Hey,
Try the following settings, (got them off another thread, not mine!)
remember to change the oil to get an HP edge over the opponents.
Race 1: Superspeedway
downforce 35/50
gears: 380 km/h
lsd: 60/60/15
ride height: 15/-15
springs: 18.5/18.5
dampers front: 8/4
dampers rear: 8/4
anti roll bars: 4/4
camber: 2.0/1.0
toe: default
brakes: 1/0
Race 2: Grand Valley
downforce 50/70
gears: 320 km/h
lsd: 60/60/15
ride height: -30/-30
springs: 18.5/18.5
dampers front: 8/4
dampers rear: 8/4
anti roll bars: 4/4
camber: 2.0/1.0
toe: default
brakes: 1/0
Hardest race for me as getting in front was difficult and rear tyres started to lose grip quite fast due to oversteer. High downforce was useful and made overtaking easier. Try to get to 1st place as soon as possible and then maintain pace around middle bar to avoid wheelspin in the corners.
Race 3: High Speed Ring
downforce 50/70
gears: 350 km/h
lsd: 60/60/15
ride height: -30/-30
springs: 18.5/18.5
dampers front: 8/4
dampers rear: 8/4
anti roll bars: 4/4
camber: 2.0/1.0
toe: default
brakes: 1/0
Race 4: Laguna Seca
downforce 50/70
gears: 280 km/h
lsd: 60/60/15
ride height: -30/-30
springs: 18.5/18.5
dampers front: 8/4
dampers rear: 8/4
anti roll bars: 4/4
camber: 2.0/1.0
toe: default
brakes: 1/0
Keys here are short gearing and high downforce... the race becomes smooth sailing after you get in front, just remember to keep some pace up
Race 5: Daytona Oval
downforce 35/50
gears: 380 km/h
lsd: 60/60/15
ride height: 15/-15
springs: 18.5/18.5
dampers front: 8/4
dampers rear: 8/4
anti roll bars: 4/4
camber: 2.0/1.0
toe: default
brakes: 1/0
I hope these help, because they allowed me to win all the races bar Daytona, which is quite frankly crazy because they just spin you off lol.