Could someone please give me a lesson on this?

+1, -2, -3...I hear everyone talking about this but don't know why they do it.

What are the pros and cons.

thanks

 

It's simple math. Reducing the number of teeth on the front sprocket or adding some to the rear adds to the torque multiplication the drivetrain puts on the motor resulting in quicker acceleration through a given gear and theoretically "more" torque, at the expense of higher running RPM, and a lower topspeed as you will bang the revlimiter earlier at a given speed. In contrast, going up in the front or down in the rear has the opposite effect, moving you closer to a 1 to 1 ratio. Think of a 10spd bicycle. Your legs are the "motor". In first gear it is easy to pedal the bike quickly up to speed but you can only pedal so fast (rev limit in 1st). In 10th gear you can go faster with less effort, but it takes more effort to accelerate quickly. Make sense. Then look at a bicycle in those gears, smaller sprocket on front larger on rear in 1st. 10th gear is larger in front, smaller in rear. Same applies to a motorcycle. Usually most people drop one -1 in front and up two +2 in rear. Some go just -1 to get a little more acceleration with out sacrificing too much top speed or a very high rpm while driving.