HBX 901a Review: durable 1/12 scale 4wd Brushless truck

HBX 901a Review

The HBX 901a is a new 4WD brushless truck from HBX. Being 1/12 scale, it is larger than the cars they typically make. In this review we will cover off the specs and build of the truck, give you all of the performance results and finish up with a summary and recommendations plus some ideas for improvements. If available I'll post a discount coupon on my coupons and discount page

HBX have made some great releases in the 1/16 scale recently of which I've reviewed both - the 16886 Spectre desert buggy and the 16889a pro monster truck. Both have performed very well - good speed, battery life and perhaps above all else, outstanding durability. It's great to see then that they have stretched themselves and extended this brushless offering to a 1/12 scale car. This larger scale can open up a bit more heavy offroad locations with the larger size - wheels, ground clearance and presence. Before we jump into the specs, you'll see I'll reference the HBX 16889a pro a lot because a lot of the parts have been lifted from this truck. That's no bad thing as you'll find out below...

Close up look at the specs and build

Motor. Although the spec says the motor is a 2847 3800kv motor I'd actually call it a 2845... splitting hairs really but worth knowing because there are more 2845 options around than 2847. In my opinion I've always through the 2845 brushless motor was the ideal size for a 1/12 scale car and should perform well especially given this is so light. Like the 16889a pro the kV they have chosen here is fairly conservative so we should expect some excellent battery life and heat management as we are finding is typical with HBX. 

Motor heat sink is a nice touch here and integrates well with mount design

I consider this motor to be a 2845 (not a 2847 as per specs

ESC/receiver. Like most ready to run cars this includes an all in one receiver and ESC unit. Upsides? It allows for a compact and tidy install. Downside? Replacement requires a specific part and upgrading requires you to purchase an ESC and radio gear at the same time. Good news then that HBX ESCs tend to be reliable compared to, say, WL toys and the radio gear has a decent range. This ESC is rated to 35a and is appropriate for this car.

Stock 35a ESC has been reliable and supports 3-wire servo plus options for LED lights or fans

Drivetrain. All gears in this car are metal and as is typical of HBX are well made and smooth. The metal 12t M0.6 pinion drives a metal spur onto a central one piece propshaft. This provides power to the front and rear metal diffs by metal crown gear. As we've come to expect, there are ball bearings everywhere here. Power is then provided to driveshafts using some rather chunky diff drive cups. There are regular dog bones in the rear and CVDs in the front, Wheels are held on by proper 4mm stubs front and rear with 12mm hexes. All in all this is an excellent drive train I would go so far as to say is over-engineered. I would not expect to see any trouble from this system at all. Final drive ratio is 12.5:1 which is rather short but appropriate given how large the wheels are.

Motor uses a 12t M0.6 pinion onto a metal spur gear

Heavy duty front CVD drive shafts

Dogbone drive shafts in the rear

Battery. The included battery is a 2s 7.4v 1600mah pack which is objectively pretty small in capacity for a 1/12 4wd truck. As mentioned above though, the fact that this truck is very light and has a very efficient motor and drivetrain means it will probably be OK. Don't forget this is the same motor from the 16889a pro and the smaller 1000mah pack gave that truck 15-20 minutes of run time. If you have trouble find a replacement, this WL toys 2s 1500mah is a good option that fits

Servo and steering. The HBX 901a uses a regular 3 wire 17g sized servo. It's not particularly fast as you'll see in the video below but the good news is that if this bothers you, it is easy and cheap to replace with something faster; for example the $10-$15 Surpass 17g metal gear servo should a direct drop in replacement (UPDATE: not a direct fit, more work to be done to confirm). The Servo horn doubles as a servo saver and the rest of mechanism although appearing flimsy is actually pretty accurate and surprisingly robust. As is typical with basher RC cars, there is no adjustment here other than steering trim

Servo saver horn in white here

Suspension. Suspension arms on this car are well suited to bashing - rather than using a lower a-arm and upper tierods, they have gone with a-arms top and bottom on both ends of the car which should make this very tough although you do miss out on camber adjustability. Horses for courses - this is a basher not a racer after all. Suspension arms are very long on this car and this allows for a larger amount of travel. Shocks are oil filled but that are small - in fact the same as those used on the 16889a pro. Mine were well filled out of the factory. However, since the shocks are short and the travel is long, shocks are mounted well in board with a lot of leverage. This means the actual dampening is not fantastic but lets give them a chance and see how they hold up in the performance section. It might be that the light weight of the cars saves the blemish here.

