Hi.
In this link from tamiyaclub one guy speack about the Super Astute pinions and show a complete chart about the gearing until the 20T pinion. I think that is easy to calculate the ratio for the 18T and 19T pinions using this chart as reference.
http://www.tamiyaclub.com/showroom_m...53812&id=17039
Anyway I take this pinions until te 18T. I hope this helps.
Bye.
