As a fellow Corally driver (15+ years) we do not have the ride height adjustment as some of the other cars out there. However to give you some dirrection, need to know what motor you are running, how you have it set up and your ground clearance.
Normally I get the roll out correct for the motor, then look at the tire dia and spur gear, yes you can get the tire to small, so the spur hits!!
Let me know and I'll see what help.