Rear brake failure, then recovery..what happened?

Phugedaboudet · Apr 19, 2009

was out with a buddy carving canyons and riding some seriously technical roads in the North Bay (Mt. Diablo and "the Wall") and after a hundred miles of this while trailbraking into a real nasty descending 180 hairpin, the rear brake pedal lost all resistance and practically dropped on it's pivot. I tried pumping it, got a little pressure for a moment, but lost it soon after.

I pulled to the side, waited for my buddy to turn around, and began looking for leaks, Pulled the side cover, the brake reservior was still full. No strange colors in the fluid. No ABS or brake error lights on the dash, no leaks, no squeaking or weird noises from the brakes before loss.

After ten minutes of looking around, buttoned everything back up and the rear brakes are back as if nothing happened. Confidence was a little shaken so we took it easy back to the highway and called it a day (we'd already put in 130 miles of twisties so it wasn't a total loss).

I'm currently at a little over 11000 miles on my 07A. I'm a little behind on service intervals (I'm doing the "longer" intervals with the last service at 5000-ish.

What happened to cause my brakes to fail so completely (rears only-fronts worked fine the whole time) and then recover? I'd only felt the smallest amount of fading in the hours before. Should I look into a different type of brake fluid?

thanks in advance.

-Rick, SJ, CA

-07 FJR1300A

FJRPierre · Apr 19, 2009

I've had this happen to me several years ago while going heavy on the rear brake down a gravel goat trail in Oregon. Brake would disappear, then i would pump like mad and they would reappear, disappear, pump etc.... Scared the crap out of me. Concensus at the time was old brake fluid w water in it and the water would boil under heavy pressure. Only happened on heavy excessive rear brake use. Never on front use. Changed fluid when I got home a week later and never happened again. YMMV

ionbeam · Apr 19, 2009

That is a normal failure mode for over heated brakes. Over heated brakes are not a normal failure.

IMO, check your brake pads for thickness, change your brake fluid and re-examine your trail-braking techniques to see if you earned over heated brakes. Did it blue your rear rotor? Bluing isn't necessarily harmful, but it is an indication of over heating.

Others will probably be along to discuss trail-braking to the point of overheating brakes.

IanS · Apr 19, 2009

Sounds like the fluid overheated with all that trail braking.

happyPuppy · Apr 19, 2009

I know the spot you were at and it is scary and a pucker area. I agree with the guys. Stuff like that trace it back from the brakes all the way. Make sure of course you change the fluid once a year and bleed of course. I have not enough miles on the FJR, but I have had that happen on other bikes. One thing I like to do is use braided cable too.

mcatrophy · Apr 19, 2009

Classic symptom of water in the brake fluid. Brake heat soaks into the fluid, water in fluid boils, steam is VERY compressible. Then you get no resistance to pedal movement. Wait ten minutes, cools below boiling point, all is well again.

Change the fluid.

browndog · Apr 19, 2009

+1 on the bleeding....overheating.

Happened one year through deals gap w/ SO on board. Scared the pudiin outta me, never let her know how close we came to being a stain.

Phugedaboudet · Apr 19, 2009

No bluing or any visual change to the rotor, the pads haven't reached their wear indicators yet. But I don't think fluid has been changed-I don't see it on the service sheet. And since it just got out of the rainy season water's sounding like more and more the culprit.

Is there any less hydrophilic fluid I can use? I hear from the Beemer crowd that mineral oil does the trick, but since I'm still under warranty I don't want to add anything that'll damage seals or cause any long term issues.

ionbeam said:
That is a normal failure mode for over heated brakes. Over heated brakes are not a normal failure.
IMO, check your brake pads for thickness, change your brake fluid and re-examine your trail-braking techniques to see if you earned over heated brakes. Did it blue your rear rotor? Bluing isn't necessarily harmful, but it is an indication of over heating.

Others will probably be along to discuss trail-braking to the point of overheating brakes.

