140 miles in one day?

Riding far isn't difficult, especially if you eat. What makes it hard is trying to do it fast. So take it steady, eat and drink frequently, i.e. ever half hour or so, and you should be fine.

+1

If you have never ridden over 100 miles, then I wouldn't try and knock this off casually. As Winston says above, average of 10/12 mph will get you there in around 12 or so riding, without spanking yourself.