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rallye bob · 07-11-2009, 08:07 AM

DOT5 brake fluid is also known as "silicone" brake fluid.

Advantages:

DOT5 doesn't eat paint.
DOT5 does not absorb water and may be useful where water absorption is a problem.
DOT5 is compatible with all rubber formulations. (See more on this under disadvantages, below.)

Disadvantages:

DOT5 does NOT mix with DOT3, DOT4 or DOT5.1. Most reported problems with DOT5 are probably due to some
degree of mixing with other fluid types. The best way to convert to DOT5 is to totally rebuild the hydraulic
system.
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.
Since DOT5 does not absorb water, any moisture in the hydraulic system will "puddle" in one place. This can
cause localized corrosion in the hydraulics.
Careful bleeding is required to get all of the air out of the system. Small bubbles can form in the fluid that will form
large bubbles over time. It may be necessary to do a series of bleeds.
DOT5 is slightly compressible (giving a very slightly soft pedal), and has a lower boiling point than DOT4.
DOT5 is about twice as expensive as DOT4 fluid.

07-11-2009, 08:07 AM	#2
rallye bob Member Join Date: Sep 2006 Location: Genoa, Illinois Posts: 489 Likes: 9 Liked 6 Times in 4 Posts	Re: brake fluid (DOT 5) DOT5 brake fluid is also known as "silicone" brake fluid. Advantages: DOT5 doesn't eat paint. DOT5 does not absorb water and may be useful where water absorption is a problem. DOT5 is compatible with all rubber formulations. (See more on this under disadvantages, below.) Disadvantages: DOT5 does NOT mix with DOT3, DOT4 or DOT5.1. Most reported problems with DOT5 are probably due to some degree of mixing with other fluid types. The best way to convert to DOT5 is to totally rebuild the hydraulic system. 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. Since DOT5 does not absorb water, any moisture in the hydraulic system will "puddle" in one place. This can cause localized corrosion in the hydraulics. Careful bleeding is required to get all of the air out of the system. Small bubbles can form in the fluid that will form large bubbles over time. It may be necessary to do a series of bleeds. DOT5 is slightly compressible (giving a very slightly soft pedal), and has a lower boiling point than DOT4. DOT5 is about twice as expensive as DOT4 fluid.