DOT 4 or 5 brake fluid?
Seasoned HDF Member
Joined: Mar 2010
Posts: 38,525
Likes: 6,406
From: Honah Lee
Dot 4 should changed out ever 2 years since it absorbs moisture. Need to be vary careful if you do it with ABS. Suck most from masters but not all. Refill and then bleed being sure to not let master get too low or pump too hard. If you get air in line only a dealer can fire the ABS to bleed it. Dot 5 is fine but I change mine ever 5. Other then losing the purple tint it looks fine. Really like the DOT 5. Harley should be spanked for not designing the ABS for it. I am careful with it anyway but it will not hurt the paint.
I seriously doubt there is any difference in the seals for the calipers and master cylinders for Dot 4 or Dot 5 as long as you start with a dry system. Note I am not talking about the ABS ones. Think the fluid viscosity class enters the picture here. However do not forget Harley calipers are one of the few brake systems that call for a special grease on the piston caliper seal. All other calipers I have worked on since 1969 say to lubricate rubber with brake fluid.
I seriously doubt there is any difference in the seals for the calipers and master cylinders for Dot 4 or Dot 5 as long as you start with a dry system. Note I am not talking about the ABS ones. Think the fluid viscosity class enters the picture here. However do not forget Harley calipers are one of the few brake systems that call for a special grease on the piston caliper seal. All other calipers I have worked on since 1969 say to lubricate rubber with brake fluid.
Last edited by Jackie Paper; Dec 24, 2011 at 03:41 PM.
Seasoned HDF Member
Joined: Nov 2010
Posts: 17,548
Likes: 7,172
From: Oxford, Nc
I don't know why it would make sense to change brake fluid every 5000 miles unless you ride in non-stop downpouring rain. Service life for brake fluid (DOT 4) is 2 years from installation, maybe sooner if you operate in extreme dirt or heat (or if it takes 2 years to go 5000 miles). But, to each his own as always.
If I understand this:
DOT 5 is ideally longer lasting and HD only went to DOT 4 because of the Brembo ABS systems?
Cruiser
Joined: Sep 2007
Posts: 157
Likes: 0
From: Port St. John, FL
Correct. DOT 5 is not compatible with ABS systems. DOT 5 is Silicone and has slightly different physical properties and compressibility, making it unsuitable for ABS systems calibrated to work with DOT 3 or 4 brake fluid.
Club Member
Joined: May 2007
Posts: 145,895
Likes: 821
From: 40 miles Northeast of Indy..
I have an 07 Heritage with 52K+ miles,, been thinking last couple yrs I need to flush the brakes and replace fluid, I even bought some Speed Bleeders, but just haven't used them..
The brakes never gave me any probs or issues and still worked great, but I knew I was past due on flushing the 8 yr old fluid out..
3 days ago I had new tires installed and ask the wrench at Indy shop I am now using How much $$$ to flush both the brakes systems... $15 each for front and rear for labor and $7. for fluid, total of $37.... No brainer for me...
My MC covers say right on them to use Dot 4.
When I picked up the bike he said the Front fluid still looked good and the Back was only a little dirty. I was happy to hear that I didn't have any internal issues because I waited to long to flush the fluids..
I'll add the the bike 99% of the time is in a Climate/temp controlled garage, being I retired in 06 the only time is has ever sit out all day is when I go on my 1 or 2 (7 day) trips a yr. So I am thinking that might have helped with not having a moisture prob in the fluids.
The brakes never gave me any probs or issues and still worked great, but I knew I was past due on flushing the 8 yr old fluid out..
3 days ago I had new tires installed and ask the wrench at Indy shop I am now using How much $$$ to flush both the brakes systems... $15 each for front and rear for labor and $7. for fluid, total of $37.... No brainer for me...
My MC covers say right on them to use Dot 4.
When I picked up the bike he said the Front fluid still looked good and the Back was only a little dirty. I was happy to hear that I didn't have any internal issues because I waited to long to flush the fluids..
I'll add the the bike 99% of the time is in a Climate/temp controlled garage, being I retired in 06 the only time is has ever sit out all day is when I go on my 1 or 2 (7 day) trips a yr. So I am thinking that might have helped with not having a moisture prob in the fluids.
Last edited by oct1949; Oct 10, 2015 at 12:20 PM. Reason: added
Road Master
Joined: Nov 2012
Posts: 1,027
Likes: 69
From: Centerville, ohio
Since ABS became standard equipment on most cars, how many have changed the brake fluid on their cars and trucks in the last 30 years ?
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