Short front and rear shock absorbers but strong upper and lower a-arms make this suspension setup pretty tough

Chassis The chassis is very small and light weight. What I mean by that is that there is no room for anything more than the stock electronics which are extremely compact. This means upgrading to a bigger ESC / battery or anything else could be tricky. With that out of the way I can't see any obvious weakspots like we saw on the WL toys 104009 1/12 scale monster truck - the front steering setup looks intricate but is well braced. Unfortunately the battery compartment allows no room for a larger battery. Hopefully the included 1600mah 2s pack will be enough...

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Body and lights Body is kind of a stadium truck/truggy design with a rear spoiler. I thought it was pretty ugly at first but it's grown on me. They include a set of decals for you to dress it up if you want. The polycarbonate feels nice and thick and it mounts very cleanly to the car. The light bar on top is actually very bright and looks great. It's a nice touch that they supply a flexible cable here so taking the body on and off is easy. Like the 16889 cars they include bumper mounted LED lights too but you must install these yourself and is very easy.

The look of this truck has grown on me

Front bumper lights come uninstalled but take all of about 2 minutes to connect and fasten

Wheels. The wheels have a  95mm diameter which is very large for a 1/12 truck. They are narrow at only 38mm which allows them to stay lightweight. They are a fairly hard rubber compound and have foam inners. They offer a really impressive ground clearance as you can see in the image below (I measure around 45mm). I'm necessarily not a fan of the look but lets see how they perform.

Real World Performance Results
In this section I look at how this car performs in all aspects - speed, acceleration, handling, battery life and durability so you can have a balance look at this car to see if it suits you.

Speed. I measured the max speed of this car at 40km/h (sorry I only screen grabbed the 39km/h run). Funnily enough this is the exact same speed as the HBX 16889a pro here that uses the same motor kV but different gearing and wheel size. I don't think this is a coincidence. This is not slow but certainly not especially fast either for a 1/12 scale car although it does get up to this speed very quickly and doesn't matter where you are on road or off - the 39km/h in the screen grab here was done on the gravel surface from the videos below. By comparison the Eachine EAT14 (brushless 144001) that I review recently got 63km/h but needed a massive run up. Even the stock brushed 144001 and 124019 can get up to 50-55km/h but need a massive run up. 

Update: This car is set up to take a 14t pinion from the factory with another set of holes in the motor mount. Going from the stock 12t to 14t should give you an extra 7kph quite easily. I have a new pinion on order...

Power / Acceleration. It's clear to me that the focus of this car was never the brag like WL toys make around the top speed but more about the acceleration and efficiency. This car accelerates really hard and makes it feel a lot faster than it actually is (I thought it was more like 45 or even 50km/h). This is much more important for a basher than top end because flat out speed is not something you are regularly doing - it's more about accelerating over or through obstables and making changes of direction rather than going as fast as you can in a straight line. This approach appeals to me more and is the exact opposite to the Eachine EAT 14 I recently reviewed that favours speed over acceleration and is probably why I enjoy driving this car more.

Cogging. There is precisely zero cogging in this car thanks to the short gearing and well sized motor. This means it is much nicer to drive at low speed and doesn't get stuck in minor obstacles. This contrasts heavily with the Eachine EAT14 which although over 50% faster has pretty bad cogging and low speed control.

Handling. First lets talk about the ground clearance. This car has massive diameter wheels for a 1/12 scale car. Between this and the large suspension range it has excellent ground clearance and seldoms gets stuck on any obstacle for a car this size including long grass. Staying with the wheels they are large in diameter but fairly narrow and light meaning the car can spin them pretty easy. Tyres are quite a hard compound and grip ok on most surfaces so long as they don't get wet. Grip on these hard compound tyres is terrible in the wet!!

As I mentioned the travel on the suspension is great but due to the way the shock are mounted, dampening is pretty poor. This could be rectified with a heavier oil but it will place more pressure on what is a fairly basic set of shocks. The upside is that this car is incredibly light and so doesn't need an awful lot of dampening. End result? It handles pretty well perhaps a little front heavy if anything. It can get a bit snakey as you can see in the below video but this was with we tyres (and me driving one-handed! Be wary over jumps, with a low level of dampening you may get some bottoming out. A bit like the HBX 16889a pro the handling on this car is good without reaching the heights of say the 124019 which is specced more like a race car.

