A little dirt never hurt: LEGO Technic 42099 4×4 X-treme Off-Roader [Review]

Here is a simple truth: these days LEGO remains one of those few common activities that give you a rest from a smartphone. For me and for many of our readers, building with LEGO has always been a pastime that requires no downloads, installing or updates; you open a box and the play begins. Obviously, winning over modern-day kids who love digital entertainment and touchscreens is a tough challenge for a toy manufacturer. They say if you can’t beat them, join them, but LEGO thinks differently: if you can’t beat them, build them into the play experience. Along comes LEGO Technic Powered Up — the first generation of LEGO Technic electric elements that bring smartphones and tablets into play. With a whole lot of sensors and features, the new smart hub and motors are among the most advanced LEGO pieces ever produced. LEGO Technic 42099 4×4 X-treme Off-Roader introduces the new play system. The set includes just 958 pieces, but the new expensive electric elements are to blame for the price tag of US $249.99 | CAN $299.99UK £199.99. It is available starting today, so we are building and testing the model in an attempt to discover the limits of the new Powered Up system and Control+ smart app.

Packaging, stickers, and building instructions

Since the off-roader rides on four huge 107x44R tires, the box is quite massive. All the 958 pieces are distributed among just 6 plastic bags, but the electric elements come in a dedicated box the size of a small LEGO set.

A large sticker sheet immediately strikes the eye. Just like the last year’s 42077 Rally Car set, the X-treme off-roader is a “victim” of stickers: more than 30 decals stick all over the vehicle’s body. Although the bright-yellowish-orange design looks fresh and cool, I won’t stop criticizing long and narrow stickers that are designed for 1×11 liftarms.

The abundance of stickers results in “building” steps that involve no new pieces. Bright and screaming design coupled with the toy’s functionality gives a hint about the products target audience; probably, kids and teenagers are much more easy-going about countless stickers than adult collectors.

The surprisingly thin building guide is only 220 pages long, which feels like a quick read after the recent Technic 42098 Car transporter’s 550-page-long monstrosity. Since the set includes no overcomplicated structures and consists of the most common LEGO Technic parts, assembling takes 4 hours, tops.

Another mildly interesting thing about the set is the color asymmetry of the core structures. Having the same pieces of different colors helps a lot when you struggle with the model positioning. This will definitely help younger builders complete the set without any mistakes.

New LEGO Powered Up electric elements

For over the last decade LEGO Power Functions remained the prime electric system across multiple LEGO themes. This year, the system is being replaced with the brand new LEGO Powered Up electric elements. From dedicated presentations held by the developers, we have learned that, unlike the older motors, with the new smart hubs and more advanced connectors the new motors will also function as sensors. Bidirectional data communication will bring much more advanced models, and the new 4×4 X-treme off-roader is just a glimpse at the new possibilities. Among other innovations is Bluetooth connectivity, which we already tested while building and playing with the LEGO 76112 App-Controlled Batmobile set.

While the said Batmobile included a smaller hub and a couple of smaller motors, the new off-roader comes with a massive tech-laden smart hub and 3 motors of two types.

Compared to the Power Functions elements, the new hub is a single unit combining a battery box and a receiver. The smart hub is the heart and the brain of the new model. It features a processor, a Bluetooth module, as well as a 6-axis sensor, consisting of a 3-axis accelerometer and a 3-axis gyroscope. The new system can indicate the model’s orientation, acceleration and even detect bumps. Four motors/sensors can be connected to the ports in the upper part of the hub. The former Power Function connectors can be stacked on top of one another, which makes them suitable for custom builds of any scale and concept. Obviously, the new connectors don’t allow staking; in this sense, they work a lot like LEGO Mindstorms RJ-12 connections.


Inside the hub, there is space for 6 AA battery elements, which is a standard for a LEGO RC system. You will also note that the hub has only 12 Technic pinholes. It’s important to mention that all of those pinholes sit right above the center of gravity of this heavy hub.

The smaller of the two electric motors is used for wheel steering. The motor looks and feels very nice and robust, however, only further testing will show how durable it is. We are pretty positive that this motor can function as a servomotor (allowing for precise control of the angular position, i.e. as a steering motor) as well as a regular motor. This is possible thanks to the new smart hub.


