Front End Shake / Chatter

I have a 2006 ZX6RR. Under hard braking there is chatter. It has to be very hard breaking. Like end of the straight hard braking. Over the winter I did some up grades to the bike. Changed brands of brake pads from EBC to Vesrah. I bought forks with Ohlins cartdriges and a TTX rear shock. Sent it to out to be serviced and sprung for me, had it put on at the track in april and had everything set. The shake showed up almost immediately. We were able to dial some out that weekend but not all of it. The suspension guy said to wait and see how it rode in warmer weather it was 35 degrees that weekend. Well I have done three more track days sense and I have been able to get the majority of the shake dialed out through softing up the compression damping and modilating the brake lever when i start to feel the chatter. I have checked the head bearings and there fine. Checked the brakes also fine. I have read on some forums that maybe lowering the forks in the tree would decrease the leverage the braking force has and not let the forks flex as much. I have thought about having the suspension guy soften the damping stack to give me more adjustment but Im not sure that is the right fix or just hiding the problem.

Anybody have any thoughts or sugestions?

 

spin the front tire - is the rim or rotor showing any signs of damage or warp? I had my rotors out of whack and it wasn't really noticeable until high speed or aggressive braking. Doesn't take much to cause issues.

 

As mentioed check the rotors first. If you are positive they are 100 percent straight, then start simple and swap the brake pads out with your previous ones ones and see what happens for a session or two. If the problem goes away with the other pads then you have found the answer.

I have seen pads cause this same issue for others and it is a simple and easy thing to try before you start digging deeper.

Ltyson


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I will double check the tire / rim and rotors tonight.

I no longer have the old pads. Maybe I'll just order another set of pads and swap them out. It's not like they'll go bad if that's not the problem.

How or what would cause a brake pad to create this problem. Too much bite?

 

The reasons could be varied but I would not say Too much bite. I do not know if I would go and get a new set of pads as that can be expensive and we are not sure it will fix the issue, but you are right in that there is no harm as it is not like they will go bad and you can always use them in the future.

In the instances I have seen, it was a case of new pads and only happened under heavy braking from high speeds, for example, braking for say turn one from a long straight. The chatter or vibration would not manifest itself under heavy braking at slower speeds and if you modulated the brake pressure in the high speed stops and backed off a little bit it would stop.

The idea would be to swap back to a stock compound pad and test the theory to see if it cures it. Also I have seen it cure itself just with more miles. It could be how the new pads have bed in and as you put on more miles the problem goes away.

Just some thoughts and ideas. Hard to say for sure.

Ltyson

 

Are your forks bottoming out?

 

No. I still have 1/2-3/4" of travel. And that was one of the things I asked the suspension guy. He said I was good. Per the zip tie.

 

Ltyson

In the instances I have seen, it was a case of new pads and only happened under heavy braking from high speeds, for example, braking for say turn one from a long straight. The chatter or vibration would not manifest itself under heavy braking at slower speeds and if you modulated the brake pressure in the high speed stops and backed off a little bit it would stop.



That is exactly what's happening.

 

It is also possible the Vesrah pads are not working properly with the transfer layer of material the EBCs left behind. It could have caused problems with the new pads bedding properly and you know have an uneven layer on the rotor surface. Vesrah specifically recommends a thorough cleaning of the rotor swept area when changing friction compounds.

Here is some info, not Vesrah specific but still a good read

http://www.braketech.com/index.php?...ed-in-procedures&catid=17:tech-talk&Itemid=69

http://www.braketech.com/index.php?...nd-wheel-binding&catid=17:tech-talk&Itemid=69

And finally the best way I have found to clean rotors:
http://www.braketech.com/index.php?option=com_content&view=article&id=83&Itemid=100

 

+1 for dirty rotors..

I had the same thing after a pad change - vibration from the front wheel when braking at 90mph or more.

 

Other things to check. Wheel bearings, triple clamp bolts loose, head bearings loose. Could also be something poorly installed in the new forks.

Heres a strange one that turned out simple. At high revs I had a chatter noise but felt nothing strange on a 150R on a kart track. Turned out to be my clutch lever rattling in the pivot. Some times it is just simple dumb shit.

 

Looks like I need to get ahold of a brake hone.

 

Dave Moss teaches a specific way to tighten your wheel in order to prevent head shake; it goes something like this:

1. Install the wheel and tighten the axle temporarily with both sets of pinch bolts loose.


2. Install the brake calipers, torque and pump the brakes till they seat. Some people apply the front brakes firmly, then tighten the caliper bolts to ensure they are centered over the rotor.


3. Torque the axle bolt using a wrench and a special tool to hold the axle.


4. Tighten and torque the right side pinch bolts.


5. Pump the front end a couple of times.


6. Tighten and torque the left side pinch bolts.

This method makes sure the forks are not pinched inward while torqueing the axle and gives the proper amount of free play in the hub stack.

He's going to be at Barber this fall with STT; the guy is amazing. He also has a website includes videos etc about suspension....

 

For ~$50 I think I'll pick one up...

 

just ordered one $40 bucks shipped from Amazon.

 

Thanks for the help. I'll let you guys know if it works.

 

I believe you get the same net result without needing any special tool if you do it this way -
1- same as above
2 - same as above
3 - tighten right side pinch (so axle can be torqued)
4 - torque axle bolt (no special tool required)
5 - loosen right side pinch
6 - pump the front brakes then hold under pressure
7 - tighten all pinch bolts, then release brake lever

I noticed my front wheel spun considerably more after resetting the pinch bolts. Normally, I wouldn't reset the right side. Thanks for the info.

 

try the above but, in my experience with these bikes,

the rotors probably need replacing. common on the 05-06 zx platforms. they are not cheap, dont buy used ones, you'll get someone elses problems. get new pads and start fresh.

Ski

 

I bet replacing rotors would help. If they are to thick they can't accommodate amount of heat produced during hard breaking. If everything is toasting there is no bite. Rotors have to be have enough heat capacity. Even if they look fine it can be not enough. That's my idea, I had this problem once and replacing rotors helped.

 

If Cleaning the rotors doesn't Fix the problem. That will probably be my next step just replace the rotors and pads. I also might try lowering the forks a little some other forms I've read says that can help. Next weekend I'll be at Grattan I'll be able to try some of these things And find out whether or not this is working.