What causes the clutch fluid to darken so rapidly?

[jgrm1]

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

[ducpainter]

The theory is it's engine heat.

[ducatigirl100]

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

[jgrm1]

The theory is it's engine heat.

I wondered about engine heat, but the brakes get pretty hot, too.

-Jeff

[ducatiz]

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.

[ducpainter]

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.

[Scissors]

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.

[jgrm1]

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

[ducpainter]

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.

j/k...your explanation does make sense.

[Buckethead]

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! 

[sofadriver]

ok, so how come my rear brake fluid gets dirty almost as fast as the clutch fluid?

[Buckethead]

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.

[sofadriver]

thank you, Quagmire

[Scissors]

ok, so how come my rear brake fluid gets dirty almost as fast as the clutch fluid?

Magic.

[Nottsbiker]

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.