MR-04 Upgrade Guide: Kyosho Mini-Z Narrow GT

The MR-04 EVO is Kyosho’s narrow-body GT platform. Built for sports car shells that look cramped on the wider MR-03 chassis. The narrower track width and lower stance give it a more scale-accurate profile, and the shorter wheelbase options suit the body shapes it was designed for.

Deciding between platforms? The MR-03 vs MR-04 Buyer Guide covers cost, parts compatibility, and which is right for your track.

The upgrade path follows the same logic as the MR-03, but the platforms are not parts-compatible in every area. Confirm fitment before ordering anything.

Start Here: Bearings

Same as any Mini-Z. Bearings before anything else. Stock plastic bushings create rolling resistance that no other mod can overcome. The MR-04 uses a set of 1150 (5×11×4mm) bearings similar to the MR-03, but verify the full set for your specific variant before buying a kit.

A full bearing replacement is the single highest return-on-investment mod on the platform. Once you’re on steel bearings and considering whether ceramic is worth it for the motor and diff positions, the Bearing Upgrades: Ceramic vs Steel guide covers where the cost is justified on narrow-chassis RWD drivetrains like the MR-04.

FastEddy Sealed Bearing Kit for MR-04EVO2 (Amazon)

T-Plate and Rear Suspension

The MR-04 uses a T-plate based rear suspension, same concept as the MR-03. Carbon fiber replacements are the second upgrade after bearings.

The MR-04’s narrower track makes it somewhat more sensitive to T-plate stiffness than the MR-03. On high-grip RCP, a medium-stiff plate works well. On carpet or lower-grip surfaces, go softer to keep rear traction planted. Oversteer is more pronounced on the MR-04 at high speed. T-plate choice directly addresses this. See the T-Plate Setup guide for full flex selection and reading the car. That’s a rear-end symptom, not a front one: if the car won’t hold center and trim can’t fix it, that’s steering, not T-plate, and the MR-04 Evo2 steering drift diagnosis starts with RF Mode before it lets you near a screwdriver. If body roll through long sweepers is still an issue once T-plate and springs are sorted, the Sway Bar Setup guide covers when a front sway bar helps and notes the MR-04 typically needs a softer bar than the MR-03 for the same front feel. Browse the full T-plate and suspension lineup on the Shop Suspension Parts page.

NexxSpeed Carbon Fiber T-Plate Medium (Amazon)

Tires

The MR-04 runs narrow tires sized for its track width. These are not the same as standard MR-03 tires. Compound selection matters the same way: match to your surface.

For RCP, 20–30° compound is the standard range. Softer compound grips more but wears faster. Start at the middle and adjust based on how the car rotates mid-corner. Whatever compound you land on, true and glue your tires before the first session. An out-of-round or unmatched pair on this narrower track width reads as an inconsistent car, and it’s often mistaken for a compound problem.

Kyosho Mini-Z Low Height Slick Tire 30° MZW39-30 (Amazon)

Motor and Drive

The stock brushed motor is a starting point. Pinion gear changes are still the cheapest tuning lever. Going smaller reduces top speed and increases punch out of corners, which suits the MR-04’s tight-turning nature. The Mini-Z Pinion Gear Ratio Reference lists the 6T-9T options and what changes on the other chassis so you can pick a ratio without guessing at it. If you’re staying in a brushed class rather than converting, the Brushed Motor Guide covers turn-count selection and motor picks for the stock mount shared across the MR-03, MR-04, and MA-020.

Brushless conversion is available and worthwhile for competitive use, but the motor mount geometry differs from the MR-03. Use MR-04-specific brushless kits rather than adapting MR-03 parts. The Motor Mount Positions guide explains what RM and MM actually change, how the mount sets your wheelbase, and what else has to move when you swap one. The Brushless Conversion guide covers motor sizing, ESC selection, and LiPo integration. For differential tuning alongside the brushless upgrade, the Ball Diff vs Gear Diff guide explains why the MR-04’s narrower track makes diff preload selection even more important than on the MR-03.

Hobbywing EZRUN Mini28 Combo. ESC + 3500KV Motor (Amazon)

Body Compatibility

The MR-04’s value is in the body shells it unlocks. Narrow GT and sports car profiles (Ferrari F12, Lamborghini variants, Porsche 911 shapes) that look better on this chassis than the MR-03. Wheelbase options cover the common range for those shells.

When selecting a body, match the wheelbase and confirm narrow-body offset. Bodies listed as MR-03 compatible are often not dimensionally correct on the MR-04. The Body Compatibility guide has the full wheelbase and offset chart.

Budget Build Path

Working with a limited budget on the MR-04? The Best Budget Setups Under $50 guide covers the universal upgrade path and includes MR-04-specific notes on tires and T-plate compatibility. For race-specific setup decisions (how the car changes from casual driving to competitive RCP) the Racing vs Bashing Setup guide breaks down the MR-04’s specific adjustments.

If you’re racing on RCP or thinking about setting up a home track, the RCP Track Setup Guide covers tile counts, layout options, and timing systems. The same information club racers use to build their practice setups. For the dedicated MR-04 setup walkthrough covering suspension geometry, spring rates, and track-specific tuning, see the MR-04 Setup Guide. And once the build is sorted, a regular Maintenance Schedule keeps bearings and fasteners in check. For the full ranked upgrade sequence across all three platforms, see Mini-Z Upgrades: The Complete Guide.

What to Buy

The MR-04 parts below are the ones referenced throughout this guide, in the order they’re worth buying. Confirm MR-04 fitment on anything not listed as MR-04 specific.

Priority	Part	Why
1	FastEddy Sealed Bearing Kit for MR-04EVO2	Replaces stock plastic bushings. Biggest single gain on the platform.
2	NexxSpeed Carbon Fiber T-Plate, Medium	Addresses the MR-04’s high-speed oversteer directly.
3	Kyosho Low Height Slick Tire 30° MZW39-30	Mid-range RCP compound. Start here, then adjust by surface.
4	Hobbywing EZRUN Mini28 Combo, ESC + 3500KV	Brushless step once the chassis is sorted. Not before.

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Product images courtesy of Kyosho.