Front Brake drag (and brake fluid debate)

[ricklee4570]

Just replaced my front brake pads. I cleaned up the pistons and did everything by the book. The pistons easily compressed back to retracted position using just my fingers. I did all the tricks such as waiting to torque the front wheel nut until I had spun the tire and hit the brake (and hold it)

Mine still has some drag. If I spin the tire as fast as I can (with it off the ground of course) it will turn exactly one additional turn on its own before stoppping. Sometimes 3/4 of a turn.

I took it out on the highway and ran it at 70 mph for about 20 minutes and then quickly pulled over using only the back brake, and I felt the rotors of the front brake. Mildly warm, easy to hold onto. When I use the front and back, the back is a lot hotter (due to a different brand of pad I have on the back that is much harder) The back also squeeks when I use it , when I apply more presssure the back brake squeek disappears.

Anyway, my conclusion is that it is normal to have a lot of drag when putting new pads on. Im sure that as the pads wear, the drag will be less, to a point where their is virtually no drag at all (As was the case with the original worn pads)

[pmackie]

One possibility is that you have a little air in the brake lines. Try bleeding the brakes as well.

Another possibility is that the master cylinder may be a little over full, which compresses the bladder slightly.

Either of these could be causing a little more drag.

[Red01]

Thanks for that, Paul. Your brake fluid "treatise" should be a sticky in the Tech section somewhere. Newbys need to know this stuff. Heck, we've all had guys ask us "What kinda oil should I use in my brakes ??", haven't we. I've actually made guys say "BRAKE FLUID" after they kept using the term "oil"
when discussing brakes.
Can you say "brake fluid", young Luke ???
   

I finally got around to doing something like that... I put it in the General FAQ.

[ZenMan]

No offense, Red... Considering your strong bias against DOT 5, I had resigned myself to letting this go. But now you put it in the FAQ, and I think your big red warning is misleading and unfair.

Speaking as one who has actually used DOT 5 silicone brake fluid, I know of no problems with it as long as you do not mix it with glycol based fluid. When we used it for racing we always drained and flushed our brake systems thoroughly before installing it. Never had any adverse effects on any components, and it out-performed glycol fluid by far.

I took the time to do some research:

DOT 5 Silicone Brake Fluid
Clearco DOT 5 Silicone Brake Fluid is a bluish-purplish viscous fluid formulated for use in hydraulic brake systems at ambient temperatures ranging from –55∞C to 55∞C. The fluid is identified by military symbol BFS and NATO code No. H-547.

Meets Mil-PRF-46176, Mil-PRF-46176B, DOT 5 & SAE J 1705 (Society of Automotive Engineers)

DOT 5 provides corrosion protection and lubrication of the brake system components. In comparison to DOT 3 & 4 fluids (glycol-based fluids), Clearco DOT 5 it is a highly compressible fluid. In addition, it has a higher dry boiling point (260∞C) and wet boiling point (180∞C). Clearco DOT 5 will not damage paint as well.

Clearco DOT 5 Silicone Brake Fluid is compatible with SBR, EP, Neoprene, Natural Rubber and other brake material systems.

Features:
 
Blue-Viscous Fluid
Silicone Based
Non-Flammable
Highly Compressible
High Temp Serviceability: 55C
Low Temp Serviceability: -55C
Will not damage paint
Will not absorb moisture

http://www.clearcoproducts.com/specialty_silicones.html

The military uses it because of it's superior qualities such as non-flammability and non-corrosiveness. We used it at the track because of it's outstanding ability to withstand high temperatures over hours of racing without fading... which came in pretty handy in endurance racing.

Here's a little info from Dragtech, it's copyright protected. 3rd paragraph down:

http://www.dragtech.com/html/brakes.html

Bel-Ray is not the only company that makes DOT 5. Besides Clearco above, there are several others:

"Russell's long life DOT 5 Silicone Brake Fluid was developed for severe service and competition applications.  Complies with Federal Motor Vehicle Safety Standard #116, and will not boil at temperatures up to 500ƒ F. Russell Silicone Brake Fluid is not hygroscopic (it will not absorb moisture from the air) and will not damage paint or chrome.  Not compatible with DOT 3 and DOT 4 brake fluids."

http://www.russellperformance.com/tech_center/motorcycle_brake_fluid.htm

Castrol also makes silicone racing fluid (SRF):

