Inferno ST-RR Gearing Question

Hello everyone.
As I am to finally get this done (after some stuff happening along the way),
I have some questions still on my mind.
Looking at the speed calculator and I noticed the following;
a 52/12 Spur to Pinion ration yields a theoritical Vmax of 37.69mph with a motor speed of 40700 RPM on a 5S battery.
A 52/13 spur to pinion on the other hand increases the Vmax a bit to 40mph and lowers the Rollout to 1.06:1 which is closer to the 1:1 ratio.
Which is the "best" one to use theoretically speaking?
Is there a way to calculate the running time on these settings?
I will try to avoid using the 50T spur gear as this is a metal one and I read that is better to opt away from metal spur gears in case the mesh fails.

[pinkpanda3310]

Originally Posted by Achaios

Which is the "best" one to use theoretically speaking?

The best one would be determined by what temps you get from the esc and motor. There is also a lot of variables like battteries, climate, driving style, where you run (boggy sand through to hard top) which affect temps. Most (if not all) people have a range of pinions in their kit. If you don't already have one get yourself an IR temp gun and check the temps regularly, cheap way to look after your gear.