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

[Cali rider]

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

[MENTION=681]Cali rider[/MENTION]
I didn't research all your post to find "what" tires you ran on the bike but here is what I am finding.

Of the Sport Tires Bridgestone makes, the S20 which I'm currently running is the softest ply sidewall & carcass they have released thus far. I've been speaking with a NW rep who said some bikes have this issues and its a product of the sidewall interaction with the suspension.

I saw in one of your posts you ran 023's. Was that both front and rear? These do have a stiffer carcass than the S20 I'm on now and what I'm finding is NEW, the tire only had this woodp@cker issue at speeds greater than 60 mph and as the tires looses tread off center it will hammer at speeds as low as 20 mph. Do note its the same rate of hammer, but we're at a different speed.

The rep suggested try stiffer sidewall tires and so I'm real curious what all tires you had on the bike and if you could tell the difference in rate of occurrence from a new tire to used up tire. i.e. did it get worse??

Observation: the S20 with no air in it is so pliable it feels as though one could stick their thumb right through the tread off center. Its VERY soft in the tread area.

I may go back to the 016 PRO or Maybe a T30 but thoughts go towards the 16 if I can find one.

Bridgestone Battlax Hyper Sport S20 Front Motorcycle Tire
Size: 120/70ZR-17,
Tire Construction: Radial
Load Rating: 58 (520 lbs.)
Speed Rating: W (168 mph)
Max PSI : 42
Load Range: B
Tread Plies: 2 Rayon 1 Steel
Sidewall Plies: 2 Rayon
Position: Front
Weight: 9.35 lbs.
==========================

FWIW: M-Spec tires are tires that a motorcycle manufacture will have modified from the original design to meet the needs of "their" production bike.

==========================

Time for some more reading I guess and find a new tire to try.
Edit: added S20 pic's as they near the end. And yes, the rightside is missing more tread!

I ran Bridgestone 023, 016 and 002, both matched sets and mixed models. I ran Michelin Pilot Powers and Pilot Road 2. I had a set of Dunlop Qualifiers at one point way back, as well as the OEM Dunlops. I don't remember if the problem was critical way back but it was common for the last 2+ years. The range of sidewall strength was softest with the PR2, and by far the stiffest sidewall tires were the 002. I agree with the possibility that sidewall strength is interacting with the suspension to initiate the pogo effect as it would explain the specific frequency of the shaking at any given road speed. I did experiment with extreme pressure differences in the front, as low as 25 and up to 38 PSI. Never made a noticeable change.

I changed out the FZ forks for a R6 setup with different spring rates, damping values and shorter overall length. I moved the fork tubes up and down in the triple clamps, altering the rake/trail values across a wide range. Still no change in feel and shaking. With all of the recent reports of frame cracks I'm starting to think that my frame had damage that I was unable to locate.

Hope this helps move the discussion along.

 

[FinalImpact]

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

I ran Bridgestone 023, 016 and 002, both matched sets and mixed models. I ran Michelin Pilot Powers and Pilot Road 2. I had a set of Dunlop Qualifiers at one point way back, as well as the OEM Dunlops. I don't remember if the problem was critical way back but it was common for the last 2+ years. The range of sidewall strength was softest with the PR2, and by far the stiffest sidewall tires were the 002. I agree with the possibility that sidewall strength is interacting with the suspension to initiate the pogo effect as it would explain the specific frequency of the shaking at any given road speed. I did experiment with extreme pressure differences in the front, as low as 25 and up to 38 PSI. Never made a noticeable change.

I changed out the FZ forks for a R6 setup with different spring rates, damping values and shorter overall length. I moved the fork tubes up and down in the triple clamps, altering the rake/trail values across a wide range. Still no change in feel and shaking. With all of the recent reports of frame cracks I'm starting to think that my frame had damage that I was unable to locate.

Hope this helps move the discussion along.

So you had this issue on the OEM forks before the R6 fork?

