Monster Truck Madness: Building a JConcepts Reactor Monster Truck Part 3

Greetings all! I hope everyone here in the States has a great Fourth of July weekend! Rather than a traditional Backyard this week, I figured I’d combine it with another installment of Monster Truck Madness. The Reactor has officially made its competition debut, and after all the planning, building, and tinkering, it’s finally time to talk about what it’s like behind the wheel.

This is Part 3 of my JConcepts Reactor build series – you can find Part 1 here and Part 2 here).

The Reactor’s competition debut came at the 2026 BIGFOOT 4×4 Open House, where it would be squaring off against other Reactors as well as a field of modified Clod Busters.

Unfortunately, Mother Nature had other plans.

The track was laid out on pavement, but it rained on and off for most of the day. At some point, the decision had to be made: either race them or don’t. We chose to race. That meant my Reactor’s very first laps in competition came on wet pavement, which certainly wasn’t how I had envisioned its debut.

Speaking of that, apologies for not having more photos of the truck in action. Due to the weather situation I was running around like lunatic trying to keep things dry as best I could and keeping the event moving, and I wound up not getting any decent usable photos. Rich from JConcepts loaned a few that he took!

Before hitting the track, I made one setup change worth mentioning. Per the Retro rules we were racing under, sway bars weren’t allowed, so I disconnected the Reactor’s front and rear sway bars. Thankfully, this is an incredibly simple process. Four easily accessible screws later, and the truck was legal to race.

I also realized I forgot to mention a couple of things in Part 2 regarding the shocks. I built all eight shocks using the included 30-weight oil and the two-hole pistons. More importantly, I took advantage of the supplied O-ring grease when assembling them. Kudos to JConcepts for including it. Surprisingly, many kits don’t, even though it’s one of those little things that makes a noticeable difference. Properly lubricated O-rings help reduce oil leakage while making the shocks noticeably smoother throughout their travel.

So…how does the Reactor actually drive?

Oh man.

As someone who’s been building and racing modified Clod Busters for many years, this thing handles like a dream.

The steering is incredibly precise, and the turning radius is far tighter than what I’m accustomed to with a Clod. Even with both sway bars disconnected, body roll is dramatically reduced compared to a traditionally modified Clod Buster.

Yes, the truck still exhibits some of that characteristic leaf spring bounce, especially over jumps, but it’s smooth and predictable. More importantly, that’s exactly what you’re buying into. The Reactor is intentionally replicating the feel of those early-1990s leaf-sprung monster trucks, and I think JConcepts absolutely nailed that personality.

Another feature I really appreciated was the adjustable slipper clutches. That’s something we’ve simply never had on traditional motor-on-axle monster trucks. I ended up tightening mine nearly all the way because I expected to be racing on high-grip pavement.

Well…in theory, pavement is high grip.

Wet pavement is another story entirely.

The best way I can describe the Reactor is this: imagine taking a Retro Clod Buster and replacing absolutely everything. New high-clearance axles. Adjustable gearboxes. Modern suspension. A purpose-built performance chassis. Every aftermarket upgrade you could possibly bolt onto a Clod, all engineered to work together from the start.

That’s what the Reactor feels like.

With that said, it’s important to remember what it isn’t.

This is still a Retro monster truck. It isn’t trying to be a Losi LMT or an Axial SMT10. It won’t soak up giant jumps like a linked coil-over truck, nor should it. The Reactor embraces the unique handling characteristics of leaf springs while refining them with modern engineering.

As far as Retro-style monster trucks go, I think JConcepts has absolutely knocked it out of the park.

I’m especially excited to reconnect the sway bars and spend some time racing on dirt later this summer, where I suspect the truck will really begin to show what it’s capable of.

If I had one word of caution for prospective builders, it would simply be this: I’d recommend the Reactor to hobbyists who already have a few kit builds under their belt.

It’s not that the kit is difficult. Quite the opposite, really. The machining, molding quality, and overall fit and finish are excellent throughout. The challenge is that the Reactor rewards careful assembly. Using a screw that’s just a couple of millimeters too long or too short in the wrong location can mean taking a component back apart to correct it. Likewise, there are a handful of illustrations in the manual that require a little extra study before everything clicks.

Take your time, pay attention to the hardware callouts, and you’ll be rewarded with what feels like a precision-built machine. Compared to assembling a Tamiya Clod Buster, the Reactor is in an entirely different league from both an engineering and assembly standpoint.

I absolutely love my Reactor.

Perhaps the biggest compliment I can give the Reactor is this: it feels like the truck many of us Clod racers have been building toward for the last 30 years.

I’m sure I’ll have plenty more to say as I continue racing it throughout the season…and don’t be surprised if this truck winds up with a brother Reactor sitting next to it before too long.

Until next time, keep it on all 4’s!