upgrading the OEM master cylinder?

Re:

Postby SanDogDewey » Fri Jan 21, 2011 2:33 pm

Randakk wrote:Spend some time here: http://www.vintagebrake.com/mastercylinder.htm
...courtesy of Michael "Mercury" Morse for more useful background info. This will answer all your questions about brake leverage ratios, etc.
Michael is an absolute genius with vintage brake matters. He operates Vintage Brake a terrific source for vintage brake information.


+1 on the Master Cylinder to Caliper ratios information offered at Vintage. Good info there. You should match your master cylinder to the caliper to ensure you're pushing sufficient volume at the calipers. Too much, and you can have some pretty touchy brakes.

I'm using a 2002 919 Master Cylinder on my '80 CBX. You can get a nice one for the cost of the rebuild kit of the CBX Master cylinder. There are usually several on eBay. On my bike it is a good match for the dual piston 900F calipers.

...oh and Dot 5 and stainless lines...hands down. nuff said. :)
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Re: Re:

Postby Mike Cecchini » Fri Jan 21, 2011 8:12 pm

SanDogDewey wrote:
Randakk wrote: <snip>
...oh and Dot 5 and stainless lines...hands down. nuff said. :)


Amen SanDog. Works like a champ. :cheers:
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Re: Re:

Postby Randakk » Fri Jan 21, 2011 11:35 pm

Mike Cecchini wrote:
SanDogDewey wrote:
Randakk wrote: <snip>
...oh and Dot 5 and stainless lines...hands down. nuff said. :)


Amen SanDog. Works like a champ. :cheers:


I realize that your post is a just quirk of how Forums work, but actually - I don't recommend DOT5 brake fluid. It's good stuff, but have my reasons.
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Re: upgrading the OEM master cylinder?

Postby Mike Cecchini » Sat Jan 22, 2011 12:40 am

Like to hear your reasson Randall.

I know levers and pedals don't come rock hard, just 98%.....and when pushed to racing levels it looses it's lubricity (sp?) .....but for us mortals it's a God-send.

20+ yrs using it and it's been the best thing since sliced bread.

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Re: upgrading the OEM master cylinder?

Postby Don » Sat Jan 22, 2011 5:14 pm

DOT 5 boils at a higher temp (good for all out racers) and it doesn't harm your paint, but it compresses more and requires annual changes, something most street users don't care for . . . . and probably don't bother to do

http://www.motorcycleproject.com/motorc ... fluid.html

Mike boils it down to this - The 'best' is whatever the manufacturer recommends for your system

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Re: upgrading the OEM master cylinder?

Postby Randakk » Sat Jan 22, 2011 6:29 pm

Mike Cecchini wrote:Like to hear your reasson Randall.

I know levers and pedals don't come rock hard, just 98%.....and when pushed to racing levels it looses it's lubricity (sp?) .....but for us mortals it's a God-send.

20+ yrs using it and it's been the best thing since sliced bread.

My best......... Mike


Mike:

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.

Having said all that, my customer base (12,000+ on the newsletter subscriber base) is overwhelmingly comprised of amateur mechanics. I've learned to be very careful to consider their unique capabilities and perspective in all the recommendations I've published as Tech Tips here: http://www.randakks.com/TechTips.htm I've written all that material so that it is primarily targeted and useful to that audience...not pro mechanics.

Here's one that mentions brake fluids in passing: http://www.randakks.com/TechTip28.htm

I've learned from first-hand reports from many of my customers horror stories involving unnecessary brake fluid catastrophes resulting from ill-advised mixing of incompatible brake fluids. Sometimes this was "intentional" by someone searching for an upgrade who failed to understand all the details. Others were "inadvertent" because they had no knowledge of the prior maintenance history by prior mechanics.

I myself bought a beautiful, museum quality GL1000 (that I still own). Shorty after purchase, I did a comprehensive service and mechanical rejuvenation which included all new fluids. Almost overnight, all the hydraulics were quickly ruined! I learned (much to my horror) that the brake fluid had been switched over at some point prior to DOT 5.0 When I asked the seller about this, he had "no knowledge." I had to do a total rebuild of all calipers and master cylinders...a huge waste of time and energy.

Sticking to the recommended brake fluid is a kind thing to do for future owners I think. If you do make a switch that would be incompatible (like to DOT 5.0), I strongly suggest that the bike and maintenance log be conspicuously marked.

In my experience, high quality DOT 3/4 combined with good lines and pads in a properly bled system delivers excellent results. In fact, on my CBX test mule, I can do "stoppies" with only 2 fingers on the lever. I'm running ordinary DOT 4 brake fluid. Then again, it does have 330mm brake rotors and 24 total brake pistons on the front...12 on each side. :)
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Re: upgrading the OEM master cylinder?

