Might as well jump in here!
First of all, I don't think you will want to remove your jewelry for a while...give the hole a chance to heal up.
Second of all, I assume that you wear proper clothes while riding. For me, this is padded biking shorts. With the padding, your PA should be well protected...and if you crash hard enough that the padding gets torn away, a piercing is not going to be an issue anyway, you will have other much worse problems!
As Dirtsqueezer said, I don't wear rings for safety reasons....but if you are man enough to brush your tires off on the fly with your PA...well, I hope I haven't said anything that offended you!!
