Brake Force One H2O hydraulic disc brakes that use water

Brake Force One has completely redesigned their unique hydraulic brakes to use water instead of mineral oil. The calipers still use their two step system to provide near instant engagement before ramping up the power, just in a different configuration. Still a closed system, too, because it’s a high volume lever system that can handle any expansion.

They say water makes the brake more heat resistant because it has a five times higher heat transfer rate, two times the heat capacity and less expansion under heat than mineral oil. It’s also less compressible, which is why many trials riders have used it. It’s also much more environmentally friendly.

Which begs the question, why doesn’t everyone just use water? “Everyone just imported the tech from cars,” they said, which meant a rethink was in order…

Brake Force One H2O hydraulic disc brakes that use water

They did everything they could to heat it up, descending 1,500 vertical meters with the brakes constantly engaged and couldn’t get the water over 90°C. On the same test, mineral oil started to fade after 800m, but the water brakes felt consistent all the way down. They say there’s no way to get enough heat energy to boil it outside of the lab.

We spoke to another brake manufacturer just to get a second opinion on the concept and they said that as long as it didn’t boil, it should work, and that most common brake fluids end up absorbing water that then settles at the bottom of the system (i.e. at the caliper), which can be problematic if it boils.

Brake Force One H2O hydraulic disc brakes that use water

So, perhaps it’s doubly smart that BFO adds 20% glycol (brake fluid, basically) to prevent freezing. Glycol raises the boiling point of water and completely mixes with it rather than separating like oil would.

Brake Force One H2O hydraulic disc brakes that use water

While it still uses a two-stage piston system, the layout has changed from the original, putting the staged pistons directly inline with the main pistons rather than along the side.

Brake Force One H2O hydraulic disc brakes that use water

The new design is quick to service and replace the hose, with only a knife needed to cut the hose. The quick connect valve locks the hose into place and releases it by depressing the surround (the round bit that the hose sticks into). The fluid outlet on the caliper can be rotated 360° with no tools.

Started testing with water more than a year ago, and the new caliper design started testing eight months ago. The new caliper is much stiffer, so there’s more power on tap and it’s easier to modulate. I test rode one in the parking lot and the brakes take action immediately, then ramp up quickly. After a number of stops I started getting a feel for it, but they are much stronger and more abrupt than the SRAM Guides, Magura MT8 or Shimano Race/Trail brakes I’ve been riding lately.

Brake Force One H2O hydraulic disc brakes that use water

System weight is 188g for front brake without rotor, easily making it one of the lightest brakesets on the market.

It’s cheaper now, too, just €594 versus €780 for the original. That one will stay in production for about another 12 months then be discontinued but will continue to be cared for with warranty service. Water is their future.


  1. Theses make me hot! Just not hot enough to boil, am I right?!? I know you guys at Brake Force One will be checking out the comments section, so just ignore the intellectually bereft derelicts on Pinkbike.

  2. I’ve thought about this a long time ago. Water definitely loses heat far faster than oil and definitely heats up more slowly. Kinda odd that no engineers in the industry thought of doing this a long time ago. They surely played with water, oil and alcohol throughout their undergraduate(even high school) studies while taking mandatory chemistry classes.

  3. I’m sure it’s not ethylene glycol, but propylene. First one is dangerous.
    I’m sure also that water should be distilled and we need anti-corrosive supplements like dinatrium diphosphate and dextrin

  4. Interesting. Article is a bit short on the negatives of the idea, e.g.: If this is so good for bikes, why isn’t it used on motor vehicles? And what’s the freezing point of the water/glycol mix?

    Also, for emergencies on tour, how well will they work when filled with tap water? (apart from self destructing below 0 deg. C)

  5. Sears (yes, the department store) many years ago made a hydraulic rim brake for their in-house road bikes that I believe used water.
    Another thing that’s totally unaffected by heat is… (drum roll)… cables. Anyways, if the heat radiating effect of water is as good as they say it is, that really is a good thing. The heat radiating ability of their calipers, rotors, and pads looks to be no different than what you’d get with any other disc brake, though. Maybe they work with the latest Shimano Ice-Tech pads and rotors?

  6. @Veganpotter

    More accurately, water does not lose heat faster than oil. It disperses heat more quickly. It heats and cools more slowly. Heat capacity is a two way street – cooling and heating require the same energy exchange. Could be what you meant… just not how I read it.

    Cool idea. Maybe I will finally ditch the much loved XTs, which no matter the generation are fantastic…

  7. The reason why people use mineral oil is because glycol based DOT brake fluid is nasty. Contrary to what marketing guy says, glycol based hydraulic fluids are the standard in the automotive industry, not mineral oil.

  8. Maybe, I don’t know. Just made an assumption on what antifreeze is used in some countries based on their weather types.

    If you ask me, I will prefer an oil with the best viscosity:boiling point ratio

  9. I like the two stage engagement concept of the old design, but I can’t tell how it works on the new design from that cross section. Also, from experience, those push to connect tube fittings are really really good at trapping a little bubble of air at the end of the tube. This is what makes olive fittings much easier to bleed.

  10. what about using whiskey? then you could always bring a flask of replacement brake fluid on your rides for… uh… servicing your brakes…

  11. Trial riders have been doing this for a while with current systems. Mainly it is easier to bleed the brakes. Bleeding the brakes is done off the bike fully submerge in water.

  12. Uh, it’s called heat capacity and colligative properties – general chemistry. If you wish to run this system at a lower temperature, run a higher concentration of ethylene glycol.

    BTW, water does not necessarily lose heat faster than oil. It depends on the thermal conductivity of the materials surrounding the fluid. Two fluids at the same temperature have the same amount of thermal energy. While it might take more energy to heat up water, water does not cool faster.

