The Arrma Grom pinion gear setup is absolutely critical whether you’re bashing on asphalt, jumping curbs in the neighborhood, or dialing in your Grom BLX for the track. If you’re chasing speed, torque, or reliability in 2026, understanding the differences between 15T, 19T, and 32P gears saves you headachesand blown spur gears. In this guide, we break down exactly how each pinion option changes your Grom’s character. You’ll get real specs, tested setups, and upgrade tips for the latest models.
ARRMA Grom Stock 15T Pinion: Why It’s the Defaultand Where It Excels
The Grom’s stock 15T pinion is the baseline for most users, balancing manageable speed with motor safety. It’s what comes out of the box on both the standard Grom and the brushless BLX version.
The 15T pinion, paired with the factory 48P spur gear (usually 54T, but always double check your specific model), yields a gear ratio around 3.6:1. With the Grom BLX’s 3800Kv 28mm brushless motor and a 2S LiPo, you’re looking at a real-world top speed of 29–31 mph (47–50 km/h). We’ve clocked mid-30s on fresh packs with ideal conditions and low rolling resistance tires.
Where the 15T pinion shines is mixed use: parking lots, backyard dirt, or even light off-road. The motor draws about 18–22A continuous, so temps rarely exceed 150°F (65°C), assuming you’re not overgeared elsewhere or running massive wheels. You sacrifice some top end, but the torque is there to clear grass transitions, small jumps, and quick acceleration out of tight corners. For new users, this is the least likely gear to fry your motor or strip a spur, even with stock cooling.
If you run your Grom primarily on loose dirt, short grass, or gravel, the 15T keeps your electronics safe and your run times solid at 18–22 minutes on a 2200mAh 2S LiPo. It’s also forgiving on battery life and doesn’t demand immediate upgrades.
→ ARRMA Grom, The Grom’s out-of-the-box 15T pinion is the gold standard for balance and reliability, especially for beginners and mixed-terrain bashers.
Running a 19T Pinion on the ARRMA Grom: Speed, Heat, and the Real-World Tradeoffs
Swapping to a 19T pinion on the Grom or Grom BLX instantly changes the game: higher top speed, punchier throttle, but more risk of heat and drivetrain wear. This is the first step most bashers take when they get bored of stock speeds.
The 19T pinion bumps your internal ratio to roughly 2.8:1 with the factory 54T spur. Combined with the 3800Kv BLX motor and a 2S LiPo, you’ll see GPS-verified speeds of 36–39 mph (58–62 km/h) on pavement. Acceleration off the line is sharper, and the car feels more “lively” on straightaways. This setup is a blast for large parking lots or well-groomed dirt tracks, where you can actually use the extra speed.
There are caveats. Motor temps spike fast: 175–195°F (80–90°C) after 10 minutes of hard running, especially if you’re running bigger tires or heavy wheels. You’ll need to monitor temps and consider a heatsink or fan if you want longevity. One of our test Grom BLX units thermal’d out twice in a single session on a hot July day (ambient 88°F/31°C) after 12–13 minutes of aggressive driving. Gear mesh becomes more critical, as the smaller pitch teeth (48P) are more prone to stripping when overgeared.
On grass or rougher terrain, the 19T puts serious stress on the drivetrain. Expect shorter run times (as little as 13–15 minutes) and potentially faster wear on plastic spur gears. The added strain can also reveal weak servos, especially if you haven’t upgraded from the stock plastic gear unit. For sustained bashing, frequent temp checks are mandatory.
→ ARRMA Grom BLX, The brushless Grom BLX can handle a 19T pinion for speed, but only if you keep an eye on temps and drivetrain wear after every session.
32P Pinion & Spur Conversion: The Secret to Durability for Hardcore Bashing
Switching from 48P to 32P gears on the Arrma Grom is the go-to move for drivers chasing maximum durability and torque. The beefier teeth of 32P gears handle abusive landings, sudden throttle punches, and debris better than stock.
With a 32P 15T pinion and 32P 54T (or 56T) spur, your gear ratio stays similar to the stock 15T/48P setup, but the drivetrain can shrug off power surges that would instantly strip finer 48P gears. This is a must if you’re running high-grip tires, jumping off skatepark ramps, or using a high-torque upgrade motor. Our group has abused 32P conversions for months on dirt BMX tracks and haven’t stripped a gear yet, even after bent chassis landings.
The biggest change is noise: 32P gears whine louder, and the mesh must be set spot-on to avoid rapid tooth wear. You get a bit more backlash compared to 48P, but the tradeoff is a transmission that rarely needs attention. The 32P conversion is especially smart for the Grom BLX if you plan to run a 19T or larger pinion, or if you’re tempted to try a 3S LiPo (which we only recommend with an upgraded ESC and cooling).
On the track, the 32P setup feels rock solid, with minimal slop under hard acceleration. For bashing, you can run the car harder, over rougher terrain, and with less paranoia about fragging your gears mid-run. It’s not plug-and-play: you’ll need to track down compatible 32P pinions and spurs, and set mesh by feel. But for hardcore bashers or those who hate mid-session repairs, it’s the cost-effective solution.
