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DoT 5.1 Brake fluid what specification do you use ?

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McCabe-Thiele (Ted):

--- Quote from: Nurse Julie on August 31, 2020, 01:05:25 PM ---
--- Quote from: Macabethiele on August 31, 2020, 12:52:39 PM ---
--- Quote from: Nurse Julie on August 30, 2020, 09:17:03 PM ---DOT 5 Silicone is what we use in all of ours now Ted.

--- End quote ---

Wow I didn't think anyone would be using Silicone based brake fluid in a motor cycle presumably that is for using in a system that has no remaining Glycol-based fluid such as Dot 4.0.  Are the existing seals suitable or do you have to upgrade for Silicone based fluid? 

I believe Dot 5.1 is a synthetic Glycol-based fluid with slightly higher boiling point than Dot 5.0 but is still hygroscopic whereas Silicone isn't of course.

--- End quote ---
All our bikes have had the complete braking systems overhauled with new seals etc fitted, so no mix or contamination from the old non compatible brake fluid.

--- End quote ---

Looks like I will be using Dot 5.0 in the Honda as it will be either new parts or new seals at the very least.

Piki:

--- Quote from: Nurse Julie on August 31, 2020, 01:05:25 PM ---
--- Quote from: Macabethiele on August 31, 2020, 12:52:39 PM ---
--- Quote from: Nurse Julie on August 30, 2020, 09:17:03 PM ---DOT 5 Silicone is what we use in all of ours now Ted.

--- End quote ---

Wow I didn't think anyone would be using Silicone based brake fluid in a motor cycle presumably that is for using in a system that has no remaining Glycol-based fluid such as Dot 4.0.  Are the existing seals suitable or do you have to upgrade for Silicone based fluid? 

I believe Dot 5.1 is a synthetic Glycol-based fluid with slightly higher boiling point than Dot 5.0 but is still hygroscopic whereas Silicone isn't of course.

--- End quote ---
All our bikes have had the complete braking systems overhauled with new seals etc fitted, so no mix or contamination from the old non compatible brake fluid.

--- End quote ---
A few months ago I changed my brake fluid to 5.0(base silicone) I actually just did a drain of the old liquid and changed the brake fluid pump mechanism...... did something wrong? Should the brake liquid pipes have changed, too?

florence:
DOT4 works perfectly well.  I think I have also used DOT3

McCabe-Thiele (Ted):

--- Quote from: florence on September 01, 2020, 10:12:30 AM ---DOT4 works perfectly well.  I think I have also used DOT3

--- End quote ---

I agree the older specification brake fluids all work okay but if you want to avoid the build up of water in the fluid caused by hygroscopic action imho the best options are later fluids unless of course you religiously change your brake fluid on an annual basis.

The amount of water absorbed by most brake fluids depends on many factors including atmospheric moisture content of the ambient air, unused new fluid storage, winter bike storage conditions & heavy braking causing fluctuations in fluid temperatures. I am minded to agree with NJ that Silicon based 5.0 is the best option especially for classic bikes that do not always get a lot of all year round use as it is not hygroscopic.

K2-K6:
"I agree the older specification brake fluids all work okay but if you want to avoid the build up of water in the fluid caused by hygroscopic action imho the best options are later fluids unless of course you religiously change your brake fluid on an annual basis."

My understanding of this topic is that the fluid (silicone) isn't subject to water ingress but the brake system still is.

Dot4 etc as described,  will ultimately contain distributed water which is the reasoning for periodic change to purge and restore it's manufactured boiling point,  plus sensitivity of some complex systems to internal corrosion.

Silicone based systems ultimately collect any water accumulation at the lowest point as the oil is lighter in sg,  so should still be routinely purged to avoid lowered boiling point conditions at the calipers.

With the above consideration,  it seems strange to bleed systems by pushing fluid in from caliper end as some advice given out on the great wide web. Can't immediately see why you do that.

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