Understanding 1/10 Scale RC Off-Road Gearing & FDR
What is Final Drive Ratio (FDR) and why does it matter?
The Final Drive Ratio (FDR) represents the total number of times your RC motor's pinion shaft must rotate in order to turn the car's drive wheels exactly once. It combines the mechanical advantage of your external gearing (spur and pinion) with the hidden internal gear ratio inside your transmission gearbox. Finding the perfect FDR is the most critical step in track tuning, as it directly determines your vehicle's balance between explosive corner-exit acceleration and high-end straightaway top speed.
How does changing my Pinion and Spur gear affect track performance?
Adjusting your mechanical gearing allows you to adapt your car's power delivery to different track conditions. Installing a larger pinion gear or a smaller spur gear creates a taller gear ratio, which increases top speed but raises motor temperatures and reduces bottom-end punch. Conversely, dropping down to a smaller pinion gear or a larger spur gear creates a shorter gear ratio, giving you massive acceleration out of tight corners while keeping thermal loads safe on high-grip carpet or heavy clay surfaces.
Why do different racing chassis have different Internal Gear Ratios?
The internal gear ratio is a fixed mechanical value determined by the number of teeth on the differential gear divided by the teeth on the top shaft gear inside the sealed transmission box. Because modern racing platforms are engineered for specific disciplines—such as Team Associated dirt buggies vs. Schumacher high-grip carpet cars—manufacturers design distinct internal gear configurations to optimize internal rotational mass and torque delivery for their respective target tracks.
Supported 1/10 Off-Road Racing Brands & Chassis
RC Gearing Calc ships with factory-accurate internal gear ratios for every major 1/10 scale off-road racing manufacturer, so you can dial in pinion and spur combinations in seconds at the track. Supported brands include Team Associated (RC10B7, B7.1, B6.4, B74.2, B84, T6.4, SC6.4), Losi / TLR (22 5.0, 22 6.0, 22X-4, 22T 4.0, 22SCT 3.0), Xray (XB2, XB4, XT2), Schumacher (Cougar LD1, LD2, LD3, CAT R, CAT LXT, Storm ST2), Tekno RC (EB410.2, ET410.2, SCT410), Yokomo (YZ-2, YZ-4 SF2, SO and MO series), Kyosho (Ultima RB7, Lazer ZX7), PR Racing, Serpent, and HPI Racing. Whether you race carpet, clay, astro, or dirt, the calculator pulls the correct internal ratio for your chassis and feeds it into the live FDR, top speed, and thermal safety engine.