Last night I had someone make a U-turn in front of me on a 3 lane highway with a speed limit of 55 mph. Going about 60 when this bozo decides to go. Had to jump on the binders hard as I was at the front of a pack of traffic that had left a light about a 1/4 mile back. Both brakes at almost lock up, front end shook violently,not side to side but more front to back.Brakes are in good order,fresh pads all around about 500 miles ago,and there was no pulsing in the lever leading me to not think its a warped rotor. The bike has 12,000 miles on it and is primarily a commuter(daily driver,no car)and weekend play toy. I've done plenty of track days in the past with other bikes and can say the Z has had an easy life compared to my other bikes which I never had rotor issues despite heavy brake use. Has anyone here had any rotor problems with similar milage or have any suggestions as to maybe another cause for this shake. Also as a side note I dont do intentional wheelies(sometimes they just happen ) and the bike has never hit a pothole or been down. Hate to think I have to get rotors at 12k miles since my last bike,02 Gixxer 1000,had 58,000 miles and I only did pads and had none of this. If anyone has any suggestions please let me know what you think.
Thanks.......Chuck

I'd bet this is just a case of "pogo-ing". It is a common hard-braking problem on pavement that may have even slight ripples. Most city roads/highways have ripples even when new, which aren't really noticeable until you're hard on the brakes. The "pogo" effect is a result of your forks going up and down to react to the changes in surface. You can make some adjustments to your damping (do you have stock forks, or zx-6r forks?), but if you brake hard enough on a less-than-perfect surface, you will experience this.

I wouldn't worry about the rotors...

Thanks Cbr thought about the road surface and have felt what your talking about especially coming to a stop at traffic lights where there are distinct ripples (almost whoopties) but this stretch was ground down and repaved about april. I've had some people mention soft springs in the z and possibly steering stem bearings may be loose. One of the techs at the kawi shop I worked at is going to check rotor runout and stem bearings for me after hours tomorrow. Been checking rotor prices and all I can say is wow must be made of gold or something. Even with employee price still 186.00 each for ebc contours (petal) and thats still 400 for both with the govenors cut.

Yeah I should have mentioned loose steering head bearings as well. Definitely another possibility...

I had a similar thing happen, I mentioned it to the guy that ownes the speed shop and he said the same as CBR, and told me the front suspension might be set a little to stiff. After I set the proper sag on the front end it hasn't happened since. Not sure that had any effect or if the road surface was the main culprit but I don't think it is a brake problem.

Stopped by the dealer I used to work at after hours Friday and my buddy who is a tech there and I went through everything. Rotor thickness,great,runout,none steering head bearings,good,and wheel bearings are good. I weigh 220 with gear and the suspension is set for good sag numbers,had to crank in some preload on the forks but still have 2 lines showing. The suspension has not been messed with since april. This shake seems to have come out of nowhere. The one thing the tech said was that the front tire is cupped,don't know if this would cause the shake or not but maybe. This set of pilot powers has about 4500 mi on them and will need to be replaced soon. I guess I'll see if this makes it go away then.

I would bet that you bottomed out the forks. Also, do you remember what gear you were in or if you took any downshifts? Sometimes, under hard braking in a low gear, the effects of engine braking can cause a chatter.

are you calling me a lard a$$...lol seriously though i doubt the forks bottomed but as you know the front forks are soft and the bike does pitch forward pretty hard compressing the springs under braking. Been doing some research and alot of people seem to think it the tire cupping that is the most likely sorrce. One guy on a vfr forum said he had done everything i have so farand when he replaced the front tire the shake was gone.we'll see

Originally Posted by SLLaffoon

Sometimes, under hard braking in a low gear, the effects of engine braking can cause a chatter.

Sounds about right. I thought it was my rear brake locking up at first..

Originally Posted by madkaw88

are you calling me a lard a$$...lol seriously though i doubt the forks bottomed but as you know the front forks are soft and the bike does pitch forward pretty hard compressing the springs under braking. Been doing some research and alot of people seem to think it the tire cupping that is the most likely sorrce. One guy on a vfr forum said he had done everything i have so farand when he replaced the front tire the shake was gone.we'll see

I'm 170lb and I have no problems bottoming out stock 636 forks. Stock Z1000 forks are softer and the bike is heavier. If you did come close to bottoming them out, any road or tire vibrations would no longer be absorbed through the suspension.

Originally Posted by madkaw88

Stopped by the dealer I used to work at after hours Friday and my buddy who is a tech there and I went through everything. Rotor thickness,great,runout,none steering head bearings,good,and wheel bearings are good. I weigh 220 with gear and the suspension is set for good sag numbers,had to crank in some preload on the forks but still have 2 lines showing. The suspension has not been messed with since april. This shake seems to have come out of nowhere. The one thing the tech said was that the front tire is cupped,don't know if this would cause the shake or not but maybe. This set of pilot powers has about 4500 mi on them and will need to be replaced soon. I guess I'll see if this makes it go away then.

A cupped tire can absolutely cause that. I wouldn't throw any money at it (or even all that much effort) until I got a new tire.

I'm amazed you could achieve proper sag at 220 - springs must be stiffer in the '05s than in the '03s. I'm only ~160 ready to ride and my '03s adjusters bottomed out at 35mm sag.