"Wobble" Causes...

So, I keep seeing a large number of posts about the "death wobble". Having working with several other bikes, the bearings are not always the reason for the issue. I just wanted to throw in my experience on the matter to give other troubleshooting to people in case the bearings don't fix the issue.

The death wobble is caused by one thing: the wheels not being perfectly aligned with each other both vertically and horizontally. You have two gyro's with the wheels. The larger is it is even slightly off from the smaller, it will always win. So, since the rear tire/wheel is larger, heavier than the front, and is much more ridgid (being mounted to the swing arm which in turn is mounted to the frame it has no horizontal movement) it will always win the fight to go where it wants to go, hence the front wobbiling.

So, if there is anything causing the two to be out of alignment it will cause the wobble. Here are a few things I have seen and known to cause this:

- rear bushings being out will cause the wheel to move at a slightly different angle.
- the rear shocks not having even amount of preload will could cause a slight torque of the rear end.
- forks being out of alignment: the top and bottom of the tripple tree being slightly off. I am not sure if the forks in our bikes are able to have this but any info would be good.
- (on chain bikes) alignment from adjusting the chain
- Wheels not being true
- Steering bearings allowing the forks to not hold the frontend straight.
- Bent frame
- Flat spotted or bulging tires can also cause something similar but it is more of a vibration than a wobble...


And any other items that could cause the wheels to be even slightly off from each other. Less than half of a degree of angle off could cause it.

A couple of notes:
- Tire pressure can cause the issue to become more apparent.
- It can cause a tank slapper... If you want to find out what that is search for videos on youtube.
- The "death wobble"... Not really unsafe unless it escalates to a death wobble.
- It can cause uneven wear on the tires (mainly the front) usually cupping of the tire. The tread will not feel even. (Thats the best way I can put it)


If anything here is incorrect or you have anything to add let me know. I am thinking about setting up a wiki to put info like this since the stickys can only hold so much.