What causes rear tire to "wiggle"

[Bizall]

When braking or turning sometimes, my rear tire wiggles from side to side for about a second ocassionally. I'm curious as to why? Is it sand, suspension settings, to much weight on the front tire, etc? Any help is appreciated. Thanks.

[*KEN*]

"
Problem: When Richard gets on the brakes aggressively while approaching a corner, the bike's rear end begins to swap side-to-side, and feels as if it wants to pivot around the front.
Cause: The cause is too much front end weight transfer under braking. The front end is compressing so low that the bike's weight tries to pivot around the steering head, causing the side-to-side movement.
Solution: The quickest solutions here are to increase the front fork spring preload and/or raise the front ride height by dropping the fork tubes in the triple clamps, or decrease the rear ride height by shortening the shock (if possible). Try increasing the fork spring preload first, and progressing in small increments until the handling begins to be negatively affected (remember to watch the rebound damping when increasing the spring preload). If that doesn't work, try the ride height modifications; watch for adverse handling reactions in other areas when doing this as ride height changes drastically affect how the bike corners. Other solutions to try--although less effective--are to increase the compression damping in the forks (if possible), or to decrease rebound damping in the rear (to allow the rear tire to follow the pavement quicker). Again, watch for adverse handling reactions in other riding situations when test riding."

[Fly boy]

I had this happen out at IMI quite a few times. Your braking to hard on front, so your rear loses traction and breaks loose. Try using your rear brake a a little more, or stop going into corners so hot :)

[DeeStylez]

I know when I first started riding my bike last summer I noticed the wiggles, when I finally decided to check the air pressure I realized I only had like 15psi something crazy like that. But I am almost sure you have the correct amount of air....:banghead:

[Bizall]

A different time I was coming around a loop to go north, constant speed around 45 mph, and it did it. Tires have good air pressure. The bike has almost 500 miles, so there shouldn't be any oil stuff on them either.