Rear Brake problem

[fuddydud]

I recently and suddenly lost all braking to the rear wheel as follows:

While practicing slow speed parking lot sharp turns and applying some rear brake while maintaing a small amount of throttle the travel of the rear brake pedal became suddenly flaccid with no resistance to travel and all braking to the rear wheel was lost.

A short time later, rear brake pedal travel resistance and rear brake function returned to normal.

Has anyone experienced this problem? If yes, please provide information and advice. Much obliged.

 

[bramfrank]

While I've never suffered the problem you describe I wish it was still Friday.

 

[JamesK]

You didn't mention how old your brake fluid is, but if it pretty old, one problem that could be the cause is that there's a sizable build up of water/moisture in the brake fluid. Thus when you used a lot of rear brake your fluid (with water in it) is heating up. As the water in that brake fluid heats up and vaporizes it effectively introduces air into the system. As the fluid cools the water vapor turns to liquid again, hence the behavior you describe.

Assuming the rear pads are in good condition, I'd replace the brake fluid, and consider using DOT 5.1 fluid, as this has a much higher boiling temp.

 

[brazos parker]

I had a similar problem...lost all rear braking ability.

Look here...Rear Brake Problem

 

[fuddydud]

Jamesk & Brazos:

Much obliged. Thank you for the comments and suggestions.

 

[Wee Willy]

Bet it's the ABS. Did you hear the sound of the ABS system while this was going on? It's a slight buzzing sound on my Gen 2.

W2

 

[Shane]

Sounds like a classic case of Brake Fade

And if you believe Wikipedia as a source, here's another link: Not peer reviewed as a source, but still in line here--Brake fade

Shane

 

[Wee Willy]

Sounds like a classic case of Brake Fade
And if you believe Wikipedia as a source, here's another link: Not peer reviewed as a source, but still in line here--Brake fade

Shane

I suspect it's something else Shane. Low speed parking lot drills won't lead to this particular effect. Fade happens from heat buildup in the brakes as noted in the article.

Vehicle braking system fade, or brake fade is the reduction in stopping power that can occur after repeated or sustained application of the brakes, especially in high load or high speed conditions.

This usually happens only after a quick repetition of several hard stops from speed or from dragging a brake for a period. You can experience it first-hand by taking your bike to the track and throwing it around in anger. Usually takes a lap or two on a typical track to get to this level of heat.

I still suspect the ABS was involved. At low speed, the speed sensors can send signals that are difficult for the computer to interpret correctly, causing it to draw the wrong conclusions about what is going on. In a tight turn, too, the two wheel speeds will be significantly different as the front is riding a larger circle than the rear and will be showing a proportionally greater speed. These kinds of speed differentials CAN trigger an inappropriate response from the ABS system, and it would be the rear that is affected.

Cheers,

W2

 

[fuddydud]

Thank y'all very much for your helpful comments. Much obliged.

 

[FiveG]

I recently and suddenly lost all braking to the rear wheel as follows:While practicing slow speed parking lot sharp turns and applying some rear brake while maintaing a small amount of throttle the travel of the rear brake pedal became suddenly flaccid with no resistance to travel and all braking to the rear wheel was lost.

A short time later, rear brake pedal travel resistance and rear brake function returned to normal.

Has anyone experienced this problem? If yes, please provide information and advice. Much obliged.

Had almost identical experience today. My '07 has about 10,800 miles on it (5300 of them mine this summer) and I rode about 350 miles this weekend. No problem. But, this afternoon, was in parking lot practicing slow, esp. with my wife riding as passenger, and was using rear brake to control speed (this two-up thing is new for us). Brake worked just fine throughout, until I then went to stop sign, and it was suddenly completely without resistence and ineffective. I had her get off the bike to see if there was something about my foot position -- remained the same. I cancelled practice immediately and rode to the dealer (which is about 10 miles away). As I did, the brake slowly regained resistance and started to work. By the time I got to the dealer, it was almost back to normal. Still, I left it there for them to look at.