The off-roader is driven by a couple of larger and more powerful motors. The larger motor feels quite bulky and heavy, but its proportions are close to the old Power Functions XL-motor. Unlike the older XL-motor, the new one has more pinholes on opposite sides of its body.


No doubt, both types of motors require further testing including speed and torque characteristics. While you are reading this review, we are busy putting the new system to the test, so stay tuned for dedicated analysis of the new elements!


NB: during the period of reviewing the set we discovered that the Powered Up elements that come in 42099 set are programmed in such a way that the application won’t let you connect to the model unless all the motors are plugged into the right ports. Even if one motor is missing the app will inform you that the model is out of reach. The current way of controlling the Powered Up elements via Control+ app doesn’t let you run your own models with a different set or number of motors connected to the hub.

New elements and part in new colors

As was mentioned above, the two main selling features of the set are its design and its functionality. While the latter is all about the new Powered Up control system, the model’s unique look is being achieved with the introduction of a new color. This is the first LEGO Technic set to include liftarms and panels in bright orange. There are not that many panels in the set, but surely enough to build a custom vehicle of a smaller scale.

Another unexpected element that we found in the set is the new 3×3 frame (aka “biscuit”) that we first met in LEGO Spike sets presented back in April. One of these in black can be spotted in the back of the rear end of the chassis, covering the tan gear. This relatively small piece helps to create a very compact yet sturdy structure.

Those who are fond of building custom crawlers will be happy to see hard shock absorbers in red. There are only 2 other sets where you will find the absorbers in this color, making them some pretty rare elements.

Finally, one of the biggest innovations of the set is the brand new wheel hubs with a planetary reduction gearbox (if you have no idea what this mechanism is, here’s a nice gif for you). Basically, this round piece houses a set of at least 5 gears that sit tightly inside and make a very soft rumble when you spin the knuckle.

The introduction of this piece is some very big news for all LEGO Technic builders. The important thing with planetary reduction gears is that it can significantly increase the motor’s torque. In this case, the gear ratio is 1:5, so the torque is 5 times more compared to direct transmission. The price for this is loss of speed, but an off-road crawler like this isn’t designed for cross-country racing. Of course, such a gearbox can be built with the regular LEGO Technic elements, but very often a massive turntable piece is required. The new pieces will anyone build a very compact off-road crawler with a very realistic drivetrain.

The chassis

The off-roader is being built in 3 major steps: the front axle, the rear axle, and the body. The chassis is practically being built around the motors; you can see exposed electric elements from all four sides of the structure. I must admit at this point I wasn’t impressed by the structure at all. It all feels very flimsy and unsuitable for outdoor testing.


But here’s a building solution that I find particularly interesting: the whole middle part of the chassis including the front axle is mounted on two turntables, so it can swing from side to side. The purpose of this structure is to give the off-roader an even wider suspension travel. This way the crawler must be able to cope with even larger obstacles than it would be using shock absorbers only.

The body

Assembling the body of the off-roader is a short, but a very enjoyable journey, stickers aside. The color of the new pieces is truly stunning, and I wish I could apply no stickers at all. Probably the model looks even wilder with all the numerous logos and patterns, but I’m happy it doesn’t feel overloaded with design elements.

The inside of the body looks very neat. No safety arches and no excessive structure elements. The body is a very light, yet solid structure.


Finally comes the “marriage”, the moment when the chassis and the body become a single whole. The body is fixed with just a pin in the front and two more axles on each side.

It took me a moment to figure out the whole wire management thing in the back of the car, and I’m still not quite happy with the result. Unfortunately, the building guide gives no hint about the best way to fold the wires inside the body.

Complete model

Once the wheels are on the off-roader is complete. Massive tires completely change to look and the character of the model giving it somewhat untenable proportions. But, again, kids will know better.

There are no large panels in the back of the car. On the one hand, an open structure gives easy access to the smart hub and the power button on the top, but on the other hand, I’d prefer some kind of protection for the wires in case the off-roader rolls over on its roof.

The bottom view of the chassis reveals a practically exposed motor. My own experience of using Power Functions motor in RC models tells me that placing the motor like this may lead to scratches and other damage to the motor’s body. However, the road clearance of the crawler shall keep the electric elements undamaged.

