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Discussion Starter · #1 ·
The title says it all, 2500 miles 3 track days, some occasional hard braking on the street from triple digits.

Front brakes rotors are shimmying, tapped the buttons on the rotors, still doing it.

Could the ABS be causing it as well, haven't tried it with ABS off, anyone else having the same problem ?

Rhody...
 

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Last summer after 2 consecutive days on the track while I was riding the bike home from the track noticed a hard shimmy when hitting the front brakes hard. It was worst above 90mph, hitting them hard, the whole upper cowl/fairing/screen would shake.... Could feel it in the bars, whole front of the bike. Felt way different than the ABS. The dealership ordered new rotors for me under warranty. By the time the rotors came in (couple of hundred miles later) the shake disappeared. Of course it only went away just as I was on my way to the dealership to get the rotors replaced. Think I had about 4000 miles on the bike at that time/bike was 3 months old. I was sure the rotors were warped, maybe it was contamination, not sure what happened.

Dunno if my issue is similar/related to whatever is happening to your bike but just thought I'd post this up.
 

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this happened to me all of a sudden on my zx10, turned out both rotors were badly warped, no idea what happened, but I replaced them with Brembo T-drives. I recommend that you put your bike up on stands, remove the calipers (suspend them with a bungee cord from the handle bars), then your front wheel can spin freely. If you have a needle measuring device great, if not use a small phillips screw driver propped & pushed right up to touch the side of your rotor disc and start to spin is slowly. You will see & hear as a bent rotor moves in & out towards the screw driver. A true measuring device will show the amount of movement. Do this for both discs.
 

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Discussion Starter · #4 · (Edited)
Since you can't turn off ABS to make sure it is not contributing to the problem, I am having my friend, shop owner and racer, ride the bike tomorrow morning.
If needed he will order new pads, and ship the rotors to a guy he uses to true his race bike rotors at the start of every season. I am heading to the track in two weeks, and don't want to be distracted in trying to get smoother and faster, I am getting a GPS data logger (no display) to see whether I am improving and notjust by the seat of the pants feel. It allows you to brake the course into sectors and analyzes it each time you make a past and displays a green segment with your best time. If you connect all segments green it means you did everything right for a whole lap which is near impossible to do. The software is pretty flexible and user friendly as well. I am not sure the brand or model, but I will post about it when I put it to use.

Rhody...
 

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Discussion Starter · #5 ·
I will be getting a QStar GPS laptimer:


I discovered in Road Racing World, May 2016, page 67, that Jorge Lorenzo's Dad uses the following book: The Talent Code:


Rhody...
 

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had the same problem at 17, 000kms. new rotors and pads fixed the problem ...all under warranty of course. for the record i never tracked my bike.
 

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Warped brake rotors (discs) can be the result of heavy braking to a standstill and then leaving the brakes to cool. The portion under the pads cools at a different rate to the exposed part and the rotor can warp.

I've used most of my recent bikes for LSR, braking quite hard from around 200mph dozens of times and never had a warped rotor. They have blued a bit but never warped. The reason would seem to be that after a top speed run there's always about a mile back to the pits taken at a slow speed and they cool evenly before the bike is stopped.
 

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Discussion Starter · #8 ·
Warped brake rotors (discs) can be the result of heavy braking to a standstill and then leaving the brakes to cool. The portion under the pads cools at a different rate to the exposed part and the rotor can warp.

I've used most of my recent bikes for LSR, braking quite hard from around 200mph dozens of times and never had a warped rotor. They have blued a bit but never warped. The reason would seem to be that after a top speed run there's always about a mile back to the pits taken at a slow speed and they cool evenly before the bike is stopped.
Thanks Bob,


I will keep that thought in mind. I can't remember panic stopping then shutting the bike off right away. I will ask my racer buddy if he has heard of this as well.


Rhody...
 

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Discussion Starter · #9 · (Edited)
Did a track day at Palmer Motorsports on Sunday, as you can see there are 3 straights (see maps below) with elevation changes that involve hills with blind corners at the end. It took about three sessions to get dialed in and smooth, however smooth is a relative term. Even with a slow turn throttle and a reflash, from off throttle to maintenance throttle, a movement of about 3 millimeters, the chassis lurches a bit, which screws you up when leaned way over trying to be as smooth as possible.

I was in the intermediate group. It was kind of funny, everyone seemed to follow me first and second sessions and about 4 or 5 guys passed me outside braking into the slowest corners, which was fine with me. After lunch I got dialed in and put in four or 5 smooth laps in a row and was having fun, and only 1 guy passed me. See map0 below, going into turn 9 braking hard from about 100 mph, the front rotor shimmy got on my nerves. I countered it with more rear brake, but to be sure it would have been better if the shimmy wasn't there. I am taking it to the dealer where I bought it tomorrow and they will get the numbers from my rotors and hopefully will replace them under warranty.

