11T pinion, 87T spur
A 11T pinion on a 87T spur is a 7.909:1 spur ratio. With an assumed 3:1 internal ratio that is a 23.73:1 final drive, which on a 1400KV motor at 2S with 4.7 in tires works out to about 6.1 mph theoretical and 5.2 mph realistic.
48P 3.175mm Pinion Gear Sets 5Pack 13T 14T 15T 16T 17T Hardened
- 1/8
Pinion sets in 48P, the pitch this 87T spur uses. Buying a set lets you step one tooth at a time instead of guessing.
$9.99 listed price, changes often
Check price on AmazonWhat final drive does 11/87 give?
The spur ratio is 87 / 11 = 7.909. Your car's transmission or differentials multiply it. The internal ratio varies by model, so here is the final drive across the common range; find yours in the manual next to the gearing chart.
| Internal ratio | Final drive (FDR) | Character |
|---|---|---|
| 2:1 | 15.82:1 | short: torque, cooler |
| 2.5:1 | 19.77:1 | short: torque, cooler |
| 2.72:1 | 21.51:1 | short: torque, cooler |
| 3:1 | 23.73:1 | short: torque, cooler |
| 3.5:1 | 27.68:1 | crawler territory |
How fast is 11/87?
Example: a 1/10 crawler (brushless 1400KV example), 1400KV motor, 4.7 in tires and an assumed 3:1 internal ratio (FDR 23.73:1). Theoretical speed is a no-load ceiling; the realistic figure assumes about 85 percent of it, which is typical on stock tires. For your own motor and tires, use the gear ratio and top speed calculator.
| Battery | Motor RPM | Theoretical | Realistic |
|---|---|---|---|
| 2S LiPo (7.4 V) | 10,360 | 6.1 mph | 5.2 mph |
| 3S LiPo (11.1 V) | 15,540 | 9.2 mph | 7.8 mph |
What does one tooth up or down do?
Speed scales with the pinion on a fixed spur. The heat rating compares each option with 11T, assuming 11T runs at a sensible temperature today.
| Swap | Speed change | Motor heat |
|---|---|---|
| 11T to 10T | -9.1% | cooler |
| 11T to 12T | +9.1% | moderate |
| 11T to 13T | +18.2% | high |
| 11T to 14T | +27.3% | high |
Which cars use a 87T 48P spur?
The 87T spur on this page is listed as fitting the Axial SCX10 1/10 crawler. Pitch matters more than tooth count: 48P gears only mesh with 48P gears. Set the mesh with a strip of paper between the gears as you tighten the motor, then remove it; there should be a tiny amount of play. See how to change a pinion gear.
Every pinion on the 87T spur
- 10T / 87T: 8.70:1
- 12T / 87T: 7.25:1
- 13T / 87T: 6.69:1
- 14T / 87T: 6.21:1
- 15T / 87T: 5.80:1
- 16T / 87T: 5.44:1
Gears and a thermometer for this swap
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Frequently asked questions
What is the gear ratio of 11/87?
87 divided by 11 is 7.909, so the spur ratio is 7.91:1. The final drive ratio multiplies that by your car's internal transmission or differential ratio, which is printed in the manual. At a 2.72:1 internal ratio it is 21.51:1; at 3:1 it is 23.73:1. Use the calculator with your own internal ratio for an exact figure.
Is 11T faster than 10T on a 87T spur?
Yes. On the same spur, speed scales with pinion teeth, so 11T is about 10.0 percent faster than 10T at the same motor RPM. The motor also works harder at every speed, so it runs warmer. Check the temperature after two or three minutes of running before going up another tooth.
Will a 11T 48P pinion fit my car?
Only if the spur is also 48P and the motor mount has enough adjustment for the pinion size. Pitch must match exactly; 48P gears will not mesh correctly with other pitches. Bore size must match the motor shaft, commonly 3.175 mm (1/8 in) on 1/10 motors and 5 mm on larger motors. The spur here is listed as fitting the Axial SCX10 1/10 crawler.
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.