2014 FSA K-Force hydraulic disc brakes

We’ve leaked quite a few details about the new FSA hydraulic disc brakes (here and here), but now we’ve got the full story:

The main point of difference is their extremely compact reservoir and master cylinder and a ton of adjustability and an elliptical cam system to drive the pushrod into the master cylinder with a very straight path and linear response.

Starting with the master cylinder, the shape allows them to orient the brakes in any way they need to. For now, that means a svelte package that places the gloriously straight lever blade close to the bar. Now, let’s take a look inside…

2014 FSA K-Force hydraulic disc brakes

Another really nice feature is their “quick draw” activation. The port timing holes are placed very close to the primary seal, so as soon as you start pulling the lever, the brakes start working.

2014 FSA K-Force hydraulic disc brakes

As a quick primer on how hydro brakes work, the timing port holes (E) let brake fluid flow freely into the reservoir (B – which holds the expansion bladder) through a port (G) when not engaged. As the lever moves the push rod into the master cylinder, the holes are moved past the primary seal (F) to close the system between the seal and the caliper, which forces fluid to push the pads toward the rotor.

Other items on the FSA brakes are the bleed port (A), stroke adjust bezel (D) and reach adjust bezel (C).

2014 FSA K-Force hydraulic disc brakes

The tool-free stroke adjust lets you dial the timing ports back a bit to add some free stroke, but that simply means you’ll be pulling the lever further before the brakes start doing anything.

2014 FSA K-Force hydraulic disc brakes

Once that’s set, you can adjust reach with another tool-free knob, and there’s a wide range of adjustment. Left to right shows it dialed all the way in and out. It’s worth noting that if you have them dialed in really close and add some free stroke, they’ll be hitting the grips before you have full braking power.

The reservoir is offset slightly from the master cylinder and has an angled interior wall so the highest point is at the bleed port when it’s level. The lever bodies are the same, so you can flip flop between normal and moto-style braking, but that means you’ll always see one bleed port facing up and the other facing down when they’re on the bike.

2014 FSA K-Force hydraulic disc brakes

The caliper is a one-piece mono block piece with a very stiff bridge between each side. Pistons are 22mm diameter. Lower bleed port is located in the center of the banjo.

2014 FSA K-Force hydraulic disc brakes

Conveniently, their brake pads are the same size and shape as Shimano pads.

2014 FSA K-Force hydraulic disc brakes

The pads are a custom semi-metallic that’s designed to break in quickly and has a very high coefficient of friction, so it’s strong. Because the lever pushes in a linear fashion, it can have that strength without being grabby.

Lastly, they’re using front and rear specific brake hoses. Each is made with different expansion rates (front has more expansion, rear is stiffer) so they feel exactly the same in both hands. The reason, they say, is that many modern bikes require very long hose runs for the rear brakes, sometimes twice as long. Since all of the opportunity for expansion comes from the hose, the solution was to tune them so they feel the same. Brake guy Joel Richardson says unless you’re running a hard line to the brakes, you’ll always get some expansion.

They wanted to offer something will all the bells and whistles most riders want and keep it light. With system weights just under 300g. That’s good on its own, but even though the top model is currently pegged K-Force, they could go much lighter in the future by losing the stroke adjust and making a tooled reach adjust.

2014 FSA Afterburner hydraulic disc brakes

Differences in the brakes are materials, not function. The K-Force gets a magnesium body, alloy caliper and carbon lever with titanium hardware. They said the reason magnesium can’t be used at the caliper is because it’s highly affected by heat, which would cause a lot of problems there. The Afterburner is all alloy with steel hardware.

2014 FSA Afterburner hydraulic disc brakes

2014 FSA Afterburner hydraulic disc brake rotors

The K-Force gets a 2-piece rotor with alloy carrier arm for aftermarket. OEM customers will have the option of this 1-piece K-Force rotor, too, but the 2-piece is stiffer since the oversized alloy spider runs pretty far out toward the braking surface. Weight between the two are very similar.

The Afterburner rotor (shown below on the scale) gets much more mass and twice the surface area for better heat management. Interestingly, FSA engineer Herb Tai says friction force is not a function of the surface contact area, it’s just that great surface area means better heat dissipation.

Graphics for each model will match those on the other K-Force and Afterburner parts.

