Go Kart Drive Systems - How Big Do I Need My Rear Sprocket?

When we ask drive train questions we usually get theA rule of thumb for horsepower matching is that the
following answer:force required to push the equals the go kart weight
"The interplay between rear sprocket and the clutchmultiplied times .175. This number represents the force
can be a confusing combination, if you don'trequired to push the go kart up a hill.
understand the dynamics of the situation."For most go karts this will be the equalization point, or
Thanks for that non-answer! That's how most of usthe point where the go kart will just stop climbing the
feel after scratching our heads and getting ready tohill. If you have some speed it will keep going.
toss in the towel for the whole go kart project.This rule of thumb gives you good overall dart around
For all of the time and effort thrown into making thisperformance and top end speed. If you decide you
go kart, when push comes to shove it doesn't move.need more hill climbing capabilities then the system
The clutch smokes and it can't climb hills worth a pilerequires either more horsepower, or a steeper ratio.
of beans.The rear wheel typically is the limiting factor, in that you
Why is it that we can't wrap our heads around thecan only make a sprocket so large to get the ratio
drive line system?that you want. But again, as another rule of thumb,
The reason comes in two forms:making the sprocket nearly as large as the rear tire
1. All we have are certain parts and we want thosegives you good, and I mean good, acceleration and
parts to workoverall performance.
2. The alternative would be to make parts, or findIf you need the sprocket larger than the wheel, well
parts that are extremely hard to findthat kind of defeats the purpose doesn't it? So other
Quite honestly those are lame reasons to pursue amethods of reduction will be required.
drive line that you are guessing is going to work.So to recap, if you have a large tire and a small rear
The first rule to drive systems layout is matchingsprocket, you had better do a rethink and evaluate
horsepower to the requirements of the system.your overall ratio.