More torque more top speed and faster backflips. I think 15t is the limit you hit near 60mph on 15t. I will never go back. I feel the truck is less stressed on 15t too because it pulls wheelies easily vs 13 who is a struggle sometimes. You can even run a loose slipper clutch(i mesn loose in the sense it wont wheelie on 13t much) and able to wheelie with ease.How do you like the 15T pinion? I have one waiting to go on after I am done messing around with speed runs on a 20T.