The best way to get to Rockford from the airport is to rent a car. All the airports have car rental options at affordable rates. You’ll also appreciate the convenience of having a car once you are in Rockford, to get to restaurants or sightseeing or pre-race errands.
If you prefer the ease of travel with car service / taxi, an Uber or Lift will be approximately $165-$185 for an XL car, and up to $350 one-way for a spacious luxury SUV.
For bigger groups:
Enterprise at ORD has the option to rent a van for 15 passengers.
Rockford Rides is also a local company that offers service in different vehicles to and from ORD.
Echo Limo provides transportation throughout the Chicago area and you can choose an Executive Van.
Coach USA has an hourly shuttle that runs to and from ORD to Rockford.