Bike had factory-style 8000 mile service, with the requisite new fluids etc.

Any clues? Hose failures? (Believe they are original, for instance.)

 

[wfooshee]

Hose failure would lead to brake fluid being sprayed all over everywhere. It also will never ever ever recover from a hose failure by itself.

This is heat buildup, leading to brake fade, even at just parking lot speeds. Sure, you didn't do three hard stops from 150 miles per hour, but you did drag the thing around with throttle and brake opposing each other, with minimal (if any) cooling time between brake applications.

The thing to do when the brake stops working would be to take your gloves off and grab the disk or caliper with your bare hand and see if it's toasty. If you get 3rd degree burns then it's brake fade. (Seriously, don't do this. . . .)

Riding away and allowing the components to cool brings gradual recovery of brake function, exactly as described by both people here who say they've had it happen.

Brake fluid absorbs water. That pool sitting in the reservoir is NOT sealed away from the atmosphere as well as you'd like to believe. As it absorbs water, the water distributes itself through the whole body of fluid: lines, reservoir, cylinders, everywhere. If the temp gets high enough, it boils, you get compressible gas in the brake line, and you can't shove the pistons against the pads.

 

[Silverbear]

Hose failure would lead to brake fluid being sprayed all over everywhere. It also will never ever ever recover from a hose failure by itself.
This is heat buildup, leading to brake fade, even at just parking lot speeds. Sure, you didn't do three hard stops from 150 miles per hour, but you did drag the thing around with throttle and brake opposing each other, with minimal (if any) cooling time between brake applications.

The thing to do when the brake stops working would be to take your gloves off and grab the disk or caliper with your bare hand and see if it's toasty. If you get 3rd degree burns then it's brake fade. (Seriously, don't do this. . . .)

Riding away and allowing the components to cool brings gradual recovery of brake function, exactly as described by both people here who say they've had it happen.

Brake fluid absorbs water. That pool sitting in the reservoir is NOT sealed away from the atmosphere as well as you'd like to believe. As it absorbs water, the water distributes itself through the whole body of fluid: lines, reservoir, cylinders, everywhere. If the temp gets high enough, it boils, you get compressible gas in the brake line, and you can't shove the pistons against the pads.

What wfooshee said.

I had the same problem. Once the brake fluid has boiled, replace it as it will happen again in the most inopportune time. It is easy to replace the brake fluid, just get yourself a MightyVac and a fresh can on DOT4 brake fluid. Follow this excellent link on FJRTech.com, but for the rear brake instead of the clutch. 20 minutes max, and you are on your way.

Silverbear

 

[steel23]

I had this experience on my previous bike based on what you have described. For mine, even after bleeding it several times, the brake still seem to be absent. So finally decided to remove the brake caliper. Turn out to be the 'o' rings within the caliper, supporting the movements of the brake pistons to be dried up and slightly crispy. Due to that, it's not providing the pressure or friction needed to perform the braking. Had the 'o' rings replaced, bleed them again and all's well again. Hope it works for you as well.

 

[FiveG]

Dealer reports that I had air in line (probably from boiling). Also some rotor discoloration etc. As matter of overcaution, getting new rotors and pads as well as better brake fluid.

But here's where I'm confused and really would appreciate insight: I've been trained, and guys like Jerry Paladino (Ride Like A Pro) teach, that you SHOULD use your rear brake at low speeds as a controlling brake. So far as I can tell, motorcycle cops do that for long periods of time. So, if that's true, why can't these rear brakes handle 5-10 minutes of being lightly ridden while in a parking lot? Strikes me that they should survive that well. Or have I done so much parking lot time using the rear brake that over time, they've simply given up the ghost?

I really would appreciate insight on the technique issue.

 

[Ignacio]

So far as I can tell, motorcycle cops do that for long periods of time. So, if that's true, why can't these rear brakes handle 5-10 minutes of being lightly ridden while in a parking lot? Strikes me that they should survive that well. Or have I done so much parking lot time using the rear brake that over time, they've simply given up the ghost?

