In One Shot, a half-press of the shutter release will lock focus and exposure; if you want or need, you can then re-compose.
AI Focus defaults to One Shot, but will automatically go to AI Servo if it detects movement on the selected focus point.
AI Servo tracks focus automatically and sets exposure when the release is fully pressed.
There's been much discussion on this forum on the usefulness - or otherwise - of AI Focus. The concensus seems to be that it's a good idea, not very well implemented. Others condemn it as handing too much control to the camera
Given the nature of cycling, I'd have no hesitation on settling for AI Servo from the get-go.
Another tip - practice panning before the event. You can do this 'dry' with passing traffic. It takes very little time to keep your subject on the selected focus point. Then practice it for real. You'll be surprised how easy it is after about 5 minutes.
ETA - Since AI Servo uses a predictive algorithm, it needs a split-second to work out approach speed.