Just want to make sure I understand this correctly (panning)

[Mark Elberson]

1) My lens doesn't have 2-mode IS, so it is better to have IS off (?)

Keep it on. The IS on that lens "knows" when you are panning where as the older versions of IS did not so that is why they had 2 modes. Your lens also "knows" when it's on a tripod (although most people will still tell you to turn it off) where as older version did not.

2) Shutterspeed of 1/100 to 1/60 would probably produce good blur (I would be shooting from about 30 to 35 feet from the riders)....maybe I need slower shutterspeed for subjects that close?

You are probably going to need slower shutter speeds since the bikes won't be moving nearly as fast as a race-car. Just experiment and see what you get []

3) I need to make sure I'm shooting in AI SERVO mode

Yep

4) I need to make sure the subject is traveling perpendicular to my viewpoint, maintaining as close to the same distance as possible from the lensthroughout the pan.

Yep

5) Have fun, be patient, experiment with settings

This is the most important one [] Be sure to post your results!