Setups
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Gearing
Stock gearing for the XRAY XB4D '21, with common pinions and their ratios.
| Pinion | Spur ÷ pinion | FDR |
|---|---|---|
| 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 |
| 28T | 2.89 | 7.23 |
Shaded rows are the pinions most 1/10 4WD buggy 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 XB4D '21, 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 XB4D '21?
It depends on your motor and the track. In the 1/10 4WD buggy class, racers gear by final drive ratio: 6T and below near 10.66, 7.5–8.5T near 10.00, 13.5T near 7.95. On the XB4D '21's stock 81T spur that is about 19T for 6T and below, 20T for 7.5–8.5T, 25T for 13.5T. Tight tracks gear down, open tracks gear up. For a starting pinion matched to your motor, use the So Dialed Pinion Recommender with the XB4D '21 selected.
What is the internal ratio (transmission ratio) of the XRAY XB4D '21?
The XB4D '21 has an internal ratio of 2.5:1. Final drive ratio = spur ÷ pinion × 2.5. With the stock 81T spur, a 16T pinion gives an FDR of 12.66 and a 28T gives 7.23.
How many teeth is the stock spur gear on the XRAY XB4D '21?
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
- 600 cst
- Rear
- 550 cst
- Front
- 7,000 cst
- Center
- 100,000 cst
- Rear
- 7,000 cst
What shock oil does the XRAY XB4D '21 come with?
Out of the box the XB4D '21 runs 600 cst front, 550 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 XB4D '21 come with?
The kit springs are 45mm Linear 2 dot (#368184) front, 60mm Linear 2 dot (#368285) rear. Stiffer springs suit high grip and big jumps; softer springs add grip on slick or bumpy tracks.
What diff fluid does the XRAY XB4D '21 come with?
The kit diff fluid is 7,000 cst front, 100,000 cst center, 7,000 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
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