Postby EMS » Sat Jan 22, 2011 7:17 pm

Considering all the advantages and disadvantages of DOT5, what it all boils down to is:

- if you don't ride your bike/vehicle often and store it for extended periods of time, DOT5 may have an edge.
- if you ride/drive your bike/vehicle often and hard, stay away from DOT5

DOT5 does not absorb water, but it absorbs air easily. If you shake it, it is full of air. If you buy it at the store and drive it home in your car, it is full of air. If you fill your brake system without having it rested for a day or so, you put that air into the system. Your system will be hard to bleed and because of the fact that DOT5 is more compressible than DOT4 for example, you may accept a sort of "spongy" lever. With the air, you introduce water into the system and that water then accumulates in a low spot in your brake system as the fluid does not absorb it. Most cases in the calipers. If you rely on DOT5 not needing a change in 5 years, woul will end up having a badly corroded part.
Any bike/vehicle with ABS should not use DOT5 and most manufacturers of these bikes/vehicles clearly spell this out.
All this assumes, of course, that if you change from DOT3 or 4 to DOT5, you have thoroughly cleaned and flushed, preferably rebuilt, your brake system. Any remnants of DOT 3 or 4 in the system and added DOT5 to it, is a recipe for desaster.
There is a good reason, real professionals, like Mike Nixon and Randakk, who worked and still work on brakes for a living, hesitate to use DOT5. I don't either.
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Re: upgrading the OEM master cylinder?

Postby Don » Sat Jan 22, 2011 7:59 pm

EMS wrote:DOT5 does not absorb water . . . .
That's actually part of it's 'problem' . . . . that and the fact that it's specific gravity is .96 . . . . lighter than water, so it floats - The water (which condenses into any brake system, regardless of the fluid used) all falls to the bottom with silicone based fluids

Moisture condenses into anything that is repeately heated and cooled. With glycol based brake fluid, it mixes with the glycol and isn't as corrosive as straight water is . . . . plus, glycol brake fluid has a specific gravity of 1.05, so the water doesn't all fall to the bottom where it can rot out your calipers like it does with silicone based fluids

DOT 3 also changes color when exposed to moisture, so you know when it needs changing - Silicone doesn't so you think you're OK even though eventually your calipers get full of water, which causes them to pit and ruin the seals

If you're a racer and you change your fluid several times a season, DOT 5 is fine - If you're an average, ordinary rider who doesn't like flushing your brake system once per year, then the DOT 3/4 stuff would be better for you

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Re: upgrading the OEM master cylinder?

Postby EMS » Sun Jan 23, 2011 11:13 am

Don wrote: If you're a racer and you change your fluid several times a season, DOT 5 is fine - Don



Don, and even then I wouldn't. The pedal/lever feel you get with DOT5 is inferior to DOT3 or 4. Most racers I know,do not use DOT5. Neither in bikes nor in cars. If one claims to feel the difference between a steel line and a rubber line, one will definitely feel the difference between DOT3/4 and DOT5.
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Re: upgrading the OEM master cylinder?

Postby Mike Cecchini » Sun Jan 23, 2011 8:23 pm

by Randakk » Sat Jan 22, 2011 6:29 pm

Mike:

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.

<snip>


******************************************
Hi Randall,

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.

My best........Mike
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Re: upgrading the OEM master cylinder?

Postby Mike Cecchini » Sun Jan 23, 2011 8:35 pm

Don wrote: <snip>

DOT 3 also changes color when exposed to moisture, so you know when it needs changing - Silicone doesn't so you think you're OK even though eventually your calipers get full of water, which causes them to pit and ruin the seals

If you're a racer and you change your fluid several times a season, DOT 5 is fine - If you're an average, ordinary rider who doesn't like flushing your brake system once per year, then the DOT 3/4 stuff would be better for you

Don



Calipers full of water ? Honestly Don.......I've not found a single indication of water in any caliper, any master cylinder in over 25 yrs of using DOT 5. And if you are worried about not knowing when to change DOT 5.... which Corvette and HD recommend every 5--10 yrs...... then just do what I do....put a small magic marker date on your master cylinder as an instant reminder.

Btw....racers don't use DOT 5 because they don't like the change in lever feel that DOT 5 has......but it does work if you aren't trying to set lap records. Is there anyone here trying to set lap records at the race track on their bike ?? Didn't think so. Everyone reading this email barely uses his brakes past 50%. and DOT 5 has so many benefits for all of us here. That's my point..... US......CBX owners.
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Re: upgrading the OEM master cylinder?

Postby NobleHops » Sun Jan 23, 2011 10:25 pm

Very informative, and nicely presented, all of you. Thanks a bunch, I learned a ton.

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Re: upgrading the OEM master cylinder?

Postby SanDogDewey » Sun Jan 23, 2011 11:56 pm

I don't know how anyone could miss that purple glow from my master cylinders and mistake it for Dot 3,4 or 5.1???
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Re: upgrading the OEM master cylinder?

Postby Mike Cecchini » Mon Jan 24, 2011 12:35 am

True.......but there are some DOT 4 brake fluids that are purple also.
http://www.tirerack.com/brakes/accessor ... .jsp?ID=21
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Re: upgrading the OEM master cylinder?

Postby Randakk » Mon Jan 24, 2011 8:21 am

Respectfully, my only reason for posting on the topic of brake fluid above was to clarify an inadvertent reference to me that accidentally seemed to imply a certain recommendation by me that was contrary to my actual position. I felt compelled to correct that before it came back to bite me.

Other than that, I don’t dispute anything said above by anyone else.

I have explained my reasons and would never recommend DOT5. I’ve seen the unnecessary heartache this can cause if installed carelessly or when the owner/mechanic does not realize this switch has been made previously. I feel that my recommendation is appropriate and reasonable for my audience.

Like I said - I have my reasons. Use whatever you like in your own machine. But, I get 200 emails a day and I don’t need any “extra” correspondence.
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