Well, as many of you know, I am trying to sell a lot of my unneeded rc car stuff to fund for a Neu motor to go into my Revo. I was originally planning on running the 1515/1y on 4s lipo, but I knew that I would want to run a higher voltage in the future and wouldn't be able to use it. The 1515/2.5d on the other hand, will run 5s great, but, not too sure on 4s. My set up is a Revo with stock diffs (soon to be 1/8 buggy diffs after these fail), Revo tranny locked into 2nd gear with wide ratio gear set, and 5.6 inch 40 series tires.
According to BrianG's calculator:
With the Neu 1515/2.5d - 20t pinion - 4s lipo - it will go 38.76MPH, but the RPMs will only be 25,160. I am afraid that it would heat up too much from having it over rev, and not having enough load on the motor. But the good news is that in the future, I will be able to run more voltage on it.
With the Neu 1515/1y - 16t pinion - 4s lipo - it will go 40.12MPH, and the RPMs would be 32,560 which is perfect for efficient running. But if I ever want to run a higher voltage, I will need a new motor as far as I know.
Let me know what you all think of this right now. I am leaning toward the 1515/2.5d and having Mike make me a custom pinion that is 22t or similar, so that it won't be underloaded. And then when I run 5s or 6s, I will just gear the pinion way lower.