CASTROL SRF Brake Fluid
Recommended for racing conditions only - this is the ultimate in racing brake fluid!
Wet Boiling Point 270C / 518F
Dry Boiling Point 310C / 590F
Available as 12-pack cases of 1 Litre Bottles

Castrol SRF Racing Brake Fluid is an ultra high performance product formulated specifically to satisfy the ever increasing stresses placed upon the braking systems used in international motorsport. Castrol SRF is less hygroscopic than conventional brake fluids - it absorbs less water in a given time. Secondly, unlike conventional glycol ether fluids, Castrol SRF reacts chemically with the absorbed water to reduce its adverse effects, thus preventing the fluid's high temperature performance and safety margins from deteriorating as rapidly as they would otherwise do.
It's ability to withstand temperatures in excess of 300 C, and its superior resistance to the effects of absorbed water, have established Castrol SRF as the world's premier fluid for the hydraulic brakes used in all forms of motorsport.

TECHNICAL NOTE: Mixing Castrol SRF and conventional brake fluids will reduce the benefits of Castrol SRF. It is strongly recommended that conventional brake fluid be drained from the system before flushing and re-filling with Castrol SRF.

http://www.performancefriction.com/pages/access.htm

And most disc-brake Harleys specifically call for silicone DOT 5.

HEAVY DUTY DOT 5 SILICONE BRAKE FLUID

Heavy Duty  (formerly Golden American)  Superior Silicone Brake Fluid  Exceeds DOT 5 specifications.
 Designed for all Harley disk brake systems where DOT 5 silicone brake fluid is specified
 Retains high boiling point even after years of service
 Non-hygroscopic - does not absorb water
 Provides good lubrication between metal-to-rubber and metal-to-plastic parts in master and wheel cylinders.
Many brake fluids deteriorate over the years due to water absorption and chemicals degradation.  Heavy Duty DOT 5 Silicone Brake Fluid retains its highest boiling point (over 500oF) over the years since it is non-hygroscopic, chemically stable and is essentially inert to system components.

Description
Heavy Duty  DOT 5 Brake Fluid is silicone brake fluid which virtually does not absorb water and, as a result, it prohibits brake system corrosion.  Its physical properties do not deteriorate with time, and it ensures long-term braking performance under extremely high and low temperatures.

Scroll down to bottom: http://www.spectro-oils.com/gadata.htm

I could go on, but I think your'e getting my point.  

Now Red, with all due respect, I consider you to be one of the most knowledgeable people on this board, and I'm not trying to start this whole thing again, but I think you need to take another look at this one.

Granted, it may have been my mistake to just recommend using it without any warning about mixing it, I should have explained it better... but I would use it again today if I was going racing again. It's great stuff.  

[Red01]

No offense taken.

I had a big, long, response to this all made up, and I was just about ready to hit submit when my browser crashed and I lost it ALL!

I should already be in bed, but I'll make this one quick(er).

I took the time to do some research:

But not quite enough...  

DOT 5 provides corrosion protection and lubrication of the brake system components. In comparison to DOT 3 & 4 fluids (glycol-based fluids), Clearco DOT 5 it is a highly compressible fluid. In addition, it has a higher dry boiling point (260∞C) and wet boiling point (180∞C). Clearco DOT 5 will not damage paint as well.

All nice features... except one. You do NOT want high compressibility in a hydraulic fluid - especially brakes.

From Sportbike Solutions' "Everything you ever wanted to know about brake fluid (but wished you hadn't asked)":

So why don't you see any sportbikes coming off the showroom floor with silicone fluid? For one reason and one reason alone. . . compressibility. That's the one difference that, despite all their shortcomings, makes glycol-based fluids the only real choice for performance automobiles and motorcycles alike.

Here's a little info from Dragtech, it's copyright protected. 3rd paragraph down:

http://www.dragtech.com/html/brakes.html

I guess you missed the tip at the bottom?
The red text is THEIRS, not mine.

Drag Tech Tip: The experts recommend not using a silicone type brake fluid in your race car; a better choice would be a high temp glycol type brake fluid. Silicone brake fluid may not damage your vehicle’s paint job, but sure will compress under high temperatures, AVOID SILICONE BRAKE FLUID!

