most people have problems off the floor when sumoing. How long have you been lifting and what is your max?
I have been deadlifting for about 12 months, but I was training stupidly for about half of that(deadlifting too often and not making progress.) My max is 435, my bodyweight is 165 if it matters.
Usually I have no problem off the floor. When I fail a PR attempt it is in the last few inches. I will research rack pulls and give them a try.[/quote]
it could be speed off the floor. If you get some momentum going, it can help with getting it all the way to lock out.
To that end you could try some speed pulls (low reps, high sets, with around 50% of your 1rm.). So something like 10x2 @50%.
Rack pulls would probably be the first thing to try, though.