  13. Shredder is correct. It’s basic thermodynamics: how fast heat is transferred out of the water solution will depend on the surface area of the water volume; the thermal conductivity of the material(s) enclosing the water; the amount of material enclosing the water; and the properties of the air flowing over the system. Thermal radiation will also play a part, albeit a very small part.

  14. Ok…heat up two similar pots on your stove to just below water’s boiling point. Wait 10 minutes and submerge one hand in each pot. Tell me that they’re the same temperature with a straight face

  15. @Veganpotter Apart from the possible burns, that experiment confuses temperature with heat capacity. Temperature is best read with a thermometer…

    @Shredder “Two fluids at the same temperature have the same amount of thermal energy.” vs “While it might take more energy to heat up water…”
    Where does the extra energy go, then? You mentioned heat capacity yourself, which seems to invalidate the first statement.

  16. I’m all about it once I see data proving fluid fade not only comes on later but is hard to reach. Once 100c is reached would vapor increase power eventually locking up the brakes, or would power be lost because vapor is too compressible?

  17. bearCol…vapor is very compressible but unless your line is half empty, its not like you actually have to push that hard to squeeze a brake and have it actuate. That would depend on lever throw and how much fluid/water pulling the lever would typically push in the line. It’ll work for a while(time to fix it) but if you keep riding with less and less fluid, you’ll eventually not have any brakes…not much different than air in the line of a regular hydraulic brake.

    Gunnstein…if I were deep frying something today, I’d test this to get a quantitative answer. I just know a cup of 200 degree water cooled next to a cup of 200 degree oil will be drinkable after 10 minutes and the oil will basically cook the inside of my mouth

  18. Interesting concept. I think oil is used most commonly because it also provide lubrication and protection from corrosion. With a water based system, you’ll get corrosion if any internal part comes in contact with air so the system has to be perfectly bled.

  19. @Veganpotter Ok, I’ll take your word for that – but until it’s measured, we don’t know if it is because the oil is hotter, or because it has higher heat capacity. (Though from the article, it would seem water has higher heat capacity than brake oil.)

    Saunas are a good practical demonstration of heat capacity. 100 degree dry air inside the sauna is perfectly all right, 100 degree humid air is damned hot, while sitting in 100 degree water means death by boiling.

  20. Great idea. With initial MTB disc brake systems there was a lot of carry over from motorcycle and automotive tech, but you’re stopping some pretty massive vehicles. On a bicycle brake, it is entirely possible that H20 dissipates enough heat throughout the entire system to never reach boiling point. Some great ideas in this design, but also, why couldn’t we just use H20 in our current brake systems anyway. As was noted, trials riders have been doing it for some time.

  21. Vegan,gunn,spliff,etc…
    You guys are dancing around two different properties.
    Specific heat capacity (kJ/kg F) and for this application thermal conductivity (W/m K)

    Veganpotter is likely right but also wrong. Water at a specific temp will hold greater than 2x the energy of oil,but it’s conductivity is also like 4-5x higher than oil, so in the same pot example given it will cool faster.

  22. I should say vegan is right with regards to a pot of water being colder after some time compared to oil, but he is wrong with regards to it holding less energy. It holds more and conducts greatly more (when compared to generic “oil”)

  23. ginsu – you probably can, but I’d wager most metallurgy in “oil” brakes wouldn’t be fond of it. Additionally, many brake manufacturers may rely on oil as a lubricant, of which water is horrible. This is surmountable by design and materials though.

  24. Specific Heat Capacity (Cp) J/kg*K: mineral oil=1670, water=4183
    Thermal Conductivity (k) W/m*K: mineral oil=0.162, water=0.670

  25. And this is what happens for not speaking explicitly 30 posts ago… All else being the same, the high TC of water allows for the system to move heat away from where it is being generated, hence it is better at dissipation. Additionally, this also doesn’t allow a gradient of temperature to develop across the fluid itself – heat is quickly redistributed. To first order heat transfer across an interface is proportional to surface area and delta T at the boundary, so a system where heat is retained locally in a hot reservoir (e.g. caliper, right around pistons) is inferior to one where the heat is redistributed over a large surface area (rest of caliper, lines, etc…) as heat may be transferred from the fluid to the rest of the system and surrounding environment more effectively. There is the added complication of heat transfer across the various interfaces between the fluid and system parts, but it is probably negligible between mediums relative to the transfer within the material.

    As mentioned by some others, the electrochemistry associated with a water system may require some thought. Could be water will act as an electrolyte and there is going to be a galvanic potential across the different materials in the system. Slowly plating the inside of your aluminum caliper with your steel hose and brass fittings can’t be good….

  26. Love the idea, not so much the price.

    Because of that will stay with my Shimanos until it will be much more affordable.


  27. Are these still being designed by that German whiz kid? Brilliant out of the box thinking, really hope these prove themselves in the long run.

  28. Brake fluid/oil is much better a lubricating the seals used in the master cylinder and calliper. However there are now seals available that are self-lubricating and can work with water. Although these tend to be more expensive, and also lifetime of seal may not be a good. However the frequency of operation is not that high on a bike, so the B10 data is probably acceptable for use.

  29. So this is basicly not a water operated regular disc brake, its a mechanical disc operated by hydralic water/anti freeze aka a hs33 like trials bike use with a water bleed, but rather than a rim brake the caliper pushes the mechanical part of a single piston caliper.

    its just not what i was expecting to see when i read water disc brake.
    but well done combining those this will be really good on bikes less oil and easier to look after.

  30. @dez coates

    It’s a water operated regular disc brake. Exactly the same as an oil or dot fluid operated one. What were you expecting?

  31. “polyethylene glycol” is Water Wetter, for anyone who has done motosports. Tracks generally don’t allow antifreeze, but Water Wetter is allowed as an addition to the radiator.

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