Ask Miles, our Setup AI that’s been trained on the MRX.
Setups
Gearing
Stock gearing for the Atomic MRX, with common pinions and their ratios.
| Pinion | Spur ÷ pinion | FDR |
|---|---|---|
| 6T | 8.67 | 8.67 |
| 7T | 7.43 | 7.43 |
| 8T | 6.50 | 6.50 |
| 9T | 5.78 | 5.78 |
| 10T | 5.20 | 5.20 |
| 11T | 4.73 | 4.73 |
| 12T | 4.33 | 4.33 |
| 13T | 4.00 | 4.00 |
| 14T | 3.71 | 3.71 |
What pinion should I run?
Tell us your motor and track and get a starting pinion for the Atomic MRX, with the range racers in the class run.
Get a recommendation →Shop pinion gears at AMain →What pinion gear should I use on the Atomic MRX?
It depends on your motor and the track. A hotter motor (lower turns, higher Kv) takes a smaller pinion; a tight track wants a lower gear than an open one. Start near the middle of the pinions the MRX shipped with, run a few minutes, and check motor temperature before going up a tooth. The So Dialed Pinion Recommender gives a starting pinion for your motor where we have class data.
What is the internal ratio (transmission ratio) of the Atomic MRX?
The MRX has an internal ratio of 1:1. Final drive ratio = spur ÷ pinion × 1. With the stock 52T spur, a 6T pinion gives an FDR of 8.67 and a 14T gives 3.71.
How many teeth is the stock spur gear on the Atomic MRX?
52 teeth. Changing the spur moves every pinion's ratio at once; most racers leave the spur and tune with the pinion.
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