anze_awesome

So my brakes are in a horrible state and I need to wait until I get the parts I need to repair them, and while I still had shimano mineral oil in the brakes, there just wasn't enough of it, and in a desperate state (I have to film a bike edit tomorrow (I have a dirt jumper)) I had to put a little bit of water in my brakes to mix with the brake fluid so my brakes at least somewhat work and I don't crash on the jump where we'll film the edit. So I know it isn't good to put water in your brakes but is there a big difference if I still had some brake fluid in the brakes and what damage can I do to my brakes?
EDIT: So I had to put a really small amount of water in because none of my friends had shimano mineral oil, and i had literary NO BRAKES, because I didn't have enough fluid in (was going to shoot a video, and it was the last day to do it, had to go on a big jump and NEEDED the brakes). I didn't have time to go to a bike shop (no car, closest one is 30min away + didn't have time). But last minute a friend suddenly found some mineral oil and I got rid of the old fluid and put that one in, and the next day went and bought some shimano mineral oil, so luckily I never even used the damn brake with some water in. Also I knew that it wasn't good to put water in, but I absolutely needed the brakes, and there was NO other option. Also yes, I realize I'm stupid

Moe Zhoost

Water will boil from high temps during braking, which may significantly affect braking. You will now need to bleed, clean (to make sure that all of the water is out), and then refill with the proper fluid. You've created a dangerous condition, mate. You need to resolve it ASAP.

Cyclist0108

If this is guerrilla marketing to get us to watch the youtube video, it is working.

trailangel

"Film a Bike Edit" WTF is that?
You shoot.... and then you edit.

People frequently do something because "they need to get the shot"... and somebody gets hurt.... that's why they have permits and insurance.

Oneder

Water can be very corrosive but you can use mineral oil

jefnvk

Assuming this is serious: you won't stop that well once the system gets warm. It is called brake fade: once a fluid starts to reach its boiling point, it starts to turn to a gas, which is very compressible, which means you don't stop. Crazy scary when it happens in a performance car. You're probably not fine for MTB, or anything else that uses alot of braking and gets the caliper warm. Also, good luck drying out your brake system. You will have moisture in the system, which will affect the performance in the future, in addition to potentially causing corrosion issues.

cyccommute 

Yup. I covered this in another thread on brake fluid. If the fluid were DOT fluid it would be less bad...still bad, however...because the DOT fluid dissolves the water.

For anze_awesome: With mineral oil, the water separates from the oil. But it’s even worse. Because the mineral oil has a lower density then the water, the water will seek the lowest point. That’s where the heat is. Get the brakes hot enough and the water will boil or even form steam. That’s a gas. Just. Like. Air. You’ll have no brakes.

You are going to want to get rid of all of the oil and you have to flush the system of any water. But the oil and water don’t mix and neither do solvents you’ll need to use. I’d start with mineral spirits to remove the mineral oil. Then follow that up with acetone to remove the water. You may need to completely disassemble the calipers...completely!...to make sure no water is trapped in pistons or other nooks and crannies.

It might be easier to just buy new brakes.

Very bad idea. You would have been better off to just use baby oil or mineral oil from CVS. That’s still a bad idea...there are viscosity issues...but it would be easier to clean.

shelbyfv

Hmmm. First post, beyond bizarre

Koyote

I've never even set up hydro disc brakes, and I know that you don't introduce water into the system.

tyrion

Seth Bike Hacks Seth actually did an experiment in which he used baby oil for brake fluid. It worked.

Cyclist0108

Were any actual babies harmed in producing that video?

hillyman

I've said many times we should all learn to work on our own bikes. I now wish to retract that statement.

Ironfish653

Wow, yeah, so much to unpack from the OP.

Water is is not a very good choice for hydraulics. It’s only stable in a narrow range of temperatures; it freezes solid easily and evaporates quickly. It’s also hard on the surfaces of metal parts, which is bad for your seals.

Brake fluid tends to absorb water easily, which then gives your brake fluid all the undesirable properties of using water in hydraulics.
Water and oil oil don’t mix well unless you use a blender, then you get mayonnaise.

I have a system that is capable of pumping seawater as the operational fluid, but it’s really for a high volume, high pressure operation, where having to tear down the pumps afterwards will be the least of our problems.

Ross520

So instead of buying mineral oil from the grocery store, brake fluid from the auto parts store, or OEM Shimano fluid from a LBS, you decided to put water in it, why?

Cyclist0108

Well, they are hydraulic.

Also, admittedly very rarely, sometimes what you read on the internet didn't really happen.

indyfabz

It’s a sign of the times.

OldTryGuy

and maybe last ???

shelbyfv

Yeah, hopefully they will czech for socks at some point....

mr_bill

Feel free to do a kitchen experiment. You will not get mayonnaise with water and oil, no matter how long you blend.

You also don’t need a blender to make mayonnaise.

A whisk will do quite nicely, though if determined enough a fork will do, or if really determined a spoon or chopsticks.

You do need an emulsifier such as lecithin found in egg yolk. A soluble thickener (such as the mucilage found in mustard) is wise too. Finally, lowering the pH with a bit of acid from lemon juice or vinegar helps too.

-mr. bill

cyccommute 

And, after doing all that, you no longer have a mixture of just oil and water.

Midou

mmm, interestung

Kapusta

I have GOT to see the video of this.

elcruxio

I don't get the whole death and destruction attitude here. Using water and glycol in shimano brakes used to be a thing on another cycling forum. They did in with DH bikes if I recall correctly. Worked great, didn't go all stiff in the cold, didn't boil etc.

The reality of the matter is, that it requires some serious work to get bicycle brakes boiling hot. Or rather, you'll easily hit hundreds of degrees celsius at the pads and rotor. However in order to transfer that heat through the caliper body into the fluid in large enough quantities and continuously enough to heat up enough fluid (a significant amount) to cause a boiling event even with water would require some monster hills and very irresponsible braking habits. ​​​I'm sure it'd be possible, but not with a dirt jumper in its natural habitat.

As to flushing it out? Empty the system as good as you can, put new oil in, presto. Good as new.

It's bicycles, not rocket science.

phughes

Not even close to surprising. Johnson's Baby Oil is mineral oil.

elcruxio

I'll actually revisit this immediately.

A cute finnish couple did a youtube video about bicycle disc brake vs lathe. The fluid only boiled well after the rotor had been red hot (so around 1000 degrees celsius?) for quite some time. I've only ever gotten my rotor brown and my wife who has worse braking habits than me has gotten her rotors blue.

There's also the brake force one H2O brake system which uses a water and glycol mixture as fluid.