It truly appears to be a product of loading and damping rates. Of late I can induce it by steep downhill decent, apply heavy brakes on a wavy surface and bam! Much easier if turning. So the tires contact patch is huge as its got all the weight of the bike on it plus stopping and turning forces.

I doubt you had a frame issue or brake issues as its seems to be all about how we're loading the nose. I was on a 7.4% downhill grade and turning and braking in sharp turns at low speeds (25 - 45). As soon as it became washboard like BAM! Its in motion even at low speed. But it was lots of break and weight transfer.

PS - forks had 10wt, swapped to 7.5wt which makes them react a bit quicker. So from last year to this year, thats the biggest change and the fact that the S20 is now real thin.

Q? What happened at the low pressures? I see the tire being destroyed with my style but others may do better.

Tks and I tossed a Rep point your way. Also, did this woodpecker action prompt the purchase of the ohlins rear shock? Did that change it?
I may have to go back to the original fork oil and see how it does. But as it stand now the front tire is down to the wear bars.

 

[FinalImpact]

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

I know, I know. I said I throw the pads on there sooner and never got back to it. And now with the S20 all void of tread on the side but good in the middle well I got bored and threw the pads on.

It is my observation that as the S20 got thinner it dribbled like basketball even at low speeds like 25 mph even at pressures as high as 37 PSI. Always while downhill, always while braking hard.

Other than my old pads heating up quicker cause they're thin, they still had life in them but I changed them anyway. I leaned a couple things along the way too!

Those of you running the R6 / R6S forks might want to take note of this even though its not an issue I may make a minor adjustment just the same. I never took to the time to measure the caliper spacer on the rotor but its far from centered.​

CALIPER IS NOT CENTERED OVER THE ROTOR (PIC is Right Front)!
NOTE: The pads are pushed outward against caliper and the gaps are different!!!:

Although this is NOT ideal, I don't see this playing a role in the threads topic. The pistons are not over extended or bottomed. They are not centered so it may impact heat displacement but its NOT causing issues here. This thread has isolated the fault to Tire and Damping rates.

Should R6 equipped owners decide to fix this: Here this info we need to replace the washer and move the caliper inboard for better alignment. (Better angle)

From the milled landing inside the caliper (Outside):

From the milled landing inside the caliper (Inside):

Spacer most of us are using:

OK - on to quick tips. Shoe String to Clean the Pistons:
First, pull the lever a bit and get a couple pistons out. Then tie the lever down so it seals the bleed port. Now when you push in a piston, one or more will pop out as its NOT going back into the MC!

Wipe the brake dust off. A horse hair paint brush, cotton towel, and shoe string work great for this:

No you don't have to use your feet! lol :
Hold the Shoe String against the piston on one side (while holding the caliper in same hand) and pull on the string with the other hand. WALLA! That narrow crack covering the piston is now clean. If you must, saturate the string with brake cleaner and give it tug! It works great!

Crack the bleeder and push all four pucks in. Fit brake pads and release the brake lever.

Pump the pistons out to hold the pads, remove the pin and drop in in the anti-rattle clip. Insert keepers and its on to brake bleeding.

Just thought I'd share.
F/I

 

[FinalImpact]

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

2014-06-24
Bedded new OEM Pads last night. As expected - this CHANGED NOTHING!
Its not a Brake issue.

It does stop nice tho! Lever is very firm and consistent! :thumbup:

^^ Also, Off the Shelf SS washers of the size needed are not easily found!

0.485" - 0.424" = 0.061"

Add this to the Existing shim:

0.088" + 0.061" = 0.149"

Wanted SS Washer:
0.149" thick ~ 0.120"
0.750" OD
0.400" ID

 

[Carlos840]

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

Are you using the rear brake when this happens?
I have had the same sort of reaction when doing some heavy braking practice, and it always came from to much rear brake, it's like the rear brake is stretching the bike and causing a weird up and down motion with some added clonking.

