RC car gear ratio chart
Spur ratio = spur teeth / pinion teeth, and final drive = spur ratio x internal ratio. An 18T pinion on an 86T spur is 4.78:1; through a 2.72:1 transmission it is a 13.0:1 final drive. Pick your spur below for every pinion worked out.
5Pack ShareGoo Steel 48P 3.175mm Pinion Gear Sets 13T 14T 15T
- 1/8
Step one tooth at a time instead of guessing: a 13T to 17T 48 pitch set.
$11.49 listed price, changes often
Check price on Amazon86T spur, 48 pitch
This spur is listed as fitting Traxxas 1/10 2WD trucks such as the Slash 2WD, Rustler and Stampede.
| Pinion | Spur ratio | FDR at 2.72:1 | Example speed |
|---|---|---|---|
| 12T / 86T | 7.17:1 | 19.49:1 | 24 mph (3S) |
| 14T / 86T | 6.14:1 | 16.71:1 | 28 mph (3S) |
| 15T / 86T | 5.73:1 | 15.59:1 | 30 mph (3S) |
| 16T / 86T | 5.38:1 | 14.62:1 | 32.1 mph (3S) |
| 17T / 86T | 5.06:1 | 13.76:1 | 34.1 mph (3S) |
| 18T / 86T | 4.78:1 | 13:1 | 36.1 mph (3S) |
| 19T / 86T | 4.53:1 | 12.31:1 | 38.1 mph (3S) |
| 20T / 86T | 4.30:1 | 11.7:1 | 40.1 mph (3S) |
| 22T / 86T | 3.91:1 | 10.63:1 | 44.1 mph (3S) |
| 24T / 86T | 3.58:1 | 9.75:1 | 48.1 mph (3S) |
| 26T / 86T | 3.31:1 | 9:1 | 52.1 mph (3S) |
| 28T / 86T | 3.07:1 | 8.35:1 | 56.1 mph (3S) |
90T spur, 48 pitch
This spur is listed as fitting the Traxxas Slash 2WD.
83T spur, 48 pitch
This spur is listed as fitting Traxxas 1/10 Slash, Stampede, Rustler and Bandit 2WD models.
76T spur, 48 pitch
This spur is sold in 76T, 83T, 86T and 90T sets for Traxxas Slash and Rustler 2WD.
87T spur, 48 pitch
This spur is listed as fitting the Axial SCX10 1/10 crawler.
57T spur, 0.8 module (32P class)
This spur is an Arrma HD 0.8 mod spur used on Arrma 1/10 4x4 3S BLX trucks.
| Pinion | Spur ratio | FDR at 2.85:1 | Example speed |
|---|---|---|---|
| 13T / 57T | 4.38:1 | 12.5:1 | 46.5 mph (3S) |
| 14T / 57T | 4.07:1 | 11.6:1 | 50.1 mph (3S) |
| 15T / 57T | 3.80:1 | 10.83:1 | 53.7 mph (3S) |
| 16T / 57T | 3.56:1 | 10.15:1 | 57.2 mph (3S) |
| 17T / 57T | 3.35:1 | 9.56:1 | 60.8 mph (3S) |
| 18T / 57T | 3.17:1 | 9.03:1 | 64.4 mph (3S) |
| 19T / 57T | 3.00:1 | 8.55:1 | 68 mph (3S) |
| 20T / 57T | 2.85:1 | 8.12:1 | 71.6 mph (3S) |
| 21T / 57T | 2.71:1 | 7.74:1 | 75.1 mph (3S) |
61T spur, 0.8 module (32P class)
This spur is listed as fitting Arrma 1/10 2WD platforms such as the Fury, Mega Gorgon and Vorteks 4x2.
46T spur, Mod 1
This spur is an Arrma Mod 1 spur for the 29 mm center diff used on Arrma 1/8 6S trucks.
| Pinion | Spur ratio | FDR at 2.85:1 | Example speed |
|---|---|---|---|
| 13T / 46T | 3.54:1 | 10.08:1 | 84.6 mph (6S) |
| 14T / 46T | 3.29:1 | 9.36:1 | 91.1 mph (6S) |
| 15T / 46T | 3.07:1 | 8.74:1 | 97.6 mph (6S) |
| 16T / 46T | 2.88:1 | 8.19:1 | 104.1 mph (6S) |
| 17T / 46T | 2.71:1 | 7.71:1 | 110.6 mph (6S) |
| 18T / 46T | 2.56:1 | 7.28:1 | 117.1 mph (6S) |
| 19T / 46T | 2.42:1 | 6.9:1 | 123.6 mph (6S) |
| 20T / 46T | 2.30:1 | 6.56:1 | 130.1 mph (6S) |
| 21T / 46T | 2.19:1 | 6.24:1 | 136.6 mph (6S) |
| 22T / 46T | 2.09:1 | 5.96:1 | 143.1 mph (6S) |
50T spur, Mod 1
This spur is listed as fitting the Traxxas 1/10 Maxx, sold with a 20T pinion.
Example speeds use the assumptions on each page (motor KV, tire size and an assumed internal ratio). Your car's numbers will differ; use the calculator with your own.
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RCCarCalc is researched guidance, not professional advice. Figures come from published manufacturer specifications, listings and verified owner reports, not hands-on testing. Speeds are theoretical or as listed; real results depend on gearing, battery, tires and terrain. See how we research.