Castrol also makes silicone racing fluid (SRF):

CASTROL SRF Brake Fluid
Recommended for racing conditions only - this is the ultimate in racing brake fluid!
Wet Boiling Point 270C / 518F
Dry Boiling Point 310C / 590F
Available as 12-pack cases of 1 Litre Bottles

TECHNICAL NOTE: Mixing Castrol SRF and conventional brake fluids will reduce the benefits of Castrol SRF. It is strongly recommended that conventional brake fluid be drained from the system before flushing and re-filling with Castrol SRF.

This is actually good stuff and IS miscable with DOT 3 & 4 and is certified as a DOT 4 fluid, even though it is silicone-based - though it's performance will be severely degraded if mixed with something else. If you're spending the $75/liter for it, you sure don't want that!

And most disc-brake Harleys specifically call for silicone DOT 5.

Again, from Sportbike Solutions' "Everything you ever wanted to know about brake fluid (but wished you hadn't asked)":

Silicone fluids aren't excluded entirely from the motorcycle industry, however. Many 'show over go' cruisers come off the floor with the purple stuff (the color of DOT 5 silicone fluid and I'll be willing to bet, OEM's aren't using Castrol SRF - Red01), which is often a suitable alternative for bikes that rarely break the speed limit in school zones, sporting paint jobs that cost more than a single family home. But if performance is your game, glycols are the only show in town. You won't see a production sport or dirt bike rated for anything else.

I could go on, but I think your'e getting my point.  

Yup, I think so... you just couldn't let it go.

Now Red, with all due respect, I consider you to be one of the most knowledgeable people on this board, and I'm not trying to start this whole thing again, but I think you need to take another look at this one.

Granted, it may have been my mistake to just recommend using it without any warning about mixing it, I should have explained it better... but I would use it again today if I was going racing again. It's great stuff.  

Thanks... I think.
I guess if you can't fight with the Gunner, you can fight with me.
I promise not to turn it into a personal attack.



Yet.  


OK, I looked at it again. I checked out your links and found more myself. Unless you want to spend $75/L for your brake fluid, I'm sticking to my guns.

Dammit, this was supposed to be short and it's almost as long and time consuming as my first try... Oh well.

[ZenMan]

And I'm sticking to my guns too.  

The only real argument against DOT 5 is the compressibilty factor.

Quoting your post: "So why don't you see any sportbikes coming off the showroom floor with silicone fluid? For one reason and one reason alone. . . compressibility."

In real life, it's really not that noticeable, especially if you have steel-braided lines. If you had ever actually used the stuff yourself, you'd know that.  

In racing, the brakes get very hot very quickly, and with the glycol fluid, any compression advantages go away fast. With the silicone, they do not fade at all as the brakes heat up.

Ask yourself this... if DOT 5 was as bad as your'e trying to make it out to be, then why is it recommended and used so extensively in high-end racing? Why are there so many manufacturer's making and selling the stuff? Why does the military use it exclusively?

Look, you and I can come up with plenty of pros and cons, but my main objection is your dire warning all written up in big red letters as if anyone who uses DOT 5 is gonna die horribly or something. That's sorta misleading, dontcha think? I mean, the issue of compressibility hardly warrants hitting the panic button like that.  

Red, CWO has nothing to do with this, I kinda resent your remark about me arguing with you because he's gone: "I guess if you can't fight with the Gunner, you can fight with me." You came down pretty hard on my comment suggesting DOT 5. I just wanted to state the facts, share my own experience and give it a fair perspective. I've done that, so I'm gonna stop now.  

[orionburn]

One possibility is that you have a little air in the brake lines. Try bleeding the brakes as well.

Another possibility is that the master cylinder may be a little over full, which compresses the bladder slightly.

Either of these could be causing a little more drag.

If you don't have one, try to pick up a Mity Vac. That little doodad makes bleeding a lot simpler. Think I only paid about $20 for it a couple years ago. You should be able to find one at an auto store or even Wallyworld.

[Red01]

Red, CWO has nothing to do with this, I kinda resent your remark about me arguing with you because he's gone: "I guess if you can't fight with the Gunner, you can fight with me." You came down pretty hard on my comment suggesting DOT 5. I just wanted to state the facts, share my own experience and give it a fair perspective. I've done that, so I'm gonna stop now.