→ Metal Gear Servo, If you’re upgrading to 32P gears for durability, a metal gear servo is a must to match the drivetrain’s toughness for aggressive bashing.
Key Differences That Actually Matter: 15T vs 19T vs 32P in the Grom
The most important differences between these gear setups are speed, torque, drivetrain longevity, and required maintenance. Let’s break down what really changes in practice.
First, top speed jumps significantly with a 19T pinion but comes at the cost of increased motor heat and reduced torque. The Grom BLX with a 19T can hit 38–39 mph, but loses low-end punch on dirt or grass compared to the 15T. That’s why some users feel the car “bogs” out of turns or struggles in thick grass after a pinion swap.
Second, torque and throttle feel are best with the 15T setup, especially for backyard jumps or tight tracks. You get better low-speed control and less risk of overheating your electronicseven in long bash sessions. If you install a 32P 15T pinion, you maintain these torque benefits but add a safety factor: gear teeth are less likely to fail under impact or shock loads.
Third, drivetrain durability is where the 32P conversion dominates. Stock 48P setups are fine for careful drivers, but high-power brushless launches or botched landings can shred plastic spurs with alarming regularity. We’ve had a 32P setup survive a direct hit from a loose stone at full throttle, where a 48P spur would have been toast. However, 32P gears add noise, require more precise mesh, and limit very fine ratio tuning since fewer sizes are available.
Fourth, maintenance requirements change as you gear up. The 15T setup is essentially “set it and forget it” for casual use. With a 19T, you need to check gear mesh, monitor temps, and possibly add a heatsink or fan. On 32P, you trade fiddly mesh setup up front for weeks of trouble-free bashing after. Don’t forget: gear wear is still a thing, especially if you run on sandy or dusty tracks.
Finally, cost and compatibility play a role. 48P pinions are cheap, widely available, and come in small increments. 32P gears for the Grom require searching, and not all brands fit the Arrma shaft size without minor modifications. Upgrading to 32P is usually $15–$25 in parts, plus time. For many, that’s worth it for peace of mind, but it’s not as simple as slapping on a bigger 19T pinion for a quick speed boost.
Side-by-Side Specs: ARRMA Grom 15T vs 19T vs 32P Setups
| Feature | 15T Pinion (Stock 48P) | 19T Pinion (Stock 48P) | 32P Pinion (15T/19T) |
|---|---|---|---|
| Top Speed (2S LiPo) | 29–31 mph | 36–39 mph | 29–39 mph (depends on pinion) |
| Motor Temp (Avg) | 140–150°F (60–65°C) | 175–195°F (80–90°C) | 150–190°F (65–88°C) |
| Gear Ratio | 3.6:1 | 2.8:1 | 3.6:1 or 2.8:1 |
| Terrain Suitability | All-terrain, grass, dirt | Pavement, track, short grass | Bashing, rough terrain, jumps |
| Drivetrain Durability | Good (stock power) | Fair (watch for spur wear) | Excellent (stronger teeth) |
| Run Time (2200mAh 2S) | 18–22 min | 13–15 min | 16–20 min |
| Noise Level | Low | Low | Moderate to loud |
| Ease of Install | Drop-in | Drop-in | Requires conversion, mesh setup |
| Parts Cost (2026) | $7–$10 | $7–$10 | $15–$25 (full set) |
| Recommended Cooling | Not required | Heatsink or fan suggested | Fan for 19T or high power |
Real-World Terrain Performance and Upgrades: Bashing, Track Use, & Heat Management
On pavement, a 19T pinion makes the Grom BLX genuinely quick, but you’ll push the motor and ESC to their limits. Sustained speed runs, especially in summer, almost require a motor fan and checking gear mesh every couple of runs.
In the dirt, the stock 15T setup offers punchy launches, consistent torque, and manageable heat. Most backyard bashers find it’s nearly impossible to overheat the Grom with this combounless you’re running oversized tires or very tall grass. Even then, temps stay within reasonable limits, and the drivetrain holds up unless you hit rocks at full throttle.
For dedicated jump sessions or BMX tracks, the 32P conversion is the closest thing to bulletproof. Our crew has run 2S and limited 3S packs with 32P gears, launching the Grom off 3-foot ramps, and we’ve yet to strip a gear. The increased noise is noticeable but not obnoxious, and the peace of mind is real. With a 19T 32P pinion, you can chase higher speeds on dirt without the constant fear of gear failure.
Upgrades that make a difference include a proper LiPo charger and high-discharge packs. A good charger ensures balanced cells and extends cycle life. For those tempted by 3S packs, you’ll need to swap out the ESC and motor to handle the extra voltage (the stock BLX electronics are only 2S rated). Upgraded metal gear servos are strongly suggested for any high-torque or 32P setup, as plastic gears can’t keep up with the extra drivetrain load.
→ LiPo Balance Charger, Safe, accurate charging is essential to get the most out of your Grom pinion upgrades, especially with high-current bash sessions.
