What's the difference ?
I am going to flush out my brakes and want to know if there's any reason why I can't switch over to the more friendly dot 5 from dot 4. My ride is a 2006 street glide.

 

I would stick with whatever is in your system - they don't mix well.

 

I have first hand experience of mixing these up, because I didn't realise they are not compatible. After many years of 'substance abuse' I found my brake internals, especially both master cylinders, suffered serious erosion from a strange jello-like stuff that accumulated in them.

DOT5 is chemically different to all the other DOT types out there. DOT 5.1 is also not compatible. They will mix while you are watching, but as soon as you turn your back they will start fighting! Use the correct stuff for your bike. If stock, that will be written on your reservoir covers.

 

Dot 4 is a higher temp version of Dot 3. Both can absorb water if not handled correctly.

Dot 5 is Silicone based and is very high temp, but as said, not compatable with Dot 3 or 4. It will absorb AIR if not handled correctly. Some use the word, "Intrain", which means the same.

Better to absorb water than air if you gotta absorb anything. Liquid not compressible.

Dot 5 is suitable for racing where it is changed out, probably every race. Along with the brake pads maybe also.

Dot 4 will do everything anybody needs on a Street bike. Especially if you live in areas where the elevation changes a lot.

Using Dot 5--Changes in elevation will pump air into the system with atmospheric pressure changes over a little time.
Not a good thing.

 

I would like to thank all of you that replied guess I'll stay with the dot 4 just have to be real carefull my front master cylinder cover is all ready ruined some wicked out and ran up hill I don't get it . I thougth liquds ran down hill not complianing though a cover is a whole lot cheaper than a master cylinder.

 

in my 06 sporty after research i drained my dot 5 flushed with dot 4 and filled with dot 4, dot 5 does not absorb moisture so it pools in the lowest point your caliper, NOT GOOD, never mix, better brakes and no problems STILL

 

Harley used DOT 5 fluid for around 20 years in their bikes without any problems I know of, so the stuff is just fine. I have read that the reason they went to DOT4 is that anti-lock braking systems tend to aereate the fluid, which DOT5 is more prone to than DOT4. That might be an internet myth, like many other things that get repeated!

As for changing from DOT5 to DOT4 there will not be any noticable difference, as the harm is done over an extended period of time. It may be several years before you discover the damage done inside. I don't consider it wise to change, unless doing a total strip down and overhaul with mostly new parts.