Monster Truck Madness – Gearing an Axial SMT10
One of the first questions an Axial SMT10 owner asks themselves after upgrading the power plant is “How should I gear this?”
There are a several ways to approach the question, depending on your battery cell count, tire selection and intended use. For the premise of this post, I’m going to assume that you are running bigger-than-stock Clod sized tires, aka those offered by Pro-Line Racing or JConcepts, that most owners seem to gravitate to. I’m also going to assume that you’ve upgraded the power plant to something else with a bit more pep and are running a 2S lipo battery.
The out-of-the-box SMT10 comes geared with an 11 tooth pinion and 56 tooth spur. They are 32 pitch. There is a 16 tooth pinion in the box, though. It comes installed with the 11t so the truck can safely handle 3S power right out of the box. If you were going to stay stock here, at the very least you need to put in the 16t option…but you don’t have the stock system anymore, right?
I currently own and compete with four Axial SMT10’s, two of which fall into the “Pro-Modified” category of monster truck. I.e. massive power. My main truck is powered by a sensored Graupner Turbo 120A ESC with 5.5t motor. Needless to say, this truck can turn asphalt to gravel when I let her eat. While my gears may be steel, I’m actually running the same tooth count as the out-of-the-box transmission. I’ve found that the 11t pinion is great for keeping temps cool and also to not immediately overpower whatever surface I’m driving on. Even with 2S, my motor is so fast that the low gearing isn’t a hindrance to top speed.
I’m running a 3900kv system in my other mod truck, and since the motor is a good deal less peppy than the Grauper, I’m rolling with 16t gearing on the pinion. That gives it more top end while still being conservative enough so as to maintain low temperatures throughout longer bashing sessions.
My remaining two SMT10’s are set-up with much milder 17t brushed motor applications. To be more specific, I’m running Traxxas XL5 ESCs with Radon 17t motors. They are set up this way to comply with my racing club’s “Sport Mod” class. Because the rules mandate a much slower motor, I’ve done a lot of experimenting over the years to try and see what works best.
My findings? An 18t pinion works great for racing and allows for plenty of hustle. If you want to bash the truck over longer periods of time, bump it down to a 17t. I have crammed a 19t in there before, but wound up blowing my motor relatively quick.
The TL;DR of this? If you have an ultra hot motor, keep it geared down in the 11t to 14t range. For almost everything else, you will be totally fine at 16t. 17t if you want to push it. Anything higher than that should be used strictly for competition or very short term bash spurts.
Phew, that’s a mouthful. Hope that helps and happy Monster Trucking!