heyos. If this is your first track day, you don't need to go too low. The chances are you will not be heating up the tires significantly. Try going with something in between 31/31 and 33/33. It should do just fine but you can try changing it around. You're not going to notice a huge difference but for sure drop it a bit because when they heat up, they will go back up to 36/38+. Remember to try to "feel" your tires and have a good idea what they are doing. What is more important I believe is having your suspension set up properly... you will feel that difference right away.