Is 2.5 SAE fork oil better than Magura Blood ?

[keener]

I am going to flush the clutch oil tonight. I have some Magura Blood and have access to 2.5w fork oil.

Which one is the better choice and why?

[uraberg]

I'd flush with what you're eventually going to fill it with.

[keener]

the question is which one is the better to replace it with. I have both.

[crazybrit]

Originally Posted by keener

the question is which one is the better to replace it with. I have both.

If you're this worried make sure you have the correct color blood

Magura makes both blue and red. I have no idea on the difference and sadly neither does Magura but they were emphatic that you should only use the red for motorcycle clutches.

I'd heard it claimed that the blue stuff (intended for mountain bike brakes) is claimed 10 weight but closer to 6 in reality.

It's amusing because a) the magura clutch bleed kit w/ syringe comes with a bottle of the blue fluid b) the large 16oz white bottles have identical labels, you can't tell the color without removing the top to look inside. Blue at the bicycle store, red at my local KTM dealer.

Anyways, I doubt there is much difference between the two colors but Magura's cluelessness amuses me ..... I think as long as you stay away from the really heavy weight generic mineral oils which can be upto 20 weight you'll be fine.

[Uller]

IMO the mineral oil isn't good for the aluminum body of the mastercylinder and eats away at the o-rings in the system. This is what causes the black, milky oil to develop. Since switching to fork oil. No issues with any of my bikes.

Use the fork oil.

[mousitsas]

Originally Posted by Uller

IMO the mineral oil isn't good for the aluminum body of the mastercylinder and eats away at the o-rings in the system. This is what causes the black, milky oil to develop. Since switching to fork oil. No issues with any of my bikes.

Use the fork oil.

+1

I am using baby oil for that same reason. Probably will switch to fork oil on first opportunity.

[crazybrit]

Originally Posted by mousitsas

+1

I am using baby oil for that same reason. Probably will switch to fork oil on first opportunity.

I'd just use Mobil-1 synthetic ATF. It's supposedly around 7 weight. Cheaper than fork oil, people use it in forks all the time.

[Sporting Wood]

Originally Posted by Uller

IMO the mineral oil isn't good for the aluminum body of the mastercylinder and eats away at the o-rings in the system. This is what causes the black, milky oil to develop. Since switching to fork oil. No issues with any of my bikes.

Use the fork oil.

I've been trying to tell peeps this for years. Swap to synthetic atf or fork oil and you'll never have a problem with the slave.


Hey Keener, Gaspe Bay!!!!

[jmandrze]

Motorex makes a mineral fluid. I used it when i swapped out the slave.


Jason

[MAXVERT]

I've been using synthetic fork oil since '04 on 5 different lc8 KTM's
and my 300 also my 690.
I think the Fork oil handles the heat better and smooth action.
I usually use 5w but 10w works fine.

Max

[Head2Wind]

2.5w or 5w Redline fork oil is what I use. 5w softens the return throw slightly. 2.5w is nice and crisp, but like fork seals it can tend to weep a little, just need to keep an eye on it. I have not tried the Ultra light (like water) stuff yet, but I am sure it would work too.

IMO synthetic fork oil is designed to be a fluid used in harsh conditions of suspension control and based upon this design it also has excellent performance properties when used in a clutch master/slave application.

[keener]

Thx guys.

Does clutch perform better or is softer to operate with lower viscosity oil?

The magura blood I have is red.

[gefr]

Originally Posted by keener

Does clutch perform better or is softer to operate with lower viscosity oil?

Yes, especially when the engine is cold.

[gefr]

Originally Posted by Sporting Wood

I've been trying to tell peeps this for years. Swap to synthetic atf or fork oil and you'll never have a problem with the slave.

I believe you are overstretching the advantages of fork oil fluids.
In my experience (5 slave cyl failed) the slave cyl piston cracks. No connection to the type of fluid that push the piston.
http://www.advrider.com/forums/showthread.php?t=171986
Cheers.

[Sporting Wood]

Originally Posted by gefr

I believe you are overstretching the advantages of fork oil fluids.
In my experience (5 slave cyl failed) the slave cyl piston cracks. No connection to the type of fluid that push the piston.
http://www.advrider.com/forums/showthread.php?t=171986
Cheers.

5 ??! I'm still on my factory original on an almost 7 year old bike!

Mineral oil is corrosive to sintered aluminum, of which the slave is composed. Heating up mineral oil in its bore accelerates solvothermic corrosion, makes the oil black with aluminum oxide, enlarging and destroying the surface of the bore. Once enlarged, the piston has the tendency to jam crooked in the slave and gets snapped by increasing pressure by the uncaring hand of the rider looking for clutch. This is clearly what's happening! Mineral oil is the problem! Run something else and viola, no more problem... Or I suppose you could sleeve your slave in stainless so you may run Magura Blood. Switch to synthetic fluid and the corrosion, indicated by black aluminum oxide, goes away.

That said, there's more issues that can contribute to failure like the deformation of the plastic spacer, air in the cylinder, excessive heat, wrong length clutch rod, messed up torque ramps, etc... IMHO, the most relevant one that affects the most though, is the choice of fluid.

JFC, 5 ! Dayam! I read your thread, most of it anyways. There's folks pointing out the issue stated above... but it reads like a spam laden advertisement for evo for the most part. I hope out figure out what is causing your failures! 5! JFC!