dot 4 or 5, need quick answer!
Road Warrior
Joined: Dec 2006
Posts: 1,716
Likes: 8
From: General Sherman's Christmas Location 1864
It took me about an hour with beer breaks
Thread Starter
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Cruiser
Joined: Sep 2012
Posts: 129
Likes: 1
From: Florissant
Doing the paint test now on a cabinet shelf, spoonful from a bottle of dot3, spoonful from the front and one from the rear. The front must have been changed with the bar change as it was a lot clearer than the rear but for the most part they both seemed more clear than any tint of purple or any other color. If all 3 samples react the same I will flush with new dot4, pretty old cabinet and paint, shouldn't take long to bubble paint. New question, any brand of fluid better or all the same? Whatever is on sale?
And thanks as always for rehashing an old topic. Always learning.
And thanks as always for rehashing an old topic. Always learning.
Grand HDF Member
Joined: Oct 2004
Posts: 3,829
Likes: 491
From: Northern WV
I buy Castrol, Valvoline or whatever name brand is cheapest and change it every other year. Usually with a tire change when the calipers are off anyway so I can push the pistons back in to get as much as the old as possible.
Extreme HDF Member
Joined: Apr 2006
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From: Roswell, GA
Carl
Seasoned HDF Member
Joined: Nov 2009
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From: Farmington ,MS
New DOT 5 is purple...but in less than a year it changes to a nice amber shade.
Seasoned HDF Member
Joined: Apr 2012
Posts: 9,975
Likes: 5,214
From: Michigan
FYI-Posted without comment.
DOT 5
DOT 5 brake fluid is also known as "silicone" brake fluid. It was designed for the US Army, who has requested permission to stop using it.
Advantages:
It does not eat paint or skin.
It does not absorb water (BUT!!! See more on this under disadvantages, below.)
It has a higher boiling point than DOT 3 and DOT 4.
It is compatible with all rubber formulations.
It is a good choice for Concours cars which are rarely driven and/or never driven hard.
Disadvantages:
It does NOT mix with DOT3 or DOT 4 or DOT 5.1. Most reported problems with DOT 5 are probably due to some degree of mixing with other fluid types. A residue of the former non-compatible fluid is sufficient to cause serious issues. The best way to convert to DOT 5 is to totally rebuild the hydraulic system. Additionally, the same advice applies if switching from Dot 5 to any of the other fluids.
Since DOT 5 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. It is hard to you without introducing bubbles and thus results in soft pedal feel. These small bubbles will form large bubbles over time. It may be necessary to do a series of bleeds.
DOT 5 is less compressible (often creating a slightly softer pedal). It is not recommended for racing application.
It is hard to pour without introducing bubbles and thus results in soft pedal feel,
It is not recommended by the brake manufacturer, especially for ABS brakes.
It is about twice as expensive as DOT 4 fluid. So silicone fluid aerates easily. Harley-Davison, one of the sole current OEM users of silicone fluid, warns buyers to let the fluid sit at least an hour before using it. If shaken on the way home, it will aerate enough to look like a freshly poured soft drink. Silicone fluid is also slightly more compressible than glycol fluid, does not change color to tip the user to its moisture content, and worst of all, neither accepts or disperses moisture, making systems using it more corrosion prone, and requiring much more frequent fluid changes. Silicone brake fluid also lacks glycol fluid's naturally occurring lubricity, making it incompatible with the mechanical valving in some anti-lock braking systems.
DOT 5
DOT 5 brake fluid is also known as "silicone" brake fluid. It was designed for the US Army, who has requested permission to stop using it.
Advantages:
It does not eat paint or skin.
It does not absorb water (BUT!!! See more on this under disadvantages, below.)
It has a higher boiling point than DOT 3 and DOT 4.
It is compatible with all rubber formulations.
It is a good choice for Concours cars which are rarely driven and/or never driven hard.