That was TOTALLY tongue-in-cheek... and why I qualified it with THREE of these>  

I was not coming down hard on you personally, I just wanted to make the point that you DO NOT want to mix DOT 5 silicone fluid with any DOT 3 or 4 glycol-based system.

Compressibilty isn't the only thing, but it IS a big enough thing to be reason enough not to use it all by itself. Don't forget, even in one of the links you provided, they say compressibilty is a big issue - and recommend it NOT be used in your race car!

For me, and the reason I put it in big red letters in my original statement and left it that way when I copied it into the General FAQ is its non-compatibility with glycol-based fluids (with the exception of Castrol SRF liquid gold) is also a BIG issue. The fact that mixing a DOT 5 fluid in a DOT 3 or 4 system that hasn't been completely purged will turn the fluid to sludge is a HUGE safety issue.

The fact that it's non-hygroscopic is also still an issue, even though it is harder for water to get in, it still can, and when it does, makes it even more compressable if you do get things hot enough to boil the water (still 212*F at sea level when not under pressure). Just the link I gave last night didn't talk about that.

Considering the FAQ is intended to answer the question of what to service your bike with, you simply do not want to add DOT 5 rated fluid to a DOT 4 rated system and if you do, the results can be disasterous, therefore, the big red letters, I feel, are still worth the effort to call attention to the matter. (Likewise, if you have a Harley or other machine with OE DOT 5, I would strongly say do not add DOT 3, 4, or 5.1 to it.

The only silicone fluid I could find that would be safe in a glycol system is the silicon-ester based Castrol SRF - which is rated as DOT 4, not DOT 5... and I haven't found anywhere where it says it's safe to put SRF in a DOT 5 system.

Here's another link for you to read:
http://www.stoptech.com/tech_info/wp_brakefluid_1a.shtml
And a few key excerpts:

Ah ha, you say - but what about the much touted Silicone based brake fluids? They are non hygroscopic and should take care of the reduced boiling point and corrosion problems. True! That’s the good news. That is why they are specified by the U.S. Military. Unfortunately the silicone based fluids are compressible themselves so they produce a soft pedal all by themselves. For the person who doesn’t care about a spongy pedal or precise modulation silicone fluids may well be the answer - but not for anyone reading this. In fact, low compressibility is a desired characteristic in a high performance brake system – lower compressibility results in more linear force output for driver input and improved driver feedback.

We won’t even discuss DOT 5 fluids as they are completely unacceptable to the high-performance enthusiast

when dealing with modern hydraulic braking systems a numerically higher DOT rating is typically considered to be compatible with a lower DOT rating (except for DOT 5, of course).

Why the heck do we use brake fluids that absorb water in the first place?

Believe it or not, one of a brake fluid’s most vital characteristics is its ability to absorb water. Yes, you read that correctly – brake fluids absorb water by design and that is really a good thing.

What?

Whether we like it or not, water is everywhere and finds its way into everything. That’s just the nature of the beast. Even our brand-new sealed brake system will eventually absorb water given enough time.

The magic of diffusion allows moisture in the air to permeate microscopic pores in the rubber brake hoses, the nylon master cylinder reservoir, and the various rubber seals in the hydraulic system. Sadly, there is nothing we can do about it and if left unchecked the water would sit in our brake system and rot it away from the inside out.

Hence the need for brake fluid to absorb this unwanted house guest. Because brake fluid absorbs water into solution, the local concentration levels are typically low enough that corrosion is slowed dramatically. As an added benefit, when exposed to low temperatures, the solution state prevents the water from pooling and freezing on its own. While water in brake fluid will certainly increase the solution viscosity at low temperatures, this is much more desirable than having little chunks of ice plugging up the system!

So why is silicone-based DOT 5 fluid more compressible than other fluids?
On their own, silicone-based DOT 5 fluids are entirely different animals than DOT 3 and DOT 4 fluids. In addition to having characteristically higher dry and wet boiling points, they also tend to have much, much lower viscosities. In other words, they flow more easily relative to temperature.

One side effect of this chemistry is that there is more “room” for air to fit in-between the individual molecules of brake fluid than in DOT 3 or DOT 4 fluids. Note that we are not talking about big bubbles of air here which are visible to the naked eye, but rather microscopic amounts of air which are finely dispersed (entrained) in the brake fluid matrix.

