Brake fluid: Dot 3 vs Dot 5
Moderator: rztom
Brake fluid: Dot 3 vs Dot 5
Replacing 4LO brake lines cause the master cylinder diaphragm melted into the reservoir - a mess created fm 10yrs of sitting idle. A friend was suggested I use dot 5 instead of 3 because 5 repels H2O due to its siclicone base properties - an advantage(?). Research lead me to this Dot 5 comment: "Silicone based fluids are great for museum cars that are never driven, because the fluid is very non-reactive. The moisture that is bound to eventually get into the brake lines will not dissolve in silicone fluid. This water forms pockets that will boil off and become steam as the brake fluid heats up, and as a result it is virtually impossible to keep a silicone based system bled properly as there will always be gas in the lines." I don't plan making my 4LO a museum piece but I won't be racing it either. Are bike brake lines systems that vulnerable to moisture when garage stored; not in my experience. So, stick with Dot 3 or should one moderize to 5 as suggested.
Re: Brake fluid: Dot 3 vs Dot 5
use DOT4 and change it every year/few years. Ive used 3,4 & 5. 4 is best i reckon.
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Re: Brake fluid: Dot 3 vs Dot 5
Yep, DOT 4 and change it every second year.
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Re: Brake fluid: Dot 3 vs Dot 5
the best thing about DOt 5 is that it will not harm the paint if spilled !!
being silicon based
being silicon based
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Re: Brake fluid: Dot 3 vs Dot 5
on board with others, DOT4
Re: Brake fluid: Dot 3 vs Dot 5
I agree with you but others (bare will chime in here soon) will tell you they have found it does, maybe it depends on the paint?two-stroke-brit wrote:the best thing about DOt 5 is that it will not harm the paint if spilled !!
being silicon based
80 XT500 Supermoto!
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82 RD421LC Hybrid
82 RD350LC decapitation project
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Re: Brake fluid: Dot 3 vs Dot 5
The DOT5 just felt odd to me when I tried it years ago. The lever had a spongy feel and I couldn't bleed it out so I went back to 4.
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Re: Brake fluid: Dot 3 vs Dot 5
DOT5 is more compressible than DOT4, the sponginess is normal and why many don't like it. Only vehicle I ever had with DOT5 was an ex-military truck, I imagine they use it to avoid moisture problems on vehicles that may sit around for a long time and need to be ready to go on short notice.waltmil wrote:The DOT5 just felt odd to me when I tried it years ago. The lever had a spongy feel and I couldn't bleed it out so I went back to 4.
Re: Brake fluid: Dot 3 vs Dot 5
That feel is what I didnt like when I used it, otherwise it worked ok... but DOT4 is the one...
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Re: Brake fluid: Dot 3 vs Dot 5
I only use DOT 5 in my bikes.
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Tim Steele in Front Royal, VA
Tim Steele in Front Royal, VA
Re: Brake fluid: Dot 3 vs Dot 5
Asked the same question, on a UK form, and the consences hovered between Dot 4 and 5. Most votes went to Dot 4 - I'm sold. Thx 2 all who responded.
Re: Brake fluid: Dot 3 vs Dot 5
I put DOT5 in my race bike back in the day when I was racing. When it came time to restore my machine, the DOT5 had turned to jelly. Obviously it reacted with something.
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Re: Brake fluid: Dot 3 vs Dot 5
DOT 5 aerates easily and is hydrophobic. I use it in the clutch M/C but avoid it for brakes. I use it there because it never turns that nasty black due to the fact it's an excellent lubricant for seals in the master and slave cylinders. Methanol (DOT 3/4/5.1) based fluids are hard on seals that move more than .040"/1MM or so.
Motul 600 synthetic DOT 4 for brakes has been my go to for awhile. Hygroscopic so it gets swapped out every spring.
Motul 600 synthetic DOT 4 for brakes has been my go to for awhile. Hygroscopic so it gets swapped out every spring.
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Salvador Dali
Salvador Dali
Re: Brake fluid: Dot 3 vs Dot 5
DOT5 reacts with DOT4 (and DOT3 etc) and creates a mess. DOT 3, 4 and 5.1 are compatible. DOT5 is not compatible with anything.heyjoe wrote:I put DOT5 in my race bike back in the day when I was racing. When it came time to restore my machine, the DOT5 had turned to jelly. Obviously it reacted with something.
And being hygroscopic is a good thing as it absorbs gets moisture out of your system when changing the fluid. A problem with non hygroscopic fluids is corrosion and build up of sludge. A common problem with older Citroëns using non hygroscopic LHM-fluid.
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Re: Brake fluid: Dot 3 vs Dot 5
4 sounds like the way to go. My next issue is ceased caliper pistons - they are seated all the way in and there is nothing to grab on to. I was advised heat would be the last option followed by 100 psi to possibly pop them lose or soak everything in tranny oil. Solution: declined using any oil or heat. Found an old stainles steel braided brake line, attached it to @ calipers and blew out each piston with compressed air. It took a few minutes but fixed without an issue.
Last edited by LC Cnd on Thu Jan 08, 2015 4:17 am, edited 1 time in total.