Hey everyone…
Been doing 5/3/1 for a few months now and loving it. I have a question about the PR set. I know we shouldn’t train to failure, but we also want to set a new PR. So when going for that PR, if say my previous PR is 5 reps, and I’ve just done my fifth rep, I know I’ve got 1 more in the tank but it would be the last rep I could push out… should I go for the PR, or stop before training to failure?
Thanks 
If you did 5 reps the previous cycle and do 5 reps in the new cycle, that’s already a PR - you’re doing the same number of reps, but with a higher weight on the new cycle.
At least, that’s what I’ve always considered “a PR”. I shot for increasing numbers on the first few cycles while I was getting accustomed to AMRAP sets (never done them before), then I simply shot to get the same number of reps at each cycle unless I was feeling incredibly good one day and could shot for an extra rep.
I recall, with a 90%TM, I was capping at 10 reps on 5+ weeks, 8-9 reps on 3+ weeks and 7-9 reps on 1+ week (first two weeks were beltless, third one was with belt, so at times I could maybe do 9 reps both on 3+ and 1+ weeks)
I stop when form starts slipping.
If you can keep good form till actual maxing I applaud you xD