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Representative image of an RCScrewZ metal-shielded bearing kit for Kyosho Mad Force 1/8 Nitro 4WD Monster Truck (31221); exact bearing sizes and quantities vary by RC model.
Upgrade Your RC Car with Metal Shielded Bearings for Kyosho Mad Force 1/8 31221 | kyo005b - High Performance Upgrade | Durable & Reliable - by J-M SUPPLIES
Infographic: 'Choose Wisely for Your Need for Speed' – Highlights Metal Shielded Bearings as the top choice for unbeatable on-road RC car performance -
Infographic: 'Choose Wisely for Off-Road Adventuring' – Recommends Rubber Sealed Bearings for maximum protection and enhanced off-road performance in RC vehicles -
Infographic: 'Choose Wisely for Your Need for Speed' – Highlights Metal Shielded Bearings as the top choice for unbeatable on-road RC car performance - kyo005b
Infographic: 'Choose Wisely for Off-Road Adventuring' – Recommends Rubber Sealed Bearings for maximum protection and enhanced off-road performance in RC vehicles - kyo005b
Infographic: 'What Matters Most to You? Performance on the Streets or Durability in the Dirt?' – Guides on selecting bearings to match your RC lifestyle, highlighting the importance of choosing based on whether your focus is speed on paved roads or resilience in off-road conditions - kyo005b
Infographic: 'Need Bearings? How to Check Your RC's Bearings for Replacement' – Instructions to remove, clean, and inspect bearings for gritty texture or improper movement, indicating the need for replacement - kyo005b
Step-by-Step Guide: Checking RC Bearings. 2. Assess if bearings feel gritty or aren't spinning freely. 3. Non-free spinning bearings impair RC performance. 4. Bearings not spinning freely may need replacement - kyo005b
RCScrewZ and J-M SUPPLIES offer high-quality RC bearing kits, available as metal shielded or rubber sealed options, suitable for diverse RC needs - kyo005b
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Infographic on RCScrewZ Bearing Kits: Highlights features of both metal and rubber shielded bearing kits, detailing high-quality components suitable for various RC models. Covers standard, flanged, one-way, and thrust bearings included in kits, with extra spares. Explains the shielding and performance benefits of each type, tailored for specific RC model needs - kyo005b
Infographic reminder: Refer to the item description for more detailed information about the product - kyo005b
Infographic reminder: Refer to the item description for more detailed information about the product - kyo005b
Notice: Check the product description for detailed information on the specific bearing sizes included in this bearing kit - kyo005b

Why Choose This Kit

Key features and intended use for this kit.

Shield type

Metal-Shielded (On-Road)

Performance focus

Low-drag, not sealed

Best suited for

Cleaner on-road / prepared surfaces

Metal-Shielded Bearings

RCScrewZ Metal Shielded Bearing Kit kyo005b for Kyosho Mad Force 1/8 Nitro GP 4WD Monster Truck (31221) | SET

RCScrewZSKU: kyo005b

Model-specific metal-shielded bearings for smooth, low-drag operation on cleaner on-road or prepared surfaces.

Fits: Kyosho Mad Force 1/8 Nitro 4WD Monster Truck (31221)
OEM / model: 31221

US
Regular price
$53.67
Sale price
$53.67
Regular price
$59.95

In stock

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Confirm this kit fits your RCMatch the RC model and OEM/model number shown above to your vehicle.

Exact model check

Confirm This Fits Your RC

Match the RC model and OEM/model number below before ordering.

RC model
Kyosho Mad Force 1/8 Nitro 4WD Monster Truck (31221)
OEM / model number
31221
Kit type
Metal-Shielded Bearing Kit — Low-Drag for Cleaner Running
Scale
1:8
Power
Nitro & Glow Fuel
View all verified kits for this model →
More compatibility details
RC brand
Kyosho
Vehicle class
Land
Kit SKU
kyo005b
Model series
Mad Force
Product information

Everything You Need Before Ordering

Review what is included, installation notes, shipping details, and complete kit information.

Kit Contents & Installation

What’s Included Model-specific bearing set with one spare of each included size.
  • All bearing sizes listed below for this model-specific kit
  • One spare of each included size
  • Bearing styles vary by RC model and may include standard, flanged, one-way, or thrust bearings

Included bearing sizes for this kit:

  • 6x12x4mm bearings
  • 8x16x5mm bearings
  • 10x15x4mm bearings
Installation & Model NotesImportant instructions and model-specific guidance.

Seat bearings fully and squarely. Do not force them into the housing or overtighten the hardware that retains them.

Keep metal-shielded bearings clean and dry.

After cleaning and drying, apply a small amount of light bearing oil.

