I have an ECX circuit 2wd and I'm looking to upgrade by pinion and spur. Currently I'm running the stock 87t spur and a 21t pinion I bought from Hot Racing. I would like to swap my pinion to a 26t but I don't know what size spur to upgrade to. What size spur is safe and how should i go about this? Is there any information I can find on the size and how that affects the torque, speed and wear? Should i get metal, or something like RPM?