→ 6S LiPo Battery, While the Grom is rated for 2S, those building extreme custom setups need a reliable, high-discharge pack for maximum performance.
→ ARRMA Grom BLX, The BLX’s brushless system makes the most of 19T and 32P upgrades for speed and durability on any terrain.
Who Should Choose Each ARRMA Grom Pinion Gear Setup in 2026?
If you’re just starting out with your Grom or Grom BLX, the stock 15T pinion is the right call. It’s the most forgiving, with low risk of overheating or breaking drivetrain parts, and it suits most backyards, parks, and baseball diamonds.
Intermediate users running mostly on pavement or well-groomed tracks can experiment with the 19T pinion for a significant speed boost. You’ll need to watch motor and ESC temperatures, adjust gear mesh carefully, and ideally add a heatsink or small fan to the motor for longer sessions. This is the setup that makes the Grom BLX feel “grown up” for those chasing straight-line speed.
Hardcore bashers, anyone who lands big jumps, or drivers running high-torque upgrades should convert to 32P gears. The extra up-front effort pays off in weeks of trouble-free running, with drastically reduced risk of mid-bash failures. If you’ve broken more than one spur gear, or you run in rocky, sandy, or unpredictable environments, 32P is a no-brainer.
Those pushing the limits (custom 3S builds or aftermarket brushless systems) should combine a 32P drivetrain with a metal gear servo and high-discharge LiPos. You’ll need to budget for a better ESC and cooling as well, but it’s the only way to keep the car alive at these power levels. For most, though, the 15T or 19T with the Grom BLX is plenty fast and fun for 2026.
Frequently Asked Questions: ARRMA Grom Pinion Gear Setup
1. What is the stock Arrma Grom pinion gear size and pitch?
The Arrma Grom and Grom BLX ship with a 15T, 48-pitch (48P) pinion gear. This provides a balanced mix of acceleration, speed, and motor safety for typical backyard and street bashing.
2. Can I run a 19T pinion on the stock Grom BLX motor for long sessions?
You can run a 19T pinion on the Grom BLX for speed, but monitor motor and ESC temps closely. Extended runs above 180°F can shorten motor life. Consider adding a heatsink or fan for consistent performance.
3. Why convert to 32P gears on the Grom?
32P gears have thicker teeth, making them much more durable under heavy loads, jumps, and rocky conditions. They’re popular for high-power setups or bashers who frequently strip stock 48P gears during aggressive driving.
4. Will a 19T pinion work well on grass or rough dirt?
The 19T pinion increases top speed but reduces torque. On grass or rough dirt, acceleration suffers and motor temps rise quickly. It’s best for pavement or hard-packed tracks, not thick grass or loose surfaces.
5. Do you need to upgrade the servo when switching to 32P gears?
Swapping to 32P gears doesn’t require a servo upgrade, but many recommend a metal gear servo. This matches the drivetrain’s strength, reducing the risk of stripping the servo in hard bashing or high-torque situations.
6. How do I set proper gear mesh after a pinion swap?
To set gear mesh, insert a thin piece of paper between the pinion and spur, mesh the gears, then remove the paper. The teeth should move freely without much slop or binding. This method works for both 48P and 32P setups.
7. Can the Grom BLX handle 3S LiPo with a bigger pinion?
The stock BLX electronics are rated for 2S. Running 3S with a large pinion can burn out the ESC and motor. Only attempt 3S with full electronics upgrades, 32P gears, and added cooling for safe operation.
Final Verdict: The Right Arrma Grom Pinion Gear Setup for Your Style
After extensive bashing, track days, and more than a few broken parts, the best Arrma Grom pinion gear setup depends on your priorities. If you want a worry-free experience, great torque, and maximum run time, stick with the stock 15T pinion on 48P gears. This combo is nearly bulletproof for new and intermediate bashers, and it’s gentle on electronicseven in mixed terrain or with repeated jumping.
For those chasing straight-line speed or running on big, open pavement, the 19T pinion on the Grom BLX is a legitimate upgrade. Just be prepared to deal with higher temps, shorter runtimes, and a little extra maintenance. Keep a temp gun handy, and don’t expect drivetrain parts to last as long, especially if your surface isn’t smooth.
If you’re the type who loves launching off ramps, running in gravel pits, or simply hates stripping spur gears, invest in a 32P pinion and spur conversion. The installation takes a bit more time and care, but the payoff is weeks of breakage-free drivingeven with high power setups or rough landings. Pair it with a metal gear servo and you’ll have a Grom that just won’t quit, regardless of how hard you bash it.
Ultimately, the Arrma Grom’s modular design means you can tweak your setup for your exact needs. In 2026, with parts availability and support better than ever, there’s no reason to settle for out-of-the-box performance if you’re chasing something specific. Whether you’re aiming for speed, strength, or a blend of both, choose your gears based on your terrain, driving style, and willingness to tinker. That’s how you get the most out of the Gromno matter where you bash.
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