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Why motorcycle brake fluid matters
November 28, 2022 Tips & how-to guides
Motorcycle Brake fluid is hygroscopic, meaning it sucks in moisture when exposed to the air. As a result, even a sealed brake circuit will absorb dirt and moisture over time. When brake fluid levels are too low, or the fluid starts to break down, it will affect your braking. It's that simple.
Signs your brake fluid is low, contaminated, or ready for replacement include:
- The brakes are no longer responding as they once did
- The brake lever/pedal feels spongy
- The brake fluid level in the reservoir is below the 'low' mark
- The brake fluid is dark and dirty
If you experience one or any of these symptoms, it's time to pull over and check your brake fluid level and quality. As a guide, fresh brake fluid is pale yellow, amber, and clear. On the flip side, old fluid is cloudy and dark.
If the fluid is not as it should be and your brakes aren't functioning properly, get your motorcycle to a professional mechanic for inspection. Poorly functioning brakes are a danger to yourself and other road users.
Additionally, if you carry out any maintenance work on the brake system or change the brake lines, again, the system will need bleeding.
Replacing the brake fluid and bleeding the system is something that you need to do once every couple of years. While this is something you are able to do yourself, it's a good idea to seek the help of a professional.
Here are the steps a skilled motorcycle mechanic will follow when bleeding the brake system
- Protect the paintwork
- Drain as much from the brake fluid reservoir and top up with new Bendix brake fluid
- Starting at the rear of the bike, place a clear tube over the bleed valve on the caliper and the other end in a container.
- Pump the brake lever and hold it in
- Open the bleed valve and watch the fluid flow through the tube and check for bubbles
- Close the bleed valve and then pump the lever
- Repeat the open and closing bleed valve sequence while topping up the revisor
- Continue until the fluid runs clear and no air bubbles are visible
- Now move to the front wheel and repeat the process on the front calipers
- Check the brake fluid level in the reservoir, put the rubber boot back on the bleed valve, and make sure everything is good to go
A skilled motorcycle mechanic will bleed your brakes in less than an hour but what brake fluid is best and what are the differences? Bendix makes two grades of brake fluid. Both are suitable for any motorcycle or vehicle specifying DOT 3 or DOT 4 in their brake or hydraulic clutch systems.
Bendix DOT 3 Brake Fluid
Bendix DOT 3 brake fluid is a high-performance polyglycol-based fluid guaranteed to give you the best braking performance.
The brake fluid meets the highest U.S. and Australian specifications. This product is your go-to brake fluid for use in any car or motorbike brake or clutch system that specifies DOT 3.
Bendix DOT 3 brake fluid minimises steel, aluminium, tinned and cast iron, copper, and brass fitting corrosion. At the same time, Bendix DOT 3 is also non-reactive to the synthetic and natural rubber found in brake lines and seals.
Brake systems can run red hot but have minimum safe working temperatures as specified by U.S. and Australian regulations. Here, the dry boiling point of DOT 3 (measured with new fluid) is 205 degrees C.
The wet boiling point of the fluid, measured with brake fluid that has typically absorbed moisture, is 140 degrees C. It should come as no surprise that Bendix DOT 3 brake fluid exceeds these specifications.
Bendix DOT 4 Brake Fluid
Bendix DOT 4 is the heavy-duty brake fluid of the duo. It is suitable for applications that build up heat faster than average. In other words, for performance bike applications, large capacity tourers, cruisers, adventure and sports bikes. Check your service manual first to see what is recommended.
Bendix DOT 4 brake fluid shares minimal corrosion properties on ferrous and non-ferrous brake fittings. Also, this brake fluid remains non-reactive to the synthetic and natural rubber in brake lines and seals.
In line with other Bendix brake fluids, DOT 4 has you covered for ABS, non-ABS, disc or drum brakes and any hydraulic clutch, requiring the heavy-duty characteristics of DOT 4 brake fluid.
As expected, the dry boiling point of DOT 4 is higher at 230 degrees C with a wet boiling point of 166 degrees C. In addition, due to the lower glycol ether content of DOT 4, it will absorb moisture faster. This action results in shorter replacement intervals.
Why Change Brake Fluid?
For brake fluid to operate at full capacity, it must stay as close to its original chemical composition as possible. Therefore, brake fluid will pick up contaminants from the brake system over time like any consumable. In addition, the hygroscopic nature of the fluid means it will also absorb moisture.
A high moisture content or contamination of your bike's brake fluid reduces braking performance by lowering the boiling point.
Ignore regular service intervals and too much moisture can vaporise and cause a vapour lock in the brake line. This dangerous condition allows brakes to become spongy and provide poor performance.
Can you Mix the Two Types of Brake Fluid?
As of 2019, to fall in line with regulation FMV33 116, DOT 4 brake fluid became amber-coloured in line with DOT 3.
Both brake fluids look the same. However, manufacturers advise staying with the specified grade as they have different glycol ether concentrations and suck up moisture at different rates. Fail to maintain your motorcycle's braking system and not only are you endangering your own life but you are also a potential hazard to other road users.
Replacing brake pads and bleeding your brake system is a simple task for a skilled motorcycle mechanic. So don't take your safety for granted; insist on the best.
Bendix Motorcycle Brake Products
Bendix Moto offers a wide range of consumables, including brake pads and brake fluids.
The ceramic Ultimate+ range of brake pads is suitable for commuter bikes and scooters, and lower capacity, lightweight motorcycles,
Meanwhile, Bendix Street Road Track sinter motorcycle brake pads are ideal for spirited riding, mid and large-capacity motorcycles, and heavier machines.
The Bendix motorcycle brake fluid range features two high-performance products, DOT 3 and DOT 4.