Now, all fluids have a certain amount of compressibility to start with, but adding even the smallest amount of air into the solution can dramatically increase the amount of elasticity in the system. In the case of silicone-based fluids, air is quite happy to take up residence between the brake fluid molecules, and as a result the fluid compressibility goes down. This is felt at your foot like stepping on a big spring. As you can imagine, more air = more spring.

Near as I can tell, today's high-end race machines are using high end Castrol SRF fluid (which is rated DOT 4) or other top quality "Super" DOT 4's or 5.1's - because of compressibility issued discovered from racing with DOT 5 years ago.

If after all of this, you still want to use DOT 5, go for it. I'm not here to stop you. I'm just giving you the info so you can make an informed decision. Just be sure your system is completely clear of any glycol based fluids.

[ZenMan]

I was not coming down hard on you personally

I know that, but you did have an extremely negative reaction to my comment recommending DOT 5.  

I just wanted to make the point that you DO NOT want to mix DOT 5 silicone fluid with any DOT 3 or 4 glycol-based system.

In that case, your warning should read "Do not ADD DOT 5 silicone brake fluid to glycol DOT 3 or 4.... or MIX it together, etc., etc.."

Simply sayng "WHATEVER YOU DO, DON'T USE DOT 5!!!" is misleading and unfair.

Compressibilty isn't the only thing, but it IS a big enough thing to be reason enough not to use it all by itself. Don't forget, even in one of the links you provided, they say compressibilty is a big issue - and recommend it NOT be used in your race car!

And other links highly recommend using it in your race car or race bike. I've used DOT 5 first-hand with great success. Many companies produce and sell it and many customers buy it and use it with great success. That's the facts, not an opinion.

We won’t even discuss DOT 5 fluids as they are completely unacceptable to the high-performance enthusiast

I really had to laugh at that. Where has this guy been? I'd like to see him make that statement to any of the many race teams that are currently using it and winning races with it.

The fact that mixing a DOT 5 fluid in a DOT 3 or 4 system that hasn't been completely purged will turn the fluid to sludge is a HUGE safety issue.

Sludge? Where did you see that?  

Though I agree that mixing it is not recommended and potentially dangerous, most of the links provided say that it will only reduce efficiency, nothing about SLUDGE.

The fact that it's non-hygroscopic is also still an issue, even though it is harder for water to get in, it still can, and when it does, makes it even more compressable

Again a totally debatable matter of opinion. Just like compressibilty, which is not that extreme in the real world. And corrosion, which most sources agree that silicone protects against much better than glycol.

All these arguments are debatable. You and I have already found many sources both pro and con. FOR EVERY NEGATIVE SOURCE YOU FIND, I CAN FIND A POSITIVE ONE. This can go on forever. My point remains regarding your dire warnings.

Considering the FAQ is intended to answer the question of what to service your bike with, you simply do not want to add DOT 5 rated fluid to a DOT 4 rated system and if you do, the results can be disasterous, therefore, the big red letters, I feel, are still worth the effort to call attention to the matter.

Calling attention to the dangers of mixing the two types together is one thing. Your FAQ post is based more on your biased opinion towards DOT 5, which you've never even used yourself. Your knowledge is only based on what you've read.

FAQ posts should be based on pure FACTS alone, or at the very least, valid first-hand experience.

If after all of this, you still want to use DOT 5, go for it. I'm not here to stop you. I'm just giving you the info so you can make an informed decision.

Red, how many times must I repeat myself? I HAVE used it. I've trusted my life to DOT 5 many times on the race track... as many people have, and still do! Not once has it failed me! Can you find any evidence that DOT 5, used properly, has ever caused a crash?

No offense bud, but your "info" is partly factual, and partly debatable opinions found on the net. I do have FIRST-HAND experience. The only reason I can think of why you dismiss that is that you must not believe me. That's ok, it's disappointing, but that's your perogative.  

And as far as ME not letting it go, look who's talking!    

I still think you are one of the most knowledgeable people on this board, and I have great respect for your experience and common sense. But nobody is right 100% of the time.  

[ZenMan]

This is starting to sound like a lot of OIL threads I've seen.  

At least we are both being respectful and keeping it CIVIL. Thank you for that.

