Setups
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Gearing
Stock gearing for the ARC R12, with common pinions and their ratios.
| Pinion | Spur ÷ pinion | FDR |
|---|---|---|
| 20T | 4.20 | 7.98 |
| 21T | 4.00 | 7.60 |
| 22T | 3.82 | 7.25 |
| 23T | 3.65 | 6.94 |
| 24T | 3.50 | 6.65 |
| 25T | 3.36 | 6.38 |
| 26T | 3.23 | 6.14 |
| 27T | 3.11 | 5.91 |
| 28T | 3.00 | 5.70 |
| 29T | 2.90 | 5.50 |
| 30T | 2.80 | 5.32 |
| 31T | 2.71 | 5.15 |
| 32T | 2.63 | 4.99 |
| 33T | 2.55 | 4.84 |
| 34T | 2.47 | 4.69 |
| 35T | 2.40 | 4.56 |
| 36T | 2.33 | 4.43 |
| 37T | 2.27 | 4.31 |
| 38T | 2.21 | 4.20 |
| 39T | 2.15 | 4.09 |
| 40T | 2.10 | 3.99 |
| 41T | 2.05 | 3.89 |
| 42T | 2.00 | 3.80 |
| 43T | 1.95 | 3.71 |
| 44T | 1.91 | 3.63 |
| 45T | 1.87 | 3.55 |
| 46T | 1.83 | 3.47 |
| 47T | 1.79 | 3.40 |
| 48T | 1.75 | 3.32 |
| 49T | 1.71 | 3.26 |
| 50T | 1.68 | 3.19 |
| 51T | 1.65 | 3.13 |
| 52T | 1.62 | 3.07 |
Shaded rows are the pinions most 1/10 4WD touring/gt setups run on the stock spur.
What pinion should I run?
Tell us your motor and track and get a starting pinion for the ARC R12, with the range racers in the class run.
Get a recommendation →Shop pinion gears at AMain →What pinion gear should I use on the ARC R12?
It depends on your motor and the track. In the 1/10 4WD touring/gt class, racers gear by final drive ratio: 6T and below near 7.34, 13.5T near 4.51, 17.5T near 4.51, 21.5T and up near 3.65. On the R12's stock 84T spur that is about 22T for 6T and below, 35T for 13.5T, 35T for 17.5T, 44T for 21.5T and up. Tight tracks gear down, open tracks gear up. For a starting pinion matched to your motor, use the So Dialed Pinion Recommender with the R12 selected.
What is the internal ratio (transmission ratio) of the ARC R12?
The R12 has an internal ratio of 1.9:1. Final drive ratio = spur ÷ pinion × 1.9. With the stock 84T spur, a 20T pinion gives an FDR of 7.98 and a 52T gives 3.07.
How many teeth is the stock spur gear on the ARC R12?
84 teeth. Changing the spur moves every pinion's ratio at once; most racers leave the spur and tune with the pinion.
Kit setup
Kit shock setup (MediumGrip). Part numbers link to AMain.
- Front
- 500 cst
- Rear
- 500 cst
- Front
- 0.28g Green #R107043 →
- Rear
- 0.28g Green #R107043 →
- Front
- Kit #R104018 →
- Rear
- Kit #R104018 →
- Rear
- 3,000 cst
What shock oil does the ARC R12 come with?
Out of the box the R12 runs 500 cst front, 500 cst rear, on Kit (#R104018) front, Kit (#R104018) rear pistons. That is the kit setup; you will need to adjust it for your track conditions. The RC Setup App can help dial it in.
What springs does the ARC R12 come with?
The kit springs are 0.28g Green (#R107043) front, 0.28g Green (#R107043) rear. Stiffer springs suit high grip and big jumps; softer springs add grip on slick or bumpy tracks.
What diff fluid does the ARC R12 come with?
The kit diff fluid is 3,000 cst rear. Thicker front adds steering on power; thicker center sends more drive rearward; thicker rear stabilizes the car under throttle.
Setup Help
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