I'd question those assumptions. Why would cops hang out in parking lots and perpetually drag their rear brake? Aren't they usually out in traffic more and occasionally using their brakes hard. The ones I've seen in parking lot training tend to be using both...I didn't notice any dragging the rear.

And "lightly" seems very subjective to me. It would seem to me a lot of heat and fuel can be used by canceling throttle by brake action...no matter how delicate it may feel at the wheel.

I guess I'm one of those that use the rear brake in parking lots only when I need speeds less than idle in first gear. I may drag from 1100 to 800 rpm...10 or 15 seconds.

I would think fresh fluid and a bleed are going to help the fade....leaving the question of how hard you're working the brakes to a matter of personal taste or training choices.

 

[cruppelt]

Dealer reports that I had air in line (probably from boiling). Also some rotor discoloration etc. As matter of overcaution, getting new rotors and pads as well as better brake fluid.
But here's where I'm confused and really would appreciate insight: I've been trained, and guys like Jerry Paladino (Ride Like A Pro) teach, that you SHOULD use your rear brake at low speeds as a controlling brake. So far as I can tell, motorcycle cops do that for long periods of time. So, if that's true, why can't these rear brakes handle 5-10 minutes of being lightly ridden while in a parking lot? Strikes me that they should survive that well. Or have I done so much parking lot time using the rear brake that over time, they've simply given up the ghost?

I really would appreciate insight on the technique issue.

They DO usually survive this kind of thing without a hitch. I believe that for you there is probably a second factor involved besides old or inferior DOT fluid that has moisture in it. BTW, not knowing exactly if they really do change the fluid out every time they are supposed to, not knowing what they put in and how long the oil can was open already when used at the dealers was the reason why I also bought a mightyvac and synthetic brake fluid to go with it a few years back.

The actuator pin right under the rear brake pedal gets gunk buildup over time, and it seems that many FJR riders frequently get some light unintended rear brake actuation out of that while riding. That would jive with the discolored and worn rotors you describe. It's an easy fix, clean and lube right under the brake pedal and it's good to go again for many miles and dusty roads. I ride a long and very steep gravel driveway every day, and use the back brake heavily on that every morning with no ill side effects.

 

[Fred W]

Oh, they can take it. It's the 2 year old brake fluid you had in there that can't take it. You can generate a whole lot of heat by dragging your brake while under power. It's a pretty small brake pad. I personally do not subscribe to that technique and prefer to just pull in or feather the clutch.

New brake fluid (taken from a sealed container) won't boil. It's the absorbed moisture in the old brake fluid that boils. Once it boils you'll have steam bubbles in your brake lines.

I suspect the rear fluid is worst because the reservoir isn't as well sealed and the volume of fluid is less. Just flush your brake fluid more often an you should be good to go.

BTW, I'm pretty sure you didn't need new pads or rotors. But it's your money...

 

[SockMonkey]

I've been following this thread with interest because I too have experienced NRB (No Rear Brake) syndrome on numerous occasions since my bike was new. I've changed brake fluid 3 times (every spring w/ Yamalube DOT 4) and have bled the system 8 or 9 times (both procedures as per the service manual using a MightyVac), yet it still happens - though not with enough frequency to merit taking the bike to the shop only for a mechanic to tell me that he can't replicate it.

Interestingly, what I find is that the more I use the front brake only, the more frequently it happens. A quick pump or 2 however is all that's required to load up the rear brake and all's well again. This certainly leads me to suspect that there may(?) be air in the system somewhere (but I'll be damned if I can evacuate it or even figure out how it got/gets in there) and that the linked brake system may somehow be a contributing factor. I've gone over the brake system mechanicals; calipers, pads, rotors, lines and ABS system (through engagement) several times and everything checks out. I cannot for the life of me figure out what's causing it. (As an aside, I've often wondered if the problem is in fact heat related; are the brake lines - and thus the brake fluid, routed through the engine bay being affected by the engine heat..?)

Thoughts?