Hey so I currently have a mamba max brushless system in my xxx bk2 that I drive on-road. Here is what I have.

Spur: 78 (switching to 90)
Pinion: 18 (switching to 14 or 16)
Motor: 7700kv
battery: 7.2v 3300 gp (switching to 7.4v Lipo 30c 5000 mah)

Once I switch the gearing, the esc shouldnt over heat anymore, nor should the battery. However, it won't go nearly as fast. How do I maximize the speed while maintaining a safe battery, esc and motor temperature? Change the motor to 5700 kv and gear down ?

The tires tend to balloon quite a bit. I dont know if that makes a difference.

Any advice is helpful. Thanks!

You might be surprised at the speed with the new gearing. The 7700 will work just about any nimh pack pretty hard, you should be much better off with the lipo and different gearing.

Are you saying that a smaller pinion and larger spur gear will make it mcuh faster some how? Or the lipo alone is what will make it faster.

I suspect the 18/78 might be overgeared, causing heat and poor output. 14 or 16/90 will likely be closer to the motors optimum gearing, giving you increased performance. When it comes to simply plain top speed a larger pinion is usually faster, but once you pass a point you are only wasting power and going smaller can actually improve top speed. In other cases the acceleration will improve so much that the car "feels" faster even if the top speed is slightly lower.

Thanks for that explanation, It makes a lot more sense now!

Edit: So I switched the gearing to 90 spur, 14 or 16 pinion and it just goes a lot slower. The 78 spur and 21 pinion went way quicker.

When I switch the lipo pack, will that makes a difference in the temperature of the esc?

So I switched the gearing to 90 spur, 14 or 16 pinion and it just goes a lot slower. The 78 spur and 21 pinion went way quicker.

When I switch the lipo pack, will that makes a difference in the temperature of the esc?

Thats a big gearing change - 78/21 is 3.714 and 90/14 is 6.429, even the 90/16 is still 5.625. May want to try upping pinion a little more.


Switching to lipo isn't going to make the esc run any hotter unless the batt you're using now isn't able to supply enough current for your setup.

So your saying by having a battery current that is too small can make the esc run hot? The lipo im switching to has 30 amps

Yes. Pesky Electrons.

voltage drops, amperage goes up for a given load.. more amps=more heat built up. More voltage, less amps for the same amount of work.

discharge rate on a lipo is measured in "C" C being the nominal Charge/discharge rate. (e.G 1C discharge rate on a 1000Mah battery pack is 1 amp/Hr. 2 amps for 1/2 hour...) Add those up to a 30C pack, on a 5000Mah battery and you get Burst current of up to 150+ amps for short times.

Now, if the pack STILL drops Voltage under load(as some Lipos do) Amperage will still go up.

I'd move to a lower Kv rated motor and that will allow you to pull bigger gearing and have the same end result. Lower Kv motor will draw fewer amps for a given speed, assuming the motor is working in it's optimum power range.