake fluid is a component of a vehicle’s brake system that lies within the brake lines, delivering the force to each of the brake shoe. The additional task of the brake fluid is the lubrication of vehicle hydraulic components and their protection against corrosion.

Brake fluid is required to have certain characteristics and meet certain quality standards: it must maintain a constant viscosity, and it must have a high boiling point in accordance with the safety standards. Nevertheless, brake fluid absolutely always deteriorates inevitably overtime during brake system operation.

Brake fluids are very hygroscopic, or in other words, they absorb moisture. The hygroscopicity of brake fluid is actually an advantage in a major way since it prevents the brake system from drops of water. Any water that enters the brake system can cause corrosion of internal parts, and this, for its part, can lead to the damage of the brake system and the following brake failure. However, more water mixed with brake fluid affects the brake system by reducing its boiling temperature. For example, only 3% of water will reduce the boiling temperature of the brake fluid from 230°C to 165°C.

Releasing excess heat during the braking process can cause brake fluid overheating. At this very moment, the water content in brake fluid starts boiling, some small air bubbles first, and then air locks accumulate in the brake system. Air, in contrast to the brake fluid, is easily compressed, which can lead to a “spongy” brake lever and, as a result, too inefficient braking or complete brakes failure.

brake fluid replacement on motorbike

In Thailand, all automatic scooters with the engine capacity of up to 200cc without exception have two types of brakes — disc brakes on the front wheel and drum brakes on the rear wheel.

During a long descent down hills and mountains, it would be preferable to use rear drum brakes. If you constantly use the front brake several kilometers along the descent down the mountain, then in this case, the brake fluid will boil, air will trap in the brake, and the brake lever will become “spongy”. So, in this case, the front disc brakes will fail.

To prevent this from happening, use the front brake at intervals. The time intervals when you DO NOT use the front brakes should ALWAYS be 5-7 times longer than the time intervals when the brakes are used.

Generally, every motorcyclist who has his own motorcycle and rides it regularly knows about these rules. But it is little known among people who rent a motorbike in Thailand for a couple of days for short trips or for few months for the winter time.

If while descending a mountain you were constantly using the disc brake with the result that the brake fluid has boiled and the disc brake has fail, in that case:

  • don’t panic;
  • stop your motorbike by using the drum brake on the rear wheel;
  • wait for the brake fluid in the disc brake to cool down during 15-20 minutes;
  • check out the functionality of the front brake by squeezing the brake lever a few times, it shouldn’t be “spongy”, at the same time the disc of the front brake is supposed to cool down;
  • continue downhill with 5-10 minute stops every 20-30 minutes;
  • if it is a rented motorcycle, please immediately report your problem to the rental company, because the boiled brake fluid is required to be changed. The majority of rentals will not pay attention to this because it demands additional works and extra costs, but for Cat Motors we change brake fluid without delay. Fully functional motorcycles and your safety on the roads are among our top priorities.

Brake fluid is a wearing out component. The fluid level and conditions must be checked at least once a year, and if necessary, changed. Otherwise, untimely replacing the brake fluid can lead to brake problems and subsequent accident, even at a low speed, as is usually the case for those rentals that scrimp on their motorcycle maintenance.

The service interval for fluid replacement is usually 1-2 years, depending on its type. You can find this information in your motorcycle manual. However, to make sure that the brake fluid is in a good condition, you need to evaluate the brake fluid’s boiling point and test it for moisture content. You can do this only with a special tool.

The brake fluid should be changed in the following cases:

  • if the brake fluid has more than 3% water;
  • during braking mechanisms repair;
  • if the vehicle hasn’t been used for a long time.

In case of buying a used motorbike, it is also recommended to replace the brake fluid immediately. This will allow you to be 100% sure that the brake system will not fail.

In Cat Motors, we check the brake fluid conditions of every motorbike with the use of special equipment two or three times a year. According to the manufacturer’s recommendations, we change the brake fluid once a year, even if the testers show that no replacement is required.

The safety of our customers on the roads is one of the basic principles of our family business.