Head shake/tank slap?

CWCobra

.060 Over
Joined
Sep 18, 2008
Messages
127
I put on new front and rear tires, balanced with Dyna Beads.
All is smooth up to 90 mph. That's when it gets exciting.
At 90 or so, I get a violent "head shake" in the front end. It goes away when I let off throttle; smooths right out again at 85 or so.

I will stipulate that 90 mph exceeds all legal speed limits, and I would never advise anyone to operate a bike at such illegal speeds.



However, can I get some advice as to what would cause the sudden emergence of these symptoms?
  • Insufficient/ineffective Dyna Beads?
  • Defective new front and/or rear tire?
  • Failure to tighten/reassemble something properly after new tire install?
  • Sudden, coincidental failure of steering head bearings?
Thanks in advance,
CW
 
The only way to know for sure is to have the tire/wheel dynamic balanced with sticky weights and try it again.

I'm a dyna bead cynic so take my suggestion with a grain.
 
yup, may have to do that.
will I have to remove beads to spin balance? That would be a real PITA!!!
And to think about all the nice things I've said about Dyna Beads, too!!

CW
 
When you say balanced with Dyna beads, did you install the product and then verify that the wheels were balanced? I don't know anything about Dyna beads so sorry if that's a dumb question.

Also, just out of curiosity, what kind of tires did you mount? A bad tire is a possibility. I've had that happen, and it can be almost impossible to balance.
 
Since I have absolutely no idea what a dyna bead is I cannot comment
 
I have the same problem over 100 Mph and my tires are speed balanced.

Front tire: Metz
Rear tire: Riken Raptor

I have a new set of Metz's that will eventually be installed and was going to use the dyna beads. I will definitely want to see how the this comes out.

Here is info on Dyna Beads if anyone is interested.

Dyna Beads for Motorcycle Riders and Dealers
 
It sounds to me like you may need to adjust the "amount" of Dyna Beeds in the tire. You might want to contact the Dyna folks and ask them about a Rocket 3. They will have specific suggestions about different bikes and tire/wheel sizes. My thought is that the number of beeds needs to be adjusted, by tire size and weight, till you have it right. Contacting Dyna will/should eliminate the trial and error part. Good luck.
 
Chart provided

When I researched the DynoBeads years ago, I came across a chart that stated how many ounces of the beads should be in specific size tires. That's how I planned mine. Surely that chart is still out there.

See ya.
 
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