Okay, so Nuhawk has a situation going on with his SH and a lot of things have been put on the table with regards to his clutch woes. Everything from mild to wild have been mentioned and the only thing left is for him to just buy a new bike. LOL!

So, wtf do I want?

Two things have been mentioned in that thread that I don't understand can happen. It defies MY idea of physics (dangerous statement!). I don't know everything so i'm asking .....

#1 - fluid expansion. It's been mentioned that the fluid (in the clutch actuation system) can expand 10 - 20%. This is brake fluid. It's oil. I can't see how it would possibly expand that much. Part of the idea of using oil is it's compression characteristics (or lack thereof in this particular instance). Does this not seem strange to anyone? If oil was going to do this to this extent then we'd never be able to set our suspension up nor would we be abe to examine proper engine oil height/level.


#2 - air leak. How can air leak into a system when the system is under pressure? If you pull the clutch lever in then you introduce pressure in the system - it's hydraulic pressure and there's a LOT of it. I don't see how it's possible for air to enter INTO the system. High pressure always travels to low pressure. Air ain't comin' in - period. If there was a leak somewhere then how does air leak into the system, but oil not leak out????

Educate me.

PATIA!

 

Ok, the first part I'll leave to somebody that understands it better...

But since I was the one stating that air CAN leak in... I'll explain that as simple as possible...

You are absolutely right, high pressure goes to low pressure, not the opposite...
This means the air isn't getting in when you press the handle in... It gets in when you release the handle...

And yes, oil goes out... but not enough to make a puddle....

In my case it was a bad crush shim at the banjo bolt on the handle...
The leak was small enough that a very small amount seeped out when you pressed the handle, when you released a small amount of air seeped in...

The amount of oil was small enough to go unnoticed for a while... It didn't drip, it just greased up the outside of the brakeline... So it wasn't invisible, just hard to spot...

However the amount was enough to make an inpact on breaking (as my leak was brake not clutch) after a few days the amount of air was enough...

 

well, you see, think about it this way. When the radiator heats up, water comes out. Water is a liquid, and therefore, theoretically speaking, incompressible. YET, it expands enough that it "leaks" past the radiator cap.

 

Oh on the oil expansion topic... That IS the reason you can set a correct oil level... If it didn't expand you could indeed do what drew_c4 suggested in the "OIL" thread... fill it until there is more room... The oil expands, and it's known how much so itäs planned for it...

 

Bah, I got screwed up. I typed fluid expansion via heat and I really meant it's low ability to be compressed. My bad. Nevermind.

 

As a hydraulic system goes from low pressure to high pressure that same pressure acts upon most seals to increase their tension on a the cylinder/bore wall increasing their ability to seal. This applies to both cup seals and the square cut seals found in most calipers. As the hydraulic systems go from high pressure to low pressure, typically the rubber seals are relaxed to a certain extent and older worn seals can allow air to pass.

Also Brake fluid is typically not considered an oil. It is very distinctly formulated to 1) be stable under pressure/tempurature. By stable I mean in terms of coefficient of expansion. 2) Brake fluid also has the ability to absorb moisture (water) from the system - which besides corroding the system has a very high coefficient of expansion. Moisture is introduced via the vented resevoir and works very poorly in the system. Moisture also contains some amount of 'air' which gets separated under pressure. This happens much less when moisture is absorbed through out the system into the fluid.

 

Apparently MY box of Wheaties are fake.

Thanks guys!