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As there have been a lot of questions recently about brake fluids I thought I would add my tuppence worth. Brake fluid is a long chain alcohol. the alcohol group gives it its "hydrophilic-water loving" property which allows it to absorb the small amounts of moisture which get into the system. This prevents "settleing out" of moisture leading to corrossion and, if there were water in the brake calipers vaporization whilst breaking leading to failure. No mater how well "sealed" the system is, small amounts of moisture and contaminents get into the system over time.

the "hydrolypic" "fat-loving" part of the molecule gives it the oily properties and stability with the normal heat from braking.

Over time a couple of things happen. moisture and contaminents get into the system . Also, the heat from NORMAL braking (okay normal for a wing is combined driver/passenger wieght of 500+ lbs and then all those du-dads and trailers we all have) causes the fluid to break down. Extreme braking, or dragging brakes can cause the fluid to scorch and burn hastening this process. Haven't you noticed that the original CLEAR fluid yellows and darkens over time.

The most over-looked fluid on your bike is the brake fluid. I change mine on about an annual basis (depending on my riding).
 

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Well said. Most of us don't bother changing or checking the fluid until it's time to change the pads.
 

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I forgot to add... the alcohol part of the fluid is NOTHING AT ALL like my favorite single malt scotch... don't try to drink it!
 

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hi all,that answers my posting today in(technical forum),before i even read this:grinner:.bri.
 

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rcmatt007 wrote:
I forgot to add... the alcohol part of the fluid is NOTHING AT ALL like my favorite single malt scotch... don't try to drink it!
Oh sure,,,,,, now you tell me!!!:shock::shock::shock::doh::doh::doh:
 

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I never knew brake fluid had alcohol. How come it doesn't just evaporate off?
 

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It's in a sealed system.
 

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englishted wrote:
I never knew brake fluid had alcohol. How come it doesn't just evaporate off?

an "alcohol" is simply an oxygen-hydrogen "OH" group added to a chain of carbons "C". hence: C-OH is methanol (makes you blind), C-C-OH is ethanol (my favorite is single malt), C-C-C-OH is porpanol, HO-C-C-OH is ethelyene glycol (antifreeze).



brake fluid is Several carbons (not sure how many) with and OH group eg. the longer the chain the more it acts like an oil and the less volatile

C-C-C-C-C-C-C-C-C-OH

hence the "oily" property and the water absorption
 

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This was sent to me by my BMW engineer friend



"Water absorption and corrosion"


"The bigproblem with DOT 3-4 fluids always cited by silicone fluid advocates is water absorption. DOT 3 or 4 glycol based fluids, just like ethylene glycol antifreezes, are readily miscible with water. Long term brake system water content tends to reach a maximum of about 3%, which is readily handled by the corrosion inhibitors in the brake fluid formulation. Since the inhibitors are gradually depleted as they do their job, glycol brake fluid, just like anti-freeze, needs to be changed periodically. Follow BMW's recommendations. DOT 5 fluids, not being water miscible, must rely on the silicone (with some corrosion inhibitors) as a barrier film to control corrosion. Water is not absorbed by silicone as in the case of DOT 3-4 fluids, and will remain as a separate globule sinking to the lowest point in the brake system, since it is more dense"

Twisty
 

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absolutly (sp?) silicone fluid do not absrob water and it settles out, whilst dot3/4 fluids do. If you could make sure NO moisture gets into the system dot 5 would work.



did you ever notice that contaminted fluids looK

like like a 14 YO OBAN.... HMMMMMM:tongue:
 
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