If i only use the front i get nothing weird.
The more i ride the less i use the rear brake, after experimenting i have come to the conclusion that it doesn't change my braking distance, and only adds something to potentially go wrong.

Also after reading the thread again i noticed you say you have little rebound, could it be that you have to little of it?
And that is allowing the bike to shoot back up to fast, increasing the issue?

Have a look at this

https://www.youtube.com/watch?v=Ikjw4IheeF4

I setup my forks using his way of setting the rebound right, as explained in the first 6 minutes, and it works great, might be worth trying...

( on the stock forks and oil i was getting 4 bounces, with 10w oil i was getting 3, now i have 15w and i get a very very slight second bounce, might try 20w next to see if i can get it perfect.)

 

[FinalImpact]

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

Are you using the rear brake when this happens?
I have had the same sort of reaction when doing some heavy braking practice, and it always came from to much rear brake, it's like the rear brake is stretching the bike and causing a weird up and down motion with some added clonking.

If i only use the front i get nothing weird.
The more i ride the less i use the rear brake, after experimenting i have come to the conclusion that it doesn't change my braking distance, and only adds something to potentially go wrong.

Also after reading the thread again i noticed you say you have little rebound, could it be that you have to little of it?
And that is allowing the bike to shoot back up to fast, increasing the issue?

Have a look at this

https://www.youtube.com/watch?v=Ikjw4IheeF4

I setup my forks using his way of setting the rebound right, as explained in the first 6 minutes, and it works great, might be worth trying...

( on the stock forks and oil i was getting 4 bounces, with 10w oil i was getting 3, now i have 15w and i get a very very slight second bounce, might try 20w next to see if i can get it perfect.)

Hey thanks and Yes, I've seen that one before. Good info! :thumbup:

I'm not sure where I implied little or to little rebound. I've played with the extremes and landed it back where it performs well (well, until the road gets rough). An extreme being noticeable pack down and then back it off with the goal being a happy medium of great corner control and sustained control while braking. Fact is, if ridden at normal street speeds NOT abusing the brakes - this is not an issue.

Just like the video, I set the rebound first as its too easy to go overkill with compression. Find the Happy spot rebound wise and THEN move on a sweet spot for compression.

Having tried various settings, I'm really thinking the springs have given up but I base this only on the fact that I had to add so much preload to get them back to 32 in the nose. That really says they are weakening. Couple this with the fact that they're for a much lighter back and are 10 years old - I think I see new springs in my future.

You're other question: Yes, I trail brake to load the suspension. Last night I tried shift weight rearward by tank gripping and pushing on the pegs vs pushing rearward on the bars. At this time it is inconclusive.

My gut instinct goes like this:

• Front carcass is soft, Rear Carcass is firm (uneven). i.e. we have a player on first base.
• Front spring rate is declining, rear spring rate is good (uneven). Players on 1st and 2nd.
• During heavy braking all weight in moved to the nose. Now add some uneven terrain and we've loaded the bases 1st, 2nd, 3rd, PLUS a batter up!
• The home run comes into play as we lean the bike over to its soft spot were the tire is designed to flex to add grip - BAM! Runners are coming in! HOLD on for the SHOW!

Take Away: Any ONE or TWO items by themselves are 100% OK. In fact, THREE of the FOUR items and 99.8% of the times its still OK. Grab ALL FOUR and Mix them at once and its too much. Not Always, but sometimes its TOO much!

The Tire mismatch is to be corrected.
The spring rate is just money...
The road I can't fix but I can pick different lines.
I can slow down or use less brake but its really about weight transfer, not speed.
The lean angle can be fixed by slowing down. :Flip:

That's what I know!

 

[Carlos840]

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

Well, it looks like you are on it!

I would still experiment with the rear brake though, it can really do weird things sometimes especially when you are using it hard...

 

[FinalImpact]

Links worthy of reading / watching....

