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Brake Fluid

Posted: Sat Nov 07, 2009 12:02 pm
by pretzladay
Read owner posting elsewhere that he had replaced brake fluid with DOT5 and had eliminated that annual chore. Good idea, or bad? Also, anybody have experience with Speed Bleeders? Good investment?

Re: Brake Fluid

Posted: Sat Nov 07, 2009 5:06 pm
by The Meromorph
Speed Bleeders are excellent.

Using DOT5 fluid is a very bad idea...
First DOT5 and DOT4 should never be mixed, to the point where you have clean out the old DOT4 to the extent that there isn't any left. The crud they produce when mixed is nasty.
Second DOT5 is not hygroscopic, so the water in the atmosphere doesnt get absorbed into the brake fluid, but neither does it mix with the brake fluid. So the lesser amount of water that does get into the brake system, falls to the lowest point (that's your calipers!). Plain water boils at normal brake caliper temperatures, so when you do get a little water in there, you are likely to lose all braking suddenly! Far from avoiding the chore of bleeding the brakes, you should bleed them (a little) to get just the (little bit of) water out very frequently! (Every day would not be too often.) Or risk having no brakes when you need them...

Re: Brake Fluid

Posted: Sat Nov 07, 2009 10:04 pm
by pretzladay
Meromorph,
Thanks for the info, on both counts. Just bought an 04 R with 1800 miles, and I don't think the brake fluid has ever been changed, let alone bled. I'm 2.5 hours from the nearest BMW dealer, so you've been a big help. Thanks again

Re: Brake Fluid

Posted: Mon Nov 09, 2009 12:56 am
by The Meromorph
With the DOT4 fluid (which you should continue to use), most times, bleeding the brakes exactly equals changing the brake fluid, because you bleed until only clean clear new fluid is coming out.
Occasionally (for example if you fail to tighten the bleed screw [DAMHIK :badgrin: ] ) you'll need to bleed only enough to get the little bit of air out.

Speed Bleeders work much better... :)

Re: Brake Fluid

Posted: Tue Feb 23, 2010 9:11 pm
by OU812
So what is the difference between 3 and 4?
Just asking and thanks for your posts!
Steve

Re: Brake Fluid

Posted: Thu Feb 25, 2010 10:13 pm
by The Meromorph
OU812 wrote:So what is the difference between 3 and 4?
Just asking and thanks for your posts!
Steve
DOT 4 is a significantly better formulation of the same basic technology.
You could use DOT 3 in an emergency, but it would get contaminated faster, and be more susceptible to boiling when it does. If I had to use DOT 3, I'd replace it with DOT 4 within 6 months. (Actually I'd replace it as soon as I could :) )

Re: Brake Fluid

Posted: Thu Feb 25, 2010 10:21 pm
by OU812
So I can flush DOT 3 out with 4?

Re: Brake Fluid

Posted: Sun Feb 28, 2010 2:51 pm
by The Meromorph
Yes.

Re: Brake Fluid

Posted: Wed Apr 28, 2010 12:29 am
by OU812
Thanks for the info! Used DOT 4 on my 98' DR350 Off Road.
Image

Re: Brake Fluid

Posted: Thu Aug 12, 2010 6:01 am
by omg1010
DOT 4 and DOT 5 are not compatible. However DOT 4 and DOT 5.1 are. It is really confusing but the development was DOT 3 -> DOT 4 -> DOT 5.1. DOT 5 is a totally different stuff as this one is based on silicone and it is not compatible with the other DOTs because of the seals used in every brake system.

Best regards
Oliver

Re: Brake Fluid

Posted: Sat Feb 26, 2011 2:55 pm
by OU812
Sounds like a computer update. :lol:

Re: Brake Fluid

Posted: Thu Mar 29, 2012 2:29 am
by cburgess594
If I haven't get into this thread. I have no idea about the break fluids "3 and 4." And there differences? Whew!! Made it here simply!

Re: Brake Fluid

Posted: Tue Aug 14, 2012 12:27 pm
by def
Not to confuse the issue but some later model motorcycles use mineral oil for the hydraulic clutch systems....don't mix it up...know what grade fluid goes where on your motorcycle, auto, tractor or whatever.

Re: Brake Fluid

Posted: Wed Aug 15, 2012 1:30 am
by omg1010
Yep, the 1200 BMW models for example. If you use brake fluid to fill up the clutch circuit you'll ruin the entire circuit (seals).

Brgds
Oliver

Re: Brake Fluid

Posted: Sun Aug 26, 2012 7:36 pm
by def
OU812 wrote:So what is the difference between 3 and 4?
Boiling point.

Re: Brake Fluid

Posted: Sun Aug 26, 2012 7:43 pm
by def
The Meromorph wrote: Far from avoiding the chore of bleeding the brakes, you should bleed them (a little) to get just the (little bit of) water out very frequently! (Every day would not be too often.) Or risk having no brakes when you need them...
Bleeding your brakes every day or more frequently than recommended is unnecessary and unwarranted.

Inspecting your brake equipment every time you take tire pressure readings (Not TPMs which IMO are useless) with a tire gauge is a good idea so you can monitor brake pads, brake calipers, brake dust, condition of wheels and tire tread depth.