Mini 4WD Gear Ratio Chart: Choosing by Course
Tamiya does not leave gear ratio to guesswork: every current chassis is tied to a specific set of counter-gear and spur-gear part numbers in Tamiya's own gear regulation page and matching list, and each combination produces one of a handful of published ratios. This chart lists those official ratios, the part codes and grade-up sets behind them, and which course type each one suits. For the mechanics of why a shorter ratio accelerates and a taller one tops out faster, see the companion gear ratio guide — this article is the reference numbers, not the theory.
Standard chassis gear ratio chart
For single-shaft chassis — Super-II, Super TZ, Super TZ-X, Super X, Super XX, VS, AR, VZ, Zero, FM and the Type series — five ratios cover the current line-up. Each row is a real counter/spur gear pairing from Tamiya's matching list, not an approximation.
| Ratio | Counter / spur gear | Representative grade-up part | Character |
|---|---|---|---|
| 3.5:1 | G17 Light Blue / G18 Yellow | Kit-stock on VZ; a high-speed grade-up ratio for most other chassis | Fastest top speed of the five |
| 3.7:1 | G24 Green / G18 Yellow | Item 15434, High Speed EX Counter Gear Set | Between 3.5:1 and 4:1; Tamiya markets it specifically for small-diameter tyres |
| 4:1 | G14 Black / G11 Light Brown | Item 15236, High Speed Counter Gear Set | Widest chassis compatibility of any ratio on the chart |
| 4.2:1 | G9 Red / G11 Light Brown | Kit-stock on several Type/Zero/FM-family chassis | Slightly more acceleration bias than 4:1 |
| 5:1 | G10 Blue / G6 Light Green | Kit-stock on VS and Super-X family kits that ship the acceleration default; check your kit's manual | Strongest acceleration and hill/ramp performance |
Two further 3.5:1 pairings exist under different part numbers rather than the G17/G18 set above: Item 15132 (Special Ratio Gearing, mustard yellow gears) for Type 5, Zero and Super-1, and Item 15187 (Lightweight Special Ratio Gearing, light-grey gears) for Super FM, Super TZ and Super TZ-X. They are not interchangeable with the standard 3.5:1 pair — check the matching list for your exact chassis before buying either.
Mini 4WD PRO (dual-shaft) gear ratio chart
MS and MA chassis run a separate, three-ratio ladder, since the PRO gearbox drives all four wheels from one dual-shaft motor rather than through a rear propeller shaft.
| Ratio | Counter / spur gear | Grade-up part | Character |
|---|---|---|---|
| 3.5:1 | G21 Light Green / G22 Pink | Item 15349, PRO Super Speed Gear Set | Top-speed ratio for MS/MA |
| 3.7:1 | G23 Yellow / G22 Pink | Item 15429, PRO High Speed EX Gear Set | Middle ground between 3.5:1 and 4:1 |
| 4:1 | G19 Blue / G20 Orange | Item 15355, PRO High Speed Gear Set — stock ratio on the PRO Nitro Thunder and Nitro Force kits | Best acceleration; Tamiya's Japanese product copy suggests keeping the set as spare gears and pairing it with small-diameter tyres |
There is no PRO 4.2:1 or 5:1 — MS/MA gearing stops at 4:1. For motor pairings that make the most of each PRO ratio, see motor and gear ratio matching.
Matching a ratio to the course
A gear ratio is a trade between how many motor revolutions turn the wheels once and how much torque reaches the tyre. A shorter ratio (5:1, 4.2:1) turns the wheels fewer times per motor revolution, which favours acceleration out of corners, up ramps, and off the start line. A taller ratio (3.5:1, 3.7:1) turns the wheels more per revolution, trading acceleration for a higher theoretical top speed once the motor is fully spun up.
- Long, open circuits with real straights: 3.5:1 or 3.7:1 lets the car actually reach the speed the straight allows before the next corner arrives.
- Short, technical layouts with frequent corners, lane changes or a Dosun-Zaka-style slope: 4.2:1 or 5:1 gets the car back to speed faster after every scrub against a rail or roller.
- Mixed layouts, or a first competitive ratio to test from: 4:1 is the widest-compatibility middle setting on the chart and a reasonable default before you have lap data to tune from.
None of this replaces testing. Tyre diameter, motor wear and battery condition all shift where a given ratio's real-world balance point lands, so treat the table above as the legal starting menu, not a guaranteed finishing order.
Legacy Type-chassis ratios
Tamiya's matching list also documents a shorter, higher-ratio ladder for the original box-shaped Type chassis family, still referenced in the current parts-compatibility catalogue for vintage and reissued kits: Type 1 runs 11.2:1 or 6.4:1, Type 2 adds 6.4:1, 11.2:1, 8.75:1 and alternate 5:1/4:1 on a 12-tooth pinion, and Type 3 runs 6.4:1 or 5:1. These sit well outside the 3.5:1–5:1 range used on every current chassis, reflecting an older gearbox design predating Tamiya's modern parts ladder, and are not compatible with Super-series, VZ, MS or MA gears — check the chassis compatibility list before assuming any gear set fits by ratio number alone.
What the rules actually allow
Official Mini 4WD Race Regulations require that "all running gears must be installed according to the set gear ratios," and that permitted pinion gears depend on the chassis used — the counter/spur pairings above, not any combination that happens to physically fit. Gear modification is limited to drilling holes or shaving material for weight reduction and fitting ball bearings; the car must stay genuine four-wheel drive throughout. The Stock Class regulations apply the same principle with extra restrictions of their own, and local BMAX or other organiser-run classes follow their own rulebook, not either Tamiya document. Whichever class you enter, the organiser's rules and on-day technical inspection are the final word, not this chart; see the official rules and tech inspection checklist before race day.
Frequently asked questions
Is a lower ratio number always the faster choice?
Only in theoretical top speed, and only once the motor reaches its usable RPM range. A 3.5:1 car that never finishes accelerating before the next corner can lap slower than a 4.2:1 or 5:1 car on the same course. Ratio, motor and tyre diameter all move the real balance point together — see motor and gear ratio matching for how they interact.
Can I use a 3.5:1 gear set from a Super-XX chassis in a Type 2 chassis?
No. The two families use entirely different counter/spur gear part numbers and, on Type 2, a different pinion tooth count. Gear sets are matched to specific chassis in Tamiya's official list, not interchangeable by ratio number alone.
Are all five standard-chassis ratios legal for Stock Class racing?
They are all published in Tamiya's official matching list, but Stock Class and any local class layer their own restrictions on top, and rules are revised over time. Confirm the current permitted list and your event's own rules before entering a tuned car.