Exterior design

The appearance of the model is pretty questionable. Unlike many other LEGO Technic sets that are based on existing machines, this off-roader seems to be a copy of a gasoline RC truck, i.e. a LEGO version of another “toy” car.


However, I really like the front guard. This is a very simple and subtle part of the design, but it contributes a lot to the model’s aggressive character. Moreover, this part indeed acts as a safety element protecting the panels behind it.

The most ridiculous part of the car’s design is the widows, thanks to a chopped roofline. Tiny openings on both sides of the car look very questionable; obviously, the problem can be fixed by lifting the roof up. Right now the seats and the steering wheel inside the car look absurd for a serious off-roader rather than a hotrod.

LEGO Control+ app

Once the model is finished it’s time to download and install the Control+ app. The app is available for both iOS and Android, but we tested it on iOS only. Control+ is a pretty heavy app (more than 400 MB), so make sure you have a WiFi connection and plenty of room on your device. It’s also important to mention that at the moment, the app is the only way to control the model; no physical controller has been announced yet, so it looks like a smartphone or a tablet will be an essential part of the play experience.

The first time you start the app it will calibrate the steering motor and give you a quick tutorial on how to control the off-roader.

The app’s home screen is the control panel with a couple of levers, fake tachometer and a couple of tilt indicators.

I’m not sure about the purpose of the speedometer as it never shows the actual speed of the car. It indicates speed up to 33 km/h (20 mph) when the car is going full-speed on even surface, but the model’s actual speed is much, much lower. Unlike the speedometer, the tilt indicators work just perfectly. They constantly indicate the car’s position and warn you if it is tilted more than 30 degrees in any direction.

The biggest surprise of the set is the one-touch control. This is an alternative way to control the off-roader. Instead of using levers you can simply tap anywhere around the car and it will immediately drive in that direction. It sounds like magic and it works like magic. You rotate the car on the screen so that it faces the same direction as the actual model, and that’s it. Now both cars are in sync; if you rotate the model, its picture on the screen will rotate, too. If you rotate the phone, the picture of the car on the screen will rotate, too. The only thing I can compare this is to the way the Nintendo Switch joy-cons work. High-tech gyroscopes in the smart hub and in the smartphone/tablet allow for amazingly precise positioning of the digital image of the car on the screen.

Controlling the car with the one-touch mode is a lot of fun. Kids and teenagers who will build and play with this set have no idea how lucky they are to play with toys like this one. Also, the speed of the car depends on the distance between the center of the screen and the place you tapped. By tapping right by the picture of the model you can make it crawl really slowly.

Another major part of the app is the challenges. Each consists of a sequence of actions that your off-roader must perform to unlock the achievement. The easiest of them is the Hairpin, which has three steps: drive forward, make a U-turn, drive forward some more. Once you chose to complete a challenge, you can follow the progress on the screen of your device. The more complicated challenges include short video tutorials demonstrating how to accomplish the mission.

Besides the basic ones, there are many additional challenges and achievements. For instance, we managed to get “8 Bumps in a Row” and “Rolled It!” while testing the car. Unfortunately, the full list of achievements is nowhere to be found, and you also can’t see detailed info on every achievement. We hope this will be fixed with future updates.

And while the motto of the set is Build for real, we had no choice other than putting the car to the test in the wild environment. A short video report captures the best moments of outdoor testing.

We used 6 fully charged IKEA rechargeable batteries (2450 mAh each). It was not before than 45 minutes of active driving that we started to notice a significant power loss due to batteries discharge.

Final thoughts and recommendations

Kids love cars and especially cars that can be remotely controlled. LEGO knows it and has been releasing proper RC car sets since 2001. The constant introduction of more and more advanced RC systems resulted in LEGO becoming one of the major players in the remote control toys market. The new LEGO Technic 42099 4×4 X-treme Off-Roader is yet another step forward: Bluetooth connectivity opens fantastic possibilities for indoor and outdoor play, while new pieces like planetary reduction gears will find their ways in many fan creations.

Although the status of Powered Up elements is yet unclear (the Control+ app is locked to the model and can’t be used in custom creations at the moment), the model offers a lot of value for its price: enjoyable assembling experience, fresh design and tons of playability including in-app challenges and free driving using one-touch control. Once again, LEGO prepared not just a toy or a set of plastic pieces, but rather a very impressing experience from the second you open the box till the moment you have to take a break to replace the batteries; this is a smart toy that is very hard to stop playing with.