Visit this!
Bike setup vid w/ Dave Moss.... https://www.youtube.com/watch?v=Ikjw4IheeF4
Bike Setup Tech article..... Motorcycle Suspension Set-up
Tire wear patterns.... Race Track Motorcycle Tyre Wear Guide - Types and Causes

TAG: Suspension Setup, Preload, Damping, Compression, Rebound, Rake, Trail, Rolling Diameter, Gearing

 

[FinalImpact]

2014-06-29 update

I made some adjustments and ran the bike over 80 miles of the more offensive roads and she behaved well! :thumbup: I will add that its difficult to push the limits knowing success means **possibly** bouncing off the road through a corner. Its not a "win" you want under your belt if you know what I mean.

Changes:
So everything points to a lack of controlled damping. From this I set off to double triple check everything I've done...
First step was something I'd never tried and was a test to see if each fork is providing about the same damping rate at the same settings. BINGO! Left fork rebound control is minimal!

In short I backed off the comp and rebound on each fork and bounced the nose. Confirmed no damping in either direction. Dial in some comp looking for control on one leg, then the other. Check! Back out comp damping to minimal.

Repeat task checking rebound rate. What do you know, Lefty is offering minimal if any rebound damping! So I pull the bars, pull the top caps and check the depth of the damper control rods. I'm not sure what I did but it was off a mm and that matters. Finding this I put it back together and tested it. Rebound damping functional on lefty! :thumbup:

Something I'd missed from before was this: The preload adjuster is supposed to be at a height of 25mm when assembling the Damper Rod Adjustment and assembling the cap. IMO this doesn't change 11mm protrusion of the jamb nut depth. But - moving the preload does change the rebound adjustment.
In short, if you change the springs preload check the effectiveness of the rebound. Compression is on the bottom end of the fork so this has no impact there.

I also played with the rear to obtain symmetry in the rebound rates both ends. So much bouncing on the bike!!!! Rear shock is healthy and I made minor tweaks to balance both ends.

Lesson learned: Don't assume anything! Back-off adjusters and test to confirm rotation = change.
I'll clock some more miles and see how it does. Mind you this only happened under very specific circumstances which may not show up anywhere but a step downhill corner under heavy braking while leaned over. Current observation is 6% grade or more was/is a catalyst.

 

[Erci]

Good work, Randy. About the pre-load / rebound. Rebound should always be re-checked after changing preload. Even though spring rate is the same, adding or subtracting spring load will likely result in having to do a minor tweak to rebound.

Keep checking the tire wear, though it's a much clearer indicator on the track. My street tires barely show anything odd after few thousand miles and I'm positive rear suspension is nowhere near where it should be, damping-wise (stock shock is junk), but it's good enough for the street.

On track.. my tires look awful and nearly used up after just 2 track days, mainly due to imporper setup

 

[FinalImpact]

Wheel was off last week and out of my sight for tire replacement so I thought it worthwhile to check rotor trueness upon installation just to confirm nothing happened that I was not aware of.

Brake disc deflection limit:
0.10 mm (0.0039 in)


Measured
Inner - Outer radius:
RS = 0.0002 - 0.0004" Less than 1/2 distance between marks.
LS = 0.0008 - 0.0013"

Each mark is 0.001" so its within spec! Steel Quick Clamp in combination with the axle bolt made the Magnetic Base on the dial stay put! :thumbup:

Needless to say the sun was evil and with a white dial, didn't stand a chance of getting a clear photo of the setup and read the dial.

LS outer....

The issue is near impossible to reproduce but unfortunately is still there. I do believe the new 016 front tire changed the rate at which is dribbles. Not that it officially happened, but there was something odd in play on a rough road.

