digest number 1506

[Susan Moorhead]

Marc, I agree, change the fluid once a year, forget about it for another 12 months, enjoy the ride, don't worry about the brakes. Just my .02 worth, Marshall in Afton, Ok '95 KLXC3 "Blackhorse" (in honor of those who served)

----- Original Message ----- From: Marc Illsley Clarke To: Barry Levine ; DSN_klr650@yahoogroups.com> Sent: Wednesday, June 27, 2001 9:19 PM Subject: re: [DSN_klr650] Re: Digest Number 1477 > Easy solution is to use DOT4 and a Mitivac to suck the contaminated brake fluid out, replacing it with fresh DOT4 fluid. 5 minute job per brake line at least once a year. > > Water gets into properly installed non-leaking brake lines. Top motocross racers change brake fluid every race to avoid mushy brakes. > > Contaminated brake fluid yields mushy brake lever feel even before the brakes heat up the brake fluid. > > -- Marc, KLR650 A12, Loveland, Colorado, USA

[Marc Illsley Clarke]

Yes. Water boils at a lower temperature than brake fluid. Brake fluid boils at about 500 F, I believe. Brake fluid boils in brake systems, causing brake fade. Water-contaminated brake fluid boils at a lower temperature than pure brake fluid. Why do you suppose brakes fade on a long downhill? Something in the brake lines is boiling (vaporizing). Ever seen the under-carriage camera shots of the red hot brake rotors on race cars? Brake pads are as hot as the rotor, since they are in direct thermal contact with the rotor during braking. Brake fluid in the piston on the other side of the thin brake pad gets really, really hot. Sintered metal pads transfer heat from the rotors to the brake fluid even more effectively than normal pads. Hot enough to boil water in a brake lIne under a few psi higher pressure than atmospheric? You bet. Think about running a long downhill with your brakes on. Then think about grabbing the rotor with your hand. Do you think the rotor would be hot enough to severely burn your hand by boiling the water in your flesh? Please do not actually try this! I do agree about air in brake lines being bad. Note that every motorcycle manual including Kawasaki's specifically says to fill brake lines with fresh brake fluid from a previously unopened brake fluid container. Why? They are concerned about the highly hydroscopic brake fluid picking up water from the atmosphere. Water contaminated brake fluid put into a sealed brake line will give poor braking performance even with no air in the freshly bled system. -- Marc, KLR650 A12, Loveland, Colorado, USA "Jim & Shannon Morehead" wrote: __________

>You can make water vapor (steam) if the temp. is high enough and the system >pressure is below the vapor pressure. Are you sure this really happens? >You might check your steam tables. In my experience, the most common source >of "mushy" brakes is air in the system. YMMV > >Jim > >----- Original Message ----- >From: "Marc Illsley Clarke" >To: "Jim & Shannon Morehead" ; "Jim Jackson" >; DSN_klr650@yahoogroups.com>; "Marc Illsley Clarke" > >Sent: Wednesday, June 27, 2001 12:08 PM >Subject: Re: [DSN_klr650] Digest Number 1477 > > >> Brake fluid contaminated with water is compressible. Has to do with the >brakes' heat boilong the water and making steam in the brake line. Steam >compresses. >> >> This is called "mushy brakes". >> >> -- Marc, KLR650 A12, Loveland, Colorado, USA >> >> "Jim & Shannon Morehead" wrote: >> __________ >> >Marc, >> > >> >Compressible liquids??? I can't think of any. >> > >> >Jim >> > >> >> -- Marc >> >> Marc Illsley Clarke >> mailto:marcclarke@... >> >

-- Marc Marc Illsley Clarke mailto:marcclarke@...

