Brake and clutch hydraulic fluid types

DoC!

DoC!

Hero member
Location
Lytham St. Annes, Lancashire (God's country)
Hi,

Looking in my 120? Jota owners manual is says to use DOT 3 hydraulic brake fluid while in both Laverda Green books (original TP book and revised TP and PT version), it says to use DOT 4. The only difference I can find is the temperature rating as below:
 
              Dry boiling point    Wet boiling point

DOT 3    205 ?C (401 ?F)    140 ?C (284 ?F)

DOT 4    230 ?C (446 ?F)    155 ?C (311 ?F)

DOT 5    260 ?C (500 ?F)    180 ?C (356 ?F)

DOT 5.1  270 ?C (518 ?F)    190 ?C (374 ?F)

Does it really matter? Would us ordinary roadgoing folk use DOT 3 while racers would use DOT 4 due to the higher temperatures involved with harder braking on race circuits.

What's the difference between 'dry' and 'wet' boiling points apart from the temperature?

Any advice, comments or wise cracks would be welcome.


Cheers

DoC!
 
Use dot3 or 4 doesn't really matter. More importantly, change whatever is in there yearly, if you are running a std Laverda hydraulic clutch change the clutch fluid every time you change the oil.



    Keith
 
very interested in

"if you are running a std Laverda hydraulic clutch change the clutch fluid every time you change the oil".

I have never done that, the fluid tends to get changed when the motor has to come out, this is usualy about 4/5 years apart, but has been known to be sooner, stripped studs etc.What is your thinkoing about this Keith, some sort of preventative maintenace I am sure, but .......

CLEM


 
The seal in the slave always lets a bit of chain lube in, that is why the clutch fluid goes black so quick. Mineral oil does not mix well with the seals in the master cylinder so flush it through every time you change your oil and you will find the clutch works a lot sweeter and the seals in the master cylinder last a lot longer.

Keith.
   
 
Doc,

Dot 3, 4 and 5.1 are Glycol Ether and are Hygroscopic, so they absorb moisture from the atmosphere with time. This in turn lowers boiling point.
The wet boiling point is measured when moisture has been absorbed, and the dry? well, you can guess.

Dot 5 (as I have found out to my expense), is Silicone oil and is not compatible with the Brembo rubber parts (they swell). It does not absorb water though.


Drikko,
Spark eroding will fix it.
 
As Simon says, do not use DOT 5 it is silicon based and doesn't go well with Brembo kit.  All the others are fine- I use 5.1 as it seems to do  less damage to your paint if you spill it.
 
laverdakeith said:
...  change the clutch fluid every time you change the oil.
Click to expand...
'Good thinking there', Batman  ;).

(Now, an intellegent man would have worked that out for himself.  But, me?  No chance ...)
 
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