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