FJRBluesman · Apr 20, 2009

Is the fluid stock from the dealer? OEM recommended is DOT4. You may want to think of using DOT5 (higher boiling point) if it's overheating. Not sure if DOT5 is recommended but they have different types with less silicone, or synthetics, etc. Remember silicone absorbs water too, so change (bleed) often.

Bogus · Apr 20, 2009

Do NOT use DOT 5 brake fluid in place of the recommended DOT 4, as they are not compatible with each other, and would require a complete flush of the brake system at a minimum, but better, a change of most brake components. Apparently, DOT 5 is more compressable than 4, and is silicone based instead of glycol based, and therefore not suited for ABS systems. Is the fluid currently in the system DOT 4? Was any fluid added to, or changed recently to another type?

SkooterG · Apr 20, 2009

Cripes!!!

Mineral oil?!?!?! You got to be kidding me! Why not try canola oil? Why not just stick with DOT4, mmm...k?

LESS rear brake! You could ride your FJR aggressively in the twisties w/o even using the rear brake at all and not be wanting for performance.

Lastly, 'trail braking' does not mean 'using the rear brake'. It means braking while initiating the turn and leaning over. And is done with either brake, but generally using more FRONT brake.

Boiled fluid from overusing/overheating rear brake. Flush and replace ASAP.

Slick · Apr 20, 2009

Had that happen up in Deals Gap. I was following a Buell (on a Harley) and I was too hard on the rear brakes.

I replaced the stock brake fluid with racing fluid (dot4) and it never happened again. The racing fluid has a higher boiling point and it is harder to lose your brakes with that.

Of course, if you do lose your brakes, you are being too hard on them...

FJRONAMISSION · Apr 20, 2009

SkooterG said:
Cripes!!!
Mineral oil?!?!?! You got to be kidding me! Why not try canola oil? Why not just stick with DOT4, mmm...k?

LESS rear brake! You could ride your FJR aggressively in the twisties w/o even using the rear brake at all and not be wanting for performance.

Lastly, 'trail braking' does not mean 'using the rear brake'. It means braking while initiating the turn and leaning over. And is done with either brake, but generally using more FRONT brake.

Boiled fluid from overusing/overheating rear brake. Flush and replace ASAP.

=========

WHAT HE SAID...........

Flush asap...... less rear brake in the twisties....

B.

luvtoride · Apr 20, 2009

Jeez, I read this forum too much. I knew the cause & solution b4 I read all of the posts... this place is a wealth of information... even for a woman.

Good luck Pha...

worldbound4now · Apr 20, 2009

There's brakes on these machines???? Ride The Pace, enjoy the twisties, and try to setup appropriately for the corner. Your brakes will thank you for it. I have 33K+ on the OEM brakes and am nowhere near considering replacement. As already stated, regular fluid changes will also prevent this from happening.

Aasland · Apr 20, 2009

I seem to recall seeing synthetic dot4 that claims it can be mixed with regular dot4 (and maybe even dot3?). Primary benefits (iirc) was less hydrophilic and higher boiling point.

Fred W · Apr 20, 2009

DOT3 and DOT4 as well as the latest DOT5.1 fluids are all polyethelene glycol based fluids. DOT4 has a slightly higher boiling point than 3. Both are hygroscopic (will absorb water directly from humid air) and hence need to be changed at regular intervals.

DOT5 is non hygroscopic silicone based fluid and is 100% non compatible with the other 3 designation fluids and has a higher BP than DOT4.

DOT5.1 has the highest boiling point of all, when new and not contaminated with water. Introducing water will lower any of the hygroscopic fluids.

The reason that you don't want DOT5 fluid is because it is NOT hydrophilic . Being non hydrophilic means that the boiling point may remain (more) stable with age as it will not readily absorb water. That's good. But, if even a small amount of water is introduced into the system it will not be absorbed by the fluid and it will find its way to the lowest point whee it will corrode the brake system parts internally.

r1byker · Apr 20, 2009

It's been said several times but I thought I would say it again. IMHO, you need to use your front brake a lot more and use your rear brake much, much less. The bike is designed to be ridden that way; that's why there're two big rotors on the front and one little rotor on the rear.

