Crisis takes to chattering, During Hard Braking that is.. .. ..

[FinalImpact]

Since the addition of the R6 forks 2 seasons ago (2012-02), in that 1st season I had one event of down hill corner braking where the nose went into a ballistic chatter that had me on the double yellow at high speeds and the only means of stopping it was letting off the brakes. However, it never repeated for 10 months (End of 2012) so I wrote it off as a conditional.

OK - so from March of 2013 to June, I've ridden allot of the same roads. I did change tires and had the chatter thing happen on a road I ride more often. I've been back and sure enough I can repeat it! The area has a pronounced washout/ripples/divets/bumps where everyone brakes before this corner. OK - i can accept that where the road is abusive it could put the ball in play. But now, its an upward trend happening about 5 times tonight which is an all time record. One of those events nearly got me in trouble and this time I couldn't see anything in the road bump wise.

• Key takeaway: this only happens going downhill, braking HARD, on rough surface, and leaning. Remove ANY of ONE factor and it never happens! That said it seems to be a tire loading issue making the tire dribble and the suspension bouncing in unison with the tire (aka "Rubber Ball"). It IS NOT a Brake issue but a loading/weight transfer issue when the brakes are used hard!
• Goal --> Change one thing at a time and try to reduce or eliminate the headset dribble!

- tire pressure same // 33.5psi
- tires good, S20s
- brake fluid - DUE, ready for bleeding
- Forks, no leaks, but two years on fluid. They are due for a fluid change.

Before she gets parked for the winter, I'll at least do the brake fluid and see if I get a run in to duplicate before weather turns (its imminent). My gut instinct says its a combo of all things. Conditions, tire pressure, fork damping, and brakes. Its still running the OEM pads from 08. They have life but, maybe they need swapped. Rotor surface looks just as it has.

I'll keep you posted as to what I find. And lets not exclude the back of the bike. No changes anywhere, but I suppose it could factor into this also.

Anyone else have chatter issues? Only saw one thread on the issue...

EDIT LIST:
*****************************
ACTUAL CHANGES / PROGRESS REPORT SNIPIT...
*****************************
NOTE: N/C = No change to performance

2014-01-05 (N/C) Dump Fork oil (10wt --> 7.5wt), measure and reset SAG, Clean calipers & bleed brakes, verify rotor deflection.
2014-04 Riding season under way!
2014-04 to 06 Minor improvements with increased Tire pressure. Played with lots of values front and rear.
2014-06-20 (N/C) New brake pads installed and bled brakes again.
2014-06-29 Improved! Synchronized rebound damping on both forks, decreased rear sag, increased rebound rate.
2014-07-26 New 016 Pro front tire. Too soon to tell. Verified rotor trueness after install.

*****************************

JJD952

 

[darius]

Re: Crisis takes to chattering, brakes that is.. .. ..

Yikes. Take care, Randy. Your gut says it's a combo yet you're only going to make a single change for now?

Why not clean/service the front calipers and get new pads, fork oil all at once?

 

[FinalImpact]

Re: Crisis takes to chattering, brakes that is.. .. ..

Once parked it's gonna geat allot more attention. Timeline says I'm not gonna do it all at once now.... Anyway, conditions have to be juuuuuuuuust right to put the ball in play. Granted I could do it all in a day, but too much going right now.

Add in the head bearings too. Still the originals... Feel fine but I'd rather see if one item solves it if possible and once parked. Its all gonna get done. Lets see what the weather does.

 

[DeepBlueRider]

Re: Crisis takes to chattering, brakes that is.. .. ..

From your description it sound like you would lock front wheel but your tires are too good to skid. But you haven't lock wheel, right ?

 

[FinalImpact]

Re: Crisis takes to chattering, brakes that is.. .. ..

Negative on that. No wheel lock on either end.

Picture -
60 mph, ease into brakes with constant increase in applied pressure (braking fairly aggressively) , could be leaned over or upright. By this time the brakes are warming and we're usually tipping into the corner and have slowed substantially by now. The nose starts a very rythmic pulse/chatter, pushing straight back on the bars so its transmitting this to me the rider. At this point, the bars rattling "likely has" my hand varying the brake pressure applied. Walla - its in full motion.... Because I've dropped the speed, I'm easing off the brakes and the chatter stops. However, a year ago and one other time I dribbled near trouble and let off to lean it over. it was bad!

One change I forget about since this stepped up, I rotated the bars up so they have more clearance over the tank during full tilt turns and I never matched my levers to the new angle. i.e. rotate them down so the line from my shoulders to to fingers is basically parallel neither pointing my fingers up or too far curled.

 

[Cali rider]

Re: Crisis takes to chattering, brakes that is.. .. ..

