Motor hot but ESC cold. Gear up or down?

[topelement]

Well, I decided to pull the old Rustler out of retirement, and put in some spare electronics.
Installed a Novak Explorer Sport II esc, a never used silver can motor, and running off GP3300 packs. Truck is geared with stock spur, and 21t pinion. That gives it a final ratio of 10.88:1, and makes rollout 28.5mm.
Truck seems to accelerate pretty nice and climbs steep hills easily, but tops out quickly. At the end of a 15 minute run, the motor is too hot to touch, but the ESC is barely above ambient temp.
My question is about pinion size, and whether the motor is getting hot from not having much load on it? Or could it be that it is overgeared and the heat is from straining too much? I only have 18t and 21t pinions right now for this truck, and wanted to get some info on which sizes I should buy.
Thanks!

[RrR]

Try the 18t.Plus is ever thing rolling/moving smoothlly?

[topelement]

Try the 18t.Plus is ever thing rolling/moving smoothlly?

Everything moves very smoothly, and it's fully equipped with bearings. Without the motor, it coasted along the floor very easily and quietly. I feel no significant drag when turning the axles either, with no motor installed.
I guess i'll give the 18t a try. However, won't the truck have an even lower top speed? It already climbs steep grass hills with no effort, so torque doesn't seem lacking, but it's worth a shot.

[RrR]

I guess i'll give the 18t a try. However, won't the truck have an even lower top speed? It already climbs steep grass hills with no effort, so torque doesn't seem lacking, but it's worth a shot.Well it might but it better then cooking your motor.Also it may need a lower gearing to go faster.

[topelement]

Ok, tested out a few different setups today.
I put in the 18t pinion, and the Rustler became boringly slow! Easily climbed the steepest hills as long as there was traction. However, it topped out in about 4 feet, and wasn't much fun. Motor got even hotter than before, which indicates it' revving with little load.
Installed a 24 tooth pinion, and the truck really woke up! Acceleration was still good, but top speed was much improved. No more whiny noise from the motor, like when it's free spinning on a motor stand. Rustler had enough power to climb hills and get up to speed quickly in between jumps. Motor temp was the lowest i'd seen so far on this truck.
Decided to try out a 30t pinion, and I was amazed the truck could move like this! Did a few runs down my street, and it was about as fast as my touring cars with Mabuchi's. Acceleration was not quite as strong anymore, but still acceptable, especially considering it's only a silver can. Top speed was pretty nice though, and really helped launch the truck off jumps. It was covering about 8ft with a little ramp only about a foot tall. Motor temp was about the same as with a 21t pinion, but finally the ESC and battery were getting a little warm too.
I'm starting to like off road now! Just gotta get a brushless system for this thing.:)

[ElectricThunder]

You were undergeared. The motor was probably over-reving and just wasn't receiving too much of a load. It was "too easy" for the motor probably.