TRX-4 Competition Build: Part 2

Portal Weights
Any competitive trail-trucker will tell you that adding weight to the front of your rig will improve climbing and crawling performance, but care must be taken not to raise the truck’s center of gravity. The lower the weight can be placed, and the closer to the wheels, the better. Since we’ve installed aluminum outer portal covers on our TRX-4 Sport, we can also install the 8267 brass portal weights.

Brass portal weights

Installed portal weights

Each machined-brass weight adds 34 grams (1.2 oz) to the truck, for a total of 68 grams (2.4 oz.) tucked inside the front wheels. The weights include mounting hardware and install in just a few minutes on the aluminum outer portal housings. The weights are not compatible with the stock plastic housings.

Servo Upgrade
The Sport’s stock, 2075X metal-gear servo is all you need for trail adventuring, but when it comes to comp-grade performance, more torque is always better. The High Torque 400 servo twists with 400 oz.-in. of torque, a 220% boost over the stock servo’s already-strong 125 oz.-in. When you need sheer servo power to push your rig off an obstacle and precisely point the tires under maximum load, big Red gets it done. In order to power the High Torque 400 servo, you'll need to install a High-Output BEC. We've used this powerhouse on several builds. If you need an installation refresher, have a look at the Maximum Mud Bronco build for detailed instructions.

Brushless 400 Red servo

Metal servo horn

Inner Fender Install & Battery Relocation
The TRX-4 Sport rolls out without inner fenders, but they’re easy to add with the 8080 narrow inner-fender set. The fenders have mounting positions for the 8026X rock lights (cool), but what’s particularly exciting for a comp rig is the integrated battery plate. It’s the ideal place for a mini-size battery (like the 2823X 3s 1400 mAh LiPo shown below), which lets you remove the stock battery tray to shift more weight over the front axle. The 1400 mAh battery reduces run time compared to a full-size LiPo of 4000 mAh or more, but 1400 mAh is more than enough “gas” for a comp run

Inner fenders

Front battery tray

The 5-piece fender set is easy to install, ready for rock lights, and the front battery position shifts more weight over the axle. The 8222 hook and loop battery strap will keep the new small pack secure, and makes battery swaps a snap. With the battery now up front, the stock battery tray can come out. This makes the Sport lighter overall, but moves more weight over the front axle percentage-wise (which is what really counts).

Front battery installed

Remove the stock battery tray

Slicker Shocks
The TRX-4 Sport doesn’t skimp on shocks. It gets the same GTS aluminum-body dampers as the other TRX-4 models, and they’re a major improvement over the plastic-body shocks found on some other brands. So why upgrade? The 8260X upgrade shocks offer even slicker operation thanks to their hard-anodized, PTFE-coated bodies that allow the piston to slide more easily in the shock bore, and titanium-nitride-coated shock shafts that are more scuff-resistant and slide more easily against the X-ring seals. In addition to ensuring absolute peak performance, these features also help the shock maintain that high performance longer, extending time between rebuilds.

GTS hard-anodized shocks w/ TiN shafts

GTS shock comparison

GTS spring options

The hard-anodized GTS shocks are sold in pairs, complete with silicone oil. Springs are not included, so just transfer the stock springs to the new shocks. Or, change your setup with optional spring rates. The stock springs are “white” (as indicated by a spot of white paint) and have a 0.30 rate. Traxxas offers a pair of softer 0.22-rate springs (yellow), and four stiffer springs, the firmest of which (blue) has a 0.61 rate. The hard-anodized bodies and gold TiN shafts look trick. The stock “white” springs are in place, we’ll experiment with rates after some trail time.

Front shocks installed

Rear shocks installed

Trick Kicks
There's nothing cooler than a real set of beadlocks for your competition rig. With beadlocks we can skip the glue and swap tires anytime we like. Method 105s in charcoal grey 8173A got the nod, along with a set of black beadlock rings 8169T. Traxxas sells the rings separately so you can choose the color you like. The Canyon Trails on charcoal Method wheels with black rings is a tough-looking combo. Tip: use the Traxxas 3415 tool set to put the wheels together—the included ratchet handle really speeds up assembly.

Method 105 beadlock wheels

We may be technically ready to hit the trail, but we're not finished yet. A true competition truck needs valuable scale points and we're about to deck this truck out with a full array of scale detail parts. Check out Part 3 where we'll add the Expedition Rack, LED light kit, and more!

Get your wrench on, and show us how your TRX-4 turned out! Post your pics to Facebook, Instagram or Twitter with #MyTRX4Build, and we’ll be sure to share some of our favorites.