Outdoor action flash photography - sync speed?

Hey everyone, I am having fun with flash photography outdoors and I'm sometimes having a hard time 'freezing the action' and getting a sharp photo with a 1/250th sync speed. Is there any way around this? I have been using a 580ex with elinchrom skyports. Do I simply need to work on my panning technique? I would like to increase my 'keeper' rate.

If no ambient or ambient is 3-4 stops less than your flash exposure then short duration of flash will setop the motion even at our sync speed of 1/250. But if ambient is strong, then you need higher ss to stop the motion but then flash won't work unless you use HSS.

What are you shooting?

Ahh ok.. that makes sense. I was at a skate park shooting with a 580ex in the afternoon/dusk, but it wasn't bright enough to overpower the ambient light. Oh how I want some big strobes..

Can my 550 trigger the 580ex off camera and still use HSS?