biglarrr This is nearly impossible question to answer. It depends on the weight of your vehicle. It depends on the tire size of your vehicle. It depends on whether your motor mount is adjustable to allow for... This is nearly impossible question to answer. It depends on the weight of your vehicle. It depends on the tire size of your vehicle. It depends on whether your motor mount is adjustable to allow for different pinion gear experimentation. The best suggestion I can offer is check to see if your motor mount is adjustable. If it is, buy the fastest in this 2845 size (the 5900), and buy a package of pinion gears (usually four different sizes). Try each size pinion and check how hot the motor gets every minute or so during your run. You should still be able to touch your motor for a few seconds at the end of your run. As soon as it's too hot to touch, shut it off and go to a smaller pinion gear. See More

Vivacious Which specific model number rc car do you use with please? you need to provide more informations