[Marc Illsley Clarke]

Yes. Water boils at a lower temperature than brake fluid. Brake fluid boils at about 500 F, I believe. Brake fluid boils in brake systems, causing brake fade. Water-contaminated brake fluid boils at a lower temperature than pure brake fluid. Why do you suppose brakes fade on a long downhill? Something in the brake lines is boiling (vaporizing). Ever seen the under-carriage camera shots of the red hot brake rotors on race cars? Brake pads are as hot as the rotor, since they are in direct thermal contact with the rotor during braking. Brake fluid in the piston on the other side of the thin brake pad gets really, really hot. Sintered metal pads transfer heat from the rotors to the brake fluid even more effectively than normal pads. Hot enough to boil water in a brake lIne under a few psi higher pressure than atmospheric? You bet. Think about running a long downhill with your brakes on. Then think about grabbing the rotor with your hand. Do you think the rotor would be hot enough to severely burn your hand by boiling the water in your flesh? Please do not actually try this! I do agree about air in brake lines being bad. Note that every motorcycle manual including Kawasaki's specifically says to fill brake lines with fresh brake fluid from a previously unopened brake fluid container. Why? They are concerned about the highly hydroscopic brake fluid picking up water from the atmosphere. Water contaminated brake fluid put into a sealed brake line will give poor braking performance even with no air in the freshly bled system. -- Marc, KLR650 A12, Loveland, Colorado, USA "Jim & Shannon Morehead" wrote: __________

>You can make water vapor (steam) if the temp. is high enough and the system >pressure is below the vapor pressure. Are you sure this really happens? >You might check your steam tables. In my experience, the most common source >of "mushy" brakes is air in the system. YMMV > >Jim > >----- Original Message ----- >From: "Marc Illsley Clarke" >To: "Jim & Shannon Morehead" ; "Jim Jackson" >; DSN_klr650@yahoogroups.com>; "Marc Illsley Clarke" > >Sent: Wednesday, June 27, 2001 12:08 PM >Subject: Re: [DSN_klr650] Digest Number 1477 > > >> Brake fluid contaminated with water is compressible. Has to do with the >brakes' heat boilong the water and making steam in the brake line. Steam >compresses. >> >> This is called "mushy brakes". >> >> -- Marc, KLR650 A12, Loveland, Colorado, USA >> >> "Jim & Shannon Morehead" wrote: >> __________ >> >Marc, >> > >> >Compressible liquids??? I can't think of any. >> > >> >Jim >> > >> >> -- Marc >> >> Marc Illsley Clarke >> mailto:marcclarke@... >> >

-- Marc Marc Illsley Clarke mailto:marcclarke@...

[Marc Illsley Clarke]

AMEN! Cheap, easy, a no-brainer. 6/28/01 11:02 "Susan Moorhead" wrote: __________

>Marc, > >I agree, change the fluid once a year, forget about it for another 12 >months, enjoy the ride, don't worry about the brakes. > >Just my .02 worth, > >Marshall in Afton, Ok >'95 KLXC3 "Blackhorse" (in honor of those who served) >----- Original Message ----- >From: Marc Illsley Clarke >To: Barry Levine ; DSN_klr650@yahoogroups.com> >Sent: Wednesday, June 27, 2001 9:19 PM >Subject: re: [DSN_klr650] Re: Digest Number 1477 > > >> Easy solution is to use DOT4 and a Mitivac to suck the contaminated brake >fluid out, replacing it with fresh DOT4 fluid. 5 minute job per brake line >at least once a year. >> >> Water gets into properly installed non-leaking brake lines. Top motocross >racers change brake fluid every race to avoid mushy brakes. >> >> Contaminated brake fluid yields mushy brake lever feel even before the >brakes heat up the brake fluid. >> >> -- Marc, KLR650 A12, Loveland, Colorado, USA > > >

-- Marc Marc Illsley Clarke mailto:marcclarke@...

[Jim & Shannon Morehead]

Marc, Sorry, but I think you are over-simplifying the problem. There are more variables in the brake fade problem than vapor in the brake lines. I think you will find that the coefficients of friction are temperature dependent. BTW, Chris Krok estimates the brake system pressure at 800psi. Water boils at about 518 degrees F. at that pressure. Jim

----- Original Message ----- From: "Marc Illsley Clarke" To: "Jim & Shannon Morehead" ; "Jim Jackson" ; DSN_klr650@yahoogroups.com>; "Marc Illsley Clarke" Sent: Thursday, June 28, 2001 11:11 AM Subject: Re: [DSN_klr650] Digest Number 1477 > Yes. Water boils at a lower temperature than brake fluid. Brake fluid boils at about 500 F, I believe. Brake fluid boils in brake systems, causing brake fade. Water-contaminated brake fluid boils at a lower temperature than pure brake fluid. Why do you suppose brakes fade on a long downhill? Something in the brake lines is boiling (vaporizing). > >

[RM]

On Thu, 28 Jun 2001, Jim & Shannon Morehead wrote:

>BTW, Chris Krok estimates the brake system pressure at 800psi. Water boils >at about 518 degrees F. at that pressure.

