I changed all my fluids just a few weeks (500 miles) ago and the clutch fluid is already dark. In contrast, the brake fluid is still clear. I've noticed this on other Ducatis. What causes the clutch fluid to darken so rapidly?
-Jeff
The theory is it's engine heat.
I've just change mine a week ago because it was rally dark!! My firth though was that it was sitting in a humid garage for 6 month whitout moving
Quote from: ducpainter on April 01, 2012, 03:09:33 PM
The theory is it's engine heat.
I wondered about engine heat, but the brakes get pretty hot, too.
-Jeff
if you completely flush the circuit then it wont turn color as quickly.
it turns from a combination of moisture cooking and the seals rotting letting some oil in.
when i flush mine it lasts for a few months. flush often and it will slow the process.
Quote from: ducatiz on April 01, 2012, 06:36:02 PM
if you completely flush the circuit then it wont turn color as quickly.
it turns from a combination of moisture cooking and the seals rotting letting some oil in.
when i flush mine it lasts for a few months. flush often and it will slow the process.
All true...
but it will still darken faster than brakes.
This isn't specific to our bikes. Pretty much all cars which have clutch fluid also see it turn dark far more quickly than the brake fluid, and the temperature for both is about the same. It isn't moisture either, since both systems have the same seals.
The real reason is that the rubber grommets/seals/o-rings (depending on the system) in a clutch piston move a far greater distance than the ones in a brake system. The black rubber particles are therefore scraped off in greater numbers, darkening the fluid.
The brake system moves slightly, but is mainly transferring force as the pads don't move very far. The clutch, in contrast, is transferring force, but over a greater distance as it disengages the clutch plates.
And now you know the rest of the story.
Quote from: Scissors on April 04, 2012, 08:03:07 AM
This isn't specific to our bikes. Pretty much all cars which have clutch fluid also see it turn dark far more quickly than the brake fluid, and the temperature for both is about the same. It isn't moisture either, since both systems have the same seals.
The real reason is that the rubber grommets/seals/o-rings (depending on the system) in a clutch piston move a far greater distance than the ones in a brake system. The black rubber particles are therefore scraped off in greater numbers, darkening the fluid.
The brake system moves slightly, but is mainly transferring force as the pads don't move very far. The clutch, in contrast, is transferring force, but over a greater distance as it disengages the clutch plates.
And now you know the rest of the story.
That makes sense.
-Jeff
Quote from: Scissors on April 04, 2012, 08:03:07 AM
This isn't specific to our bikes. Pretty much all cars which have clutch fluid also see it turn dark far more quickly than the brake fluid, and the temperature for both is about the same. It isn't moisture either, since both systems have the same seals.
The real reason is that the rubber grommets/seals/o-rings (depending on the system) in a clutch piston move a far greater distance than the ones in a brake system. The black rubber particles are therefore scraped off in greater numbers, darkening the fluid.
The brake system moves slightly, but is mainly transferring force as the pads don't move very far. The clutch, in contrast, is transferring force, but over a greater distance as it disengages the clutch plates.
And now you know the rest of the story.
I only use the clutch for starts.
It still gets black. :P
j/k...your explanation does make sense.
Quote from: Scissors on April 04, 2012, 08:03:07 AM
This isn't specific to our bikes. Pretty much all cars which have clutch fluid also see it turn dark far more quickly than the brake fluid, and the temperature for both is about the same. It isn't moisture either, since both systems have the same seals.
The real reason is that the rubber grommets/seals/o-rings (depending on the system) in a clutch piston move a far greater distance than the ones in a brake system. The black rubber particles are therefore scraped off in greater numbers, darkening the fluid.
The brake system moves slightly, but is mainly transferring force as the pads don't move very far. The clutch, in contrast, is transferring force, but over a greater distance as it disengages the clutch plates.
And now you know the rest of the story.
Would you look at the giant brain on this guy! [beer]
ok, so how come my rear brake fluid gets dirty almost as fast as the clutch fluid?
If your rear brake lever is like mine, same reason mentioned above.