Personal attacks are completely uncalled for, I know you have not attacked or insulted me, and I am puposefully avoiding doing the same to you.

We are friends, after all. I'd really enjoy going for a ride with ya, and discussing this over a beer or three.    

[leedogg]

Maybe a new thread??

Did the guys brakes get better or not?  Not sure if I saw that or not.

[Red01]

I was not coming down hard on you personally

I know that, but you did have an extremely negative reaction to my comment recommending DOT 5.  

I only came down hard on your original post because of the difficulty in getting ALL the DOT 4 fluid out. You do not want DOT 3, 4 or 5.1 coming in conact with DOT 5. It's just plain unsafe.

I just wanted to make the point that you DO NOT want to mix DOT 5 silicone fluid with any DOT 3 or 4 glycol-based system.

In that case, your warning should read "Do not ADD DOT 5 silicone brake fluid to glycol DOT 3 or 4.... or MIX it together, etc., etc.."

Simply sayng "WHATEVER YOU DO, DON'T USE DOT 5!!!" is misleading and unfair.

Considering the extreme difficulty in getting all the DOT 4 out to put DOT 5 in when you can only clean brake systems with brake fluid purging or complete disassembly and cleaning with brake cleaner, I still don't think it is unfair.

Compressibilty isn't the only thing, but it IS a big enough thing to be reason enough not to use it all by itself. Don't forget, even in one of the links you provided, they say compressibilty is a big issue - and recommend it NOT be used in your race car!

And other links highly recommend using it in your race car or race bike. I've used DOT 5 first-hand with great success. Many companies produce and sell it and many customers buy it and use it with great success. That's the facts, not an opinion.

Every site I've found that's got an article on brake fluid performance says DOT 5 is not for racing & high performance use due to compressibility and the problem only gets worse as the fluid temp rises, despite its high boiling point. They do admit it is used by the military & show vehicles for its other properties. The links you've given either agree or are sales sites for a particular brand of DOT 5.

We won’t even discuss DOT 5 fluids as they are completely unacceptable to the high-performance enthusiast

I really had to laugh at that. Where has this guy been? I'd like to see him make that statement to any of the many race teams that are currently using it and winning races with it.

That was written by James Walker, Jr. Here's his bio:

James Walker, Jr.
StopTech Consultant    
         

James Walker, Jr. is currently the supervisor of vehicle performance development for brake control systems at Delphi Energy & Chassis. His prior professional experience includes brake control system development, design, release, and application engineering at Kelsey-Hayes, Saturn Corporation, General Motors, Bosch, and the Ford Motor Company. Mr. Walker created scR motorsports consulting in 1997, and subsequently competed in seven years of SCCA Club Racing in the Showroom Stock and Improved Touring categories.

Through scR motorsports, he has served actively as an industry advisor to Kettering University in the fields of brake system design and brake control systems. In addition, Mr. Walker contributes regularly to several automotive publications focusing on brake system analysis, design, and modification for racing and other high-performance applications. He is a recipient of the SAE Forest R. McFarland Award for distinction in professional development/education. Mr. Walker has a B.S. in mechanical engineering from GMI Engineering & Management Institute.

To find out more about Mr. Walker and scR Motorsports, visit their website at http://www.teamscR.com.

So I guess he's full of BS because he's not a world champion?

The fact that mixing a DOT 5 fluid in a DOT 3 or 4 system that hasn't been completely purged will turn the fluid to sludge is a HUGE safety issue.

Sludge? Where did you see that?  

Though I agree that mixing it is not recommended and potentially dangerous, most of the links provided say that it will only reduce efficiency, nothing about SLUDGE.

Castrol SRF is the only silicone fluid that's safe to mix with glycol fluids, but then it's rated as a DOT 4, not 5. The Castrol site doesn't say if it is or is not compatible with DOT 5.

Hmmm... I'm wondering if your own prejudices are jading you so that you don't see the words when they're right there in front of you. In the Sportbike Solutions link they said in the second paragraph, third sentence - on:
(Emphasis is mine.)

Mixing the two within your brake system, even in small amounts, can result in the formation of a thick sludge, which naturally doesn't make for very effective braking action. Inadvertantly combining the two mandates not only a thorough drain and flush of the affected brake system, but in some cases, a rebuild of the entire system. If you're thinking this could possibly wind up being a very costly mistake, you're quite correct. So the bottom line is this: If your bike started life with glycol-based fluid, stick with glycol. If it came with silicone, stick with that. And if you feel like mixing them - fine - just make the check out to Sportbike Solutions. And leave the amount blank.