...then ya leggo of the lever. Pressure returns to near atmospheric but the heat remains. Now what?

[Marc Illsley Clarke]

If Chris has 50 lbs grip strength on a KLR brake lever, he is an animal. I've done a lot of physical therapy on my hands -- I think 20 or 25 lbs might be more in line. I think his 800 psi estimate is probably quite high. I don't think rubber lines can even withstand 800 psi. I am going to have start looking at some hydraulics catalogs. Are you contending that brake fade is due to hot brake pads having a lower coefficient of friction than cool brake pads? You may well be correct. I think you are right about my over-simplifying. I had neglected the fact that heat severely degrades brake fluid and lowers its boiling point. That is why brake fluid changes color. I am still thinkong about how air enters the system. It must come in past the piston in the caliper. Everything else is sealed. -- Marc, KLR650 A12, Loveland, Colorado, USA "Jim & Shannon Morehead" wrote: __________

>Marc, > >Sorry, but I think you are over-simplifying the problem. There are more >variables in the brake fade problem than vapor in the brake lines. I think >you will find that the coefficients of friction are temperature dependent. > >BTW, Chris Krok estimates the brake system pressure at 800psi. Water boils >at about 518 degrees F. at that pressure. > >Jim > >----- Original Message ----- >From: "Marc Illsley Clarke" >To: "Jim & Shannon Morehead" ; "Jim Jackson" >; DSN_klr650@yahoogroups.com>; "Marc Illsley Clarke" > >Sent: Thursday, June 28, 2001 11:11 AM >Subject: Re: [DSN_klr650] Digest Number 1477 > > >> Yes. Water boils at a lower temperature than brake fluid. Brake fluid >boils at about 500 F, I believe. Brake fluid boils in brake systems, >causing brake fade. Water-contaminated brake fluid boils at a lower >temperature than pure brake fluid. Why do you suppose brakes fade on a long >downhill? Something in the brake lines is boiling (vaporizing). >> >> > > >Visit the KLR650 archives at >http://www.listquest.com/lq/search.html?ln=klr650 > >Post message: DSN_klr650@yahoogroups.com >Subscribe: DSN_klr650-subscribe@yahoogroups.com >Unsubscribe: DSN_klr650-unsubscribe@yahoogroups.com >List owner: DSN_klr650-owner@yahoogroups.com > >Support Dual Sport News by subscribing at: >http://www.dualsportnews.com > >Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ > >

-- Marc Marc Illsley Clarke mailto:marcclarke@...

[monahanwb@yahoo.com]

--- In DSN_klr650@y..., "Marc Illsley Clarke" wrote:

> If Chris has 50 lbs grip strength on a KLR brake lever, he is an

animal. He gets that strength from constant perusing of the J.C. Penney lingerie catalog. Butcher Bill "you can beat our prices, but you can't beat our meat"

[Barry Levine]

--- In DSN_klr650@y..., monahanwb@y... wrote:

> --- In DSN_klr650@y..., "Marc Illsley Clarke"

wrote:

> > If Chris has 50 lbs grip strength on a KLR brake lever, he is

an

> animal. > > He gets that strength from constant perusing of the J.C.

Penney

> lingerie catalog. >

"Left hand - can't zip up his fly... ... right hand - can crush a Volkswagen Beetle" *grin *

[tismybutt@yahoo.com]

--- In DSN_klr650@y..., RM wrote:

> > On Thu, 28 Jun 2001, Jim & Shannon Morehead wrote: > > >BTW, Chris Krok estimates the brake system pressure at 800psi.

Water boils

> >at about 518 degrees F. at that pressure. > > ...then ya leggo of the lever. Pressure returns to near

atmospheric but

> the heat remains. Now what? > >

Who cares? You're stopped!