For a bike race, you'll want to go with a
faster shutter speed. I'd say 1/500 sec at the very minimum, but probably 1/1000 sec ideally.
To achieve these higher shutter speeds, you'll want to go with a
larger aperture (smaller f-number) and a
higher ISO. For ISO, I'd start with ISO 400, and possibly consider going up to ISO 800, depending on how bright it is during the "early morning".
Of the 3 lenses you've got, I'd go with your Sigma + the Canon 50mm f/1.8. The 50mm lens is small enough that it shouldn't be too much of a burden to carry around.
I would also set your focus mode to "
AI Servo". AI Servo is the autofocus for moving subjects. We recently discussed AI Servo in one of the threads last week:
http://www.disboards.com/showthread.php?t=2432827
I wouldn't bring a tripod. You're not taking pictures using slow shutter speeds. And the shutter speeds of 1/500 - 1/1000 sec are fast enough that you don't have to worry about camera shake from hand-holding.
The only downside to using such fast shutter speeds is that you pretty much freeze the action, so there's no sense of motion. The bike wheels are frozen, so it'll look like your brother is stopped right in the middle of the road. Overall, though, it's probably a very minor consideration.
One other intermediate photography technique you can consider trying is
panning. Here's an example of panning from Flickr:
As you can see, panning photos convey a sense of motion. Not only does the background appear to be moving, the bike wheels are also spinning in this photo.
Panning takes a lot of trial and error (mostly error). You'll need to use a slower shutter speed (1/30 sec? or slower) and follow your subject with your camera, keeping your subject in the exact same part of the frame during the slower exposure. The best and most stable way to do this is to keep your camera held close to you, with your elbows tucked tight into your body. Use your waist to pivot your entire upper body as you track your subject. Your entire upper body should move as one. Even using this technique, some say about 1 in 10(?) panning photos actually come out pretty good.
Be sure to take some test shots of other bikers as they pass you by. That way, you can adjust your settings as necessary.
Hope that helps. Do you have any kids or neighborhood kids that you can practice on between now and the weekend? Be sure to show us some photos!