LEGO Technic 42099 4×4 X-treme Off-Roader comes with 958 pieces and is available starting today, August 1st for US $249.99 | CAN $299.99 | UK £199.99. as well as some third parties on Amazon, Bricklink and eBay.

The LEGO Group sent The Brothers Brick an early copy of this set for review. Providing TBB with products for review guarantees neither coverage nor positive reviews.

15 comments on “A little dirt never hurt: LEGO Technic 42099 4×4 X-treme Off-Roader [Review]

  1. Dave Nelson

    Those connectors look like WeDo 2.0 connectors, I wonder if they would be compatible. It would be great to have a WeDo controller with 4 connectors.

  2. Alexander Post author

    @Dave Nelson right you are. These are the same connectors. LEGO SPIKE system should be using these connectors as well. The great news is that the SPIKE hub will work with every LEGO Boost and WeDo 2.0 external motor and sensors. I hope that the Powered Up system will support Boost, SPIKE and WeDo as well, but we can’t say for sure right now.

  3. mwendell

    Do we know if there’s a way to buy the new 3×3 Lego “biscuits” without buying Spike Prime or this kit? For that matter I’d love to find any of the new Spike Prime Technic pieces like the wheels or the new larger frames. I haven’t found any of them on Bricklink yet.

  4. Brian H.

    This looks like a nice RC car. Always wanted one and to get it in lego form even better. One thing that bugs me is the rechargable battery part with these. How do we get this included in the buy of the system I wonder? Is it easy to change the 6x batteries in a timely fashion? Having to spend 15 minutes taking it apart and putting it back together seems off putting.

  5. Russell Chapman

    I had a little chuckle when I saw the tyre fitment in the photos, but when I watch the video and see it fail to climb, I have to wonder how much of that is because the tyres are on wrong.
    Is it feasible to fix the tyres and run it up an embankment and report back in the comments? It just seems like it would do a lot better given the chance.

  6. Alexander Post author

    @Russell Chapman this is a very interesting point. Honestly, I don’t think the tire fitment really changes the car behavior, but we will try to test it outdoors once again. In that shot from the video, the main problem was the weight distribution, while wet sand wasn’t the most suitable terrain either. Additionally, depending on the type of terrain you driving around, stuff like wet sand and dirt stick to the tires pretty easily, so that the gripping pattern practically makes no difference.

  7. Alexander Post author

    @Brian H. as it is mentioned in the middle of the review, the body of the car is fixed with 1 pin and 2 short axles. You can remove it in just under 10 seconds. Then, you get full access to the chassis, and the hub sits right on top of it. Replacing batteries is actually as easy as it can be. Additionally, it looks like the hub can also fit a Li-po rechargeable battery that may be announced soon.

  8. Nico S.


    The tires on the right side of the vehicule are set in the wrong rotation direction. Not sure that would help lot for climbing, but it would at least feel more pleasant to the eyes.

  9. mwendell

    @chris – Thanks, I didn’t even know Bricks & Pieces existed! At first I assumed you meant the online Pick-A-Brick, which is almost useless. I just ordered a bunch of black biscuits by looking at the inventory for this truck. I also found and ordered a bunch of the magenta biscuits.

    None of the other Spike Prime parts are available yet (the larger frames, wire holders, wheels, etc.), but I’ll keep looking. The Bricks & Pieces site doesn’t find anything when you look up Spike Prime (45678), or the individual part numbers specifically, other than the biscuit and the brick with the cross axle holes. I did find a part-by-part inventory for Spike Prime on BrickOwl which was helpful in looking up those pieces individually.


  10. Jimmy

    WTF am I reading this correctly -I cannot use the motors/battery/controller from this set to build my own creation? That goes against one of the most central ethos of Lego toys! Please confirm if I am just misreading things or if that is really the case.

  11. Dutch

    The direction of the passenger side tires is shown incorrectly in the building instructions. The wires in the back should be covered by the outer shell if you follow the instructions very precisely.

    It’s an awesome set to build, lots of fun. The truck’s power isn’t very impressive at all though. Lego’s previous 4×4 crawler did have insane amounts of torque, this doesn’t come anywhere near that.

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