Longer shaft movement (giggity!) through a rubber boot (giggity?) each time you use it (that's what she said).
Seriously.
thank you, Quagmire
Quote from: sofadriver on April 04, 2012, 08:12:18 PM
ok, so how come my rear brake fluid gets dirty almost as fast as the clutch fluid?
Magic.
Quote from: Scissors on April 04, 2012, 08:03:07 AM
This isn't specific to our bikes. Pretty much all cars which have clutch fluid also see it turn dark far more quickly than the brake fluid, and the temperature for both is about the same. It isn't moisture either, since both systems have the same seals.
The real reason is that the rubber grommets/seals/o-rings (depending on the system) in a clutch piston move a far greater distance than the ones in a brake system. The black rubber particles are therefore scraped off in greater numbers, darkening the fluid.
The brake system moves slightly, but is mainly transferring force as the pads don't move very far. The clutch, in contrast, is transferring force, but over a greater distance as it disengages the clutch plates.
And now you know the rest of the story.
Totally obvious now you have mentioned it! This bugs the hell outta me on my Tuono but at leats I've learnt how and why it happens.
Quote from: Scissors on April 04, 2012, 08:03:07 AM
This isn't specific to our bikes. Pretty much all cars which have clutch fluid also see it turn dark far more quickly than the brake fluid, and the temperature for both is about the same. It isn't moisture either, since both systems have the same seals.
The real reason is that the rubber grommets/seals/o-rings (depending on the system) in a clutch piston move a far greater distance than the ones in a brake system. The black rubber particles are therefore scraped off in greater numbers, darkening the fluid.
The brake system moves slightly, but is mainly transferring force as the pads don't move very far. The clutch, in contrast, is transferring force, but over a greater distance as it disengages the clutch plates.
And now you know the rest of the story.
I have to say that I always really like your posts... always well thought out and well explained. [thumbsup]
If anyone has polished aluminum, it creates 'blackness' - on your fingers, on the rags. The brake and clutch cylinders are aluminum and the seals polish the bores each time you use them. I guess I use the clutch many more times than the brakes - that is the theory anyways. YMMV
To expand on these systems, some of the newer guys might not be aware that there is a rubber diaphragm on the brake and clutch reservoirs. The purpose is two-fold:
1. To provide a seal against the outside elements.
2. To prevent differences in pressure between the brake/clutch system and the outside atmosphere from introducing water to the system, or causing fluid to escape.
For example, if the pressure within the clutch system decreases in comparison to atmospheric (either because the outside pressure increases, or you pull the clutch lever, draining some fluid from the reservoir temporarily), the diaphragm sinks downward as the outside air displaces the volume necessary to equalize the pressure on both sides.
Another way to think of it: If you put a plastic bag over your mouth (and don't breathe through your nose) you'll see that attempting to breathe in brings the bag into your mouth, and attempting to breath out bulges the bag outwards. Yet no moisture is exchanged with the outside air even though you are able to breathe in and out (slightly). In some circles this is referred to as "kinky".
I've seen some bikes, including my own, where the diaphragm has dropped in the center down into the reservoir so that it forms a cup. This is improper and should be corrected. The diaphragm should form a "flat" shape composed of up and down pseudo-circular folds. When looking at your reservoir, you should see the fluid at the bottom, then completely empty air above it, with the diaphragm "hidden" by the cap up in the top. If your diaphragm is touching or below the surface of your fluid you need to either fix it, or think of another form of birth control.
Quote from: Bill in OKC on April 05, 2012, 11:33:47 AM
If anyone has polished aluminum, it creates 'blackness' - on your fingers, on the rags. The brake and clutch cylinders are aluminum and the seals polish the bores each time you use them. I guess I use the clutch many more times than the brakes - that is the theory anyways. YMMV
This is what I believe the problem is, plus, as scissors stated, the length of the stroke as compared to the brakes. Hard anodizing, like they do on aluminum car brake masters would prevent this.
Almost forgot to also add: One tends to cycle the clutch more often than one tends to cycle the brake, multiplying the effect of the longer stroke.