wanaride

~SPONSOR~
Jul 18, 2003
492
0
A riding buddy of mine recommended I flush out the stock brake fluid (DOT3?) and replace with higher quality fluid (DOT4?). He said my braking would be much improved after doing this.

The brakes seem to be working fine, but then again, this is the only dirt bike I have ridden in 10 years, so the brakes could suck and I wouldn't know it (well, within reason of course).

Am I crazy to think about doing this? :think:
 

canyncarvr

~SPONSOR~
Oct 14, 1999
4,005
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Probably not noticeable, agreed.

Still a good idea. It should be changed regularly! Get one'a those neat pressure bleeders (around $45) and change the fluid in brakes, front AND back at least once a year.

Oh do not 'improve' your braking system to DOT5! You'll ruin the whole mess.

DOT 3/4 and 5 do not mix!!
 

Henk

Member
Apr 15, 2000
63
0
DOT5 is a bad idea all round. If you get the itch to go that way don't. DOT 5 is silicon based and will cause all sorts of problems. DOT5.1 is compatible with most brake systems but you probably won't need the higher temp ratings it gives and any advantages are outweighed by the fact that you have to change it much more often as it is hellishly hygroscopic.
 

MikeT

~SPONSOR~
Jan 17, 2001
4,112
11
I had a thread on this about a year ago. I changed my brake fluid that was in my old bike for about six years. No difference when I was done that I could tell. I will say that my fluid change after all those years was a good idea though just to freshen it up though.
 

KSHAFFER

~SPONSOR~
Sep 10, 2001
142
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if you race you should change it often, like once a month. just bleed the brake to get fresh fluid in there. when you use your brakes, they get hot. when it gets to hot it will boil. when it boils it will leave air trapped in the system and air contains water which will contaminate your fluid and make you have to use more of the lever to get the same amount of brake. it's simple maintence.
 

KDXFreestyle

Damn Yankees
Member
Nov 19, 2002
645
0
do you have to have any special toold to bleed the lines besides a wrench to open and close the valve? Could someone please explain how its done Properly without any special tools? Also... How much fluid is needed for the front and rear brakes? Thanks a lot guys!
 

BRYDEN1

Member
Sep 22, 2003
97
0
Dot 4 has a higher dry boiling point than dot 3 but is also is more hygroscopic(ability to asborb moisture). As brake fluid absorbs moisture the boiling point drops and the fluid degrades(turns black and sooty). Dot 4 starts out with a higher boiling point but degrades faster, so if you change your brake fluid every 5 years stick with dot 3. A better idea is to flush the fluid when it starts to darken. Your caliper and master will stay smooth and last longer if the soot never gets a chance to turn into sludge.
On a bike the best way to flush or bleed brakes is to reverse flush. I rigged up a cap with vent line that screws right on top of a bottle of brake fluid. (save the spout caps off of gear oil bottles) Make sure the cap and vent line will not leak or pop off . Fill the line with fluid and pop it onto the caliper bleeder screw. I just lay the bottle of brake fluid on the floor and use my foot to apply pressure. Open the bleeder and let the fluid flow from the caliper up to the master. As the fluid fills the master keep sucking it out and keep flushing until the fluid is totally clear and the air is gone. Its easiest to get all the air out if you flush all the fluid in one step, don't stop and start, keep the fluid moving up at all times. Close the bleeder and your done. Its a lot easier if you can find a bottle that is nice and soft so you don't have to fight the bottle. A CLEAN AND DRY 700ml pop bottle will work in a pinch. BTW never reverse bleed your cars brakes, The ABS will not be happy.
Hope this doesn't sound complicated because it really isn't.
 

chris kuba

Member
May 31, 2003
83
0
I just posted about this last month. Go the the nearest bike shop and buy the smallest bottle of DOT4 brake fluid they have. It takes very very little to fill both front and back. Buy a small syringe (20 to 50cc) at a local pharmacy. Buy the 1/4" clear hose at Sears for 10 cents a foot. Use about 1 foot of the hose on the bleeder nipple and 1 foot on the syringe. Remove the top of the master cylinder. Suck entire brake system clear of old junk through the bleeder. It will be very ugly looking. Discard. Fill the syringe with new fluid, put the hose onto the bleeder nipple and force the fluid in from the bottom. Doing this will allow the air to flow upward in the line making it much easier. If old junk comes up first just suck that out of the master cylinder and continue to fill with new. Once it is full check for feel. I discovered that sometimes the air won't come all the way out even when bleeding the right way. What I did was bleed in the normal fashion, pump handle, hold, release bleeder....continue until OK. If there is still bad pressure put the syringe onto the bleeder and pull some fluid out through the bottom, this will useually draw that last bubble out that is stuck at the end. This is really simple and you'll get it once you get started. Good luck.
 
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