XB4 Gearing

[MarkM]

looking for advice on starting pinion size for my 2013 XB4 (4wd) Ive looked in here but can only find info for 6.5 or quicker motors. Our club limit is 10.5, track is on high grip carpet and a section of medium grip wood. Its running the standard 81 spur. Got a Reventon Pro v1.1 esc and Trackstar 10.5 in it. I normally run a TC so got no idea where to start with a pinion size, any advice welcome