by Randakk » Sat Jan 22, 2011 6:29 pm
For what's it worth, I approach projects in my own shop as most any other pro "wrench" would. Also, I sponsor a vintage race team, so I have a fair understanding of the technical merits of various brake fluid formulations.
Thanks for the intelligent and experienced comments to this DOT3/4 vs DOT 5 discussion. I've read your information and have considered it's lessons, intent and facts...... all very good stuff. Thank you.
I do have my own thoughts and comments which I will try to make into a short, concise discussion.
I've raced (SCCA) in the 70's and have done all my own work on many different British, Italian, German and Japanese machines since the mid-60's. This along with many years of extensive training in the U.S. Navy then working for the Navy Dept in several electrical and mechanical venues which led me to Utilities Supervisor of the U.S. Naval Observatory which (among other things) houses and supports the Atomic and Cesium clocks used by the U. S. Government for NASA space activities and Dept. of Defense activities. Both of these require precise time acquisition well into fifteen decimal places, so my knowledge, abilities and decisions were a constant challenge to keep these systems and the entire base at operational performance level for these demanding services that gave me an excellent foundation and background for my work in motorcycles and cars all these years.
As you might suspect, I've always had is a very inquisitive mind-set. This mind-set has me questioning many blanket rules laid before me.....for life is in the details if one wants to know how and why these rules exist. Many times these blanket rules fall apart when they are examined in detail and oh so many times these blanket rules are established because manufacturers have had enough of the idiots that find endless ways to hurt themselves and others which end-up in costly lawsuits. Also, this "one rule fits all" mentality has a great tendency to shut down the learning process and many of us that want to know "why' and "how come"....of which I am very much a part of.
Ok.....with the above said, your reference at http://www.randakks.com/TechTip28.htm
, the on to Stop-Tech, http://www.stoptech.com/tech_info/wp_br ... d_1a.shtml
that says: "However, DOT5 brake fluid is silicon-based and not compatible with any other type of brake fluid"
Actually, in fact, DOT 5 brake fluid is compatible with other types of brake fluid, but it's the REACTION of DOT 3/4 brake system RUBBER components to DOT 5 brake fluid is the real issue...not mixing brake fluids. Yes.... I know the results are the same.....brake failure.....and many find this out the hard way, but life is in the details...... not blanket statements.
For instance..... Brembo says (another blanket statement)..... "Never use DOT 5 brake fluid in a Brembo brake system".....but they don't tell us why. The "why" is because once a brake system (specifically the rubber components) is exposed to DOT 3 or 4 brake fluid, then DOT 5 is introduced to the system (even when the system is flushed clean) ......the rubber components begin to swell to a point where they loose their ability to control and contain brake fluid.
But what Brembo doesn't tell us is when a completely clean and VIRGIN brake system that's never had any DOT 3/4 or 5.1 brake fluid in it.....when you install DOT 5 in this system.....it works perfectly. How do I know this ? Because I challenged this blanket statement in 1995 when DOW Corning introduced DOT 5 silicone brake fluid and installed it in my Ducati Brembo brake system that I had completely rebuilt with all new Brembo rubber bits and completely flushed the brake lines with denatured alcohol. The bike still has the same DOT 5 brake fluid in it today, some 16 years later, clear and clean. The bike gets ridden every 2--3 yrs at a special track event and the brakes work perfectly.
You and I know perfectly well why Brembo makes this blanket statement and this is because very few individuals will follow instructions 100% and completely drain, clean and install all new rubber components just to install DOT 5 brake fluid. Some slacker will do just the calipers or just the master cylinder rubbers....or he will do both and not flush out the brake lines, then months later he kills himself or others and they sue Brembo when brake failure is discovered.
Frankly, if you really want to split the hair on DOT 5 brake fluid (and learn further), I've removed old rubber parts that DOT 4 fluid was used, soaked them in denatured alcohol for several weeks and changed out the alcohol several times, then dried out the rubber bits for several days.....and put them back in service with DOT 5 with perfect results. Why ? Because I couldn't get the brake rebuild kits so it was worth a try. Try getting Brembo to (officially) admit to this. Not hardly.......but it does work if you do the job right and look beyond blanket statements.
Now onto your Gold Wing GL1000 with DOT 5 issues. First, I've not come across a Japanese motorcycle that had a bad reaction to DOT 5. God only knows what the previous owner did to that brake system to make it act like that, but I can look God right in the eye and say it wasn't just the DOT 5 that messed things up......it was something else added to or in conjunction with.
In conclusion...... your statement: "In my experience, high quality DOT 3/4 combined with good lines and pads in a properly bled system delivers excellent results." is absolutely true......but this is exactly the same results I have in my 80X presently.....but I don't have to worry about:
1. Paint damage, should you spill, drip, spray or get some DOT 3 or DOT 4 on my gas tank or fender....... which is SO easy to do. With DOT 5 I never have to worry about any paint issues.......and many of my paint jobs are well over $2k and some much more......not to mention even if the bike is painted it will never be original.....which is VERY important with high end collectable motorcycles ($50K+).
2. DOT 5 lasts 5--10 yrs with zero issues.
3. For those who say there's always air in a brake system and air contains water......and water sits in the bottom of DOT 5 systems..... all I can say after 20+ yrs of using DOT 5 I've not found a single indication of water in 15+ motorcycles or 5 cars I've put DOT 5 in.
4. Yes .... DOT 5 is a little harder to bleed.....but it's well worth the effort......just like many things in life.
5. I (and many race shops that have tried it) do not recommend DOT 5 for racing because once above 650 degrees it looses it's lubricating properties at piston to wall contacts. However, even with this blanket statement there's a lesson to be learned and passed along.
Is there a single person reading this email exceeds 600 degrees in their street or track motorcycle brake systems ? Damn few......if any. I've done track days with my DOT 5 bikes at speeds well above 150 mph and never have reached 600 degrees. I checked temps with temp marking crayons made to check brake caliper temps and never exceeded 500 degrees while in the top 5% of the fastest riders group at Mosport, Grattan and VIR for 12 yrs.
Bottom line...... DOT 5 works and it works really well....."IF" the installer does what they should when installing it. DOT 5 works for many many cars and many many bikes that sit around for years......it also works for many many cars and many many bikes that get ridden everyday.......both for so many reasons.
As with all things in life where your safety is effected.......do your homework, make informed decisions and do the job right. If not......then all bets are off.
Btw........this is the third time we've discussed this DOT 5 issue and I've explained it completely in each previous discussion, yet there are those who still respond with hear-say and mis-information. I thought one of the big reasons for Forums was previously explained and discussed issues could be reviewed and offered to newbies and not regurgitate the same mis-information that leads to yet further mis-information.
Thanks for your patience in reading all this.......the third time around.
It's not what you ride.....it's how you ride.