The fact that it's non-hygroscopic is also still an issue, even though it is harder for water to get in, it still can, and when it does, makes it even more compressable

Again a totally debatable matter of opinion. Just like compressibilty, which is not that extreme in the real world. And corrosion, which most sources agree that silicone protects against much better than glycol.

What is opinion to debate?

There's no arguement that water vapors will permeate the rubber/rubber-like compounds of hoses and reservior covers.
It is fact that silicone doesn't attract water like a sponge the way glycol does, but water WILL eventually get in and when it does, it's fact that since it is heavier, it will sink to the lowest point.
It is fact that the lowest point is the caliper which is also the first to heat up during use.
It is fact that boiling water releases air into the system.
It is fact that water will corrode the materials today's calipers & pistons are made of.
Compressibility is a fact, even the makers of DOT 5 tell you that.
It is fact that the hotter DOT 5 gets, the more compressible it gets.

It is also fact that glycol based fluid, because of its hygroscopic nature, needs to be changed more often.
It is also fact that since the water is in suspension in glycol fluids, it will not boil at 212, but will degrade the boiling temp of pure glycol fluid.

Compressibility is DOT 5's #1 detractor. The rest you could live with, especially if you changed it on a regular basis like you are supposed to do with glycol fluids.

All these arguments are debatable. You and I have already found many sources both pro and con. FOR EVERY NEGATIVE SOURCE YOU FIND, I CAN FIND A POSITIVE ONE. This can go on forever. My point remains regarding your dire warnings.

You claim DOT 5 is still popular with racers. Find me some sites to back that up. To my knowledge, DOT 5 fell out of favor with racers almost as fast as it came it in. It was purported to be the next best thing for racers when introduced, but the compressibility issues quickly put the brakes on that... pun intended.

Calling attention to the dangers of mixing the two types together is one thing. Your FAQ post is based more on your biased opinion towards DOT 5, which you've never even used yourself. Your knowledge is only based on what you've read.

FAQ posts should be based on pure FACTS alone, or at the very least, valid first-hand experience.

I've given plenty of facts in this and other posts as well as the PM's we've exchanged. Even with a brake engineer to back me up. The ball is in your court now. You find an industry engineer that backs you up.

If after all of this, you still want to use DOT 5, go for it. I'm not here to stop you. I'm just giving you the info so you can make an informed decision.

Red, how many times must I repeat myself? I HAVE used it. I've trusted my life to DOT 5 many times on the race track... as many people have, and still do! Not once has it failed me! Can you find any evidence that DOT 5, used properly, has ever caused a crash?

You need to step out of the past and realize DOT 5 is not the be-all, end-all of brake fluid technology anymore. Time and technology have marched on. Castrol SRF DOT 4 is widely recognized as the best, but there are several other Super DOT 4 or DOT 5.1's that are almost as good - and don't cost $75/liter like SRF does.

No, I can't easily find you crashes caused by DOT 5 because the most likely case would be a racing accident from years ago.

No offense bud, but your "info" is partly factual, and partly debatable opinions found on the net. I do have FIRST-HAND experience. The only reason I can think of why you dismiss that is that you must not believe me. That's ok, it's disappointing, but that's your perogative.  

I believe you didn't experience troubles. OTOH, I can't dismiss the facts presented by industry experts either, and if I have to choose between an ametuer racer and several industry experts, I'm sorry, but you loose. I believe I've been open-minded and admitted to the advantages DOT 5 has, but it does have a major detractor. YOU say it's no big deal, but several performance experts disagree. (Here's an opinion >>> ) IMHO, it is for this reason that we don't find DOT 5 on every car, truck & bike out there, but instead find DOT 4 in 99% of the vehicles on the road and can't walk into the local discount auto parts store and pick up a bottle of DOT 5 from both major and discount brands. I don't know about where you live, but I can't even find a major brand on the shelf. Granted, I haven't walked into the Harley shop though.

