Realistic RC Speed Planning
RC speed looks simple at first. A motor spins. Gears reduce that spin. Tires turn it into distance. Real cars are less perfect. Batteries sag. Tires grow. Drivetrain parts waste energy. The surface can make the wheels slip. This calculator combines those effects in one place. It gives a theoretical speed and a corrected speed. That helps you compare parts before buying them.
Why Gearing Matters
Pinion and spur teeth set the first ratio. Transmission and differential ratios add more reduction. A smaller total ratio gives more speed. It also raises motor load. A larger ratio lowers speed. It usually improves launch control and heat behavior. Use the rollout value to see how far the car moves per motor turn. Big rollout can feel exciting. It can also punish the motor.
Battery And Motor Inputs
Motor KV means revolutions per minute for each volt. Higher voltage or higher KV raises motor rpm. The rpm limit field is useful for real motors, ESC settings, and safe operating targets. Sag reduces voltage during load. Heavy cars, weak packs, and tall gearing increase sag. Enter a realistic value when planning speed runs.
Tires And Losses
Tire diameter controls distance per wheel revolution. Foam and belted tires may expand less than soft rubber. Expansion can increase speed at high rpm. Slip and drivetrain efficiency reduce actual road speed. Small losses can change results a lot. That is why corrected speed is often more useful than the perfect value.
Using Results Safely
Treat the number as a planning guide. Real speed depends on air drag, road texture, balance, bearings, temperature, and body shape. Check motor heat after short passes. Watch tire condition. Confirm radio range. Use open space. Change one part at a time. Record each setup. Good notes make tuning faster and safer.
Setup Comparison Tips
Use the example table to compare normal, aggressive, and conservative builds. Start with the conservative setup when parts are unknown. Then raise pinion size slowly. Keep the motor below safe temperature. A small GPS logger can verify the estimate. If measured speed is lower, check sag, drag, tire ballooning, and wheel slip. Repeat testing after each change, because clean data prevents expensive mistakes later.