Soft Front Break Pull

[bagman1]

It is the Dot 5 fluid. When dot 5 heats up it aerates and the pedal or lever will get soft. Do a goggle about brake fluids, thats why they dont use dot 5 in ABS because the heat of compression and rapid cycling it get hot and will cause fade.

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[Maguyver]

on the bottle its says DOT 5 goes up to 525 degrees

[bagman1]

But it doesn't necessarily have to heat up to do this either, it is the make up of the fluid. The rubber orings and seals in a dot 3 system is not compatible with dot 5 fluid, you maybe bypassing fluid thru the seals internally. It sound like your problem might be this as you stated after a while it goes soft. Im sorry I cant explain more now Im out the door to work.

[Maguyver]

thanks bagman, do you think this is irreversible, like if i flush out the system and replace it with DOT 3 or 4 would it fix the problem you think?

[bagman1]

I did a google search and I copied an excerpt from the posting. Pay particular attention to the last paragraph.

According to knowledgeable road racers, the stock fluid works fine with the stock pads, as the pads will cook before the fluid will boil. However, the use of aftermarket pads should be accompanied by a fluid change. The most recommended fluid seems to be Motul RBF 600 fluid. However, examine the notes below carefully, paying special attention to the comments for Ford Heavy Duty fluid.

The importance of moisture: The amount of moisture in brake fluid definitely affects its performance. The big problem is that brake fluid absorbs moisture quickly. SAE field tests have shown that the average one year old car has 2% moisture in the fluid. A random test of vehicles in the U.S. showed an average water content of 2.6% for vehicles with an average age of 8 years. And 25% of these vehicles had water content greater than 4%.

As water content in brake fluid increases over time, the boiling point decreases. Fluid with a reduced boiling point (or high water content) can create vapor by boiling in the caliper, or wheel cylinder. The result is sudden brake failure. And water in the brake fluid can contribute to corrosion of parts such as steel pistons and ABS modulators.

The end result is even though DOT 3 fluid is "rated" at greater than 401F, in the typical 3 to 4 year old car with 3 to 4% moisture content, it could boil under 300F.

Bottom line: Flush any brake fluid every year or so. If you go with a fluid which attracts moisture quicker, change it more often than that.

DOT 3 and DOT 4 are polyglycol-based fluids and can be mixed with each other. DOT 5.1 can also be mixed with DOT 3 and DOT 4, even though it is based on a different chemical and has about half the viscosity. If DOT 5.1 is specified for an ABS system, do not add or use any other fluid type. DOT 5 is silicone-based (not less than 70% by weight of a diorgano polysiloxane) and must not be mixed with or contaminated by DOT 3, DOT 4, or DOT 5.1.

[bagman1]

I couldnt find any info on the effects of mixed fluids on the internal parts, but here is some more interesting information. Again I highlighted paragraph 6 for you.
My personal recommendation is dont compromise your brakes. This is the thin line between life and death. If it were me I would flush the system and reseal the componants, that way I know it is right from the start. Good luck to you.

Fluid Dynamics
Paying Attention to Brake Fluid

0509Sc Fluid 01 Z

Automotive braking is, as we all know, a really important factor in performance car building. The forward thinkers pay an equal amount of attention to stopping as they do to making their vehicles go fast. But, here's a fact that not too many realize: when you step on the brakes, you command a stopping force that's 10 times as powerful as the force that puts the car in motion. Hard to believe isn't it? No wonder the performance brake market has been vying for and finally receiving our attention. But now that they've educated us in the importance of quality components, it's now time to pay attention to the fluid that activates and allows these awesome components to work.

It only makes sense that after you've spent big bucks and a lot of time upgrading your vehicle, the completion of your job must go beyond adding just any old fluid into the system. It's extremely important to always use a high quality fluid. Let's face it, that quart of Elmo's Wonder Brake Fluid and Windshield Washer Solvent combo you picked up at the swap meet may end up as the only thing between the ball of your foot and a brick wall. So, let's at least pay a fraction of the attention spent on choosing components on choosing brake fluid. The following information should help you better understand the differences between various types of fluids.