Battery Life. As I've mentioned this car has short gearing which limits the top speed but really helps the acceleration. The other thing it really helps is battery life. Even with this relatively small 1500mah battery and the light weight of the car it means you are getting an easy 15-20 minutes before you hit the low voltage cutout which is mighty impressive compared to the 10 or so minutes from the Eachine EAT14 and the 5-7 minutes compared to a stock 144001 / 124019. This is a relief because there is no real room to mount a larger capacity battery cleanly here. My recommendation would be to buy the car with 2 or 3 batteries as they suit the car well. Battery life is definitely a strong point of this car and was one of the reasons the HBX 16889 and 16889a pro have been so popular.

Durability. Like the 16889a pro I reviewed here, this car is very, very durable. There are 3 key reasons for this:

1. It is very light so carries little kinetic energy into a crash
2. Design of the chassis, suspension, steering and other system have no obvious weak points
3. The plastic that HBX makes its cars out has just the right amount of flex and springs out and back rather than snapping like a stiffer material would.

Furthermore the shell is mounted well and is made of decently thick polycarbonate for a car of this scale. I think the only real weak point on this setup is the rear wing which I know from long-term ownership of the 16890 is not especially strong following repeated crashing. It is there for looks only anyway and serves little to no real function at these speeds.

This guy is my official durability tester

These wings don't hold to the abuse that the rest of the car can handle

Range. This car uses the standard HBX 2.4GHz controller which is basic but works well. Unlike the WL toys remotes it can control reliably at 50m range without difficulty. Since this is not a speed run car it is not really important to be able to go beyond that anyway. I should note that this remote also include a throttle dual rate which is a really useful feature to limit top speed for beginners or for little people.

Other little things from having played with the car for a while. It sounds silly but the power switch setup and location is really nice. You don't need to power the car on before putting the lid on. By integrating the switch into the chassis siderunners it can be turned on and off with lid on or off. Minor detail but a nice feature nonetheless. I mentioned earlier but the lights are a really nice little touch as well. The top mounted lights especially are very bright.

Summary And My Recommendations
So for a quick summary this car is only modestly fast but accelerates strongly, handles ok with big ground clearance, has a long lasting battery and will stand up to a lot of punishment. Clearly this car is not for a speed runner (I'd recommend the Eachine EAT14 there). It's not really for the modder neither (I'd recommend the 124019 here) because of the limited space available and that upgrading the motor / ESC etc will make the car heavier and more prone to damage. Who is it for then? It is perfect for the beginner or for someone who just wants to run a decently quick car offroad without the fuss of having to repair it every 5 minutes and having a battery that lasts for a decent run. Funnily enough this competes most directly with another HBX car, the 16889a pro. This 901a however is bigger with more ground clearance though and so is more capable off-road.

So, in conclusion if you are looking for a reliable small scale basher you can take out for a decent run knowing you are unlikely to break it then this is a simply fantastic car. If you don't want to spend quite as much and don't need quite the off road capability then consider the HBX 16889a instead which is a little cheaper and smaller but runs the same key electronics.

I ordered my car from Banggood here: 
HBX 901A RTR 1/12 2.4G 4WD 45km/h Brushless RC Cars Fast Off-Road LED Light Truck Models Toys

Basic upgrades worth considering
As I mentioned above I wouldn't recommend bigger motors and ESCs to upgrade this car or it will compromise the durability of the car. With that said here are some tune ups and lower level mods I think would improve this car. If you would like to see a write up of these in the future then let me know in the comments below!

• Servo: upgrade to Surpass hobby 17g metal gear (direct fit)
• Shocks: upgrade to heavier shock fluid
• Diffs: pack with a thick grease or 20,000wt + diff fluid to stop open-diffing
• Motor: swap 2845 3800kv motor out for a 2845 4500kv motor but keep a close eye on motor temps. This should take top speed up to about 47km/h which would be good with this car. Update! I've just found out this car has provision to increase pinion from 12t to 14t. Doing this with stock motor should also take you to around 47km/h. I recommend the surpass hobby M0.6 pinion sets
• Wheels/tyres: Consider the 1828 wheels I reviewed here for more grip offroad but bear in mind the lower diameter will decrease ground clearance and top speed.

Screaming out for a 14t pinion instead of the stock 12t!!!!

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