Mini-Z Spring Rate Reference Chart: Front and Rear by Chassis and Surface

The Mini-Z spring color system is a great idea that somehow ends up confusing almost everyone. Kyosho uses color codes, PN Racing uses color codes, Yeah Racing uses color codes, and none of them match each other. You end up at the track with a pile of springs and no idea whether your PN “medium” is the same rate as your Kyosho “medium.” It is not.

This guide cuts through that by giving you reference baselines in the only terms that matter at the track: which end of the car to start with, which direction to go from the baseline, and why. The chassis-by-chassis and surface-by-surface breakdown below is what you build your own setup log from, not what you copy and race without adjustment.

If you want to understand the diagnosis layer (what the car tells you when springs are wrong and how to read it) the spring rate tuning by symptom guide covers that in full. This guide is the reference. That one is the mechanic.

How Mini-Z Springs Work (The Short Version)

Spring rate controls how much load transfers to each tire when the car accelerates, brakes, or corners. A stiffer spring transfers load faster and limits the chassis from flexing. A softer spring lets the chassis move more, which keeps tires in contact with the track through bumps but slows initial response.

The critical point that trips people up on Mini-Z: RWD rear suspension is primarily controlled by T-plate, not rear springs. On the MR-03 and MR-04, the T-plate handles rear flex behavior. Springs on these platforms are primarily a front-end tuning variable. The MA-020 AWD is different: it has both front and rear springs as active tuning variables.

This means if you are fighting rear exit behavior on an MR-03, changing rear springs will do less than swapping T-plate stiffness. Spring changes on MR-03/04 rear are a fine-tuning tool after T-plate is sorted. See the T-plate setup guide if you have not set your T-plate baseline yet.

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MR-03 Spring Reference Chart

The MR-03 EVO is the most tuned platform on this site. Spring changes on MR-03 are front-focused. The rear is covered by T-plate. The chart below reflects this.

Surface	Front Spring	T-Plate Flex	Notes
RCP (high grip)	Medium	Medium carbon	Standard club racing baseline. Start here before any adjustments.
RCP (fresh, very high grip)	Medium-stiff	Medium-soft	Fresh RCP can cause traction roll with too-soft front. Go stiffer if car tips.
Carpet (mid-grip)	Medium-soft	Medium	More compliance than RCP. Entry push is the common complaint.
Carpet (worn, low grip)	Soft	Soft-medium	Low-bite carpet rewards compliance everywhere.
Asphalt (outdoor)	Soft	Soft	Surface variation outside needs the most compliance.
Drift	Stiff	Stiff	Stiff everything for chassis rigidity through slides.

Beginner default: Medium front spring, medium T-plate. This covers 80 percent of indoor running conditions and is where any new setup should start.

Experienced driver adjustment: Most fast MR-03 drivers on RCP end up one step stiffer on front than the beginner default after they have dialed in their tire choice and T-plate. The stiffer front reduces corner-entry rotation just enough to make the car predictable at race pace. Beginners find a stiff front understeery because they are not carrying enough corner speed to load it properly.

What to Buy: MR-03 Springs

The Kyosho OEM spring set covers the full rate range for MR-03. If you want a wider rate spread and color-coding that makes pitting faster, the PN Racing set is the aftermarket standard at most clubs.

Kyosho Mini-Z Spring Set (Multi-Rate, MR-03/MA-020) on Amazon

Kyosho Front Spring Set (MR-03) on Amazon

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MR-04 Spring Reference Chart

The MR-04 is narrower than the MR-03 and more reactive to spring changes as a result. The narrower track means weight transfer happens faster and the car is more sensitive at both ends. One important note: not all MR-03 springs fit the MR-04, and the MR-04 EVO2 has its own spring set (MZW701). Confirm compatibility before ordering.

Surface	Front Spring	T-Plate Flex	Notes
RCP (high grip)	Medium	Medium	Same baseline as MR-03 to start. The narrower track will make adjustments feel more pronounced.
RCP (fresh)	Medium	Medium-stiff	MR-04 is more prone to traction roll than MR-03 due to narrow track. T-plate stiffness helps more than front spring here.
Carpet (mid-grip)	Medium-soft	Medium-soft	MR-04 on carpet benefits from softer T-plate more than front spring change.
Asphalt	Soft	Soft	Same logic as MR-03. Softer everything outdoors.
Drift	Stiff	Stiff	MR-04 drift setup requires stiffer settings to prevent the narrow chassis from flopping sideways.

Key difference from MR-03: The MR-04 is more sensitive to T-plate changes than to front spring changes. If you are chasing balance on MR-04, move the T-plate first, front spring second. That is the reverse of the natural instinct (which is to change springs first because they are more familiar).

