Major Headache

[rc4x4nut]

Why is picking the right motor such a pain? Anyways I've been looking to to get a good motor for my emaxx 3905. I want to gear it for 40. My problem is I still want to use the factory batter retaining bar which means 4s lipo. The truck wieghs about 10 lbs ready to go. Motor choices are 1515 1y or 1515 1.5d. I would even do a 1521 1d. I dont really see me going to a 5s setup for a while. What do you guys think about the motor selection?