There is no general admission seats on race day for the NASCAR Brickyard 400, unless you buy a season pass which costs $120
General Admission for the Indy 500 - There are grassy viewing hills all along the back straight and third turn. The viewing hills to the south (by Turn 2) are alcohol free, intended for families and people who might be offended by the partying that goes on in the Turn 3 infield on Race Day.
Indy 500 general admission costs only $20 at the gate - CASH ONLY.
General Admission for the MotoGP - There are grassy viewing hills along the infield portion of the track. See map
Sitting inside the oval has its good points. It is easier to access all the amenities inside such as Gasoline Alley, the Museum, and entertainment stages. There are always things to see in tents in the plaza east of the Museum as well.
If you park in the infield, you can return to your car to fill up your cooler or drop souvenirs off, etc. If you park outside the track, then you cannot leave the track to go to your car and come back inside as there are No Passouts
You can save some walking by taking the trams that run around the infield. They pick up people who park in the 3rd turn and run up the middle of the infield and over toward the Tower, and then up to the museum where they turn around. They also run outside the track to the North 40 parking.
Many of the stands that line the outside of the track are generally closed during practice days in May.
While the infield may be crowded on race day, the viewing hills make a nice relaxing place to picnic during other times. Bring a lawnchair, football, etc. Also little children enjoy rolling down the hill.