RPM Rear A-arms for ARRMA Kraton Outcast 4S BLX Suspension Upgrade RPM80742

Overview

RPM Rear A-arms for the ARRMA Kraton and Outcast 4S BLX represent a serious upgrade for UK RC enthusiasts looking to improve their brushless RC monster truck or stadium truck setup. Whether you're bashing at the weekend or pushing your RC car UK to its limits, these rear A-arms deliver enhanced durability, precision handling and the kind of performance upgrade that makes a real difference on track or off-road. Designed specifically for 4S BLX V1 versions of the ARRMA Kraton and Outcast, these suspension components transform how your RC vehicle responds to throttle input and maintains consistent geometry through aggressive cornering.

RPM has engineered these rear A-arms with one primary philosophy: strength and durability combined with smart performance enhancements. If you've experienced A-arm breakage with stock components, or simply want the reassurance of a proven upgrade that will withstand pounding terrain and competitive racing conditions, these are the suspension arms you need. All RPM A-arms are moulded from their nearly indestructible blend of engineering grade nylons, delivering the kind of reliability that serious RC bashers and racers depend on when conditions are at their worst.

Available as a pair and ready to bolt onto your ARRMA 4S, these rear A-arms replace stock ARRMA #AR330521 components. They're a straightforward suspension upgrade that requires no special tools or technical knowledge to install, making them ideal for anyone running a brushless RC car in the UK who wants immediate performance gains.

Key Features

• Slop Elimination Technology — RPM's rear A-arms reduce the amount of movement at the hinge pins, which directly translates to better steering response and more consistent camber and toe angle settings during high-speed driving, meaning your RC truck handles predictably in every situation.
• Extra Shock Mount Hole — An additional shock mounting position is provided between the two stock mounting holes, giving you a third suspension geometry option that serves as an ideal mid-point for fine-tuning your setup without the extreme compliance or stiffness of the stock positions.
• 25% Thicker Than Stock — These A-arms are massively engineered at almost 25% thicker than the original ARRMA components, providing significantly enhanced strength and durability that will take a pounding and come back for more, even in the harshest bashing conditions.
• Uniform Thickness Design — The A-arms feature uniform thickness across their entire length, ensuring consistent performance characteristics throughout the suspension geometry range and eliminating weak points where stock arms might flex or fail.
• Engineering Grade Nylon Construction — Moulded from RPM's specially formulated blend of engineering grade nylons, these A-arms deliver the near-indestructible durability that separates premium suspension upgrades from budget alternatives.
• Direct Stock Replacement — These rear A-arms replace ARRMA stock #AR330521, making installation straightforward for anyone familiar with basic RC maintenance and suspension setup on their 4S BLX machine.
• Sold as Pairs — You receive both rear A-arms ready to install, eliminating the need to source components separately and ensuring matched performance across both sides of the rear suspension.
• Optional Mud Guard Compatibility — RPM offers optional lightweight yet rigid Mud Guards (sold separately) that mount directly to these A-arms for additional protection in muddy or wet conditions.

Technical Performance

RPM's engineering approach to these rear A-arms focuses on eliminating the compromises present in stock ARRMA suspension components. The substantial increase in material thickness — nearly 25% more than factory spec — combined with uniform thickness across the entire arm length, creates a suspension component that absorbs impact forces more effectively whilst maintaining dimensional stability. The reduction of hinge pin slop addresses one of the most frustrating aspects of stock RC car geometry: unwanted movement at pivot points that degrades steering precision and camber consistency. For UK RC enthusiasts running their brushless ARRMA 4S on a variety of terrain from smooth tarmac tracks to rough field bashing, this translates to throttle response that feels sharper and more direct, with suspension angles that remain true to your intended setup rather than wandering as the arm flexes under load. The additional shock mount hole is engineered as a genuine mid-point geometry option, providing a suspension stiffness and ride height option that sits perfectly between the two extreme stock positions. For those dialling in their RC truck setup, this third mounting point can be the difference between finding the perfect balance for your driving style and local track conditions. The materials science behind RPM's engineering grade nylon blend has been proven across thousands of high-performance RC cars, delivering the kind of durability that commands respect in the competitive RC community.

What's in the Box

• RPM Rear A-arms for ARRMA Kraton and Outcast 4S BLX V1 (pair)

Frequently Asked Questions

• Will these RPM rear A-arms fit my ARRMA Kraton or Outcast 4S? — Yes, these A-arms are designed specifically for 4S BLX V1 versions of the ARRMA Kraton and Outcast. They replace stock ARRMA #AR330521 rear A-arms directly. However, please note that these are version 1 components — if you have a V2 model, RPM produces different A-arms (SKU 81792) specifically engineered for version 2 vehicles.
• How much stronger are these A-arms compared to stock? — RPM's rear A-arms are engineered at nearly 25% thicker than the original ARRMA stock components, combined with uniform thickness across the entire length of the arm. This substantial material increase, combined with the specialised engineering grade nylon blend, delivers dramatically improved durability and resistance to breakage under demanding conditions.
• Will these A-arms improve my RC truck's handling? — Yes, significantly. By reducing hinge pin slop, these A-arms provide a much tighter fit at the pivot points, which directly improves throttle response and maintains more consistent camber and toe angle settings. This means your brushless RC car will feel sharper and more predictable through corners and during acceleration, particularly noticeable on high-performance setups.
• What's the benefit of the extra shock mount hole? — The third shock mounting position is engineered as an ideal mid-point between the two stock mounting holes, allowing you to fine-tune your suspension stiffness and ride height without the extreme options of the stock positions. This gives you greater flexibility in dialling in your setup to match your driving style and local track or terrain conditions.
• Do I need any special tools to install these A-arms? — No. These rear A-arms are a direct replacement for stock ARRMA #AR330521 components and require only basic RC maintenance knowledge and standard tools (Allen keys, screwdrivers) for installation. The bolt holes align perfectly with your existing suspension pivot points.
• Can I use these A-arms with optional mud guards? — Yes. RPM manufactures optional lightweight yet rigid Mud Guards (sold separately) that are specifically engineered to mount directly to these rear A-arms, providing additional protection when bashing in muddy or wet conditions.
• Are these suitable for beginners? — These A-arms are suitable for anyone running an ARRMA Kraton or Outcast 4S, from weekend bashers to serious competitors. The installation is straightforward enough for a beginner with basic RC maintenance experience, and the performance upgrade will be immediately noticeable regardless of skill level.
• How do RPM A-arms compare to other suspension upgrades for the ARRMA 4S? — RPM's engineering grade nylon blend, combined with the 25% thickness increase and uniform arm design, sets these A-arms apart through proven durability and precision. The additional shock mount hole and slop reduction features address specific geometry compromises in stock setups, making these among the most technically considered rear A-arm options available for the ARRMA platform.

Why Buy from RC Model Shop?

RC Model Shop is a trusted UK RC retailer and authorised dealer for all the brands we stock, including Traxxas, ARRMA, Losi, FTX, Hobbywing, Spektrum and more. Based in Walsall, we have a physical store where customers are welcome to come in, view products and purchase in store. Whether you are a seasoned competitor, a weekend basher, or just discovering the world of RC for the first time, our team of experienced RC enthusiasts is here to help you find the perfect setup and provide ongoing support. Order the RPM Rear A-arms for the ARRMA Kraton and Outcast 4s BLX RPM80742 Upgrade for AR330521 today with confidence, knowing you are buying from an authorised retailer with genuine products, expert knowledge and a commitment to customer satisfaction. Shop online or visit us in Walsall — we look forward to helping you get the most out of your RC experience.