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MA-020 Spring Reference Chart

The MA-020 AWD platform is the most complex spring setup on this list because both front and rear springs are active variables. All-wheel drive means load transfer is split between all four wheels, which changes how springs behave compared to RWD.

The key MA-020 insight: front springs control rotation; rear springs control traction compliance. On RWD, you tune front springs for entry and T-plate for exit. On AWD, front springs still handle entry, but the rear spring adds a traction management variable that does not exist on RWD platforms. Softer rear on AWD increases rear compliance and smooths out throttle bumps. Stiffer rear reduces rear squat and firms up mid-corner stability.

Surface	Front Spring	Rear Spring	Notes
RCP (high grip)	Medium	Medium-soft	Softer rear than front is typical on AWD. Prevents rear from being too rigid through high-grip corners.
RCP (fresh, very high grip)	Medium-stiff	Medium	Stiffen both one step on very high grip to prevent traction roll.
Carpet (mid-grip)	Soft-medium	Soft-medium	Balance matched. Carpet grip is lower and more even front-to-rear.
Carpet (worn)	Soft	Soft	Low bite everywhere means max compliance.
Asphalt	Soft	Soft	Outdoor surface variation needs compliance at both ends on AWD.

MA-020 spring interaction with gyro: MA-020 drivers often run lower gyro gain than equivalent RWD setups because AWD drivetrain provides its own stability. When adjusting springs on AWD, check whether the gyro gain needs to come down as well after stiffening. A stiff spring setup plus high gyro gain on AWD creates an overcontrolled car that fights itself mid-corner.

What to Buy: MA-020 Springs

The Kyosho OEM spring set works for both MR-03 and MA-020 front springs. MA-020 rear springs are a separate part.

Kyosho Mini-Z Spring Set (Multi-Rate, MR-03/MA-020) on Amazon

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Spring Rate Tuning Quick Reference: Symptoms and Fixes

Use this after you have set your baseline from the charts above. If the car does not behave as expected, match the symptom to the fix.

Symptom	When	Most Likely Cause	First Fix
Pushes on corner entry	Braking into corner	Front spring too stiff	Soften front one step
Rear snaps out on entry	Before you have turned in	Front spring too soft, nose dive unloads rear	Stiffen front one step
Rear snaps out on exit	As you roll power on	T-plate too soft (RWD); rear spring too soft (AWD)	Stiffen T-plate (RWD) or rear spring (AWD)
Mid-corner understeer	Steady-state through apex	Rear spring too soft, chassis rolling and unloading front	Stiffen rear (AWD) or T-plate (RWD)
Car feels bouncy / skips	Any phase	Springs too stiff for surface variation	Soften front by one step; re-evaluate T-plate
Car feels numb and slow to respond	Any phase	Springs too soft overall	Stiffen front one step first
Car is fast for 3 laps then falls off	End of a long stint	Tire wear more likely than springs	Check tire condition first

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One-Change Rule

Every piece of spring advice comes with the same caveat: change one variable at a time. Change front spring, drive five laps, note the result. Then change T-plate, drive five laps. Mixing spring, T-plate, and compound changes in the same session produces results you cannot explain or reproduce.

The fast drivers at club nights do not have exotic setups. They have known setups they can reproduce. That consistency comes from logging what they changed and what happened. A setup sheet you wrote yourself beats a borrowed one every time because it is specific to your track, your tires, and your driving style.

For the symptom diagnosis method in full, the spring rate tuning by symptom guide covers the diagnosis layer. For how spring setup interacts with tire compound selection, the tire compound by surface guide has the axle-isolation tuning process. For how springs, T-plate, droop, and camber all fit together as a system, the droop and camber setup guide is the foundational reference to work through before chasing spring rate fine-tuning.

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Related Guides

• Spring Rate Tuning by Symptom: diagnose the car before you change anything
• T-Plate Setup Guide: the primary rear-end tuning variable on MR-03 and MR-04
• Droop and Camber Setup: the variables that spring rate cannot fix
• Tire Compound by Surface: how compound interacts with spring rate decisions
• Mini-Z Setup Sheet by Surface: full surface baseline chart including diff oil and gyro
• MR-03 Platform Guide: full RWD upgrade context including suspension
• MA-020 Platform Guide: AWD platform-specific setup notes

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Reddit thread angle: “I made a Mini-Z spring rate chart organized by chassis and surface because I keep second-guessing which direction to go at the track. Here is what actually worked for me and why I ended up there.” Post for r/miniz, invite the community to share where their own baselines differ from the reference and why.