So awhile ago when I was gathering parts and oils for when the time came to rebuild my bike, the dealer gave me a thing of DOT 5 silicone brake fluid.. i didn't think much of it.. well now going through the owners manual and service manual, everything refers to using DOT 4 brake fluid (glycol, etc etc).. So either: which is right, and what do you guys use?

My dad has DOT 5 in his 2000 NightTrain, and has always had problems with his brakes not functioning properly and leaks and bad seals and everything and never realized that he was actually using DOT 5..and had a moment of clarity when he realized that he might have been using the wrong stuff for a few years now

ps this is for a non-ABS system.

 

Dot 5 silicone..

 

Dot 4 and Dot 5 are definitely two different types of brake fluid. It is strongly advised that you DO NOT MIX brake fluid types. The main advantage of Dot 5 ( silicone ) fluid is that it will not absorb moisture from the atmosphere. Fluids that absorb moisture ( Dot3 and Dot4 ) are hygroscopic. In most brake hydraulic systems that use conventional fluid ( Dot3 and Dot4 ) there is mositure. Generally about 2% of the fluid in the hydraulic system is water. Water is bad for two reasons ... 1. It has a lower boiling point so when the brakes get hot the water boils and turns to vapor meaning that there is now air in the system. 2. Water is corrosive and will contaminate the system with rust. Do yourself a favor and service your system with Dot 5. You will have to evacuate your old fluid before you install the Dot5 but you will have no further worries. Hope this helps.

 

I use the type that is shown on the brake fluid reservoir cap.

 

That's actually the best advice.. I already knew the differences between DOT 4 and DOT 5, the dealer told me DOT 5 was the right fluid, although every book i own says DOT 4.. then i read that and was like "Oh yeah..it's daggum labelled".. and the Master Cylinder Cap says clear as day "DOT 4".. so i'm gonna try to exchange my unopened bottle tomorrow and be like "Stop lying to me you bums.. now gimmie a free tshirt.".. mostly because i'm a pretty "by the book" kind of guy, especially when it comes to machines and what fluid goes into them.. i'm sure DOT 5 wouldn't hurt me, but i'd rather just do what 2 different books + 1 cap says and go with the 4.. also where I am, it doesn't really get hot enough that the higher boiling point would be a factor

 

PS thanks for the responses.