SNIP....Anyone else have chatter issues? Only saw one thread on the issue...

JJD952

Yes, I did. I think you are referring to this long post I made... http://www.600riders.com/forum/fz6-technical/46100-what-brake-pads-do-you-use.html#post502270

My problem was exactly word for word what is happening with you. I could duplicate that shaking/pulsation at will but it would also happen at unexpected times. I could make it happen at 5 MPH as well. The only remaining item I wished I had checked was the swingarm pivot bearings. I can tell you that I completely lost confidence in riding the FZ6 and that became the primary reason I sold it.

I consider myself VERY technically adept. I have designed tools, repaired everything from watches to 2000 ton presses and have the patience to methodically troubleshoot complex problems. I spent upwards of 80 hours trying to cure this problem. I NEVER found the cause.

If I can be of any assistance Randy let me know...I would love to resolve this issue in my mind.

 

[Cali rider]

Re: Crisis takes to chattering, brakes that is.. .. ..

And I'm making this topic a Sticky as it's critical that it gets noticed by other members.

 

[yamihoe]

Re: Crisis takes to chattering, brakes that is.. .. ..

2 things, mine (r6 forks and calipers) does it sometimes when theres a dust buildup, It goes away if I spray down the calipers and pads with brake parts cleaner, It got me in trouble once as well. try that first!!

Second: I was working on a cbr where any use of the front brakes would make the whole bike shudder, like shake your hands off the bars type of shudder, the rotors have little shims that had come out and you could wiggle the rotor, but it was true, not warped at all.

that also lead to the headbearings going bad, that also made the bike shudder horribly, but that was much more consistent.

 

[greg]

Re: Crisis takes to chattering, brakes that is.. .. ..

is the front too soft? have you lowered the front at all or raised the back?

could be that when braking hard, the front end is being pushed down, reducing the trail, making steering a lot more sensitive and causing a bit of a slapper

the rate of rebound could also be too low, to it can't track the road as well

 

[FinalImpact]

Re: Crisis takes to chattering, brakes that is.. .. ..

Yes, I did. I think you are referring to this long post I made... http://www.600riders.com/forum/fz6-technical/46100-what-brake-pads-do-you-use.html#post502270

My problem was exactly word for word what is happening with you. I could duplicate that shaking/pulsation at will but it would also happen at unexpected times. I could make it happen at 5 MPH as well. The only remaining item I wished I had checked was the swingarm pivot bearings. I can tell you that I completely lost confidence in riding the FZ6 and that became the primary reason I sold it.

I consider myself VERY technically adept. I have designed tools, repaired everything from watches to 2000 ton presses and have the patience to methodically troubleshoot complex problems. I spent upwards of 80 hours trying to cure this problem. I NEVER found the cause.

If I can be of any assistance Randy let me know...I would love to resolve this issue in my mind.

Thanks! I will keep this in mind. Fwiw: on a smooth road I can panic brake from 80 without issues. Its when the road, forks, pads and me all work together out of harmony that this condition occurs. So, didn't want bring this up, but some of you may recall I found her taking a nap in the parking lot. That pushed the bars over an. inch and is when I raised them.
I may put them back and see what happens. If you think of the tire as rubber ball it wants to bounce. So independently all things are ok. However, the riders grip on the brake lever is a variable...
Thanks for your input on this. I do want to single step it and see what is the biggest contributor. Hopefully it can be solved!

PS - Cliff mentioned build up on the rotor in that other thread, why would this not be factor all the time? Ya, it just needs the right conditions to propagate.

Thanksa all!!

 

[Motogiro]

Re: Crisis takes to chattering, brakes that is.. .. ..

PS - Cliff mentioned build up on the rotor in that other thread, why would this not be factor all the time? Ya, it just needs the right conditions to propagate.

Thanksa all!!

No build up. Contamination on a specific area of the rotor.
I've read where if you get oils/contaminate on an area of the rotor and there's high heat it can create a hard spot where that oil heats and creates a glazed area on the rotor. As the pad squeezes the rotor there are two different grip surfaces that shows up as a shutter/vibration during hard braking. New EBC pads aren't cheap.

I sanded the rotors put new EBCs and it reduced the problem and it went completely away after a few rides. Prior to the problem I had the bike dyno'd and they asked if I'd like them to change to new brake fluid. I let them..... :disapprove:Not any more!

Hope you find it!

 

[aclayonb]

Re: Crisis takes to chattering, brakes that is.. .. ..

If the vibration or pulsing is rhythmic, I'd have to agree with Moto. The only thing that is going to product a rhythmic vibration in the front end is the wheel or the rotor. Anything else is going to product an a-rhythmic vibration or shudder.

