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Discussion Starter · #1 ·


Whats the difference between 'Silicone' based DOT 5 brake fluid and 'non-silicone' DOT 5.1 fluid? except for the ovious!
Is it moisture 'absorbency'?

And if I flush out my system and put in 'non-silicone' will it do any damage to the seals etc?
 

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When I had my stainless cables installed, I noted that , when bleeding the brakes, some spilled out. He indicated the synthetic would not ruin paint like the "normal" brake fluid. He also said that if I used non synthetic it would cause LOTS of problems. Not sure, though, if he meant accidentally mixing them, versus totally flushing, as you asked.

Curious, why would you want to change?

greg
 

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Discussion Starter · #3 ·
gbenner said:

Curious, why would you want to change?
greg


I'll be changing the Bars to chubbies and putting on Braided lines. Also, I.ve got 'Harrison Billet' calipers on the front, real easy to change pads and I'll be putting one on the back too.
Just not rich enuff to do it all at the same time! :rolleyes:

The stealers is the only place I can find silicone DOT 5 over here, and they charge a small fortune for it!!!
I can get 'Non-silicone' DOT 5.1 for about a quarter of the price at most car accessory stores!!! :mad:

AND I'm curious ................. :D
 

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harleyhog, this is what I found after some quick research :

1. DOT 5 : Made in the USA-used exclusively by the US Military and specified as standard by Harley Davidson. Non-toxic and long-life, silicone fluid is safer and more user-friendly than glycol. It never needs changing, will not catch fire easily and does not damage paintwork; neither will it boil below 260°C (500°F), even after 5 years. Non-hygroscopic (i.e. will not pick up moisture, thus reducing corrosion), silicone fluid retains a virtually stable viscosity through most temperature extremes.

2. Because of this, DOT5 often marketed as a premium "lifetime" brake fluid. It is often used to preserve brake systems in antique vehicles and those that sit for long periods of time between use.

3. DOT5 silicone brake fluid is also very expensive (costing four to five times as much as ordinary brake fluid), and it won't mix with glyco- based brake fluid (creating concern over sludging if all old fluid isn't removed when a system is refilled with silicone).

4. DOT5 does NOT mix with DOT3 or DOT4. They also maintain that all reported problems with DOT5 are probably due to some degree of mixing with other fluid types. The proper way to convert to DOT5 is to totally rebuild the hydraulic system.

5. Reports of DOT5 causing premature failure of rubber brake parts were more common with early DOT5 formulations. This is thought to be due to improper addition of swelling agents and has been fixed in recent formulations.

6.DOT5 is compatible with all rubber formulations.

7. 2 applications not to use DOT5 are race cars and antilock brake systems.

JMS
 

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Leave the 5 in and DO NOT mix with 5.1 - they are incompatible. The 5 doesn't absorb moisture and is easy on the paint. For more info go to this link and scroll down a couple of questions.
 

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Discussion Starter · #6 ·


Thanks JMS & Maj.
I think that link has answered the question nicely.

DOT 3, DOT 4 and DOT 5.1 brake fluids are glycol based compounds that are compatible with one another. DOT 5 brake fluid is silicone based and should never be mixed with DOT 3, DOT 4 or DOT5.1. DOT 3, DOT 4 and DOT 5.1 fluids may damage painted surfaces and DOT 3 and DOT 4 have lower boiling temperatures than DOT 5 (DOT 5.1 has the same boiling point as DOT 5). Furthermore, DOT 3, DOT 4 and DOT 5.1 fluids are "hygroscopic", which means they absorb moisture from the air. This causes the fluid to turn dark, indicating that it is time for the brake fluid to be replaced. DOT 5 fluid will not damage paint, has a boiling temperature in excess of 500ƒ F, and is not hygroscopic.
 
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