Disadvantages:
It does NOT mix with DOT3 or DOT 4 or DOT 5.1. Most reported problems with DOT 5 are probably due to some degree of mixing with other fluid types. A residue of the former non-compatible fluid is sufficient to cause serious issues. The best way to convert to DOT 5 is to totally rebuild the hydraulic system. Additionally, the same advice applies if switching from Dot 5 to any of the other fluids.
Since DOT 5 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. It is hard to you without introducing bubbles and thus results in soft pedal feel. These small bubbles will form large bubbles over time. It may be necessary to do a series of bleeds.
DOT 5 is less compressible (often creating a slightly softer pedal). It is not recommended for racing application.
It is hard to pour without introducing bubbles and thus results in soft pedal feel,
It is not recommended by the brake manufacturer, especially for ABS brakes.
It is about twice as expensive as DOT 4 fluid. So silicone fluid aerates easily. Harley-Davison, one of the sole current OEM users of silicone fluid, warns buyers to let the fluid sit at least an hour before using it. If shaken on the way home, it will aerate enough to look like a freshly poured soft drink. Silicone fluid is also slightly more compressible than glycol fluid, does not change color to tip the user to its moisture content, and worst of all, neither accepts or disperses moisture, making systems using it more corrosion prone, and requiring much more frequent fluid changes. Silicone brake fluid also lacks glycol fluid's naturally occurring lubricity, making it incompatible with the mechanical valving in some anti-lock braking systems.
Thread Starter
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Cruiser
Joined: Sep 2012
Posts: 129
Likes: 1
From: Florissant
Well good news bad news. Tried the paint test and didn't really see anything goin on. Tried the water test. First put a spoonful of known dot3 in a can of water, dropped straight down and dispersed. Ok good. Took a spoonful from the front reservoir and it dropped a bit and then bubbled back up. Ok weird. So tried the rear and it did the same as the 'control' fluid, it dispersed. Ok really weird. So in conclusion I believe the PO had the handlebars dealer installed and they replaced fluid with dot5 and obviously the rear still has dot4. Great. So replace both with dot5 then since the front already has it? Better to go from 4 to 5 than 5 to 4? It for sure doesn't have ABS so 5 should be ok? I really only commute to work with some short weekend runs. Don't really run hard.
OR should I replace the front with 5 and keep 4 in the rear? Not broke just not right.
OR should I replace the front with 5 and keep 4 in the rear? Not broke just not right.
Last edited by eberg; Feb 24, 2013 at 08:35 PM.
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Road Warrior
Joined: Nov 2008
Posts: 1,296
Likes: 3
From: Cheltenham, UK
Good info and in general I agree with it, apart from this statement which is not correct and a dangerous generalisation, especially where the seals have already been exposed to other formulations of brake fluid
Road Warrior
Joined: Nov 2008
Posts: 1,296
Likes: 3
From: Cheltenham, UK
Well good news bad news. Tried the paint test and didn't really see anything goin on. Tried the water test. First put a spoonful of known dot3 in a can of water, dropped straight down and dispersed. Ok good. Took a spoonful from the front reservoir and it dropped a bit and then bubbled back up. Ok weird. So tried the rear and it did the same as the 'control' fluid, it dispersed. Ok really weird. So in conclusion I believe the PO had the handlebars dealer installed and they replaced fluid with dot5 and obviously the rear still has dot4. Great. So replace both with dot5 then since the front already has it? Better to go from 4 to 5 than 5 to 4? It for sure doesn't have ABS so 5 should be ok? I really only commute to work with some short weekend runs. Don't really run hard.
OR should I replace the front with 5 and keep 4 in the rear? Not broke just not right.
OR should I replace the front with 5 and keep 4 in the rear? Not broke just not right.
Beyond that, in my opinion I would
1. Return the bike to factory standard, although this could cost more and be a hassle
2. Failing that, stick with it as is
If you choose option 1, commit do doing a thorough job, replacing seals throughout and doing a proper flush. Personally I would replace all hoses as well (chance to upgrade to smart stainless braided...)
If you don't want to go this route, stick with what is working in there now. A "half job" is by far least preferred