brake fluid, is it all the same?

andybrad

Sorry for the potentially daft question but can you tell me if all brake fluid if the same? i.e. cycling stuff as opposed to car stuff. and why should you use 5.1 over dot4?

craker

No you need to use the type recommended for your braking system; Shimanos use mineral oil for example. Sorry I can't be more specific... what brakes have you got?

nicklouse

andybrad wrote:

Sorry for the potentially daft question but can you tell me if all brake fluid if the same? i.e. cycling stuff as opposed to car stuff. and why should you use 5.1 over dot4?

DOT3 DOT4 and DOT5.1 can all be mixed but you will reduce the specs of the higher spec fluid. (yes they are the same as car fluid)

Mineral oil is not usable in DOT systems and the other way round.

andybrad

ok thanks folks, just normal dot4 for the hope mono minis then.

cavegiant

You can potentially get an improvment by putting 5.1 in a dot 4 system.
It has a higher boiling point and lower viscocity.

Not sure for that particular brake however

cooldad

Just watch out for DOT 5 (not to be confused with DOT 5.1)- not common but silicone based and not compatible with any MTB brakes.

nicklouse

cooldad wrote:

Just watch out for DOT 5 (not to be confused with DOT 5.1)- not common but silicone based and not compatible with any MTB brakes.

and basically only used by the US military and no one else.

cavegiant

nicklouse wrote:

cooldad wrote:

Just watch out for DOT 5 (not to be confused with DOT 5.1)- not common but silicone based and not compatible with any MTB brakes.

and basically only used by the US military and no one else.

They spray it over countries they are about to invade, rendering their braking systems unreliable.

Mr OCD

nicklouse wrote:

cooldad wrote:

Just watch out for DOT 5 (not to be confused with DOT 5.1)- not common but silicone based and not compatible with any MTB brakes.

and basically only used by the US military and no one else.

Not quite... also used a lot in Classic cars as its not hygroscopic like DOT 4 / DOT 5.1 so ideal for vehicles that are stored a lot.

Also worth noting that some high spec DOT 4 brake fluid is higher spec than some DOT 5.1 so read the bottle... you should be looking at high boiling temp figures.

cooldad

I did not know that. I remember guys with Harleys using it, and some people used it for racing (not sure why), but that was rather a long time ago. Maybe an American thing. Just remember they weren’t supposed to mix.

nicklouse

Mr OCD wrote:

nicklouse wrote:

cooldad wrote:

Just watch out for DOT 5 (not to be confused with DOT 5.1)- not common but silicone based and not compatible with any MTB brakes.

and basically only used by the US military and no one else.

Not quite... also used a lot in Classic cars as its not hygroscopic like DOT 4 / DOT 5.1 so ideal for vehicles that are stored a lot.

and that is the main reason I would not use it in any classic car. As the fluid is not hygroscopic the water pools and causes rust and also as it sits at the lowest point can cause brake fade faster than a water full 3/4/5.1brake fluid.

andybrad

you would generally put silicone fluid in a classic car to stop it stripping the paint if you spilled some. its not very good for performance and sometimes causes the pads not to retract properly

nicklouse

andybrad wrote:

you would generally put silicone fluid in a classic car to stop it stripping the paint if you spilled some. its not very good for performance and sometimes causes the pads not to retract properly

Nope never would and never did. you just do not spill it.

Performancewise it aint that bad.

diy

Generally I would go with DOT 5.1 if its certified, as its thinner than 4 and a lot easier to get the air out of.

'Merkin motorbikes use 5.0, because they like their brakes to feel like poo and actually value the spongy feel you get as a result. Its possibly something to do with the low centre of gravity, tyres treated with ronseal, lack of wet riding experience, the fact that they are tought to skid the rear wheel in an emergency stop or possibly just an all round inability to ride?

I do know some HD riders who are good riders, but not many :?

dommccabe17

cavegiant wrote:

nicklouse wrote:

cooldad wrote:

Just watch out for DOT 5 (not to be confused with DOT 5.1)- not common but silicone based and not compatible with any MTB brakes.

and basically only used by the US military and no one else.

They spray it over countries they are about to invade, rendering their braking systems unreliable.

"I love the smell of DOT 5 in morning"

Anonymous

diy wrote:

'Merkin motorbikes

What the hell is Merkin motorbikes? Is it a bike shop?
Why would they name themselves after a pubic wig?

diy

harley and buel are 'Merkin bikes as in "A-Meri-Kin" I thought the term was a popular as septic?

Anonymous

I've heard "septic tank = yank" before, but if you'd just written "septic motorcycles", I wouldn't have a clue what you were on about.

Never heard of "merkin", I prefer my interpretation

Deputy Dawg

George Bush used to say he was "proud to be a merkin" quite often

TuckerUK

Don't say George Bush, just call him Shrub (small bush), saves on typing.

One of Shrubs favourite opening comments was “My fellow Merkins…”

Slightly off topic, but a big advantage of silicone brake fluid (DOT 5) is that it doesn’t instantly burst into flame when contacting a hot exhaust manifold like regular brake fluids do (the cause of a great many post-accident vehicle fires). Interestingly petrol and diesel don’t burst into flame when contacting a hot exhaust manifold.

Bad side of silicone fluid (DOT5) is that it is very hard to remove air from, and hence getting a rock firm pedal is next to impossible (talking cars here obviously). It's why it went out of favour very quickly for any performance use.