Uhh.
Well.
I don't use a Wii wheel, but you tilt the Wii wheel upwards to do a wheelie. That ony works on a bike. The wheelie makes you go faster for a time, and if you get a Pow block, and do a wheelie on the third time it shows up, you can avoid spinning out as much. Also, do a wheelie on jumps,and you can do tricks. You can do tricks with kart or bike, but wheelies only work on bikes. And, you can also throw items backwards and hold items. To hold items I think you just hold the item button, but again, I don't use a Wii wheel or Wii remote. To throw them backwards with the Wii remote, i'm not quite sure. I suggest looking in the game guide that came with the game to figure out how to do this stuff. It can explain better than me.