Last reviewed: November 13, 2026 · By the RaceYear team
Short answer: To calculate final drive ratio (FDR) or rollout, multiply (Spur Teeth / Pinion Teeth) by your car’s internal transmission ratio. Common baselines: Team Associated B7 / B6.4 is 2.60, TLR 22 5.0 is 2.43, Traxxas Slash 2WD (Mudboss) is 2.72, Custom Works Outlaw 4 is 2.61, Tekno EB410 is 2.50, and direct-drive pan cars and Mini-Z are 1.00. Plug your number straight into our free RC gear ratio and rollout calculator.
Key takeaways
| Chassis / Platform | Class | Internal Ratio | Transmission Notes |
|---|---|---|---|
| Team Associated RC10B7 / B7D | 1/10 2WD Buggy | 2.60:1 | 3-gear and 5-gear laydown gearboxes share 2.60 internal math |
| Team Associated RC10B6.4 / B6.3 / B6.1 | 1/10 2WD Buggy & Oval conversions | 2.60:1 | 3-gear laydown / layback transmission (52T diff / 20T top shaft) |
| Team Associated B74.2 | 1/10 4WD Buggy | 2.50:1 | 4WD gear differentials (40T ring / 16T input bevel) |
| TLR 22 5.0 (DC / AC / Elite) | 1/10 2WD Buggy & Dirt Oval | 2.43:1 | 3-gear laydown transmission; requires ~1-2T smaller pinion than AE 2.60 for equal FDR |
| Traxxas Slash 2WD (Stock / Mudboss) | Salvas Mudboss / Short Course | 2.72:1 | Magnum 272 / 272R 2WD gearbox |
| Custom Works Outlaw 4 / Enforcer 7 | 1/10 Dirt Oval Sprint & Late Model | 2.61:1 | 2.6-class dirt oval transmission |
| Tekno EB410 / EB410.2 | 1/10 4WD Buggy | 2.50:1 | Shaft-driven 4WD (40T diff ring / 16T pinion, sometimes listed ~2.47-2.50) |
| XRAY XB2 (2024-2026) | 1/10 2WD Buggy | 2.65:1 | Check manual if running optional diff/top-shaft gears |
| 1/12 & 1/10 Direct-Drive Pan Cars (CRC, Awesomatix, Schumacher) | Carpet Oval & On-Road Pan Car | 1.00:1 | Spur sits directly on solid/ball-diff rear axle; tune by foam tire rollout |
| Kyosho Mini-Z RWD / MR-03 / MR-04 | 1/28 Scale On-Road & Mini-Z | 1.00:1 | Motor pinion drives axle spur directly; ratio = Spur / Pinion |
If your car or aftermarket oval conversion transmission is not in the table above, open the exploded gearbox diagram in your kit manual and count only the driven and driving gears (idler gears only reverse rotation and cancel out of the math):
Internal Ratio = Differential Gear Teeth / Top-Shaft Gear Teeth (for example, 52 / 20 = 2.60).Internal Ratio = Differential Pulley Teeth / Center Layshaft Pulley Teeth (for example, 38 / 20 = 1.90).Internal Ratio = Diff Ring Gear Teeth / Input Bevel Gear Teeth (for example, 40 / 16 = 2.50).Once you have your internal ratio, open our free RC gear ratio, FDR and rollout calculator to see your exact FDR plus a five-pinion lookup table (-2 to +2 teeth), or open the RC top speed calculator to pair KV and LiPo voltage with your gearing. Want those numbers saved permanently with your shock oils, tires and lap times? Download RacerRX on iOS or Android and start a 14-day free trial.
No. Adding or removing idler gears (such as switching between a 3-gear and 4-gear or 5-gear transmission) changes motor rotation direction and torque reaction, not the numerical gear ratio between the top shaft and differential.
If your friend runs a Traxxas 2.72 gearbox and you run a TLR 2.43 gearbox, the same spur and pinion gives you a numerically lower FDR (taller gearing), working your motor harder and building heat. Always match FDR or rollout, never raw pinion tooth count across different brands.
Use rollout whenever tire diameter changes across runs, especially on foam-tire carpet oval pan cars, Mini-Z, or spec classes where tire truing shrinks diameter every race day. Read our full guide on RC gear ratio and rollout.
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