I've built around 20 SCX24s and most of them are comp rigs. A comp build is a different animal from a trail build. Different priorities, different parts, different tuning. If you've never run a gated comp course, the short version is: it'll humble you, and the rig you trail-bash with isn't going to win. Here's how I build mine.
This article assumes you already know what brushless, portals, isokinetics, and servo specs mean. If those terms are unfamiliar, start with the first upgrades guide and the servo explainer.
What makes a comp build different
Comp courses test slow-speed control on technical lines. Priorities:
- Maximum traction. Stickiest tires, brass at the contact patch, no compromises.
- Slow, controllable throttle. Brushless with FOC or sensored, low KV, aggressive drag brake.
- Maximum steering angle. Isokinetic CVDs or portals. The 27 degrees of stock just isn't enough.
- Low CG. Tip-over costs you the run. LCG chassis and brass low and forward.
- Predictable suspension. Oil-filled shocks, tuned damping, even pre-load.
- Durability. Hardened gears, CVD shafts, metal axle housings. Comp runs put hours on a rig in one weekend.
Scale realism, top speed, and runtime are all secondary. A comp rig is allowed to look weird and only run 15 minutes per pack. The job is gating the course cleanly.
The build
Chassis
LCG carbon fiber, ideally with brass cross-braces. INJORA Universal LCG is the budget starting point. Treal's LCG is the mainstream upgrade. LGRP or Mofo for premium. Pair with a 5 to 7 degree skid plate angle.
Axles
This is where the real decision lives. Three setups I've run on comp builds:
- MEUS Isokinetic V2 front, portal rear. “Mullet Setup.” 52 degrees of steering up front, clearance and 25% reduction in the rear. The best all-around comp setup I've found.
- LGRP Spider 9 portals all around. Maximum durability and consistency. Heavier. Premium money.
- MEUS aluminum portals all around. Value pick. Less premium machining than LGRP, performs nearly as well.
Avoid INJORA Planet Axles on comp builds. They're straight axles with a marketing name and they flex under load.
Motor and ESC
Furitek Lizard Pro with a Mini Komodo V2 in the 1400 to 1800 KV range. FOC firmware, Bluetooth tunable, more current headroom than the standard Lizard. Drag brake at 50 to 70%. Soft throttle curve. Soft punch. This gives walking-pace control off idle and predictable response on technical lines.
Premium alternative: LGRP Ultimate SCX24 Performance Bundle if you want the full comp-grade combo pre-paired.
Servo
Holmes Hobbies HV150 if I can spec a stiffer BEC. AGFRC A20BHM (brushless, around 11 kg-cm) on most builds because it works with standard BECs. 3Flow9RC Torrent Mini HV if I want lower weight. Pair with a 25T mini aluminum horn and a steel or brass drag link. The flex in a stock link costs precision on the tightest gates.
Tires and wheels
Pit Bull Growler 1.0" (Alien Kompound) directional tread, mounted left and right correctly. Dual-stage foams (Pro-Line PRO616900 or Crawler Innovations Lil' Nova). Brass beadlock wheels (Samix or INJORA brass) to add rotating mass.
Alien rubber picks up dirt fast. Wipe down between runs or save it for clean rock. Some comp builders carry a second set with RC4WD compound for dusty courses.
Brass
Brass knuckles (LGRP or Mofo), brass front diff cover, brass skid plate, brass wheel weights or brass beadlock wheels. Target 80 to 120g of added brass on a comp build because you've also upgraded the servo and motor to handle the weight. Keep weight low and forward.
Shocks
43 to 45mm oil-filled aluminum shocks. Pro-Line Big Bore Micro if you want maximum tunability. Medium spring rate, 30 to 40wt oil, slightly more pre-load on the front than the rear to bias the chassis forward on climbs.
Electronics path
Flysky GT5 with FS-BS6 (6-channel) or FS2A (4-channel micro) receivers. Separate receiver lets me run any ESC and gives me the channel headroom for LEDs or four-wheel steer. The GT5 holds up to 20 model bindings, which is the right thing when you run a fleet. The bound-to-the-board approach (Furitek Lizard with built-in receiver) is fine for most builds but locks you in.
Tuning
A comp rig is tuned, not just built. Things I dial in over the first few sessions:
- Drag brake. 50 to 70%. Higher holds position on slopes; lower lets the truck creep forward. Find the line where you can stop on a ledge without rolling back.
- Throttle curve. Exponential. Most of the stick travel should be the lowest 30% of speed.
- Servo endpoints. Just inside the knuckle stops on both sides. Stalling the servo into the stops kills it.
- Pre-load. Slight forward bias. Truck should sit roughly level with a tiny nose-down attitude under full weight.
- Oil weight. Start at 30wt. Run a course. Step heavier if the truck pogos, lighter if it feels stiff.
Spares to bring to a comp
- Three or four 2S packs charged before you leave.
- Spare CVD or dogbone set.
- Spare servo (yes, even a $50 servo can fry mid-comp).
- Hex driver set, threadlock, electrical tape.
- Tire cleaning brush for Alien compound.
- Spare shock oil if you'll be tuning between heats.
What to skip on a comp build
- Scale realism. The body doesn't matter; the chassis does. A bare LCG chassis with a thin body shell beats a fully-detailed scale build every time.
- Sticker bombs and accessories. Weight is weight. Add brass instead of plastic.
- LED light kits. Heavy, draws BEC current, scratches body, doesn't help you gate.
- Long-travel comp suspension on a truck you also trail. Comp shocks tuned for slow lines aren't great on rough terrain.
For finding comp events near you and what to expect at one, see the how to get into comp guide. For the broader upgrade context, see the staged upgrade path.