MA Chassis Tuning Guide
The MA chassis — Midship AERO — is Tamiya's aerodynamics-focused take on the midship dual-shaft layout, alongside MS and ME as one of the current double-shaft PRO-motor platforms. It ships as a single-piece monocoque frame with six low-friction rollers and a rear skid bar already moulded in, which is why MA assembles faster than a plate-and-screw chassis but also why "tuning" one differs from tuning MS or VZ. Very little structure is left to swap out. What remains to control is precision: shaft alignment, gear mesh, roller height matching and where you place mass and dampers on a frame that does not flex to forgive a sloppy build. This guide works through that baseline in order, with published dimensions and the official rules bounding what you may change.
What makes the MA chassis different
MA is a midship layout: the motor sits between the front and rear axle centrelines, the same broad family as MS and ME. What separates it is the monocoque itself — Tamiya moulds the chassis, six roller mounts and rear skid bar as one piece, where MS and VZ rely on separate FRP or carbon stays bolted to a plate chassis for roller and brake positions. That construction is both MA's strength and its tuning limit: it is dimensionally consistent and resists warping, so a fresh MA starts closer to "true" than a plate chassis with loose screws. But because the roller towers are moulded in, you cannot relocate a roller the way you can on a multi-hole FRP stay — you tune height, tension and alignment within fixed geometry, not redesign it.
MA takes the double-shaft Mini 4WD PRO motor family exactly like MS and ME — Torque-Tuned 2 PRO, Hyper-Dash PRO, Mach-Dash PRO and the rest — because the gearbox drives all four wheels directly with no propeller shaft. A single-shaft standard motor will not fit; check shaft count against chassis type before buying by name alone. For the current PRO motor lineup with published RPM, torque and current, see the Mini 4WD motors guide.
MA chassis reference specifications
Tamiya publishes these figures on its official chassis and compatible parts reference. Treat the dimensions as the as-moulded baseline: fitted wheels, tyres, rollers and stays change the car's actual width, height and weight once assembled.
| Spec | Published value |
|---|---|
| Chassis type | Midship, double-shaft (Mini 4WD PRO) |
| Frame construction | Single-piece monocoque with six integrated rollers and rear skid bar |
| Length | 156 mm |
| Width | 97 mm |
| Wheelbase | 80 mm |
| Tread | 59.5 mm |
| Weight | 78 g as moulded (125.9 g with motor and batteries) |
| Ground clearance | 2.2 mm |
Compare these against MS or VZ before deciding a chassis swap will fix a handling problem — a narrower tread or shorter wheelbase changes how a car reacts to bank angle and lane transitions. The chassis compatibility list covers checking which body and option parts fit a given chassis before you commit to one.
Baseline tuning order before you touch speed
Because MA's frame is rigid and largely fixed, most of what separates a fast build from a slow one is removing avoidable drag and error before adding power. Work in this order:
- Shaft and bearing inspection. Spin each axle by hand before fitting rollers or tyres. A bent shaft or off-centre gearbox shows up as uneven resistance, and no motor upgrade fixes it — it only worsens vibration at higher RPM.
- Gear mesh. MA shares its counter-gear and crown-gear architecture with the rest of the PRO double-shaft family. Too tight binds and draws excess current; too loose costs efficiency and adds noise.
- Roller height matching. With six roller positions moulded into the frame, the achievable adjustment is spacer stacking and screw tension, not repositioning. An uneven pair reads as inconsistent lap times more than an obvious crash.
- Tyre roundness. A tyre not fully seated, or cut off-centre, creates a once-per-rotation wobble that worsens with speed.
- Motor and gear ratio, last. Once the drivetrain turns freely, choose motor and ratio for the course. See motor and gear ratio matching.
Damper and brake placement on a rigid monocoque
MA's single-piece frame does not flex the way a screwed-together plate chassis can, so a landing a more compliant chassis would absorb slightly shows up on MA as a sharper bounce if brakes and dampers are not positioned to catch it. The fix is placement before mass: a damper mounted too far from the impact point, or a brake sponge at the wrong height for the track's slope transitions, lets momentum carry through the landing instead of settling it. Move the damper or brake first and retest before adding ballast weight — weight low and central helps once geometry is correct, but stacked onto a car still bouncing from placement it just makes the bounce heavier. See the brakes guide for sponge height and material, and the stays guide for how FRP and carbon trade compliance for rigidity beyond MA's built-in rollers.
Race-legal modifications and weight
Tamiya's official race regulations set hard limits for an MA build like any other chassis: overall width under 105 mm, height under 70 mm, length under 165 mm, ground clearance at least 1 mm, and minimum total weight (including motor and batteries) at least 90 g. Tyre diameter must fall between 22 mm and 35 mm, width between 8 mm and 26 mm. Only Tamiya-branded AA batteries are permitted, and the car must remain genuinely four-wheel drive. Chassis modification is restricted to cutting away plastic material or holes from the stock chassis — homemade chassis are prohibited, and the original part shape must stay identifiable after any cut. Opening a motor to change its coil winding is explicitly banned. Stock Class racing adds further restrictions on top of these, and officials hold final authority over anything not explicitly covered, so verify current wording against Tamiya's official race regulations and Stock Class regulations; see the official rules and technical inspection checklist for how inspection typically runs.
Frequently asked questions
Can I fit MS or VZ stays and rollers onto an MA chassis?
Only where a part is specifically listed as MA-compatible. MA's roller towers and skid bar are moulded into the frame rather than bolted on, so parts designed around a plate chassis's mounting holes often do not transfer. Check the part's listed compatible chassis, and use the chassis compatibility list as the starting reference rather than assuming "midship" alone is enough.
Why does my MA car bounce on landings even though the chassis is rigid?
Rigidity is exactly why: a monocoque frame does not absorb impact by flexing, so mass distribution, damper position and brake height carry more of that job than on a chassis with more give. Work through damper and brake placement above before adding weight.