FLUID REQUIREMENTS
Brake fluid must function through heat, cold, and all the variations of temperatures affecting all brake systems. In other words, brake fluid must be and must remain viscous (fluid) and resistant to severe conditions. It must also absorb water without having an affinity for doing so. Brake fluid must be pure and contain no contaminants, which will have a harmful effect on rubber components. It also should serve as a lubricant for the moving parts in a brake system and be able to withstand time and service--in other words, its boiling point and chemical properties must remain stable. One more important factor is that brake fluid should cause an electrolytic action that will decompose or degrade metal brake parts.

0509Sc Fluid 02 Z

FLUID CLASSIFICATIONS
These factors are taken into consideration by the Department of Transportation, National Highway Safety Administration in Federal Motor Vehicle Safety Standard 116. FMVSS116-classified fluids fall into three categories: DOT 3, DOT 4, and DOT 5. DOT 3 meets the minimum specifications, while DOT 4 and 5 meet more stringent requirements. The purpose of these requirements is "to reduce failures in the hydraulic brake systems of motor vehicles which may occur because of the manufacture or use of improper or contaminated brake fluid." In addition to setting the minimum wet and dry boiling points for all brake fluids, Federal Standard 116 deals with fluid viscosity, temperature and chemical stability, corrosiveness, water tolerance, compatibility (between formulations), and effects on brake system components.

OK, WHAT'S THE DIFFERENCE?
It seems logical that if DOT 3 is good enough then DOT 4 must be better. And, if DOT 4 is better, then DOT 5 must be better still. OK then, why? It all boils down to boiling point. When brake fluid begins to boil (from the heat that's generated in the system during braking) it forms gas bubbles. As these bubbles collect and grow, they form pockets of gas in the system. And since gas is much easier to compress than fluid, these pockets cause the pedal to easily compress or go soft. This is what as known as a spongy pedal--a condition that causes the heart to race.

BOILING POINTS
The following chart shows the aforementioned FMVSS116 minimum boiling points. These boiling points are the biggest difference in the fluid classifications. You'll notice there are two points for each classification of fluid. The dry boiling point is for fresh fluid that has not yet absorbed moisture. The wet boiling point is for fluid that has been in use (or in an opened container) long enough for it to absorb moisture from the atmosphere.

0509Sc Fluid 03 Z

CONNECTING THE "DOT"(S)
The different DOT spec fluids have chemical or formulation differences, as well as boiling point differences. There are (at this point) three commercial formulations for brake fluids; two are glycol-based and the third is silicone-based. DOT 3 brake fluids are a mixture of polyalkylene glycol ether and other glycols (all start life as ethylene glycol--antifreeze); DOT 4 fluids add borate esters to raise the boiling point. DOT 5 is silicone oil based with additives.

SILICONE BASE BRAKE FLUID (SBBF)
The U.S. DOT defines silicone brake fluid as that which consists of no less than 70 percent of adiorgano polysiloxane by weight. Silicone-based fluids are regarded as DOT 5 fluids. They are highly compressible and can give the driver the feeling of a spongy pedal. The higher the brake system temperature, the more the compressibility of the fluid--increasing the feeling of a spongy pedal. Silicone-based fluids are non-hydroscopic, meaning that they will not absorb or mix with water. When water is present in the brake system, it will create a water/fluid/water/fluid situation. Because water boils at approximately 212 degrees F, the ability of the brake system to operate correctly decreases, and the steam created from boiling water adds air to the system. It is important to remember that water may be present in any brake system. Therefore, silicone brake fluid lacks the ability to deal with moisture and will dramatically decrease a brake systems performance. Silicone brake fluid has a number of strengths and drawbacks.

Strengths:
1) It has a high boiling point since it does not absorb water. Therefore, there's no so-called wet boiling point.

2) Doesn't absorb moisture.

3) Doesn't remove paint.

4) The viscosity is more stable over the extremes of temperature.

5) With the exception of some formulations used in external boots, silicone brake fluid is compatible with all standard brake components.

Drawbacks:1) It's hard to pour without entraining air bubbles--hence an application will generally have a softer, spongier pedal feel.

2) It doesn't absorb water, so any water already in the system accu-mulates in the lowest point of the system and stays there, causing rust.

3) Glycol fluids begin to compress near their boiling points, whereas silicone fluids begin to compress at around 300-350 degrees Fahrenheit.

4) Additives in the fluid can vaporize at comparatively moderate temperature, increasing the spongy feel.

5) Silicone fluids expand significantly when hot.

