Brake fluid

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ashman

ashman

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Hi All I am running a full Grimica brake system on the front of my Norton and I am just about to flush the brake fluid and replace with new fluid, just can't remembeber if this systen uses DOT3 or DOT4 brake fluid, I think I used DOT4 when I set the brakes up its been a few years now and the old memory isn't as good these days, better have another beer.

Thanks Ashley
 
Main thing is both are safe to mix but not other numbered fluids. DOT 4 boils a bit higher than DOT 3 is only advantage. Dry fresh fluid is main thing that matters.
 
Thats what I throught as I had a bottle in the shed that was DOT4 its half full but will be using a new bottle.

Ashley
 
DOT 3, 4 and 5.1 are all mixable, DOT 5 will not mix with any of 3,4 or 5.1.
 
DOT 3, 4 & 5.1 are all glycol based and can mix and match with only downside being possible lowering of 5.1 boiling point. Can even combine with silicon DOT 5 which is denser so does not really mix but 5 ends up at bottom of system like oil on water but otherwise no danger as long as seals can take it. DOT5 does not retain or absorb moisture so mainly developed for military storage then museums followed suit though if left long enough in system open to ambinant, ie: not air tight diapharm seal on mastercylinder, instead of suppending water in solution it allows puddle at low points. DOT 5 can expand more in summer heat so possible to lock brake w/o using lever if the piston can't retract enough to bleed off pressure. So beware what works fine in shady home testing may catch ya out and about.
 
daveparry said:
I think DOT5 is the only one NOT to use!
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No idea what this conclusion is based on, I have used DOT 5 for over 10 years without any ill effect.
Although, just like any other brake fluid , DOT5 should be refreshed occasinally also.
 
What Ludwig says +1

I don't know what, if any, component compatibilty issues there may be between older seals and DOT 5 and not about to experiment to see.

I have seen first hand what DOT 3/4 does to a system designed for DOT 5 and I can say with confidence that you do not want to go there.
 
From what I remember from a long time ago that they came with Dot5 fluid new so I have always used that. IIRC I was told that the rubber bits were not compatible with 4 or 3.
I think now it doesn't matter as long as you don't mix DOT5 with 3or 4.
I could be wrong.
 
Guido said:
From what I remember from a long time ago that they came with Dot5 fluid new so I have always used that.
Click to expand...

What are "they", exactly?

Certainly not Commandos! :?
 
Brake fluid

Both containers

Brake fluid

Dot 5.1

Brake fluid

Dot 5.0


Dot 5.1 is compatible w/ 3.0 and 4.0

As Ludwig stated Dot 5.0 is not compatible with anything but itself and seals should be changed to avoid problems
 
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