"MR-03 or MR-04?" is the most common Mini-Z buying question — but it is really four cars, because each generation has a brushed base version and a brushless EVO race version. The MR-04 is the first full redesign in 14 years (about 98% new parts), yet a lot carries straight over, and most of what makes a Mini-Z fast bolts onto what you already own. Here is the plain-English breakdown.
The Mini-Z lineage (base vs EVO)
Sorting out the names clears up most of the confusion:
| Chassis | Motor | Electronics | Who it is for |
|---|---|---|---|
| MR-03 (base) | Brushed | Proven, simpler board | Bashing, casual, budget |
| MR-03 EVO | Brushless | Separate ESC + receiver; ICS-adjustable; far faster ESC; can switch back to brushed | MR-03 racers |
| MR-04 (base) | Brushed | New, larger board | Newcomers wanting the latest chassis |
| MR-04 EVO2 | Sensored brushless (8500 / 5600 / 4100 KV) | New potentiometer + redesigned steering program; V2 gyro w/ own CPU; faster, Mini-Z Cup-legal RC unit | MR-04 racers |
Key point: the base MR-04 is still a brushed car — only the EVO2 gets the sensored motor and upgraded electronics.
What changed from the MR-03 to the MR-04
| Area | MR-03 | MR-04 |
|---|---|---|
| Front suspension | Limited up-travel (racers hand-do the "kingpin flip") | Factory kingpin flip — more travel out of the box; integrated-kingpin knuckle |
| Steering geometry | Baseline | Kingpin moved ~1.5 mm shorter per side (scrub) → sharper, more linear steering |
| Motor position | Higher in the rear pod | Sits lower (bottom of the rear pod) → lower centre of gravity |
| Battery position | Higher | Lower → lower centre of gravity, more corner stability |
| Front bearings | Smaller (smaller front axle) | Larger — all 7 bearings are now identical (MR-03 fronts do not fit) |
| Servo feel | Calmer; "tracks straighter" | Quicker and more sensitive (it may buzz hunting centre — normal) |
What the EVO versions add
MR-03 EVO turns the MR-03 into a race chassis: brushless power, a separate ESC and receiver (works with multiple transmitter brands), an ICS-adjustable board (tune throttle and steering, or even switch back to a brushed motor), and far faster ESC response. MR-04 EVO2 adds a sensored brushless motor (smooth from a standstill, where sensorless motors can cog), a redesigned steering program with a new potentiometer, a V2 gyro with its own CPU, and a faster, Mini-Z Cup-legal RC unit. In both generations, "EVO" means the brushless, adjustable-electronics race upgrade.
What carries over between the two
Trading up never wastes your collection:
| Part | MR-03 ↔ MR-04 |
|---|---|
| AutoScale bodies | Yes — all Mini-Z bodies fit both |
| Wheels & tyres | Yes — same narrow 8.5 / wide 11 + offset system |
| Rear differential | Yes — identical (only LM vs mid-motor diffs differ) |
| Rear shock | Yes — same shock (the mount differs) |
| Rear motor pod (low-CG) | Retrofittable to an MR-03 — see below |
| Front bearings | No — MR-03 fronts are smaller |
| Front knuckles / kingpins / springs | No — MR-04-specific |
| Board / servo | No — the chassis is shaped around them |
Bonus: put the MR-04''s low rear motor pod on your MR-03 for about $10
One of the MR-04''s best features — the lower, lower-CG rear motor pod — bolts onto an MR-03. Kyosho sells the whole conversion as a single part, MZ714 (about $10–13): motor housing, ride-height pills, motor plates and shock hardware. Because the rear shock and differential are identical, you reuse them. Two small gotchas: the MR-04 motor wires exit forward (re-route or re-solder if you keep your MR-03 motor — or just fit a fresh one), and the non-drive-side rear spacer is about 1 mm shorter (trim your MR-03 one, or buy part MZ206C; some also lightly file the MR-03 drive hub). About 5–10 minutes of work for the MR-04''s lower-CG rear end on your existing chassis.
Should you buy an MR-04 or upgrade your MR-03?
Upgrade your MR-03 for cheap speed and grip — bearings, a ball diff, an alloy mount, good tyres and brushless all bolt on, and you can even retrofit the MR-04''s low rear motor pod for about $10. Step up to an MR-04 (or EVO2) mainly for the front-end steering geometry (the factory kingpin flip and revised scrub/caster) and, on the EVO2, the sensored power and V2 gyro — those are the parts that do not retrofit to an MR-03. Either way your bodies, wheels and rear diff come with you. Note that MR-03s are being phased out (not restocked), so availability may make the decision for you.
The smart upgrade order for an MR-03
If you are upgrading rather than rebuying, this is roughly the order that gives the most return per dollar (there is no single right answer — buy to your budget and skill):
| Order | Upgrade | What it does |
|---|---|---|
| 1 | Ball bearing set | Always first — less friction means more speed and longer runtime |
| 2 | Hard front A-arms | Stock arms are deliberately soft (crash protection); hard arms sharpen on-track steering — cheap, big gain |
| 3 | Alloy motor mount | Stock plastic flexes, cracks and traps heat; alloy adds rigidity (drive efficiency + durability) and ride-height shims |
| 4 | Ball differential | Lighter, with tunable left/right balance |
| 5 | Brushless motor (+ board/module) | The biggest top-end gain — but on a RWD it needs a board/module, so it is the pricier step |
Fitting a body to whichever chassis you land on? Use our Mini-Z wheel offset calculator, and see the full guide to Mini-Z rear pods, wheelbase and fitting an AutoScale body.
Dialing in your wheels? See Mini-Z wheels: offset, play & a fit that won''t wobble or crack.
