dot 5 brake fluid
Road Warrior
Joined: Dec 2008
Posts: 1,476
Likes: 23
From: Summit, Mississippi
Yep...it would be best to put in what came out, but I don't always play by those rules. If I do a major brake repair like new lines.....I swap over to 4. Arguments abound concerning the pros-n-cons of DOT 5 vs. the glycol based (3, 4 and 5.1) fluids and each one has it's advantages and disadvantages. You can go "read-up" on the internet and discover for yourself the differences. The biggest advantage people usually like is that the DOT 5 won't harm the painted surfaces, but if I spill anything on my paint...be it 5, 4, oil, transmission fluid or beer...I am going to clean it up right away anyhow. 4 is much cheaper and much, much easier to find.
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Cruiser
Joined: Sep 2009
Posts: 189
Likes: 7
From: Wantagh, ny
Yep...it would be best to put in what came out, but I don't always play by those rules. If I do a major brake repair like new lines.....I swap over to 4. Arguments abound concerning the pros-n-cons of DOT 5 vs. the glycol based (3, 4 and 5.1) fluids and each one has it's advantages and disadvantages. You can go "read-up" on the internet and discover for yourself the differences. The biggest advantage people usually like is that the DOT 5 won't harm the painted surfaces, but if I spill anything on my paint...be it 5, 4, oil, transmission fluid or beer...I am going to clean it up right away anyhow. 4 is much cheaper and much, much easier to find.
the only real answer i could come up with is that dot 3, 4 and 5.1 are glycol based and dot 5 is silicone based. lol
i know not to mix glycol with silicone, i would purge the lines and put all new fresh. just cant get a handle on which is better.
i guess i'll just stick with what willie g put in at the factory.
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Cruiser
Joined: Sep 2009
Posts: 189
Likes: 7
From: Wantagh, ny
yep, thats one of the things that is confusing.
after a quick scan of other threads( both here and on other hd forums) ,
i aint the only one confused! seems h-d is too.
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Elite HDF Member
Joined: Jul 2005
Posts: 3,968
Likes: 34
From: Lockport Township, IL
Dot 5 doesn't destroy the paint if you spill some. All the others do. I THINK - BUT AM NOT SURE - Dot 5 also does not absorb water like the others. DO NOT MIX DOT 5 with any others. They do not get along well.
Last edited by rh8234; May 26, 2010 at 05:19 PM.
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Road Warrior
Joined: Dec 2008
Posts: 1,476
Likes: 23
From: Summit, Mississippi
Guys...I swear that I am not trying to argue one way or another, because either works just fine. Harley has switched back-n-forth and I think you HAVE to use DOT5 in the ABS brakes (not sure).
I have done a good bit of research and I prefer the DOT4 because it is easy to find and is not nearly as expensive as the DOT5. The difference in the money doesn't matter a great deal as brake fluid is something you don't change every day. I have cut a rear brake line out in the middle of nowhere and not a drop of 5 could be had at any auto parts store.....3 and 4 are everywhere.
DOT5 does not absorb moisture, but the moisture will still enter the system, find a place to puddle-up and cause corrosion. It is recommened to change DOT5 on a more regular schedule than any of the glycol based fluids....like annually. DOT5 is suppose to be paint friendly, but you'd wipe anything off your bike that got on there anyway, so that does not matter a lot to me either...just for that advantage. DOT5 does have a higher boiling point....but ask yourself...do you race this thing or ride it for pleasure. DOT5 is also more compressable than DOT4, but that does not matter most of the time. For lots of reasons...DOT5 is not necessarily a superior fluid.
DOT 3, 4 and 5.1 are glycol based and will mix with each other (although I would only use the 4). The 5.1 is just a glycol replacement for the higher boiling point of the DOT5.
I routinely replace 5 with 4....but DON'T MIX the two. You can bleed a couple of bottles of 4 through the system and then run the 4....IF you want to.
I have done a good bit of research and I prefer the DOT4 because it is easy to find and is not nearly as expensive as the DOT5. The difference in the money doesn't matter a great deal as brake fluid is something you don't change every day. I have cut a rear brake line out in the middle of nowhere and not a drop of 5 could be had at any auto parts store.....3 and 4 are everywhere.
DOT5 does not absorb moisture, but the moisture will still enter the system, find a place to puddle-up and cause corrosion. It is recommened to change DOT5 on a more regular schedule than any of the glycol based fluids....like annually. DOT5 is suppose to be paint friendly, but you'd wipe anything off your bike that got on there anyway, so that does not matter a lot to me either...just for that advantage. DOT5 does have a higher boiling point....but ask yourself...do you race this thing or ride it for pleasure. DOT5 is also more compressable than DOT4, but that does not matter most of the time. For lots of reasons...DOT5 is not necessarily a superior fluid.
DOT 3, 4 and 5.1 are glycol based and will mix with each other (although I would only use the 4). The 5.1 is just a glycol replacement for the higher boiling point of the DOT5.
I routinely replace 5 with 4....but DON'T MIX the two. You can bleed a couple of bottles of 4 through the system and then run the 4....IF you want to.