Details & Support

Kit Details Lower-drag metal shields for clean, dry running conditions.
Shield Type
Metal-Shielded Bearings
Performance Priority
Lower drag
Protection
Not sealed; best kept clean and dry
Best For
Cleaner on-road or prepared surfaces when lower drag is the priority
Not Ideal For
Dust, dirt, sand, mud, water, or frequent wet-condition use
Prefer Rubber-Sealed?
Choose Rubber-Sealed bearings for off-road use, dust, dirt, sand, mud, water exposure, or lower-maintenance protection.
Shipping & Returns Handling time, current delivery estimate, and return policy.
Free shipping on all U.S. orders (USPS Priority Mail).
Ships within 1–2 business days (Mon–Fri); some Saturday shipments by 12:00 PM ET.
Most orders ship from Canton, MI 48187. APO/FPO/DPO & PO Boxes welcome.
Priority Mail typically delivers in 2–3 business days (estimates; not guaranteed).
Easy 30-day returns with prepaid USPS label; refunds issued within 3 business days after the return is received.

Over 99% positive over ~14,000 orders on eBay (last 12 months) — as of October 2025. View on eBay

Full Product Description Read the complete product specifications and details.

Exact RC Model Fitment

Confirm the exact RC model and RC vehicle OEM/model number below before ordering.

Compatible RC Model
Kyosho Mad Force 1/8 Nitro 4WD Monster Truck (31221)
Compatible RC Brand
Kyosho
RC Vehicle OEM / Model Number(s)
31221
RCScrewZ Kit Part Number
kyo005b

Vehicle Compatibility Details

Review these vehicle details to help confirm compatibility with your RC model.

RC Vehicle OEM / Model Number(s)
31221
RC Chassis Compatibility
Kyosho Mad Force ladder-frame chassis (31221)
Compatible Vehicle Type
1/8 Nitro GP 4WD Monster Truck
Terrain Compatibility
Compatible Scale
1:8
Compatible Fuel Type
Nitro & Glow Fuel

What Is Included

Included bearing sizes for this Metal-Shielded Bearing Kit:

  • 6x12x4mm bearings
  • 8x16x5mm bearings
  • 10x15x4mm bearings

What Is Not Included

Only the bearings identified in the included-bearing-size list are part of this kit. 

The RC vehicle and separately sold parts are not included unless specifically listed.

Installation & Model Notes

Metal Shielded Bearing Kit Compatibility:

Quick Fit Summary:

  • Compatible Brand: Kyosho

  • Fit: Model-specific fitment for Kyosho Mad Force.

  • Compatible RC Model/OEM Numbers: Kyosho Mad Force (31221)

  • Scale: 1/8

  • Power Source / Fuel Type: Nitro GP

  • Battery / Cell Count: Not applicable - nitro engine powered.

  • Drive Type: 4WD

  • Vehicle Type: Monster Truck

  • Chassis: Kyosho Mad Force ladder-frame chassis (31221)

  • Era: Modern Transition (2000-2009)

  • OEM / Models: 31221

  • RC Model Terrain: Off-Road: Dirt, Grass & Rough Terrain

  • Release Date: 2002 Release

This Kit Details:

  • SKU: kyo005b

  • MPN: kyo005b

  • Kit Type: Metal Shielded Bearing Kit

  • Bearing Type: Metal-Shielded Bearings (On-Road / Low-Drag)

  • Sealed Bearings: No

  • Water/Dust Protection: Low-drag, not sealed

  • Bearing Size Details: 6x12x4mm, 8x16x5mm, 10x15x4mm

  • Product Material: Carbon Chrome Steel Bearings

  • Product Color: Silver

OEM / Model Code / Alias Coverage:

Verified OEM/model code coverage for this listing: 31221.

Model Family Coverage:

Mad Force.

Product Benefits:

  • Metal shielded bearings reduce rolling friction for cleaner running conditions.

  • Best for on-road, display builds, light-duty use, or buyers who prefer lower drag over maximum contamination protection.

  • For off-road or dusty use, consider rubber shielded bearings for added dirt and debris protection.

Fitment Note:

Check your Kyosho model number before ordering. This kit is configured for Kyosho Mad Force (31221) and should not be assumed to fit other Kyosho variants unless separately listed.

Search-Friendly Notes:

Kyosho Mad Force, Mad Force, 31221, 1/8 Nitro GP 4WD Monster Truck.

Metal-Shielded Bearing Kit Details

Review the bearing-kit details below before ordering.

RCScrewZ Kit Part Number
kyo005b
Product Brand
RCScrewZ
Shielding Type
Metal-Shielded (On-Road)
Sealed Bearing Status
No
Bearing Material
Carbon Chrome Bearings
Approximate Piece Count
Color
Silver

Before Ordering

  • Confirm your exact RC model, RC brand, and OEM/model number whenever possible.
  • Review the included-bearing-size list before purchase.
  • Read the installation and model notes before disassembly or installation.

Vehicle versions, chassis revisions, and model-year configurations can differ. 

Confirm fitment before purchase when your RC vehicle differs from the details shown above.

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Rubber-Sealed Bearing Kit

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Fits: Kyosho Mad Force 1/8 Nitro 4WD Monster Truck (31221)
$53.67