Speaking of Harleys & DOT 5... Today at work, I wandered thru the bike parking and looked at the Harleys. 5 had DOT 4 spec'd on the front master cylinder covers, 1 had DOT 5 and the other two had custom covers with no markings. The DOT 5 bike was an older non-Evo Sportster, all the others were fairly new.

[Nitro]

Do you two ever stop? You've both made your points and it looks like neither of you are going to give up.

[ZenMan]

I only came down hard on your original post because of the difficulty in getting ALL the DOT 4 fluid out. You do not want DOT 3, 4 or 5.1 coming in conact with DOT 5. It's just plain unsafe.

Considering the extreme difficulty in getting all the DOT 4 out to put DOT 5 in when you can only clean brake systems with brake fluid purging or complete disassembly and cleaning with brake cleaner, I still don't think it is unfair.

Then why not explain it that way in the FAQ? Instead of inferring that even the proper use of DOT 5 will be "disasterous"?  

Every site I've found that's got an article on brake fluid performance says DOT 5 is not for racing & high performance use

That is completely contradictory with the fact that name-brand companies are producing silicone fluid and selling it as racing fluid for competition applications:

"Russell's long life DOT 5 Silicone Brake Fluid was developed for severe service and competition applications."

"CASTROL SRF Brake Fluid (SILICONE)
Recommended for racing conditions only - this is the ultimate in racing brake fluid!"

And another brand (Cartel), sold by Ire Racing :

"Silicone Brake Fluid (DOT 5)                                                                                                
Non Hygroscopic -Does not absorb water- thus eliminating corrosion and deterioration.
Dry boiling point exceeds 600 deg.
Compatiable with DOT 3, DOT 4, and foreign brake fluids.
Compatiable with natural and synthetic rubber compounds.
Never needs replacement.
Doesn't harm painted surfaces.
Lubricates moving parts.
Simple changeover - just perform normal brake bleeding job.
Packaged in 8 oz., 32 oz., 5 gallon and 55 gallon drums."

http://www.lreracing.com/silicone_brake_fluid.htm

And then you keep going on about compressibilty... from your PM:  

From your Clearco link:
"In comparison to DOT 3 & 4 fluids (glycol-based fluids), Clearco DOT 5 it is a highly compressible fluid."
As I said before, highly compressible is not a good feature for brake fluid.

Again, quoted from the Dragtech link:

"Less compressibility of brake fluid will increase pedal feel (firmness), but in either case the effect is minimal."

As a matter of fact, I remember the slight sponginess of the silicone fluid... but as I've stated several times now, the effect is barely noticable, and the huge advantage of having fade-free brakes over the fade-fast glycol bikes made it more than worth it.

You still fail to answer important questions I've put to you... such as:

"If DOT 5 was as bad as your'e trying to make it out to be, then why haven't there been any lawsuits against all these manufacturers that make and sell it as racing brake fluid?"

Or:

"Can you find any evidence that DOT 5, used properly, has ever caused a crash?"

Or:

"How can you dismiss the fact that DOT 5 is fade-free, and thus gives a huge advantage over fade-fast glycol fluid?"

If you going to continue to ignore certain facts or questions I've stated, then why should I put all the effort forward to debate the rest of your long post? As I've said, for every con, there is a pro, and I'm tired of playing this game.

I'm wondering if your own prejudices are jading you so that you don't see the words when they're right there in front of you.

The very same thing can be said of you, my friend.  

I think "winning" this debate is more important to you than being objective, and you are trying to wear me down with long quotes and arguments. I think your own prejudices and need to defend your original position prevents you from conceding my points.    

I think that you painted yourself in a corner with your initial extreme reaction and ensuing negativity towards my DOT 5 comments, and now you'd rather drag it on forever than admit you over-reacted.    

No problem, I've found myself in that position before too, and being just as stubborn, also found it difficult to find a graceful way to concede.  

Therefore, I'm going to stop here. I really mean it this time!  

I don't want an unending argument about brake fluid to come between friends, and I do consider you one. In fact we are a lot alike, stubborn as mules. I'm looking forward to meeting you someday and laughing about all this.  

I'll even bring the DOT 5 if you bring the beer...  

No hard feelings.  

[ZenMan]

Do you two ever stop? You've both made your points and it looks like neither of you are going to give up.

You're right. This is unfair to all the rest of ya'll, I'm sure you are not the only one tired of it.

So I'm stopping right here and now. I mean it!