Many H-D motorcycles use DOT 4 brake fluid. As the fluid ages, its chemical properties deteriorate and it absorbs water. This changes the physical properties of the DOT 4 brake fluid, which can lead to brake performance issues including soft or spongy brakes. Left unchanged long enough, the brake fluid could eventually deteriorate so much that there could be a loss of either front or rear braking.
Brakes can develop a significant amount of heat, particularly when used repeatedly. Consequently, another consideration for brake fluid is its boiling point, which can be affected by the amount of water content absorbed by the fluid. DOT 4 brake fluid can absorb water. Because water boils at 212°F, less than half the temperature of brake fluid, any water in the brake fluid dramatically reduces its boiling point.
However, boiling converts any water in the fluid to gas. And because gas is more compressible than liquid, when brake fluids boil, the brake lever or pedal can start to feel “soft,” requiring the rider to pump the brakes to create sufficient pressure to slow the motorcycle. This chemical deterioration and absorption of water changes the physical properties of the DOT 4 brake fluid, which can lead to brake performance issues, including loss of either front or rear braking.
Besides changing the fluid every two years, there’s a few other instances that brake fluid (any type, not just DOT 4) should be replaced:
- After the brake line, master cylinder or caliper has been disassembled
- Whenever the brake lever or pedal seems “spongy”
- Anytime the brake system has been operated in a spongy state caused by boiling fluid, even if operation has returned to normal
THE SCOOP ON SERVICE
Our Factory trained Service Technicians have the tools and knowledge to replace your brake fluid as recommended. If they ever find your motorcycle’s brake fluid has 3.7% or higher water content by volume, they’ll recommend changing it, even if it’s been less than two years since your last brake fluid change.
As brake fluid can be corrosive to paint, our Service Technicians take great care to protect all of your motorcycle's finishes in case of a splash or spill.
Make your next appointment for brake service to keep your Harley-Davidson motorcycle maintained to factory specifications at Oakland Harley-Davidson.
Want to check out some more Basic Maintenance for Your Harley-Davidson Motorcycle?