If the race is a criterium, basically a lap race on a closed course, a photographer can easily shoot great pictures with a 645 and 75 mm. A good place to be is on the inside of a turn whose apex draws the riders single file near the photographer. As a priveleged person ( the sponsor's photographer ) you can claim this place and let them come to you. You will need two friends, to keep people out of your way. A 4 foot ladder helps sometimes.
A fast rider will be moving about 50 mm in 1/250 of a second, a slow rider half that. So, figure if the camera is standing still, you won't get anything in an 8x10 sharper than a 5mm blur. But panning, moving the camera with the riders as they sweep past, fixes that. If you are shooting with a leaf shutter or fast sync, a little flash can help, by letting the background go a little dark: just don't shoot a flash into their eyes.
If you can get a meter or two from the cyclists, a wide angle lens is great.
In any case, practice before the day. Cars going by, cyclists practising on the course... anything. If you're a rider, drag a couple friends out to let you get the hang of it.
If you are shooting a road race, you will either be in an official car off the front, or on a motorcycle... on on the ground. Then, a longer lens is needed, but seldom longer than a 180 on a 35mm. Well, that depends on how fast the rider is, and how experienced the driver. If you are on the ground, find a big ladder, cherry picker, or SUV to shoot from.
Have the club give you a written list of the shots; shoot negs and make incident readings on the generous side; have fun.
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