Tech Tip - Brake Fluid

Brake systems have come a long way on Harley-Davidson motorcycles.  Powerful Brembo , 4-piston calipers, ABS systems and stainless lines have all greatly increased stopping power of today’s Harley-Davidson motorcycles.  Brake fluid continues to play a vital role in braking system.  Prior to 2005 most late model Harleys used DOT 5 or silicone based brake fluid.  The silicone based formula offers a more stable viscosity index at extreme temperatures.    Starting in 2005 with certain touring models, Harley-Davidson began to spec DOT 4 brake fluid in their braking systems.   By 2007 all models used DOT 4.  
 

Both types of fluid are susceptible to overheating and moisture contamination.  Old or broken down fluid can cause poor stopping performance and a weak feel at the lever.  When moisture in the system heats up it will expand which can cause a drag of the brake pads on the rotor. The recommended service interval for changing brake fluid is every 2 years or when the moisture level exceeds 3%.   The dealership has test equipment that can test for moisture in the fluid and can determine the contamination level.

Be careful when adding or checking fluid not to mix fluid types.  DOT 5 does not mix with DOT 4.  And always top off using fluid from a sealed container to avoid adding any moisture contaminated fluid. 

Common Symptoms of contaminated brake fluid

• Poor Braking Performance
• Soft or spongy feel at the lever or pedal
• Fluid has a dark or cloudy look
• Brakes drag and cause the rotor to overheat

Solutions

Have your brake system tested for moisture content or flushed at least every two years

The fluid service consist of draining, flushing, refilling & bleeding the brake lines of both the front and rear systems.  We also replace the master cylinder cover gaskets and inspect the brake pads and rotors. 

Keeping your brake fluid fresh will ensure that you will get the most out of your stopping power. 

Thanks, Tony D. & The Wild Fire Service Team