Today i ran between a 28 and a 34 tooth pinion on profile 7 and middle hole timing on a Ion 2 17.5. I found my fastest laps were coming with the 31 tooth even though it was heaps faster with the bigger pinions it was just too fast and the brakes and punch out of the corners and up the hills were heaps better with the smaller pinion. Temps started maxing out around 185f at 34 tooth so i did not go any higher obviously. Anything under 28 was not fast enough.