Heres a question for you guys. What color is the DOT 5 fluid when you bleed it out? Its a very bright purple going in.[]

Reason is, my dealer told me that mine will change color because of the aluminum in my master. By change color I mean this-[:-]

I'm real interested to hear from all.

 

Intersting from all I could find on Google the color change isn't from aluminum its from water being absorbed. DOT 5 is silicone-based and does not absorb water, but is more expensive and more compressible. The one big word you need to know is hygroscopic meaning “readily absorbs water”. All DOT 3/4/5.1 fluids are glycol-based and absorb water over time.

As the DOT number increases, so does the boiling point. Please note that there is a good amount of overlap between the classes. Some higher grade DOT 3 brake fluids have higher boiling points than some lower grade DOT 4 fluids. This is precisely why you often see these days “DOT 3/4″ brake fluid. Anyway, here are the differences in boiling points (BP) for DOT 3/4/5.1 fluids:

DOT 3: DRY BP = 401F; WET BP = 284F
DOT 4: DRY BP = 446F; WET BP = 311F
DOT 5: DRY BP = 518F; WET BP = 375F

Using the 2% annual water content increase, you can see it takes less than 2 years to go from new fluid or DRY BP to the WET BP condition. That is why most manufacturers recommend a brake fluid flush every two years. The visual for WET fluid is that it has turned from a clear yellow to an orange or almost brown color.


So from what I can make of this is that your system either has 3, 4, or 5.1 and not the 5 "Purple Stuff". If thats the case I would recommend having a "serious talk" with the dealer, and then stick with 5 as if it where the "Hygroscopic" and you put prple into the system you would never get all the "Silcone Base" out of the syatem. Just you would need to bleed them 2 or 3 times a year vice the once every 2 years. You may want to look around and find out what was in it. What year is your bike?

 

My bike is a 2002 FXD. I'm still researching the fluid issue with a couple of dealers. One told me that by smelling the fluid you bleed out you should be able to tell if its 3 or 4 (has a smell) or 5 (doesn't smell). Thanks for your input.

 

I just flush the lines every Spring.