There aren't many aspects of motorcycle maintenance you can put off, but some are essential to your safety. A late oil change means more wear on your engine and consequently, reduced efficiency. But if you don’t take care of your braking system, the risk of brake failure gets higher.
What brake fluid does
Brake fluid is that magic elixir that allows you to reduce speed in demanding situations, responsible for transmitting force from the brake lever to the brake pads.
Brake fluid classification
Department of Transport grade
Boiling point (dry/wet)
- Glycol-based: DOT 3 (205/140 °C), DOT 4 (230/155 °C) and DOT 5.1 (270/180 °C). Mixable. However, the boiling point won’t be as high as the highest grade mixed.
- Silicone-based: DOT 5 (270/190 °C). Non-mixable with any other type of fluid.
The main difference between glycol-based fluids and silicone-based DOT 5 is that glycol is hydrophilic, which means attracts and absorbs moisture from the air, and DOT 5 is hydrophobic, so its service life is longer.
DOT 5 is more expensive than DOT 4 or any other glycol-based fluids. Also, glycol-based fluids can cause damage to the paint while DOT 5 is harmless to painted surfaces.
However, most Harley-Davidson® motorcycles use DOT 4 as DOT 5 compressibility and viscosity are not suitable for ABS. Remember to use always the recommended grade for your motorbike or higher.
Change your fluid every two years
- Whenever the brake pedal/lever seems “spongy”.
- After disassembling the brake line, master cylinder or caliper.
- Anytime the brake system has been operated in a spongy state caused by boiling fluid, even if the operation has returned to normal.
- When recommended by the H-D® Service Technicians.
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