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Rock Island Grand Prix course may look like a simple 6 turn course, but its far from simple.  Every turn is different with various bumps, surface changes due to the crown in the road, brick crossings, this tack is very challenging indeed.

 

Top speeds for a shifter down the 740' front straight tops 84 MPH.  Carrying speed out of Turn 6 is essential yet difficult as the kart skips across the exit of the apex just about where you would be trying to apply full throttle.  Lots of spins in practice here.

 

Our data and perspective is from a 125 Moto so we'll speak in terms relative to the shifters.

 

Approaching each turn is a "funnel" that narrows the entry into the turn-in point.  passing the Start/Finish line at 70 MPH the track is wide and glass-smooth.  At the library, the track begins the funnel for turn 1 - it's still pretty wide with ample room for passing, but late apexing will take the kart all the way out to the barriers on the exit.

 

Turn 1 is a 52 MPH turn with a series of bumps about at the apex.  The kart doesn't settle much until just the turn is about completed so bind isn't a problem here.  Down the 20th St straight, the funnel comes up quickly about 2/3 of the distance down.  Here's where it gets tricky.

 

As you approach turn 2 there are different bumps on different lines.  The right lane is slower then the right center, but "defending" your position may move you a little closer to center.  Setting up for turn 2 you'll move a bit back to the right to get the best radius, but there is a fine line on how far you can go with the as crossing over the road stripe paint can cause a we=heel to lock under braking.  That turn-in point changes throughout the weekend, depending on the rubber build-up and the marbles.  Peaking about 84 MPH,  Turn 2 is a fast 56 MPH turn.  Its usually an exciting place to watch too.

 

The short chute between 2 and 3 isn't too difficult being smooth and wide, it's hard to make a pass.

 

Turn 3 is deceiving.  The bumps at the turn-in point make that the slowest part of the turn, and getting power down may favor a softer rear axle.  Binding becomes a small issue out of turn 3.

 

Exiting 3 its a relatively short distance (about 180') to turn 4, the only right hand turn on the course.   Despite having only one right turn, it seems hard to get used to it.  Some teams set their karts up with a little bias for the left hand turns so there are more passing opportunities then it might appear.  Its also one of the bumpiest turns on the track.   Don't take the exit out to the wall.  Turn 4 is a 56 MPH turn.  Lots of spins here, so watch for the yellow flag.

 

Exiting 4 is a challenge with the bumps.  A few passes are made on the 180' straight between 4 and 5 mostly due to the difficulty in getting the power down. 

 

Turn 5 is about 54 MPH, and forces you to swing from the left to the right side of the track on the setup.  Just past the turn 5 exit is the pit lane on the left.  Coming around the turn its almost blind and you sort of get a tunnel vision that lures you towards the pit exit.  You'll figure it out in practice, but in the heat of battle don't forget its there.  If you get too wide into the exit, you will visit the pits or hit a barrier head-on.

 

Turn 6 is the last turn, and approaching it you'll probably lock the brakes - there is a bump at the deepest point of braking.  That will favor pitching the rear of the kart around into what will feel like it's totally out of control - because it is.  At the apex is another bump where the kart kind of lands "catie-whompus" and you may not know which tire is going to land and grab first - leading you to an understeer or oversteer.  In any case expect the kart to move over about 3 feet.  Turn in speed is down to about 55, and at the apex the speedo is showing 70 - because your airborn and not back on the throttle hard yet.  About the time the kart gets settled from the "jump", you'll roll on the throttle like a Rotax.  Any binding in the kart will show up here.