pinion/spur gear question
 

Ok I dont know what to search for to find my answer so I'm gonna just ask here.

This would be for 1/12th scale if it would make a difference

Roll outs:

1) 1.8(tire)x3.14x40/72=3.14

2) 1.8(tire)x3.14x50/90=3.14

Now the question I have is there an advantage to gearing either way to get the same rollout?

Good day!

I like to keep any moving mass as little as posible so the 40/72 would be my choice.

It really depend on your track size. For smaller track the 40/72 lighter setup would be better, more punch out of the corner. But for large track as the heavier setup will get you a little more top speed (more momentum) on the straight, and the spur least a little longer too. :) But to be hornest, the different is very very small...

I have to ask, how can a heavier car be faster? It will take more power to get it going and yes, more momentum or kinetic energy so it will take more to stop it or to chainge direction. Because it takes more power to push it it will slightly be slower.

I also like having the spur higher of the ground so it dosnt pick up as mutch crap off the track.

yes, it will need more "energy" to get it going so the pickup for the heavier setup will be slower as said earlier. But as the momentum is more so on long striaght the motor is able to reach slightly higher max rpm so the top speed is slightly faster. And to be hornest I don't really think it makes a big different for the dirt part as the spur is so close to the ground and it is not cover by anything..... unless you run a bigger spur and very small rear tires and the spur is almost touching the ground..... :) Cause the track I run on have a long striaght (around 50M, it is more for mod touring than 1/12, lol). And the different is quite noticeable but not very big. :)