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Improve TRX-4M's Performance with Brass Components
Just like the “big” TRX-4 series trucks, the TRX-4M Bronco and Defender models can be upgraded and optimized to suit your style of trail-trucking adventure. And if your style puts the focus on extreme climbing and crawling performance, the full line of Traxxas brass components should be at the top of your gotta-get list. The brass parts’ extra strength and bright finish are added bonuses, but the real advantage is the considerable weight the components add to your rig, and the gains in traction and stability that weight brings. Let’s take a closer look at just how dramatic a difference brass parts can make when you push your TRX-4M to the limit. How Much Weight Does Brass Add? Brass is much denser than molded composite or aluminum, machines easily, and is stronger than aluminum—all of which makes it ideal for weight-increasing RC components. How much weight exactly? We’ve got the actual measurements below, but in general, a brass version of a part may weight three times more than the same part in aluminum, or up to ten times more than a molded-composite component. It’s a big difference! 
When you bolt all the available brass parts to your TRX-4M, you’ll add 5.4 ounces of terrain-flattening weight to your ride. 
The wheel weights replace the optional beadlock wheels’ tire inserts to increase each wheel’s weight by 28 grams—that’s nearly two ounces added to the front axle. 
Here are the weights for the brass components versus the stock molded parts. The heaviest hitters by far are the wheel weights. 
Swapping the stock TRX-4M parts for brass only takes a few minutes. How Much Do the Brass Parts Affect Weight Distribution? Time to bust out the scales. With each pair of wheels on its own scale, we first weighed the TRX-4m Bronco in stock form, then with brass parts installed on the front axle only (but no wheel weights); with all the front-end brass parts plus front wheel weights; and with all the available brass parts installed front and rear. Adding only the brass caster blocks, steering blocks, hubs, spring retainers, and axle cover altered the Bronco’s weight distribution enough to give it a slight front bias, with 51.2% of weight over the front wheels. Adding wheel weights makes a more dramatic difference, with nearly 57% of the truck’s weight up front. Going “full brass” including weights in all four wheels brought the truck back to nearly 50/50 weight distribution. 
These figures show the percentage of weigh distributed over each axle. In this example, the rear of the truck is completely stock, and weight is only being added to the front end. 
Note the last row of the chart; when wheel weights are used front and rear, weight distribution is nearly 50-50. If your trail adventures don’t subject your TRX-4M to a lot of extreme climbing angles but you do need maximum tire-pressing weight for rugged and/or loose surfaces, installing wheel weights front and rear may be a good setup. Incline Testing: Stock vs. Brass Equipped We built a variable-angle test rig to see how steep an angle the Bronco could climb in stock form and with various brass configurations. The test surface is covered with grip tape for nearly endless traction, so tire slippage did not interfere with determining the maximum angle the Bronco could scale without flipping over. All tests were performed by climbing the incline under power (as opposed to parking the truck and raising the test-rig angle until it flipped over). In addition to adding the brass parts, one modification was made: we removed the Bronco’s spare tire cover to increase its departure angle. 
Removing the Bronco’s spare tire cover trims a few grams, but the real benefit is improved departure angle. Angles greater than 42° will drag the tire cover. Removing it allows the TRX-4M to handle up to a 49° angle without dragging the rear bumper. 
The test rig is covered with grip tape to prevent the Bronco from sliding, and an inclinometer app measured the angle for each test. 
Testing showed the single biggest increase in climbing ability came from the wheel weights, which upped the maximum scalable angle by five degrees. Adding the brass axle cover, lower spring retainers, caster blocks, and steering blocks to the wheel-weight-equipped truck increased the maximum scalable angle to 55°. 
Adding weight also improves side-hill ability, though not as dramatically due to the track width of the truck being much smaller than the wheelbase. A gain of 4 degrees can still be the difference between conquering an obstacle and rolling down the hill. Worth the Weight We knew increasing front weight distribution would improve climbing performance but seeing the actual difference between stock and brass-equipped climbing ability was impressive—especially when the stock truck is already so capable. The biggest gains come from adding the wheel weights, which is convenient because it only takes a few seconds to remove and reinstall the front tires. You can hit the trail with unweighted wheels for best all-around drivability and longest battery life and keep a pair of weighted wheels in your pocket for quick installation if you need them. Adding the rest of the brass parts increase weight by another 1.5 ounces to improves climbing ability a bit more and boost off-road capability in general, with the added benefit of increased strength. Plus, they look great! |
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