The pain starts to set in about 6-7 hours after the shot... a dull bearable pain at first that soon turns into a 2-3 day sore-fest. I can't even turn around in my sleep without waking up because of the pain.
Having said that, it tends to get better midway through the cycle.
PS: I love Sus. Ripped me the last time I used it. Its doing the same thing now. If only I can get around the backne...