6) Silicone fluid is functionally incompatible with systems that have held glycol-based fluids for any length of time, requiring flushing and seal replacement (there are counter opinions on this, which state that the modern silicone formulations are in fact compatible with only a flushing, rather than a complete reseal). The actual DOT specification requires chemical compatibility, so as far as that goes, the two fluids won't cause reactions if used in the same system, but they certainly won't mix, either.

7) It's pretty much incompatible with anti-lock brakes because the silicone fluids tend to be more viscous, which can cause problems with the timing of the pulses that are intended to work with the thinner glycol-base fluid. This sometimes leads to damage of the ABS valving. The rapid pulsing necessary to anti-lock functions tend to cavitate the fluid, as the tiny bubbles collapse and coalesce into larger ones, and then collapse and reform into smaller ones. This tends to counteract the ABS effect and can diminish the actual effective braking. This condition also heats the fluid and can lead to even more sponginess and possible damage to the ABS controller. Thirdly, silicone brake fluid tends to foam when expressed from a small orifice under pressure, reducing its hydraulic effectiveness greatly.

Minimum Dry Boiling Point Minimum Wet Boiling Point
(All degrees in Fahrenheit)
DOT 3 401 28
DOT 4 446 311
DOT 5 500 356

[Maguyver]

Hey bagman I really appreciate the time you took to help a fellow Harley rider out, now I need to figure out what brand of after market brakes this bike has so I could get the rebuild kit... I know the calipers are Arlen Ness butt the forward controls are definitely not again thanks a lot man....oh one more question, I’ve heard about using alcohol to flush the system out, what do you think

[bagman1]

Not a problem, glad I was able to help. Post back if you have any more questions.

[ORA]

Originally Posted by bagman1

I did a google search and I copied an excerpt from the posting. Pay particular attention to the last paragraph.

According to knowledgeable road racers, the stock fluid works fine with the stock pads, as the pads will cook before the fluid will boil. However, the use of aftermarket pads should be accompanied by a fluid change. The most recommended fluid seems to be Motul RBF 600 fluid. However, examine the notes below carefully, paying special attention to the comments for Ford Heavy Duty fluid.

The importance of moisture: The amount of moisture in brake fluid definitely affects its performance. The big problem is that brake fluid absorbs moisture quickly. SAE field tests have shown that the average one year old car has 2% moisture in the fluid. A random test of vehicles in the U.S. showed an average water content of 2.6% for vehicles with an average age of 8 years. And 25% of these vehicles had water content greater than 4%.

As water content in brake fluid increases over time, the boiling point decreases. Fluid with a reduced boiling point (or high water content) can create vapor by boiling in the caliper, or wheel cylinder. The result is sudden brake failure. And water in the brake fluid can contribute to corrosion of parts such as steel pistons and ABS modulators.

The end result is even though DOT 3 fluid is "rated" at greater than 401F, in the typical 3 to 4 year old car with 3 to 4% moisture content, it could boil under 300F.

Bottom line: Flush any brake fluid every year or so. If you go with a fluid which attracts moisture quicker, change it more often than that.

DOT 3 and DOT 4 are polyglycol-based fluids and can be mixed with each other. DOT 5.1 can also be mixed with DOT 3 and DOT 4, even though it is based on a different chemical and has about half the viscosity. If DOT 5.1 is specified for an ABS system, do not add or use any other fluid type. DOT 5 is silicone-based (not less than 70% by weight of a diorgano polysiloxane) and must not be mixed with or contaminated by DOT 3, DOT 4, or DOT 5.1.

Sorry for the long quote, damn iPhone. I must comment on this. You may have read that Motul is the most populer amongst amatuer roadracers, but those that know, use Castrol SRF. It has the closest spread between wet and dry boiling point. It is not needed nor recomended for your HD.

Most moisture gets into your system by leaving the master cyclinder cap off to long, drinking that beer while working on your brakes. Open it, fill it, close it.

Don't ever mix fluid types or brands.

Never bleed your brakes from the bottom up. Is that how you eat or drink? That pushes all the dirt up into the tiny holes in the master. Just like you threw up. Making it perform like crap.

I'm curious to know the names of the knowledgable roadracers you're referring to.

[bagman1]

Actually I dont know who they are. I was looking for an explanation of the different types of fluid and their characteristics. I wasnt satisfied with a racers explanation so I posted the second excerpt.