RPM Front Left Upper and Lower A-arms for ARRMA Kraton Outcast 8S RPM81522

Overview

The RPM Front Left Upper and Lower A-arms for ARRMA Kraton 8S and Outcast 8S represent a significant upgrade over stock suspension components for one of the most aggressive RC monster trucks available today. The ARRMA Kraton 8S and Outcast 8S are 26 lbs (12kg) of high-flying, dirt shredding, jump-killing fun that demand suspension parts capable of handling extreme abuse. If your stock A-arms aren't up to the punishment these massive monsters can dish out, RPM's replacement front A-arms are the perfect solution for any serious RC enthusiast in the UK looking to improve their truck's durability and performance.

These replacement A-arms are specifically engineered for the backyard basher and weekend warrior who wants suspension components that can handle serious abuse and come back for more. Made in the USA from RPM's trademark blend of ultra-durable materials, these A-arms represent genuine engineering innovation designed to address real-world failure points found in stock components. Whether you're running your brushless RC monster truck at the local bash spot or tackling challenging terrain, these front A-arms are built to survive impacts that would destroy lesser components.

RPM has invested considerable research and development into designing front A-arms that don't just match stock performance—they substantially exceed it in durability, impact resistance, and structural integrity. The company's reputation for producing some of the finest RC suspension components has made them the go-to choice for RC car enthusiasts across the UK and beyond who demand the very best in aftermarket upgrades.

Key Features

• Triple Beam Lower A-arm Construction — The front lower A-arms feature an innovative triple beam design specifically engineered to spread impact energy across all three beams rather than concentrating stress on a single point. This design philosophy means that when your truck lands hard or crashes into an obstacle, the impact force is distributed more evenly, reducing the likelihood of catastrophic failure that plagues stock A-arms.
• Massive Beam Cross-Sections — Each beam in the lower A-arms has a substantial cross-section measuring 5/8 inch (15.8mm) tall by 3/8 inch (9.5mm) wide. These whopping dimensions reduce unwanted flex during normal suspension movement while simultaneously allowing controlled impact-absorption during those not-so-perfect landings and crashes that are inevitable when pushing your RC truck to its limits.
• Dual Beam Upper A-arm Design — The front upper A-arms employ a robust dual beam construction where each beam measures a hefty 1/2 inch (12.7mm) tall by 3/8 inch (9.5mm) wide. These dimensions provide the structural rigidity needed for high-speed cornering and aggressive landings whilst maintaining the flexibility necessary for proper suspension articulation.
• Eliminated Droop Stop Design — RPM moved the inner cross brace away from the chassis, entirely eliminating the droop stop that exists on stock A-arms. While this design choice might seem counter-intuitive, RPM's extensive testing revealed that during extreme impacts, their test truck's chassis was actually being bent at the droop stops—clearly illustrating that stock chassis plates cannot handle the forces these massive RC monsters generate. By eliminating this weak point, RPM protects your chassis from bending damage.
• Redesigned Hinge Pin Support — RPM eliminated the tube shape over the hinge pin found on stock components, which removes built-in molding stresses whilst significantly beefing up the leading edge hinge pin support. This engineering refinement adds much-needed strength and durability exactly where it matters most in aggressive driving conditions.
• Fingernail Access Slots — Both upper and lower A-arms are moulded with convenient fingernail slots that allow easy access to remove the aluminium support ring at the pivot ball, making maintenance and adjustments straightforward without requiring specialised tools.
• Weight Savings — These RPM A-arms are lighter than stock ARRMA components by 4.5 grams per upper and lower A-arm pair, contributing to improved acceleration and handling characteristics whilst maintaining superior strength and durability compared to the original equipment.
• Direct Stock Replacement — These components directly replace the front left upper A-arm from stock ARRMA part number ARA330561 and the front left lower A-arm from stock ARRMA part number ARA330589, meaning installation is straightforward for anyone familiar with basic RC maintenance.
• USA Manufacturing — Made in the United States using RPM's proven ultra-durable material blend, these A-arms represent genuine quality engineering rather than cost-cut components designed purely for profit margins.

