Car Not Handling Right?
Diagnose understeer, oversteer, traction rolling and more — by symptom.
Setups
Have a setup for the T4 '21?
Share your setup sheet with the community — we'll fill in the details automatically.
Gearing
Stock gearing for the XRAY T4 '21, with common pinions and their ratios.
| Pinion | Spur ÷ pinion | FDR |
|---|---|---|
| 20T | 5.50 | 10.45 |
| 21T | 5.24 | 9.95 |
| 22T | 5.00 | 9.50 |
| 23T | 4.78 | 9.09 |
| 24T | 4.58 | 8.71 |
| 25T | 4.40 | 8.36 |
| 26T | 4.23 | 8.04 |
| 27T | 4.07 | 7.74 |
| 28T | 3.93 | 7.46 |
| 29T | 3.79 | 7.21 |
| 30T | 3.67 | 6.97 |
| 31T | 3.55 | 6.74 |
| 32T | 3.44 | 6.53 |
| 33T | 3.33 | 6.33 |
| 34T | 3.24 | 6.15 |
| 35T | 3.14 | 5.97 |
| 36T | 3.06 | 5.81 |
| 37T | 2.97 | 5.65 |
| 38T | 2.89 | 5.50 |
| 39T | 2.82 | 5.36 |
| 40T | 2.75 | 5.22 |
| 41T | 2.68 | 5.10 |
| 42T | 2.62 | 4.98 |
| 43T | 2.56 | 4.86 |
| 44T | 2.50 | 4.75 |
| 45T | 2.44 | 4.64 |
| 46T | 2.39 | 4.54 |
| 47T | 2.34 | 4.45 |
| 48T | 2.29 | 4.35 |
| 49T | 2.24 | 4.27 |
| 50T | 2.20 | 4.18 |
| 51T | 2.16 | 4.10 |
| 52T | 2.12 | 4.02 |
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 XRAY T4 '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 T4 '21?
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 T4 '21's stock 110T spur that is about 28T for 6T and below, 46T for 13.5T, 46T for 17.5T, 57T 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 T4 '21 selected.
What is the internal ratio (transmission ratio) of the XRAY T4 '21?
The T4 '21 has an internal ratio of 1.9:1. Final drive ratio = spur ÷ pinion × 1.9. With the stock 110T spur, a 20T pinion gives an FDR of 10.45 and a 52T gives 4.02.
How many teeth is the stock spur gear on the XRAY T4 '21?
110 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
- 450 cst
- Rear
- 450 cst
- Rear
- 5,000 cst
What shock oil does the XRAY T4 '21 come with?
Out of the box the T4 '21 runs 450 cst front, 450 cst rear (XRAY oil), on 4 x 1.1mm (#308037) front, 4 x 1.1mm (#308037) 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 T4 '21 come with?
The kit springs are 2.5-2.8 (#308264) front, 2.6 (#308286) rear. Stiffer springs suit high grip and big jumps; softer springs add grip on slick or bumpy tracks.
What diff fluid does the XRAY T4 '21 come with?
The kit diff fluid is 5,000 cst rear. Thicker front adds steering on power; thicker center sends more drive rearward; thicker rear stabilizes the car under throttle.
Setup Help
All Touring Cars →
Free to start · iOS & Android
Setup App & Race Log
Your XRAY T4 '21 is in the RC Setup App
Save every setup change you make to your XRAY T4 '21, get AI tuning answers for that exact car, and log your races — at the track or back in the pits.
- Setup Tracking
- AI Mechanic answers
- Find & Share Setups
- Race Log
- Gear Ratio Calculator
- Free to use
