When we talk about hydraulic or cable clutches, we’re just referring to how the clutch is actuated. With a cable clutch, lever force is transferred via a Bowden cable, which has steel wire running within a flexible sheath. With a hydraulic clutch, fluid is used to convey force just like in hydraulic brakes, except instead of a caliper at the other end of the hose, there’s a slave cylinder that acts on the clutch’s pressure plate in the same manner that a cable does.
If a cable clutch and hydraulic clutch do the same thing, why would a manufacturer or a rider choose one over the other? Each system has its pros and cons, and we’ll start with the cable clutch since it’s the most common setup.
Cables are common for one simple reason: They’re cheap to make and easy to fit. That’s a big plus, whether you’re manufacturing motorcycles or just maintaining your own bike. On the topic of maintenance, cables need a fair amount of it. For starters, you have to adjust the slack frequently to account for clutch wear—let the cable get too loose and you won’t get complete disengagement when you pull the lever. Too little slack and you’re going to get clutch slip and cook your clutch plates. Also, cables need to be lubricated periodically and they’re susceptible to corrosion and breakage, and binding if they’re bent too sharply.
On the other hand you don’t have to worry about messy lube or fraying cables with a hydraulic clutch, and you don’t have to deal with adjusting anything either. That’s because as long as there’s fluid in the reservoir, a hydraulic system will self-adjust as the clutch plates wear, so the engagement point remains the same throughout the life of the clutch. Speaking of engagement, hydraulic clutches are generally easier to modulate and have a lighter, more consistent lever pull since there’s a master cylinder and a slave cylinder amplifying your grip strength.
That’s a lot of pluses for hydraulic actuation, but this is a more expensive setup, both to build initially and to repair later on if a seal fails. And while you don’t have to fuss with cable tension all the time, for those hydraulic systems use brake fluid, you’ll need to replace it every few years.
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And what if your bike didn’t come with a hydraulic setup, but you’re convinced it’s what you want? There are evidently enough people looking to cut the cable that Magura has created the Hymec conversion kit. It sounds like a maneuver you’d do to someone who’s choking, but “Hymec” stands for Hydraulic from Mechanical, which is what the kit does—it allows you to convert your cable clutch to hydraulic. It offers all the benefits of a hydraulic setup and it comes fully assembled, pre-bled, and ready to install. And because it uses mineral oil instead of hydroscopic brake fluid, you never have to replace the fluid, so it’s maintenance-free.
So there you have it, a snapshot of the pros and cons of the two kinds of clutch actuation. Combine that with our How a Clutch Works video, our Wet vs. Dry Clutch video, our Slipper Clutches Explained video, and our How to Replace Your Clutch video, and you’re going to be pretty well versed in motorcycle clutches.