[VFRman]

My 03 636 has a bad front end shudder when braking hard and I was wondering if anyone knew what the problem could be. My brake pads all still have 3.5mm left, the rotors are straight and allow the wheel to spin freely while up on a front stand, and I already replaced the brake fluid. Any advise would be appreciated.

 

[Nigel]

You're not running out of front suspension travel, are you?

 

[VFRman]

Nope. My suspension has been the same for 2 years and I never noticed the shudder during both track schools I attended. its just recent so I figured it was the pads but they look great.

 

[tweakmon]

Maybe its junk on the rotor / pad surface.

Try cleaning them real good and see if the prob goes away.

 

[Nemesis6R]

Steering head bearing?

 

[quiksilver636]

[:+1]

 

[Apotheosis]

I don't know what you are refering to, but my bike shutters when I break hard, but I believe it is from the weight of my body going forward and the back tire skipping on the ground.

 

[warbuk]

my 04' has started too. i strongly believe it's the rotors on mine. i can put it on a stand and it rolls and looks fine. but i get on the street and brake hard and it shutter's. try braking softly with the front brake and see if you get that "grab" effect on your front brake. tried it on mine using only the front brake and i could feel that grab-release, grab-release deal on the rotors. if not, check ur head bearing.

 

[RedFinn]

I'm no mechanic, but still:

-steering head bearing phucked/loose
-rotors/front axle warped/bent
-discs not floating like they should
-front axle clamp bolts loose (you'd loose the bolts pretty fast if this was the case)
-rear rebound setting too soft/hard
-front comp/rebound

some of those you eliminated already.

 

[Ernie]

Put a zip tie on the fork and see if you are bottoming out. As we go faster we use more brake.

The only way to see if a rotor is bent is to use a dial gauge

 

[VFRman]

Zip tie is already there and I never had any problems during the last 2 track days. I'll check the head bearing. Thanks for the replies. Keep them coming and I'll update if I find the problem.

 

[jdgun_13]

As Stated clean the rotor swith some brakeleen and a green 3m pad.
Had the same Problem on my 2005 ZX6R after a track day,accumalated residue on the rotors.
DO NOT use a metal scrub pad as small peisce of metal will get into your rotors and rust,not good.

 

[RedFinn]

Btw Ernie.
You were right and I was wrong in a previous thread, when I had a pretty bad case of front end chatter. It wasn't the front end at all, new Ohlins spring and internals helped some, but not enough. Tightening rear rebound (a lot) helped a tiny bit as well, but it was only when I got the Ohlins shock that I got rid of it. Well, almost rid of it. Now it's perfectly rideable, even braking hard while leaned over. It does still vibrate/shake a bit in some places, but not enough to prevent me from turning in or braking properly.

 

[VFRman]

Checked and its not the head bearing so I'll try cleaning the rotors. I also have a Hyperpro shock with Ohlins spring set to my weight but the bike did this with the stock setup too so not sure what's going on. I want to have it fixed in time for my wife's first track day with the bike so will see what I can do. Thanks again everyone.

 

[EA6BMECH]

For a joke, when was the last time you changed the fork oil???

 

[VFRman]

Never changed the fork oil so maybe that could be it?

 

[Ernie]

It's not the fork oil.

Get a dial gauge and measure the runout on your rotors, one of them is shaped like a taco.

 

[VFRman]

Cleaned the rotos and absolutley no change except my wallet is now $7 lighter. I'm goign to run to my mechanci friedn and see if he canmeasure the rotors. They spin freely on the front stand and don't drag at all but guess there could be a problem. My pads still have 3.5mm of wear but do you think new pads would cure the problem if its not the rotors?

 

[Ernie]

Check the rotors. Dont worry about the pads.


You can't see 10 thou out, it is only 4 thou more than OEM allows. It does not drag, vibrate at low speed or create any problems until you have a high speed hard stop, then there is enough discrepancy to vibrate.

You can try putting the bike on a front stand holding a long rod against the fork just touching the rotor. Then rotate and listen and feel. If it is out you will hear a variance in sound and feel it too.

 

[danthony12321]

How old are your chain, and sprockets? If they are shot, the chain could be skipping over the sprocket teeth under heavy desceleration, and causing chatter.