brake fluid-what and why?

Dnyce · 03-30-2009, 10:18 PM

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.

tached1000rr · 03-30-2009, 10:19 PM

interested in hearing others replies...

JoshuaTree · 03-30-2009, 10:39 PM

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...

azoomm · 03-30-2009, 10:56 PM

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.

BobTheBiker · 03-30-2009, 11:14 PM

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.

bmblebee · 03-31-2009, 09:53 AM

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

marko138 · 03-31-2009, 10:13 AM

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

Yamerhaw · 03-31-2009, 02:02 PM

Dot 4

zed · 03-31-2009, 02:13 PM

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.

OTB · 03-31-2009, 02:54 PM

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

03-30-2009, 10:18 PM	#1
Dnyce flyin high Join Date: Mar 2008 Location: cali Moto: 10speed huffy w/cards in the spokes Posts: 2,318	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. __________________ "Racing Is Life, Everything Before and After is Just Waiting" Steve McQueen

03-30-2009, 10:39 PM	#3
JoshuaTree DILLIGAF? Join Date: Nov 2008 Location: Austin, Texas, USA, Earth, Sol, Western Spiral Arm, Milky Way Moto: 1993 K75SA Posts: 483	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... __________________ "Quis custodiet ipsos custodes?" "Learn to do the counter-intuitive things that may one day save your ass..." "... Love Much, Laugh Often..." - Amanda Kay Corso (January 18, 1980 - April 15, 2008)

03-30-2009, 10:56 PM	#4
azoomm moderator chick Join Date: Feb 2008 Location: Hill Country TX Moto: Pasta Rockets Posts: 8,917	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. __________________ We have enough youth. How about a fountain of "smart"? Come Play at the Track!! http://www.elitetrackdays.com

03-31-2009, 09:53 AM	#6
bmblebee Community Curmudgeon Join Date: Nov 2008 Location: Tallahassee Moto: '04 F4i Posts: 373	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 __________________ Alcohol, Tobacco and Firearms should be a convenience store and not a government agency If You Don't Know What Your Rights are...You Won't Have Any

03-31-2009, 02:02 PM	#8
Yamerhaw Country Boy Join Date: Nov 2008 Location: Hicktown in NC Moto: 07 R1 Posts: 797	Dot 4 __________________ “If trees could scream, would we be so cavalier about cutting them down? We might, if they screamed all the time, for no good reason.” It takes a big man to cry, but it takes a bigger man to laugh at that man.

03-30-2009, 10:19 PM	#2
tached1000rr WERA White Plate Join Date: Dec 2008 Location: NC Moto: 2009 GSXR 1300 Posts: 2,448	interested in hearing others replies...

03-30-2009, 11:14 PM	#5
BobTheBiker too much time on my hands Join Date: Jul 2008 Location: the northern district of god damn Moto: 01 ZX6R, looking for more now. Posts: 1,802	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.

03-31-2009, 02:13 PM	#9
zed yellow don't corner well Join Date: Feb 2009 Location: Kansas City, KS Moto: 06 ZX10R Posts: 1,243	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.

03-31-2009, 02:54 PM	#10
OTB The Man Join Date: Feb 2008 Location: CrabTown USA Moto: 00 Bimota DB4 Posts: 823	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