Unless you are riding your bike like my grandma drives her Taurus, always assume that you can or will lose your rear tire at some point. I don't remember where the quote came from but it's saved my ass a hand full of times
- When in doubt, throttle
I was on a moderately paced group ride once when I hit a good sized "puddle" of gravel midway through a loose sweeper. I remember losing my front for a second (most terrifying thing ever) but my back swung out a substantial amount more. I'm sure I over estimate how far I really slid, but I just keep the throttle where it was (or maybe backed off the tiniest bit) and rode it out. Whatever you do, don't just chop the throttle off like this guy
http://www.youtube.com/v/pDVFL_RlPLw&hl=en&fs=1If you keep your throttle running and the wheel spinning, you can control the ass end. If the wheel is spinning or otherwise loosing traction and suddenly there is no power there (throttle) to keep it moving, it will grip hard and very suddenly.