i am making a robot which will be driven by two wheels(rubber light used in rc cars about 7cm in dia) .my overall weight will not be more than 3.5kg .Which stepper motor with which current,voltage do u recommend .i will use gears with load...

 

It all depends on how fine you want the motor to rotate. Also by the Supply that you have to power the car comes in to picture to choose the motor operating voltage and torque.

Rifaa

 

Stepper motors are a bad choice for that, even if you gear it down enough to be reliable they have very poor energy efficiency for robot traction.

Why not just buy a couple of geared dc motors??