Red rubber grease and DOT 5?

Joined
Sep 4, 2015
Messages
816
Location
Munich, Germany
Gentlemen,

i am planning to switch the clutch fluid in Motorcycle from DOT 4 to DOT 5 (Silicone). I will rebuild the master and slave cylinder with new seals and clean the parts and lines with alcohol.

My question is, when i work on brake parts i usually use "red rubber grease" or "ATE Bremszylinderpaste" for installing the rubber parts.
I just looked up the data sheet of the "ATE Bremszylinderpaste" wich says that it is not compatible with DOT 5 brake fluid.

Any idea for a substitute?
 
Whats the purpose of using dot 5? vs dot 5.1 seems alot of work.. for what gain(s)?

Maybe use a silicone based product such as sil-glyde or 3m silicone paste.
 
Last edited:
Thanks. SS braided Lines fitted allready.

I had done this before on my Suzuki. You maybe think that i am crazy, but the clutch needs less effort to pull and the shifting was smoother after the switch to DOT 5. And i had rebuild it before.. couldn´t be by accident.

Let´s try it again. Its Winter. Time for some wrenching. :)
 
No need to rebuild anything simply because of the change in fluid types. Just suck the current fluid out of the master, fill it with DOT 5, and bleed til you see purple. I’ve done quite a few cars/bikes like this over the years with no problems.
 
Most sources say that a glycol based rubber grease and silicone oil are not compatible, but there's not a whole lot of good resources.

I went down a little bit of a rabbit hole on DOT 3/4 to DOT 5 conversion, there's a write up I was trying to find documenting one of the first tests in converting military vehicles to SBF...

Not what I was looking for, but the official report from the first test the US Army did:


Here's the initial US Army Technical Bulletin (TB 43-0002-87) for converting from polyglycol (Military DOT 3) to Silicone Brake Fluid (Military DOT 5), they just did a straight Flush/Fill!


The Australian Military (MRL-TN-491 / AD-A159 501) found this method unsatisfactory, residual polyglycol fluid, such as that trapped in low points of wheel cylinders and calipers, ended up with very high water content and would boil and cause loss of braking under heavy / prolonged braking. They also noted an issue with the mixed fluids causing swelling and severe degradation of a particular rubber cup seal at 120C, sadly there's no details.


This led the US Army (SAE 860633) to develop a solvent flushing method?


Also found a newer US Army study looking at SBF in ABS systems, it didn't end well...

 
Back
Top