Where are you shooting mtn bike stuff at? I have plans of getting into some more downhill photog this summer!
I'm in Tahoe, so primarily just stuff around northern CA. I'm mostly into video so when something like those good IS lenses find themselves on my camera, my stills just look a lot better. I'm not a good stills shooter by any means. Most of my stills are just timelapses.
Here's the kind of stuff we shoot
https://vimeo.com/user2429028/videos
If you really want to get some good bike shots, I'd say try to get up to whistler during crankworx. Plenty of nutty things going on all over the place.
Or check the Northwest Cup series for races all over WA/OR. There used to be a huge race they'd do up at schweitzer years ago but I haven't heard much about the scene up there lately. Not really sure what's going on in Idaho these days.