Over the past 6 months, I have gone through 3 proportional valves that are part of my disc brake conversion kit I bought from Inline Tube. Long story short : The company and myself thought the valves were faulty. Turns out, the rubber used in their braking system components, ie: proportional valves, Is not compatible with the silicone dot 5 fluid. The fluid eats away at the rubber (seals, etc) which then is the site where leaks develop. I talked to a company rep for inline tube and they said dot 5 is the only fluid that you cannot use with their components. I learned this the expensive way. Hopefully this will help others.