Tamiya Lightweight Special Gearing (For Super FM/TZ Chassis)(15187)

A lightweight special-ratio gear set built for small-diameter-tire Mini 4WD chassis. The 3.5:1 gearing is aimed at raising top speed on Super FM, Super TZ and Super TZ-X chassis cars. The spur gear has weight-saving holes machined into it to keep rotating mass down, and the set is completed with a matching counter gear, counter shaft, a 620 ball bearing, and two types of gear cover for fitment.

• Gear ratio: 3.5:1
• Weight-reduced spur gear (holed)
• Includes counter gear, shaft, 620 ball bearing, 2x gear covers
• Compatible chassis: Super FM, Super TZ, Super TZ-X

Tamiya's own fitment note calls it out specifically for small-diameter-tire builds, where a taller ratio like 3.5:1 helps keep top speed competitive against a smaller-radius wheel. It sits at the opposite end of Tamiya's Grade-Up gearing range from the High Speed Counter Gear Set (No.236), which pairs a 4:1 or 4.2:1 ratio with large-diameter wheels instead. The two included gear cover types account for the differing gearbox housing shapes across the Super FM, Super TZ and Super TZ-X shells this set fits.