MAD G8X S58 Axleback Exhaust – BMW M3 / M4 (G80/G82)

In Stock: Ships in 1-2 business days
Available to Order: Ships in 3-4 Weeks

Looking to give your G8X a deeper, more aggressive exhaust note while retaining full valve functionality?

The factory axle-back keeps the S58 relatively subdued and leaves plenty of room for improvement in both sound and exhaust flow.

The MAD Axle-Back Exhaust replaces the restrictive factory rear section with a larger 76mm T304 stainless steel system, delivering a deeper exhaust note, improved flow, and significantly more character when the valves open.

Deeper tone.
Full valve functionality.
OEM+ fitment.

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Why this Axle-Back

The axle-back plays a major role in determining how your G8X sounds — especially when paired with an upgraded midpipe.

MAD increases the tubing diameter from the factory 70mm to 76mm, helping reduce backpressure and allowing exhaust gases to flow more efficiently. MAD reports gains of up to +5 HP and +5 lb-ft of torque while improving throttle response.

The valved design retains the factory exhaust valve actuators, allowing the system to remain deeper and more controlled during normal driving while opening up to a much more aggressive exhaust note under load.

It can be paired with the factory midpipe or combined with the MAD Resonated Single Midpipe for a complete exhaust setup.

Larger 76mm piping.
Factory valve integration.
Designed specifically for the S58.

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Installation Overview

• Directly compatible with the MAD Single Midpipe with no cutting required
• Can be connected to the factory midpipe with cutting required
• Retains factory exhaust valve actuators
• Extended valve harness included
• Includes necessary mounting hardware
• Professional installation recommended

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Fitment

BMW G8X Platform:

• G80 M3
• G81 M3 Touring
• G82 M4
• G83 M4 Convertible

Compatible with the factory midpipe and MAD Single Midpipe configurations.

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Performance & Sound

• Deeper and more aggressive exhaust tone
• 76mm tubing compared to the factory 70mm system
• Reduced exhaust backpressure
• Improved exhaust flow
• Up to +5 HP and +5 lb-ft of torque claimed by MAD
• Valved design for greater control over exhaust volume
• Drone-abatement design helps reduce unwanted cabin resonance
• Approximately 7 lbs lighter than the factory axle-back

Factory Axle-Back: approximately 44 lbs
MAD Axle-Back: approximately 37 lbs

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Construction

• 100% T304 Stainless Steel
• 76mm Exhaust Tubing
• TIG-Welded Construction
• Brushed Stainless Finish
• Quad Clamp-On Exhaust Tips
• Designed for Factory Exhaust Cut-Outs
• Corrosion-Resistant Construction

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Exhaust Tip Options

• Quad 4” (100mm) Silver Tips
• Quad 4.5” (114mm) Black / Carbon Tips

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What's Included

• MAD G8X S58 Axle-Back Exhaust
• Four Exhaust Tips
• Extended Valve Harness
• Required Mounting Hardware

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Warranty & Returns

• Eligible for a 90-day return window if unused, uninstalled, and in original condition
• Backed by a lifetime warranty on defects and fitment

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Automaz Approved

If you want more sound out of your G8X without giving up the functionality of the factory exhaust valves, the MAD Axle-Back is a great way to complete the rear section of the exhaust.

The larger 76mm piping improves flow while the valved design gives you the flexibility to keep the car more controlled during normal driving and let the S58 open up when you want to hear it.

Pair it with the MAD Resonated Single Midpipe for a complete setup designed to deliver the deep, bassy S58 exhaust note these cars are capable of.