Technical Performance

The RPM Front Left Upper and Lower A-arms represent a substantial performance upgrade in terms of structural engineering and impact resistance. Built from RPM's proprietary blend of ultra-durable materials proven in countless competitive and recreational RC applications, these components offer measurably superior strength compared to OEM ARRMA parts. The triple beam lower A-arm construction is particularly noteworthy, as it fundamentally changes how impact energy is handled during hard landings and crashes. By distributing force across three substantial beams rather than concentrating it in one location, RPM has created a suspension component that simply doesn't fail under the kinds of abuse that quickly destroy stock A-arms. The massive 5/8 inch by 3/8 inch beam cross-sections in the lower A-arms and the 1/2 inch by 3/8 inch dimensions in the upper A-arms represent some of the largest and strongest A-arm sections available for 1/5 scale RC trucks. The engineering decision to eliminate the droop stop entirely, whilst appearing unconventional, reflects real-world testing data showing that stock chassis plates bend before the A-arms fail. By removing this weak link, RPM shifts the failure point away from your expensive chassis. The A-arms are compatible with ARRMA spring perches part number 330569 fitted to the 8S versions of the Kraton and Outcast. However, owners using EXB models with ARRMA spring perches number 330740 may experience interference issues at both the shock mount and sway bars, and RPM does not recommend using these A-arms on those vehicles as modification may be necessary. The 4.5-gram weight reduction per pair compared to stock components contributes to improved acceleration and handling without compromising the structural rigidity that makes these parts worth the investment. Like stock A-arms, RPM Kraton 8S A-arms are sold without threads in the pivot ball holes, and RPM recommends thread tapping the hole for 3 to 4 threads if difficult to thread using the pivot ball itself—but no further, as additional cut threads will negate the thread-locking capability of RPM's materials.

What's in the Box

• 1x RPM Front Left Upper A-arm for ARRMA Kraton 8S/Outcast 8S
• 1x RPM Front Left Lower A-arm for ARRMA Kraton 8S/Outcast 8S

What You Need to Complete

• 1x RPM Front Right Upper and Lower A-arms (part number RPM81562) — required to complete the front end of one vehicle
• Thread tap (if pivot ball holes are difficult to thread) — RPM recommends tapping 3 to 4 threads only
• Aluminium support ring at the pivot ball — not included

Frequently Asked Questions

• Do I need both left and right A-arms to upgrade my ARRMA Kraton 8S? — Yes, one complete front end upgrade requires one left A-arm kit (RPM81522) and one right A-arm kit (RPM81562). Each kit contains both the upper and lower A-arms for that side of the vehicle. To fully upgrade your truck's front suspension, you'll need both the left and right sets.
• Will these RPM A-arms fit my ARRMA Outcast 8S? — Yes, these A-arms are fully compatible with both the ARRMA Kraton 8S and ARRMA Outcast 8S models. However, they are specifically designed for 8S versions using ARRMA spring perches part number 330569. If your Outcast is an EXB model using ARRMA spring perches number 330740, RPM does not recommend these A-arms as they may require modification to eliminate binding at the shocks and sway bars.
• How much lighter are these A-arms compared to the stock ARRMA parts? — RPM's front left upper and lower A-arm pair is 4.5 grams lighter than the equivalent stock ARRMA components, contributing to improved acceleration and handling responsiveness without sacrificing the structural strength that makes these parts worth upgrading to.
• What makes the triple beam lower A-arm design so effective? — Instead of concentrating impact force at a single point like stock A-arms, the triple beam construction spreads the energy across three separate massive beams, each measuring 5/8 inch by 3/8 inch. This distribution of force dramatically reduces stress on any single beam and allows the A-arms to absorb impacts that would crack or bend stock components.
• Will I need tools to install these A-arms? — Installation requires basic RC maintenance tools. Like stock A-arms, these RPM components are sold without threads in the pivot ball holes. If you find the pivot ball difficult to thread, RPM recommends thread tapping the hole for 3 to 4 threads—but no further, as additional threading will compromise the thread-locking properties of RPM's materials. A tap tool is not included but is readily available.
• What do the fingernail slots do? — Both upper and lower A-arms feature convenient fingernail slots moulded into the design, allowing you to easily access and remove the aluminium support ring at the pivot ball without requiring any special tools. This makes maintenance and adjustments much more straightforward.
• Why did RPM eliminate the droop stop? — During extensive testing, RPM discovered that their test truck's chassis was actually bending at the droop stop during extreme impacts before the A-arms failed. This finding illustrated that the weakest link wasn't the A-arms but the chassis plate itself. By eliminating the droop stop screws entirely, RPM shifted the structural advantage away from what was causing chassis damage and towards a design that protects your expensive chassis from bending.
• Are these A-arms suitable for competitive racing or just casual bashing? — RPM designed these A-arms specifically with the backyard basher in mind, engineering them to handle serious abuse and come back for more. However, their robust construction and superior strength also make them excellent for competitive use where durability is as important as performance.

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 Front Left Upper and Lower A-arms Arrma Kraton/Outcast 8s RPM81522 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.