2014 FSA Afterburner hydraulic disc brake actual weights

The K-Force brakeset comes in at 195g with 185cm of hose (it ships with 160cm). Bolt kit is 9g.

2014 FSA Afterburner hydraulic disc brake rotor actual weights

Rotors are 98g for K-Force two-piece and 95g for one-piece. Afterburner rotor is 142g. All are 160mm.


  1. These look awesome. One piece caliper, compact levers, light weight, brake hose sorcery to maintain the same ‘feel’, and gianormous freaking pistons, oh and the same pads as shimanos! In my experience these seem to be a mighty threat to one of the best and lightest brakes out there, formula the one dh pros. Great intro to the brake world FSA.

  2. Sounds good on paper, but why is the lever so freaking ugly? What was so hard about just making it look nice? Fire the industrial designer and give his entire paycheck to the engineering team lead.

  3. Aesthetics are completely subjective, but I wouldn’t say it’s ugly. They’ve just gone with a more raw mechanical aesthetic and not concealed that fact that the lever is a complex hydraulic mechanism. But even with that I’d hardly say this is the least “designed” lever on the market. Design is function and form in harmony, but sometimes the product calls to be tipped a little more in one direction. They’re not winning any RedDot awards, but I think FSA’s ID team is doing just fine.

  4. Mindless: Thank you for the question on the IceTech pads and will do that research and get back to you.
    Andrew: Beauty is in the eye of the beholder? I have been on them for the past year and they have a great feeling to the hand (xl size mitts here). Everyone has their favorite brakes and all I can ask for is that you give ours a try.
    Long shot but….. If you are ever in our NW neck of the woods (Seattle) give us a call and we can hit the local trails to try them out. Thank you, Chad

  5. @Chad/FSA I don’t suppose FSA is hiring graphic designers? I’m not saying these don’t look great, because they do. I wanna learn.

  6. Even if Ice Tech do not fit, having an out of the box Swissstop Disc28 options is great, if original pads are not what somebody prefers… But Ice tech rotors and pads are a real deal. Would be nice to pair it with lighter brakes.

  7. After playing around with them today, I can say that the lever feels great in the hand.
    As a bad finger braker, their positioning is excellent.

  8. Ok, sorry for the delay since doing both OE and AM projects right now.

    Brattercakes—send your resume to me and I can forward it to the correct parties.
    We do this work in our Mukiteo Wa, Milan and Taichung offices–game for an adventure if your resume is strong enough?!

    Steely Dan–thank you for the input. Yell Hodala! and sees what happens at a industry party tonight.

    Vincent—mineral oil

    Mindless–I do not have this info on the Ice pads and guessing/assuming would only get me in trouble. I have written to the person in charge and hope to have an answer soon. The brake lead is in Germany right now. Ahh the life of a world traveler..hear that brattercakes?

  9. Nice work. Before starting this new project did you happen to put any time into fixing the terrible tooth profiles on your 386 cranksets?

  10. @Chad: If they work well then how they look just doesn’t matter. But in a marketplace saturated with a LOT of average product, looks go a long long way. Despite my misgivings I will say that they are aesthetically far better looking than the weird new formula brakes and if they really (really ;-)) work I could still be convinced away from Shimano.

  11. I like how the Afterburner looks, but not keen on garish K-force logo. I wonder if you can rub it off or something (cause K-force is what I would buy, if they are good).

  12. “Interestingly, FSA engineer Herb Tai says friction force is not a function of the surface contact area”
    ‘Interestingly’?! How do you get a job reporting on brakes when a titbit of info like that is ‘interesting’ to you?

  13. @Mindless, I was actually thinking of the old old pad style, but looking closer at the pictures the pad “arm” does appear the have the characteristic knurling of the newer non-Ice-Tec-but-Ice-Tec-compatible pads… My bad.

  14. Interesting. Like the idea of a stationary primary seal and building the timing port holes into the master cylinder piston. Any air that is in the system has an automatic escape route to either the reservoir or in front of the secondary seal on the back side of the piston, resulting in minimal if any effect on braking. A smoother transition in the reservoir at the bleed ports would allow air in the res to move more freely out of the system during bleed, but I’ll withhold judgment til I get a set to play with. Only q is how those same timing port holes will interact with the primary seal over time. As long as they don’t nip the seal over use and abuse to create a leak path, then game on. But a big +1 for designing the brake to use commonly available pads. My pad stock board thanks you.

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