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Setups
Gearing
Stock gearing for the XRAY XT4.2, with common pinions and their ratios.
| Pinion | Spur ÷ pinion | FDR |
|---|---|---|
| 14T | 5.79 | 14.46 |
| 15T | 5.40 | 13.50 |
| 16T | 5.06 | 12.66 |
| 17T | 4.76 | 11.91 |
| 18T | 4.50 | 11.25 |
| 19T | 4.26 | 10.66 |
| 20T | 4.05 | 10.13 |
| 21T | 3.86 | 9.64 |
| 22T | 3.68 | 9.20 |
| 23T | 3.52 | 8.80 |
| 24T | 3.38 | 8.44 |
| 25T | 3.24 | 8.10 |
| 26T | 3.12 | 7.79 |
| 27T | 3.00 | 7.50 |
Shaded rows are the pinions most 1/10 4WD truck setups run on the stock spur.
What pinion should I run?
Tell us your motor and track and get a starting pinion for the XRAY XT4.2, with the range racers in the class run.
Get a recommendation →Shop pinion gears at AMain →What pinion gear should I use on the XRAY XT4.2?
It depends on your motor and the track. Racers in the 1/10 4WD truck class run a 16–25 tooth pinion in most setups, usually on a 81T spur for a final drive ratio near 10.93. Hotter motors (lower turns, higher Kv) take a smaller pinion; tight tracks gear down, open tracks gear up. For a starting pinion matched to your motor, use the So Dialed Pinion Recommender with the XT4.2 selected.
What is the internal ratio (transmission ratio) of the XRAY XT4.2?
The XT4.2 has an internal ratio of 2.5:1. Final drive ratio = spur ÷ pinion × 2.5. With the stock 81T spur, a 14T pinion gives an FDR of 14.46 and a 27T gives 7.50.
How many teeth is the stock spur gear on the XRAY XT4.2?
81 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. Part numbers link to AMain.
- Front
- 650 cst
- Rear
- 450 cst
- Front
- 30,000 cst
- Center
- 100,000 cst
- Rear
- 10,000 cst
What shock oil does the XRAY XT4.2 come with?
Out of the box the XT4.2 runs 650 cst front, 450 cst rear (XRAY oil), on 2 x 1.6mm (#368031) front, 2 x 1.7mm (#368031) 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 XRAY XT4.2 come with?
The kit springs are 45mm Linear 4 dot (#368186) front, 60mm Linear 3 dot (#368286) rear. Stiffer springs suit high grip and big jumps; softer springs add grip on slick or bumpy tracks.
What diff fluid does the XRAY XT4.2 come with?
The kit diff fluid is 30,000 cst front, 100,000 cst center, 10,000 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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Setup App & Race Log
Your XRAY XT4.2 is in the RC Setup App
Save every setup change you make to your XRAY XT4.2, get AI tuning answers for that exact car, and log your races — at the track or back in the pits.
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