If you read the book, it tells you. But since you asked nicely, heh... You don't redo your 1 rep max on the 5/3/1 program, it has nothing to do with 1 rep maxes, it has to do with getting stronger. One of the 1st things he talks about in the book is folks worrying about 1 rep maxes too much, saying for example,'well my max is 315 , I did it two months ago', whether the guy can do it now is anyone guess, JW set up the program so you have new Personal Records(PR's) for reps with a certain weight all the time, not maxes.
Once you get to a point where you can't make the minimum reps, you drop your working max 10-20% and continue on, doing the 5's, 3's and the 5/3/1 week with a lighter weight, and when you work back up to the 'sticking weight' again, you should be stronger and able to go on by it. There is never a reason to re-figure your 1 rep max at all for the program. Only for your vanity, hehe.