Another side note, my racer buddy and shop owner took it out at 3 pm and came in after only two laps. He said, I don't know how you can be smooth on that thing, because he is used to his butter smooth race ZX6 with built motor and pig rich power commander map from 1 - 3K rpms, which is very soft off the bottom, but gives you a very smooth throttle. He said for him it was too hard to ride with precision, but he said he had respect for my ability to ride at the level I was at at the track. I respect his opinion because he really knows how to set up his race bike which makes about 140 HP at the rear wheel.

I couldn't use the Qstar lap timer because the software wasn't installed correctly which was a bummer, because it would have been nice to see my improvement during the day. Long story short, my BMW on the same track is about 2 to 3 seconds faster by the seat of the pants feel and speed on the straights and in the corners. I will say this, minus the shimmy from the front, the Pirelli diablo corsa's stuck like glue, as I was using warmers and the edge grip felt great. For most the of the track I used 2nd, 3rd gears and 3rd only on the short straits. I shifted into 4th on the long curvy front straight, but just cruised before turn 1, then a quick double down shift into 2nd for the 70 mph apex at turn 1.

I would like feedback, maybe from turbo if he is following on taking turns in 2nd between 8 - 12 K rpm, which I got comfortable with as the day wore on. I tried 3rd in the same slower sections as well, but with all the torque available all it did was make me have to brake harder and earlier before entering the corners to compensate. I will say this though, learning to ride my BMW S1000RR without traction control paid dividends with throttle control. I had to refine that skill to move the throttle about 80% less on the H2 to get the same result.

Track Maps
Track Maps

Rhody...

P.S.

This video with Rich Becker was taken the same day I was at Palmer, he was right next to me in the garage, nice guy. He crashed at 21:30, looks like shoulder, collar bone injury.
You can get a feel for the track and the pace which was close to what I was capable of at the end of the day. He had to shift more than I did though, lol. Hope he is OK.

 

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Discussion Starter · #11 ·
His crash was around 4 pm at the end of the day, he had ridden all day and had no problems squaring off that corner. I quit around 3 pm because I was getting tired and making small mistakes, not enough to be dangerous, but enough to get your attention. The front brake shudder was worse in the afternoon as well. As far a target fixation goes, I can't be sure, when I asked him about he crash he said, "I overcooked the corner and couldn't slow down enough". He was a long time track day rider and former racer as well.


Rhody...
 

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Discussion Starter · #12 ·
I had the front rotors checked by two shops they were 0.04 thousandths out left and right, the manual says they need to be at least 0.06 out to be replaced under warranty.
It was suggested I scotch brite both rotors which I did and finish with brake cleaner. If I don't do another track day with it, it shouldn't be a problem. I abused my 2011 BMW S1000RR's rotors way worse than this, have gone through four sets of pads no problem, but then again the bike it about 90+ lbs lighter which may mean more heat. Just for giggles next time I bring either bike down from high speed I will put my IR gun on them just to see what temps they are at.

Rhody...
 

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Discussion Starter · #13 ·
And that's target fixation 101. Wow...Looked right at it and hit it.

NOLA
Nola,

He was right next to me in the garage that day, used to race bikes, his crash was after 4 pm, last session and at the end of the session. I was tired at 3 pm, making small mistakes and decided to call it a day. He had been through that corner dozens of times during the day, successfully and at a good pace. He separated his shoulder, but otherwise was ok, bike not too badly damaged. He had been doing track days for years and years, I don't think target fixation was the cause. Like I said earlier, when you feel you are off your game, it is time to call it a day.

Rhody...
 

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Discussion Starter · #15 ·
I got a surprise today out of the blue. The shop I bought my last three bikes from called to say that they spoke to the regional Kawasaki rep about the front rotors being out of true by .04 thousandths. He said he would replace them under warranty, which I did not expect, but was happy to hear. They should be in a a week or two, so hopefully track days next year will be with a smooth stopping front end.

Rhody...
 

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Discussion Starter · #16 ·
I just had the front rotors replaced under warranty, remember at the beginning of this thread i complained of brake shimmy ?
I never mentioned it but right after swapping for new tires around 3000 miles I was getting a high speed shimmy as well, well into triple digits. It turns out the wheel nut on the swing arm was looser than it should have been, this has been corrected.

The second picture is of the steering head bolt. At the first oil change this was loose as well. For those who run your bike hard, I suggest you all check the rear wheel bolt tension and the steering head bearing torque. I am a bit surprised that this was not done on Kawi's pride and joy at the factory, these are pretty important items to not check and double check. For those of us who ride track days or who ride speed sanctioned events it is essential. I am fortunate to have caught these two things before something unwanted happened.

rear wheel and nut, safety clip

steering head

Rhody...
 
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