my card is a sandisk ultra pluse 64gb it has xc1 on it
The ultra plus can accommodate about 48MB per second data transfer. The Extreme Plus (a far better card) and accommodate 90+MB per second of data transfer. This is the card we recommend in our standard GoPro configuration page:
http://www.lynkspyder.com/support/gopro-configuration
And when you say your video isn't smooth, is this playback on your computer or when uploaded to YouTube. If it is on your computer, I would recommend a couple things:
1.) Download and use VLC player to play video locally. This program uses it's own "CODEC" (which is nothing more than a translation system). This plays video much more efficiently.
2.) If you are recording at 60FPS, try bumping down to 30. Some computers will struggle at 60FPS and 30 generally fixes the problem.
EDIT: I saw from another post above that you are already shooting at 30FPS. Try VLC and see if that helps. Also, I am assuming you are not useing the "PROTUNE" option. If you don't know what it is, you probably are not. If you are, definitely turn that off.
Hope this helps,
Josh Greer
LynkSpyder