When I do track days, I rarely use the rear brake; I brake so hard with the front the rear is pretty light anyways, and sometimes in the air. Even in those extreme circumstances, I've never boiled the fluid on my front brakes, nor have people who go a lot faster than me. I basically do the same thing with the FJR on the street with a little more use of the rear brake to settle the bike.

I remember reading an article several years ago about "boiling" the brake fluid, and since I had done it a couple times with my work truck, I took special interest. If I remember correctly (and I emphasize my memory could be wrong), it said that brake fluid, even fresh fluid, contains "atmospheric" (at least, I think that was the term) moisture. That's what turns to steam, and is thus compressible, resulting in the brake pedal going all the way down. When it cools down, the moisture reverts to its solid state and thus you have functioning brakes again. If indeed I remember all this correctly, that means changing the brake fluid with the same specs will have little effect. I particularly don't think any water got into your braking system due to the rainy season; that would mean that, in some way, there's a leak in your system, in which case you wouldn't have any brakes.

Fred W · Apr 20, 2009

r1byker said:
It's been said several times but I thought I would say it again. IMHO, you need to use your front brake a lot more and use your rear brake much, much less. The bike is designed to be ridden that way; that's why there're two big rotors on the front and one little rotor on the rear.
When I do track days, I rarely use the rear brake; I brake so hard with the front the rear is pretty light anyways, and sometimes in the air. Even in those extreme circumstances, I've never boiled the fluid on my front brakes, nor have people who go a lot faster than me. I basically do the same thing with the FJR on the street with a little more use of the rear brake to settle the bike.

I remember reading an article several years ago about "boiling" the brake fluid, and since I had done it a couple times with my work truck, I took special interest. If I remember correctly (and I emphasize my memory could be wrong), it said that brake fluid, even fresh fluid, contains "atmospheric" (at least, I think that was the term) moisture. That's what turns to steam, and is thus compressible, resulting in the brake pedal going all the way down. When it cools down, the moisture reverts to its solid state and thus you have functioning brakes again. If indeed I remember all this correctly, that means changing the brake fluid with the same specs will have little effect. I particularly don't think any water got into your braking system due to the rainy season; that would mean that, in some way, there's a leak in your system, in which case you wouldn't have any brakes.

Negatory on that. Sort of...

You may recall (somewhat quizzically) that brake system eggspurts generally recommend only using brake fluid from new containers with unbroken seals. That's 'cause (as I mentioned before) brake fluid is hygroscopic, which as you somewhat surmised, means it will absorb (some limited amount of ) H2O directly from the atmosphere (if exposed to the rancid stuff). So, if the fluid is wicked ultra fresh stuff, right out of the recently un-hermetically-sealed bottle, and immediately forthwith injected into said brake system and then resealed (you know, with the reservoir cap thingee) the amount of water in the system will be infinitesimally small.

OTOH, if you leave an open bottle on the shelf in your carport in Floriduh in July when the RH is 150%, well... you might as well be mixing it with tap water.

Rear brake failure, then recovery..what happened?

Help Support Yamaha FJR Motorcycle Forum:

Well-known member

Making up for lost time...

2 FUN

Active member

Well-known member

Privileged to ride a 2018 FJR1300AS

Well-known member

Well-known member

Some call me... The STIG!

Well-known member

Purveyor of Crooked Facts

Well-known member

Flying at the speed of smell ;))

My Indian name is &quot;Pants On Fire&quot;

Well-known member

Depleted

1 Wheel Drive

Well-known member

1 Wheel Drive

Similar threads

Join the conversation!

Join today and get all the highlights of this community direct to your inbox. It's FREE!

My Indian name is "Pants On Fire"