Recommended Brake Fluid MK II Front Brake?

Good thing they call it " fluid " or we'd be into yet another " oil " thread . Speaking only for myself , the question to ask would be ..What is my biggest concern when selecting a brake fluid ? The three factors to consider are water , potential paint damage and loss of braking due to over heating fluid .

Potential paint damage ?? It can happen but why blame the product when it is usually the fault of the operator . Cover up the paint before you start your work .

Over heating the fluid ?? Maybe on a track but regular street riding with a bit of fun added to it will not boil the fluid in my opinion

The water factor ?? The absorption rate in Dot 3 is less than Dot 4 and Dot 4 is less than Dot 5.1

Each of these fluids serve a purpose ............ which one that best suits you is something only you can decide .

Mart UK said:

I was a lad when my dad's brake fluid boiled descending an Alpine pass. We survived because nothing was coming in the opposite direction. I take the view it costs peanuts to replace and less than half an hour. Even dot 5 can suffer. It doesn't absorb the water in the system, but doesn't stop the water getting in.

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If it's not hydroscopic (as Dot 5 is) why would water get in?

robs ss said:

why would water get in?

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You are feeding in fresh air with new water vapor above the rubber gator in the master cylinder chamber every time you operate the brake through the bleed hole. Even sitting in the garage that bleed hole allows some air to circulate. The rubber gator above the fluid in the master cylinder is not completely water proof so over years water will leak in. Its very small amounts but adds up over time.

robs ss said:

If it's not hydroscopic (as Dot 5 is) why would water get in?

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That's right: In the extreme case, leave the fill cap off for a while and Dot 3 etc will "grab" moisture out of the air. Leave cap off if you have Dot 5 silicone in and nothing happens. Reason enough for me to stick with Dot 5.
Jaydee

I think the real reason that Dot 5 is not recommended for anti lock brake systems is because it is just a bit thicker than the Dot 3, 4 and 5.1. The original reason that the military went with Dot 5 was so that they could just have one fluid through their entire vehicle fleet. The Girling brake systems required Dot 4 because Dot 3 would eat the seals. Dot 5 is compatible with all types of rubber seals. (At least all the types the military had at the time.) They probably still only need one type of fluid since all those Girling brake systems have aged out by now. Any way, I use Dot 5 in my Commando and it will stop the front wheel with no problem. No spongy feel at all. Amazing how little maintenance the system requires.

My main wish is that we had some practical thinkers running the DOT. Why was Dot 5.1 not called 4.1 since it is glycol based? Then the whole "5" series could have been reserved for silicone fluids and their subsequent versions.

Article is a few years old but still relevant.

Chuck_Wagon said:

Article is a few years old but still relevant.

Brake Fluid Expose - Geno's Garage

Without a doubt, changing brake fluid is at the absolute bottom of most owners’ lists of “fun things to do with their trucks."

blog.genosgarage.com

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Too funny - I actually know the author, taught a lot of braking and vehicle dynamics courses for the SAE, and was a consultant for StopTech - great guy

Good article - thanks for sharing!!

You can make yourself crazy worrying about differences that make no difference...

Derek Wilson said:

Too funny - I actually know the author, taught a lot of braking and vehicle dynamics courses for the SAE, and was a consultant for StopTech - great guy
Good article - thanks for sharing!!

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I run Dodge cummins trucks and outfits like the Turbo Diesel Register use J. Walker as their go to guy for all matters concerning brakes. He's very knowledgeable and has numerous instructional articles for all types of things regarding brakes.

MexicoMike said:

You can make yourself crazy worrying about differences that make no difference...

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Uhm - isn't that what we do here?? LOL

MexicoMike said:

You can make yourself crazy worrying about differences that make no difference...

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True enough.
However brake fade from heat can be a serious safety issue, most certainly on a MCycle.
For the majority of us, me included, while doodling around town on my ride there isn't really much concern.
But get a little spirited or for the race folks, paying attention to dry/wet boiling points could mean the difference between staying upright or leaving strips of meat on the asphalt

I think the moral of the story is whatever you choose to use, change it regularly. If the system is already bled it's a 10 minute job.

This was mine when I opened it up. The fluid had turned to jelly and was blocking the passages.