The Nitro 4-Tec is definitely a fun machine with its TRX 2.5 Racing Engine™ and two-speed transmission. Blasting the Nitro 4-Tec™ across a parking lot at speeds exceeding 60mph is a thrill no one can forget. Although many people are content with just making insane speed runs back and forth with this nitro-powered bullet, the Nitro 4-Tec is also a very capable track performer. With a few accessories and proper set-up techniques, you'll be knocking out some pretty fast laps at your local raceway. The format of this guide will be similar to the Maxx and Revo series of articles, where I separated the guide into three categories. In this first article, I'll cover tips for tuning the suspension of the Nitro 4-Tec. Be sure to stay tuned for the following articles that will cover critical setup and building tips for the Nitro 4-Tec, and also tips on adjusting the drivetrain and tuning with tires. These setup tips and performance upgrades are not only useful for racers, but will also be beneficial for just ripping around a parking lot. Let's get started!
There are two mounting holes in the front and rear suspension arms of the Nitro 4-Tec. The outside holes make the suspension more progressive as it's compressed, giving the car a firmer feel. The inside holes allow a little more chassis roll in the corners. Keep in mind, this is a fine tuned adjustment and will not give you big results. It should be one of the last adjustments once you're at the track. For most track conditions, I recommend starting with the shocks mounted in the outer positions.
Camber is measured in degrees. A good base starting point for camber on the Nitro 4-Tec is 1 degree up front and 1.5 degrees in the rear. Camber is normally adjusted to make the tires wear evenly. It's also used as a tuning tool.
Caster is the angle of the axis that the front hub carriers pivot on, when looking at the side of the chassis. More caster will allow more weight to be transferred to the front of the chassis off throttle or under braking. This promotes more steering. While under throttle, the weight is shifted to the outside rear tire providing more traction from this tire to pivot the car around the corner more easily.
To adjust front caster, simply move the caster spacers located on the upper suspension pin next to the upper suspension arm.
Start with all of the shims placed to the front of the arm then move one shim at a time, from each side, back to the rear as you need more steering.
Placing the thicker side of the wedge toward the front of the chassis will increase caster as the suspension is compressed. Placing the thicker side of the wedge toward the rear will kick up the backside of the upper suspension mount. This takes away caster as the suspension is compressed. There is also a zero-degree lower suspension mount (part #4329) available for the Nitro 4-Tec. It takes away more steering (for smooth and extreme high-bite conditions).
The use of caster wedges is a fine-tuning adjustment that should be one of the last items to adjust. A good base starting point for re-active caster the stock three-degree lower suspension mount, stock three-degree upper suspension mount and the Nitro re-active caster wedges. Use the wedges as they're described above as needed.
A good starting point up front for the Nitro 4-Tec is zero-degrees, then adjust in or out according to what's needed. In the rear, the 2.5-degrees hub carriers are typically used. The zero-degree carriers are not used in racing conditions. Some aftermarket companies offer different angles for the rear hub carriers. Start with the 2.5-degree rear carriers, then decide what's needed for current track conditions.
Ride height is adjusted by adding or taking away spring pre-load spacers on the shocks. Important: Do not use the length of the shock to determine ride height. This will make a very twitchy and unpredictable car. Also, do not use extra pre-load spacers to give the shock a firmer feel. If you want to firm-up the suspension, use a firmer spring. Pre-load spacers are only used for adjusting ride height. Generally, it is best to run the chassis as low as you can without causing contact between the chassis and the track surface.
Traxxas offers a front and rear sway bar set (part #4875) for the Nitro 4-Tec. Sway bars are essential for fast lap times on smooth high-bite surfaces. The sway bars are adjusted by placing the eyelets in the bars that pass through in one of four positions. The positions farther away from the pivot point are softer than the positions closer to the pivot.
Down Travel (Droop)
To measure rear down travel, remove all of the shocks and sway bars so the chassis sits flat on the set-up surface. The arms should be able to move freely and fall down to the position in which they are set to fall. A good starting point for the rear is about six mm from the surface to the arm (see photo below). More down travel for the rear will allow more weight to shift to the front giving the front more bite off throttle.
