4x4

An offroader’s review of the TRAXXAS TRX4 model scale radio control rock crawler

24 Jul 2017

Robert Pepper 4

Who wouldn’t love the TRAXXAS TRX4, a scale model rock crawler?

FIRST I NEED TO SAY that this model is the epitome of “shut up and take my money”, and exactly why will become clear. Next I need to make clear that I am not a radio-control (RC) expert. Like most people, I’ve owned the odd RC car here and there, never really taken the hobby seriously. There’s lots of good RC expert reviews out there, and this isn’t one of them.

What I can claim is a good background in full-sized 4X4 vehicles as a journalist, driver trainer, owner and trip leader, so that’s the perspective I’m coming from with this review.

The reason the TRAXXAS TRX4 is so much fun for us offroad drivers is because all the skills we have learned and enjoy using in full-sized vehicles apply directly to the smaller-scale world of RC rock crawling.  For example; adjusting your line a fraction here and there. Locking and unlocking the diffs to turn or avoid wheelspin. Judicious use of momentum. Thinking your way around an obstacle. It’s all very good fun, challenging and enjoyable at least as much as full-size driving.

I would say that if someone is a good offroad driver they would be a good TRX4 driver, and if you can drive a TRX4 offroad then you will find the same skills apply in full-size vehicles. The only caveats are that with the RC vehicles you can use momentum to a much greater degree than with full-size vehicles, you tend not to worry about panel damage, and you have a god’s eye view of your situation.  Scaling down a vehicle does not accurately scale down the entire vehicular experience, but it is close enough that driving the TRX4 is fun, rewarding and educational. And who hasn’t been in a 4X4 and wished for the Almighty Hand of God to reach down, grab your truck and lift to safety? Well, now you are that hand, and rollovers don’t mean a trip home on a trailer! Take risks, no consequences.  How good is that?

I haven’t driven any other RC rockcrawler, but this one has some great design attributes. The  tight turning circle is the first one – the wheels turn a full 45 degrees – and then there’s the lockable cross axle differentials which were a major factor in my purchase decision. Locking and unlocking them never gets old.  The suspension is great too and the gearing – high and low range – allows very precise control. Thanks to the smooth under body and portal axles it never seems to get hung up either. I rolled mine several times and it appeared undamaged…wish that was true of the big cars, not even a wingmirror was bent! That rollcage isn’t just for looks, it actually works.

You may find it useful to enable the instant reverse option. When I first started with the TRX4 I found it wouldn’t go straight into reverse. Eventually figured out you had to neutralise the trigger/throttle first. In fairness, this was explained in the manual, along with the long button press to disable that ‘feature’. Which I did and am now much happier.

Reverse can also be used on steep descents. Remember when we used to select reverse in automatic 4X4s and come down steep hills forwards? Same sort of deal here, a little backwards throttle can be useful when descending. Actually, it’s all electric now so ‘throttle’ isn’t even the word but you know what I mean. One thing the TRX4 does show is just how good electric drive is at low-speed, precision manoeuvring. Internal combustion engines are definitely on their way out, unfortunately…but good as electric is, the whirr of an electric motor will not send shivers up your spine like the full-throated roar of a V8.

I think the best fun for a TRX4 is on a real 4WD track. Like this one:

TRAXXAS have also used portal axles for extra clearance, like you see in Unimogs and Pinzgauers. That’s a good move as not only is it cool, it seems that torque twist is an issue with RC cars, as I guess it would be with all that torque and such little weight.  You can see a little torque twist in some high-powered full-sized cars; when you accelerate hard in low gears the torque delivered through the differential imparts a twisting moment, and you end up turning when you want to go straight. That’s not the same as torque steer, by the way, but that’s another topic. It is more like the twisting you get when you fly a rubber-band powered model aircraft.

Portal axles fix this by providing reduction gearing in the hubs, where the gears are arranged in line with the vehicle, and at each hub so there’s no lateral torque twist, and it’s equalised. Plus, you get extra ground clearance – TRAXXAS claim to match the TRX4’s ground clearance you’d need tyres that are another 25mm taller, so it adds another 12mm of ground clearance compared to a conventional live axle. My measurements bear out that claim. And being a small, light car you’re not actually driving then there’s no worries about unsprung weight or dealing with the odd alignment issues you have to handle with portals.

There’s more to the TRX4 than fun though. Read on to page 2…