brake fluid-what and why?
 

i usually just buy some dot 4 or 5 as im walking out the store, but they make synthetics, 5.1, 6, and even 7 i think. what do you guys use, and why?

i gotta buy some cuz i got some galfer superbike lines, but b4 i do em i was wondering if i should care what i used.

interested in hearing others replies...

Maybe someone else can chime in with the chemistry specifics, but some brake fluids are not compatible with some lines/seals. I'm pretty sure that mixing the wrong types can cause the fluid to become a paste/grease consistency that will not be good news for your brakes or braking ability.

In general, unless you know you have a need for 'higher boiling point' rated fluid in your specific brake fluid's chemical family (i.e. racing, heavy trackday usage, etc.), I wouldn't bother "upgrading". Its MUCH more important to change your brake fluid regularly (i.e. yearly or every other year at the latest), and to have the system bled properly at all times.

When you replace the brake lines, if you have to remove a 'banjo bolt' fitting, always ALWAYS use new sealing rings. ;)

Put rags around and under drip areas - brake fluid and painted/powder coated finishes are not happy with each other. If you do have a spill, flush the area with water (you might invest in a simple spray bottle with water in it).

As always, YMMV... :shrug:

After learning more than I ever wanted to know about brake systems, I have come to learn this... unless your bike can take a synthetic, don't go to a higher number than recommended. And, do not mix. There will be no benefit, and the 5.1, 6, etc. may eat parts that aren't compatible.

I just run standard DOT4 fluid in my brakes and clutch. I dont ride hard enough or use the brakes aggressively enough to warrant anything else, plus I change the fluid frequently to keep the system in top shape.

I use the fluid that is called for on the cap of my master cylinder reservoir. I can't claim to know more than the people who designed the system

I generally use what's called for. I have a bottle of Bel-Ray Super DOT 5 I need to put in soon.

Dot 4

I put a synthetic dot4 in mine last time because that is what I had on hand at the shop. thought it was castrol but their site don't show it as synthetic.

Dot 3 and 4 are Glycol based and are hydro attractant; Dot 5 is Silicone based and is NOT compatable with the other types. Mixing Dot 3/4 with Dot 5 can cause catastrophic seal failures/seizures.

The difference between Dot 3 and 4 is the amount of additives used to elevate the boiling point.

Dot 5 Fluid won't hurt your paint, but usually gives a spongier feel, and since it is non-miscable with water, the water gavitates to the lowest points of the sytem and causes corrosion.

Unless your system is specifically designed for Dot 5 and above, using it will garner few benefits.

JMHO

Check that...It's Super DOT 4 I have.

Motul RBF600 is the prime track shit... a little pricey though.

Dot 4 for me.

been using DOT 4 even on the track bike and had no issues. its tough finding the DOT 4 in the auto stores and the dealers charge an arm and a leg for it so I usualy just order a bottle when purchasing other things.

tom

Dot 5.1 is sometimes compatable with Dot 4 systems. Dot 5 is not the same as 5.1 nor do they mix. My HD has Dot 5, and my Aprilia says Dot 5.0 (4.0 compatable) which I think is what they call 5.1 in Europe.

I will have to double check but am 99% sure the futura used dot 4 for the brakes and the clutch.

Tom

Use whats called for w/ the specific brake system you have. if you've got aftermarket parts on your brakes i'd consult them, rather than what the OEM calls for.

I've heard that using High Temp DOT 5 will reduce Spongy feel during intense/frequent braking. have yet to test it, but i've got some in the mail.

If you're getting US Dot 5, be careful about mixing it with even a trace of Dot 4, as it turns to goop. There a whole procedure for switching it over you need to follow.

Dot 5 doesn't absorb moisture, which reduces the boiling point of Dot 4 brake fluids, But your brake system will still collect condensation, and then you get water settling to the lowest point it can get to, and if it gets into the calipers, you still boil it, and it corrodes everything it touches.

Apparently, there have been a lot of expensive cars that had dot 5 put in during restorations, and had the brake systems ruined from condensation.

I'm still unsure about my fluid. My 929 says DOT 4 on the caps, and I have a quart of DOT 4 Castrol Synthetic sitting here on my workbench at work. Is there a DOT 4 that's not synthetic? Will this be OK in my bike? I've never messed with anything other than DOT 3. :( :idk:

I use whatever it says to use.

without looking it up somewhere I don't know the answer, did you look on the container and see if it says not to mix with other DOT4 fluids?

I'll quote it when I get back to work tomorrow, but it never stated that it either could not mix, or could mix with DOT 3/4 fluid. ??? That's what threw me.... :idk:

I mean, my cap says DOT 4, and this fluid is DOT 4 Synthetic. How do I know if mine is synthetic or not and if they will combine if mine isn't. I'm at a loss on this one. Can you even get DOT 4 that's not synthetic?

Here's what I have.

http://www.amazon.com/Castrol-Synthe.../dp/B0002JMAKW

If you read the specs, that's exactly what it says on the bottle. Not one word mentioned about mixing or changing/flushing out the DOT 3 or non-synthetic DOT 4.

Motul 5.1...the suspension guy told me to run it. Didn't notice any difference.