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04 R1 shakes violently during hard braking, but only occasionaly(video included)

4K views 33 replies 10 participants last post by  ChR1z 
#1 ·
Hey Everybody,

I have been struggling with this issue since I got the bike. :frown2:
Braking is always very smooth, but every now and then, especially when driving a bit more aggressively, the front shakes like crazy when braking hard. The funny thing is, when I release the brake a little bit, and immediately brake again, most of the time it brakes smoothly the rest of the way?
Also once it has happened one time it tends to happen easier afterwards. (Hot brakes?)
It's quite dangerous, because it comes unexpected.

Luckily I got it on camera: Around the 0:50 mark you can see what I mean.


Discs are not warped (guess the problem should always be present)
Forks arent bumping at the end (tested with tiewraps)
I've cleaned the floaters.
Ive tightened steering stem, no free play.
Forks are visibly in good condition.
Brakepads are 50%

I'm going to change the brake fluid.
Next check the state of steering stem bearings.

But If any of you guys have any idea/or experience with a similar problem. I would love to hear suggestions.
thanks so much!

(Also if anybody notices the red light, oil is a bit low, gonna service it this week :wink2: )
 
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#2 ·
Air pressure good in the tires? Had the wheels balanced? How did you check the rotors?

Being that it comes and goes I'd check suspension and if it's properly set for you. Looked like a little head shake under acceleration after the brake shake. Has the suspension ever been serviced?
 
#3 ·
Yep I always check the tire pressure. Wheels are also balanced. Rotors I checked together with a friend, front lifted, rotating the wheels, and very carefully looking for any kind of wobble in comparison to the calipers. Absolutely nothing visible.

I did try all kinds of settings following a diagnosis table, the problem didnt become worse or less, so it probably hasnt anything to do with the settings.
On the movie when accelerating the wheel was probably barely touching the ground explaining the shaking, doesn't bother me, seems normal to me.

But indeed:
About the suspension, I don't know the history, bike has 36k km on the odometer.
So complete check/service/overhaul will be third on my list. Thanks for your input.
 
#5 ·
Well I would check fork alinement, may have a slight twist. then head bearing. Then I would pull rotors off and lay them on something known to be flat (thick piece of glass or marble counter top) tapping around edges listening for clinking noise. Then look at brake pads ( piece of pad missing), and caliper mounts. Also when you crack loose mono block bolts spin tire and grab brake lever couple times and then hold brake lever and tighten caliper bolts. Good luck!!!
 
#14 · (Edited)
Maybe - could also be head stem bearings especially if they never been touched and he does a lot of wheelies and/or stoppies.

Two things to check. First (I'm 99.9% thinking its this) hold the front brake and bounce the front end up and down on the suspension. Push it down and then pull up on it as hard as you can and see if you can feel a clunk right at the top of the stroke. If you can then the head is loose and you need to remove the top plate and tighten the ring nuts. I usually tighten them until I can feel resistance as I turn the bars (They'll feeling sluggish as if you have a flat tire) and then back it off about 1/10 a full rev or roughly 35 degrees counter clockwise..

If that test doesn't reveal anything then you need to try it from the opposite end which will focus on the forks. There's a design feature of the forks so that the very last bit of travel is 'reserved' so that when braking very hard the forks don't bottom out fully so there's a little travel left for bumps. You could have an issue with this or something else inside the forks. The easiest way to do that is to jack up the front end up with the bike on the side stand, remove the front wheel and with the forks unloaded pull them down and push up. See if there's any up and down play/slop in them. There should be no point where the forks don't resist being compressed. If there is DON'T RIDE IT ANY MORE. Get it fixed immediately. If the adjuster rod lock nut is loose the fork could come apart.

Unless you feel it more through one clip-on than the other I would suspect its just a loose triple / ring nut assembly. I'm leaning towards that b/c they are notorious for needing constant adjustment especially if you are wheelie happy. I know I had/have to adjust mine nearly every ride - or so it seems`

What kind of pipe is that? Maybe its the camera mic but it sounds pretty ragged.
 
#21 ·
How often do I do it, or how often are you supposed to do it? :grin2:

I do it when the front end doesn't feel right under braking, which is technically probably too late.

You are supposed to do it every 2 years... So the bike in question above should have been done about 6-7 times and I am betting it is the original factory grease...
 
#29 ·
I've been thinking about this since I posted the other day. I reread the thread but didn't see you post up how many miles were on the bike. The reason I'm wondering is that maybe the bushings inside the forks legs are worn and under hard braking are allowing the fork to move inside the tube enough to cause what your are experiencing. And when you let off the brake lever this allows the suspension to rise a little and allow the fork to move into a place where is doesn't shimmy around.

Of course I would consider this after the stem nut has been checked and properly torqued.
 
#30 ·
Fast update: Roads were dry so I put the bike together to make a test drive.
Tested braking as hard as possible for a few km's, this all felt fluently. Even stoppies.
Until the last corner from my home, out of nowhere, it happened again. one single time :frown2:
could brake hard 3 more times, those went fine.
But there's this thing, i don't like it, when using the brake lightly, the braking force is not smooth. Don't know how to describe it, fluttery? :p It's like in the video but only 5%, just noticeable.

OK, what did I do:
Stem nut bearing was indeed out of adjustment, with the upper bracket removed I could feel the play. (upper bracket should not have any influence, guess it wasn't properly put together the last time.)
Anyway, So I thought I found the issue.
Took the complete forks out to have a look at the bearings, looked brand new.
Did all the testing following the service manual, no problems.
Forks, seemingly no weird behavior.
Brakes, 1 out of 4 pads was worn differently?
Gonna have a look at the brakes again.

And I changed the oil&Filter:laugh:
 
#33 ·
OK, what did I do:
Stem nut bearing was indeed out of adjustment, with the upper bracket removed I could feel the play. (upper bracket should not have any influence, guess it wasn't properly put together the last time.)
If the bearing assembly is loose you will feel a 'clunk' when you engage the brakes. This is the entire triple and fork assembly moving up an down in the frame. If its really loose you can get what you describe but not without feeling that clunk when you initiate hard braking just about if not every time. When you put it back together, how much did you tighten the bottom ring nut? You should crank it until the steering gets stiff and then back it off just enough to free it up - just enough and no more.

Did you check each fork fully extended with the wheel off to see what the fully extended action feels like? If its suspension this could save alot of time.


Someone else said it could be a master cylinder issue and that is possible. I've seen this w/ cheap or bad pads and or pad / disc combinations. If you have a hung piston in the caliper while the others are normal that could do it, you could get a back and forth oscillation like slapper but between piston sides. It could be a fork problem too. See if you can induce it while leaned one way or the other, a slight lean - not trail braking when cranked over.
 
#34 ·
FYI - I did not see your detailed response until just now - so sorry for the useless reply. Do you have an old set of front pads you can swap. Maybe you got some brake or other kind of fluid on them and its coming out when they get hot - hitting the disc, boiling off - repeating quickly.... I recall a member of a stunt team had this problem when he was doing rolling stoppies - you could see the disc binding and releasing in slow motion - I'll have to see if I can find the video.
 
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