Going to the Brickyard for MotoGP, what lens to rent?

[xsists]

Just wondering what some of you guys are using at Indy for lenses. I won't have "credentials" so I'll be shooting from spectator areas. I was looking at the Canon 100-400 f/4.5-5.6L IS but is that too slow? Its a cheap rate to rent for the weekend to shoot some bikes but if its going to be too slow, I might bump up to something nicer. I have a 70-300 Sigma but the quality is not the best and its pretty soft.

I guess I'm just looking for suggestions or maybe samples of what I should be looking for in a lens for Indy.

Thanks in advance!

[DC Fan]

MotoGP pictures from the Indianapolis Motor Speedway:

http://www.kevinlillard.com/racing/20090829a1306.jpg

Turn 2 from a Tokina 80-400mm.
Focal Length: 400.0mm
Aperture: f/8.0
Exposure Time: 0.0020 s (1/500)
ISO equiv: 400
Exposure Bias: none
Metering Mode: Matrix
Exposure: program (Auto)
White Balance: Auto
Flash Fired: No
Color Space: sRGB


http://www.kevinlillard.com/racing/20090829a0968.jpg

Turn 6 from a Canon 70-300mm IS.
Focal Length: 300.0mm
Aperture: f/14.0
Exposure Time: 0.0080 s (1/125)
ISO equiv: 400
Exposure Bias: none
Metering Mode: Matrix
Exposure: shutter priority (semi-auto)
White Balance: Auto
Flash Fired: No
Color Space: sRGB

Looks like the 100-400mm lens would be a very good choice.

[dmayesjr]

It's not too slow. If the race was indoors, it might be. I'm looking to rent it as well.