I'd check my bolts on the caliper, rotors, front axle, and steering head, just for kicks. I've never heard of hard spots in a rotor but it makes sense. I can see where a slightly loose axle or bad bearing could let the forks shift ever so slightly or a loose/worn head bearing could do the same.

 

[Nelly]

Re: Crisis takes to chattering, brakes that is.. .. ..

Hi Randy,

Did this issue arise before or after the rear shock upgrade? Could the problem be a result of mismatched suspension?
Other members who have completed the R6 fork mod haven't posted up any issues. I know that Pete had a really hard time trying to get the R1 shock work in his FZ6.
Nelly:thumbup:

 

[FinalImpact]

Re: Crisis takes to chattering, brakes that is.. .. ..

The combo has been on there all season and works awesome. The balance front to rear has been perfect. I am on the brakes hard when this occurs. All other times its flawless braking from all speeds. One addition that plays a role is its almost always when braking going down hill. I.e. more weight transfer going forward.
I'm 95% certain it has a direct relationship to tires and fork damping. A bump gets the dribble in play which depending on body position gets my hand (caused by my body) varying the applied pressure.
As mentioned, the last change was rotating the bars which changes how I interact with the brake system. Let's start there... sounds like the ONE thing no one else change. Maybe? Just thinking out loud...

 

[TownsendsFJR1300]

Re: Crisis takes to chattering, brakes that is.. .. ..

With it occurring most of the time braking downhill, especially hard braking , as you mentioned, the forks are compressing more than on flat ground.

I would strongly look at a slightly longer spring spacers (or if there's an adjustment-extend it) to keep the forks from dipping quite so far.

I don't know why they would chatter unless the front tire is "skipping" on the road, perhaps too much dampening, not allowing the forks / wheel to extend back out.

All the above is after ruling out crap on the disc's / pads.

Just a thought..

 

[aclayonb]

Re: Crisis takes to chattering, brakes that is.. .. ..

As mentioned, the last change was rotating the bars which changes how I interact with the brake system. Let's start there... sounds like the ONE thing no one else change. Maybe? Just thinking out loud...

A wise man once told me that "it's always the last thing you fu*#ed with." I don't think that's the case here but.....

 

[FinalImpact]

Re: Crisis takes to chattering, brakes that is.. .. ..

is the front too soft? have you lowered the front at all or raised the back?

could be that when braking hard, the front end is being pushed down, reducing the trail, making steering a lot more sensitive and causing a bit of a slapper

the rate of rebound could also be too low, to it can't track the road as well

I never answered this;
Is the front too soft. No. Its actually very firm on compression. Rebound is just enough to not induce pack down, while tracking the road well over small bumps. I have not changed the settings this year. Well other than to record them and put them back.

I have not checked the sag since last year to see if a spring has "sagged". Off hand, I'm going to say No that has not occurred but need to check it.

As for slapper. No. Just a straight push back on the bars. No Tank slap.

Note to self, full fuel tank 17 miles ago... Perhaps a summary of all things in another post.

 

[FinalImpact]

Re: Crisis takes to chattering, brakes that is.. .. ..

If the vibration or pulsing is rhythmic, I'd have to agree with Moto. The only thing that is going to product a rhythmic vibration in the front end is the wheel or the rotor. Anything else is going to product an a-rhythmic vibration or shudder.

I'd check my bolts on the caliper, rotors, front axle, and steering head, just for kicks. I've never heard of hard spots in a rotor but it makes sense. I can see where a slightly loose axle or bad bearing could let the forks shift ever so slightly or a loose/worn head bearing could do the same.

If I understood you correctly, I think you're saying (FOR EXAMPLE), if there is fault with say the 10 O'clock section of the rotor, that every time it comes past the pads @ the 10 O'clock, it will pulsate. That is not the case. It is NOT dependent on speed/rotation. Its rate of pulse is actually pretty consistent. Considering the speed when it starts and the speed when its all over could be 30 mph less than when it started, the rate the ball bounces throughout the session is the one thing that is consistent. It hardly changes. Neither speeds up or slows down. The change in this area is the intensity, not the rate.

Does that make more sense?

The day I planned to test was rained out. So no changes and no test rides.

 

[aclayonb]

Re: Crisis takes to chattering, brakes that is.. .. ..

I don't know. I'd still be checking all of my suspension bolts, sprocket bolts, engine bolts, etc.

How old are your wheel bearings?

 

[Nelly]

Re: Crisis takes to chattering, brakes that is.. .. ..

Could it be that with the updated suspension and better braking system you are more confident to push the limits causing the tyre to brake traction?

Nelly

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