It's a combination of the tires getting worn and 260 ponies at the crank!
(You should see my rear end wander when I get on it...
)
If you put new tires on and the problem is reduced and/or eliminated, I wouldn't worry about it....
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"The Yellowjacket"
Ricer 1: What the heck was that!?
Ricer 2: I don't know. It looked kind of like a yellow SN95 Mustang.
Ricer 1: Nah, fast SN95 Mustangs don't exist... Must have been a mirage or something...