[VintageMA]

From a few trials with the E-Revo, don't gear for 40mph with the stock tires. My first gearing was 24/68 on a 1515 running at about 30,000rpm geared for 35mph - at 35 mph the stock tires balloon enough (about a full 2" in diameter)to make the speed closer to 50mph+ and will drop your overall ratio tremendously and you will get some serious heat (got up to 180* on a 1515 in 10 minutes - a 7XL would become a griddle)

I just switched out to a 1515 running at ~36,000rpm on 6S and geared it at 18/62 with the Badlands MT (again ~35mph) and it was running much smoother and motor temps around ~130*.

The badlands do not balloon much at all. The Talons are cookie cutters - if you gear for 40 you're going to balloon close to 55-60mph gearing with the tire expansion.

I would say to gear up to closer to 30-32mph and with a little tire ballooning you'll be around high 30's. When you get better tires you can then gear back down to a 20-22T pinion.