• Note: The bike is a joy to ride and it works flawlessly in all ways except when pushing it on rough roads! That said, you have to be ridiculously hard on the brakes!!! So for all practical purposes, its a none-issue! But I like to solve mysteries so the chase continues! :Flip:

 

[FinalImpact]

Well I Hate to Admit it, but the problem lives on (although near impossible to induce these days). At this point it takes huge upset in the highways surface to inspire it, but if rough enough, the pounding will occur. In this last instance it was a break and drop in the roads surface isolated to riding on a volcano which has the earth shifting hence the highway is full of large cracks, raised and lowered sections.

Anyway - thank god there was no cars in the oncoming lane as I had to stand the bike up and use it. Could have been a life changing moment! Sadly I've been chasing this for a year now. I'm thinking new springs are in my future as these are loosing ride height due to fatigue.

I'll keep ya posted.. .. ..

 

[Cali rider]

Well I Hate to Admit it, but the problem lives on (although near impossible to induce these days). At this point it takes huge upset in the highways surface to inspire it, but if rough enough, the pounding will occur. In this last instance it was a break and drop in the roads surface isolated to riding on a volcano which has the earth shifting hence the highway is full of large cracks, raised and lowered sections.

Anyway - thank god there was no cars in the oncoming lane as I had to stand the bike up and use it. Could have been a life changing moment! Sadly I've been chasing this for a year now. I'm thinking new springs are in my future as these are loosing ride height due to fatigue.

I'll keep ya posted.. .. ..

Randy, I wish I could help. You seem to be following in my footsteps which is very discouraging! Remember I had the shaking problems both with the stock forks/shock and the R6 forks/Ohlins shock which makes me think it is not spring related.

It's time to take a hard look at swingarm bearings and incremental wheel alignment testing. Something moves/flexes/changes during operation as the random nature of your problems AND MINE attest to.

 

[FinalImpact]

Randy, I wish I could help. You seem to be following in my footsteps which is very discouraging! Remember I had the shaking problems both with the stock forks/shock and the R6 forks/Ohlins shock which makes me think it is not spring related.

It's time to take a hard look at swingarm bearings and incremental wheel alignment testing. Something moves/flexes/changes during operation as the random nature of your problems AND MINE attest to.

I can't say the problem was never there in the original configuration (as released by Yama) as I never pushed it that hard when it handled so poorly bouncing everywhere. So it may have been there but I never experienced it.

This past weekend limits were pushed and the front tire wear looks perfect as far damping rates go. No tearing, no cupping, no weird anything up front. The rear has a bit of cupping but I don't recall which edge ATM. Usually if it's on the leading edge rebound is too slow, and if it's on the trailing edge it's too fast, so I'll look into that a bit more.

An observation about forks:
If you look back in this thread you'll see I filled the forks when the temps were near freezing, cold and dry. As it warmed up and I began riding it made the fork seals weep until the air pressure equalized. In short, the fork seals didn't care for having air pressure added. We're talking a 50°F swing or better which changes the pressure in the forks. After I had the caps off to verify rebound control rod, temps were in the 70°F and they ceased weeping at the seals.

Other potential faults:
- bottom of rear shock lost a few section of the membrane separating the bearings and was leaving chatter marks on the machined shaft. I'm sure both are trashed at this point. Repair it this winter.

- As stated, front springs are losing height as shown by SAG values changing.

Looking back tho, yes, I had experienced this one time two plus years ago on the OEM shock w/R6 forks. Do keep in mind I'm running the stock FZ6 rear spring. That's all I've got for now. Because I have been able to change it, it seems likely spring/damping/loading pressure issue. I don't think anything is bending or it'd be cracked by now. Esp that cast frame.

Adding PN:
3 93109-17071-00 OIL SEAL 2 $4.24 (have this)
4 93315-31758-00 BEARING 1 $12.06 (have this)
8 90387-1012B-00 COLLAR 1 $6.89 (on order...)

 

[FinalImpact]

I can't say the problem was never there in the original configuration (as released by Yama) as I never pushed it that hard when it handled so poorly bouncing everywhere. So it may have been there but I never experienced it.