Front down travel adjustment
The rear roll center on the Nitro 4-Tec can be adjusted by positioning the rear camber links in a variety of different holes. The upper holes on the bulkhead will make the car easier to drive, the lower holes will increase steering and response (start with the upper/inner position on the bulkhead). The inner holes on the bulkhead will change the camber curve less aggressively, while the outer holes will affect the camber more aggressively. Only use the upper holes on the rear hub carrier. The lower holes can make the car too unpredictable in the corners.
All of the cool accessories you see in this set-up guide are featured on the Nitro 4-Tec accessories pages.
Critical Setup and Building Tips for the Nitro 4-Tec
Adjusting the Drivetrain and Tuning with Tires
Welcome to my third and final leg of the Nitro 4-Tec performance series. In this installment, I will discuss ways to get the most out of your drivetrain, and also shed some light on tire choice options for concrete parking lot racing. Correct shift points and properly adjusted differentials are key to fast and consistent laps. These items listed below are the more important areas to concentrate on.
Adjusting the two-speed to shift at the correct moment is very important for making fast and consistent lap times. The engine needs to clear out in first gear before shifting into second, but it's not good to let the engine rev-out too high in first gear before shifting. Set the two-speed to shift just as soon as the engine reaches its upper rpm range.
Caution: An early shift point can bog the engine down, resulting in higher temperatures and poor performance. A late shift point can cause excessive wear and strain on the moving parts inside of the engine, and also higher temperatures. Always adjust the two-speed in small increments.
Two-speed adjustments are necessary when changing the gear ratio in the transmission. Changing the gears on the clutch bell to a higher number of teeth, and/or changing to spur gears with a smaller number of teeth, will result in higher top speeds and take away a little bit of low end punch. This will also cause your two-speed shaft to turn at a higher RPM, thus causing the two-speed to engage sooner.
If you are going to clutch bell gears that have a lower number of teeth and/or spur gears that have a larger number of teeth, then the two-speed will react just the opposite. Turn the adjustment screw clockwise for a later engagement or turn the adjustment screw counter-clockwise for an earlier engagement.
Again, always adjust the two-speed in small increments (1/8 turn), this is a fine adjustment and can get way off quickly if large adjustments are made.
Traxxas Pro ball differentials can be adjusted to get the car to react differently in the corners, as mentioned earlier.
A tighter front differential will typically give the car a little bit of a push going into the corners. A tighter rear differential will allow the rear end to come around a little quicker coming out of a corner.
Use small adjustments and try not to adjust both of the differentials at the same time. This could cause the chassis to change too much, worsening your results. On tracks with a high-bite surface, you can run both diffs a little tighter than on a track with less traction.
Larger tracks may also allow you to run both diffs tighter. The car will be under acceleration a lot more on larger tracks, and the tighter diff adjustment will keep the power from unloading as much allowing you to get more power to the ground.
Tires are the single most important part of chassis tuning. Without the right tires it may be impossible to get your car to handle well.
It's always a good idea to see what the faster racers at the track are using. Get some ideas from them on what works well in the front and what works well on the rear of the car for that particular track. Start there, and use a good base set-up on your car. Try to get the best performance through tires first before making adjustments to the chassis. When you get to point where the car works consistently well, start fine-tuning the handling with chassis/suspension adjustments.
Tire compounds range from very soft to very firm. The softer compounds provide more traction but also wear faster. Keep this in mind when racing in long mains. Temperatures affect compound choices too. Hot temperatures will require harder compounds, and colder weather requires softer compounds.
A good base set-up on the chassis is very important. This can vary from person to person, so the more experience you have with the car, the more you'll learn what set-up is for you... so get out there and practice!
For all of the cool accessories you've seen here on the Nitro 4-Tec in this article, check out the Nitro 4-Tec pages on this website found here: Nitro 4-Tec hop-ups & accessories.
Traxxas offers an incredible list of aftermarket accessories for turning your RTR into a killer racing machine. By practicing the tips in this guide, you'll be sure to make faster, more consistent laps at the track.
I hope everyone enjoyed my Nitro 4-Tec Performance Guide for getting Traxxas' ballistic pavement-pounder dialed in at the racetrack. Remember, the most important aspect of racing is practice. There's nothing better. So, take what you've learned here and go to the track and practice, practice, practice… Happy racing!!!