Coincidentally I swapped to my m520 pedals this pm, and I was suprised how loose the T3 pedals were; hardly any force needed. (sorry Alex11). I noticed the thread had grease on, but I put some copper grease on the m520 threads before putting them on. I did use a the 15mm pedal spanner from my existing tool kit though..(third blue in from the right), but tbh i'm pretty sure an adjustable would have done the trick.
http://www.chainreactioncycles.com/Models.aspx?ModelID=40997 (btw had to buy 17mm cone spanners for the T3 as were not in kit)