This past weekend limits were pushed and the front tire wear looks perfect as far damping rates go. No tearing, no cupping, no weird anything up front. The rear has a bit of cupping but I don't recall which edge ATM. Usually if it's on the leading edge rebound is too slow, and if it's on the trailing edge it's too fast, so I'll look into that a bit more.

An observation about forks:
If you look back in this thread you'll see I filled the forks when the temps were near freezing, cold and dry. As it warmed up and I began riding it made the fork seals weep until the air pressure equalized. In short, the fork seals didn't care for having air pressure added. We're talking a 50°F swing or better which changes the pressure in the forks. After I had the caps off to verify rebound control rod, temps were in the 70°F and they ceased weeping at the seals.

Other potential faults:
- bottom of rear shock lost a few section of the membrane separating the bearings and was leaving chatter marks on the machined shaft. I'm sure both are trashed at this point. Repair it this winter.

- As stated, front springs are losing height as shown by SAG values changing.

Looking back tho, yes, I had experienced this one time two plus years ago on the OEM shock w/R6 forks. Do keep in mind I'm running the stock FZ6 rear spring. That's all I've got for now. Because I have been able to change it, it seems likely spring/damping/loading pressure issue. I don't think anything is bending or it'd be cracked by now. Esp that cast frame.

Adding PN:
3 93109-17071-00 OIL SEAL 2 $4.24 (have this)
4 93315-31758-00 BEARING 1 $12.06 (have this)
8 90387-1012B-00 COLLAR 1 $6.89 (on order...)

Leading edge of REAR tire shows cupping. As an experiment, I'll back off the rebound on the tail and see how it looks. Cupping was not present a week ago from the local rides, just upon bearing into it here --> http://www.600riders.com/forum/showpost.php?p=594489&postcount=24 for a cpl hundred miles.. .. ..

I don't see that being enough to cause this. but WTFK?

 

[DeepBlueRider]

Sorry for digging old thread out of grave, but I might have interesting information.

One of the racers told me such chattering under hard braking could be result of tire skidding (rotating) on the rim

So you have enough traction, your brakes are good enough, but there is not enough friction on the rim keep everything together and tire starts to slip on the rim.

Does it sound as something that might happen to you ?

 

[FinalImpact]

Sorry for digging old thread out of grave, but I might have interesting information.

One of the racers told me such chattering under hard braking could be result of tire skidding (rotating) on the rim

So you have enough traction, your brakes are good enough, but there is not enough friction on the rim keep everything together and tire starts to slip on the rim.

Does it sound as something that might happen to you ?

Thanks for posting something insightful. But I would have to say no way. Plus I saw the old tires come off; well two so far. Not a hint of anything like that.

Biggest single contributor was the S20 tire. No steel belts and a soft carcase.

 

[FinalImpact]

Big change for 2017...
Dunlop Q3 at 36 psi.
7.5 wt oil yamalube filled 1.25" higher than stock. This maybe the ticket. Bike rides good and remains very predictable in every way. I've pushed it hard and was predecting woodpecker like pounding but nothing.

I'll let you know if woody comes back!

 

[FinalImpact]

Solved solved solved...

Big change for 2017...
Dunlop Q3 at 36 psi.
7.5 wt oil yamalube filled 1.25" higher than stock. This maybe the ticket. Bike rides good and remains very predictable in every way. I've pushed it hard and was predecting woodpecker like pounding but nothing.

I'll let you know if woody comes back!

!!!!SOLVED!!!!
OVERFILLING the fork made all the difference. It has not repeated the jack hammer like pounding since this was done.

 

[agf]

Re: Solved solved solved...

just re reading this thread I think I have the same issue
I had my oil upgraded fro 5 to 7.5 wt about 12months ago and its only since I got back on the bike after my heart op that I have really hit the anchor hard.

I want to redo the springs so I'll ask for the oil to be over filled
any idea how much was "too" much Randy?