Hydraulic clutches

[pete376403]

Anyone know why hydraulicly operated clutches use mineral oil as opposed to brake fluid? I've been looking at a Magura hydraulic clutch system and wonder why they specify mineral oil rather than the well proven DOT 3, 4, or 5 fluids that have been used fo rthe best part of 60 years.The slave cylinder lives on the outside of the engine so heat shouldn't be an issue and calipers get pretty hot under sustained braking anyway

[Grumph]

That's a new one on me but I've not had much to do with hydraulic clutches.

Less damage from leaks maybe ? Heat shouldn't be a factor.

[pete376403]

https://www.thumpertalk.com/forums/topic/1429001-prevent-arm-pump-with-the-magura-hymec-hydraulic-clutch/
...and the system uses mineral-based oil instead of corrosive brake fluids... which would mean something if brake systems regularly leaked all over the bike. However, looking further: Why does Magura use Magura Royal Blood mineral oil and not DOT break fluid?

Unlike break fluid mineral oil does not age with time and therefore offers consistent performance over many years. Furthermore break fluid absorbs water over time, which leads to a loss of heat resistance and a reduction of the boiling point. This notably affects the performance of the brake. DOT brake fluid is also poisonous and corrosive. A small drop is enough to erode the finish on a bike or damage the skin. Mineral oil is in comparison much easier to handle and offers consistent performance over a long period of time.

[F5 Dave]

Yeah it is a strange one. However my dot5 YZF750SP slave cylinder eventually failed. There was a corrosion spot at the bottom where water had sat. Maybe oil would have stopped that? If it did leak into the gearbox, it's just oil, I've heard arguments.

My dirtbikes seem to use oil.

Just remember seals on oil cant be Nitrile should be epdm and vice versa for dot5.

[SaferRides]

The ZZR1200 clutch used brake fluid. I remember changing the fluid when I bought the bike, which was black and smelled disgusting. I changed it annually after that!

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[husaberg]

Anyone know why hydraulicly operated clutches use mineral oil as opposed to brake fluid? I've been looking at a Magura hydraulic clutch system and wonder why they specify mineral oil rather than the well proven DOT 3, 4, or 5 fluids that have been used fo rthe best part of 60 years.The slave cylinder lives on the outside of the engine so heat shouldn't be an issue and calipers get pretty hot under sustained braking anyway

Euro magura spec them no idea why? well my Berg does. i assume its not hydroscopic?

[F5 Dave]

Fork oil will be fine.