A Complete Guide to Boom Racing BRX PHAT™ Axles

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The BRX PHAT™ axle ecosystem is a modular scale performance platform supporting straight, offset, portal, and pass thru configurations across linked and leaf sprung setups. Built for flexibility, the system allows builders to configure and evolve their rigs without replacing the entire axle platform.

Built Around Modularity

The BRX PHAT™ axle platform was designed around one core principle: adaptability.

Instead of separate axle systems for every application, the BRX PHAT™ ecosystem shares a wide range of compatible components across multiple configurations. Builders can mix and match parts depending on the vehicle, terrain, or driving style they want to achieve.

This modular approach allows the platform to evolve alongside your build.

Straight Axle Configurations

Straight axles are the foundation of the BRX PHAT™ platform. Designed for scale realism, durability, and predictable handling, they are ideal for traditional trail trucks and scale builds.

Available in BRX70, BRX80, and BRX90 widths, the system supports a wide range of body styles and chassis setups.

Features include:

AR44-style triangular keyed gears available in standard, overdrive, and underdrive ratios
Reversed-cut rear gears for counter-rotating driveshafts
BADASS™ heavy-duty steel universal driveshafts
High steering angle geometry
Realistic scale dimensions
Heavy-weighted cast alloy housings for a lower center of gravity
Durable construction for heavy hardbody trucks
Compatible with linked and leaf sprung setups
Reversible bevel gear positions
Detachable truss and link mounts
Adjustable caster angles
Removable third member for 6x6 and 8x8 pass thru configurations
High pinion angle design for improved clearance

Specification

List of the widths and weight information with part numbers for each axle.

Axle width pin-to-pin	Part #	Type	Straight	Weight	Part #	Type	Portal	Weight
BRX90 Front	BRD9022	Straight	176mm	290g	BRPT9022	Portal	188mm	322g
BRX90 Rear	BRD9023	Straight	176mm	220g	BRPT9023	Portal	188mm	262g
BRX90 Pass-Thru	BRX026623	Straight	176mm	200g	Nil	Nil	Nil	Nil
BRX80 Front	BRD8022	Straight	162mm	277g	BRPT8022	Portal	174mm	320g
BRX80 Rear	BRD8023	Straight	162mm	205g	BRPT8023	Portal	174mm	256g
BRX70 Front	BRLC7022	Straight	149mm	260g	BRPT7022	Portal	160mm	306g
BRX70 Rear	BRLC7023	Straight	146mm	198g	BRPT7023	Portal	160mm	248g

Note that all of the above axles come with standard rotational gears, while BRX01 and BRX02 replacement rear axles (part numbers not listed above) come with reversed gears.

Offset Pumpkin Configurations

The offset BRX PHAT™ axle system expands the platform further with offset differential housings for improved scale realism and driveline alignment on specific vehicle platforms.

The offset system includes:

Reversible offset axle housings
Dedicated BADASS™ offset universal driveshafts
Aluminum upper link truss system
Compatibility across BRX70, BRX80, and BRX90 straight axles
Conversion parts for existing BRX PHAT™ centered axle setups

Offset pumpkins are especially useful for builds requiring more realistic driveline placement and scale accuracy.

Portal Axle Configurations

For builders looking for increased ground clearance and enhanced crawling capability, the BRX PHAT™ ecosystem also supports portal axle configurations.

Portal axles provide:

15mm or 0.59" additional axle clearance
Reduced drivetrain torque load
Improved obstacle capability
Enhanced technical crawling performance
Hardened steel gears
Four machined heavy-duty steel gears for strength and durability
Reverse gear compatibility for rear axle setups
Anti-twist steel brackets for 0° and 10° caster configurations

Full portal axles and portal conversions are currently available for straight and centered axle configurations within the BRX PHAT™ ecosystem.

Pass Thru Axle Configurations

The BRX PHAT™ platform also supports pass thru axle configurations designed for multi axle trucks and specialty builds.

Pass thru axles allow drivetrain power to continue through the axle assembly, making them ideal for:

6x6 and 8x8 trucks
Heavy utility builds
Military style platforms
Custom multi axle projects

This adds another level of flexibility while maintaining compatibility across the PHAT™ ecosystem.

Linked and Leaf Sprung Compatibility

The BRX PHAT™ ecosystem was designed to work across multiple suspension architectures.

Compatible configurations include:

4-link suspension
Leaf sprung setups
Panhard configurations
High clearance link systems
Hybrid linked and leaf sprung setups
Custom chassis configurations

Builders can tailor the axle setup to match the realism and performance goals of their project.

Optional BRX PHAT™ Axle Accessories

The BRX PHAT™ axle ecosystem is supported by a wide range of optional accessories and tuning components designed to enhance durability, performance, adjustability, and scale realism.

Available upgrades and accessories include:

Brass steering knuckle weights
Brass lockout weights
Brass portal knuckle and lockout weights
Stainless steel brake disc hexes
Optional XT diff cover
Aluminum Centered and Offset Link Trusses
Overdrive and underdrive gear sets
Link and leaf spring mounts

These optional components allow builders to fine tune weight distribution, steering response, driveline configuration, clearance, and overall performance while maintaining compatibility across the BRX PHAT™ ecosystem.

Shared Components Across the Ecosystem

One of the biggest advantages of the BRX PHAT™ ecosystem is shared component compatibility.

Many parts are interchangeable across multiple axle configurations, including:

Ring and pinion gears
BADASS™ universal driveshafts
Steering components
Wheel hubs and hexes
Brass upgrades
Bearings and hardware
Suspension mounting components

This allows builders to upgrade or reconfigure their rigs without replacing complete axle assemblies.

Built to Evolve

The BRX PHAT™ ecosystem continues to expand with new configurations, upgrade parts, and tuning options.

Whether building a scale expedition truck, heavy hardbody crawler, competition style rig, or multi axle utility vehicle, the platform was engineered for long term flexibility and compatibility across the BRX lineup.

The BRX PHAT™ axle platform is more than just an axle. It is a modular scale performance system built to adapt, evolve, and grow with your build.

Author:Jason Tsang

Published Date:12 May 2026