Supersprint BMW 1 Series F20/F21 M135i M140i Rear Silencer/Back Box/Muffler | Valved Switchable Flap Axle-Back Exhaust | Twin 80mm Polished Tips | Stainless Steel Performance Upgrade | PN 522324

Valve‑controlled rear box for BMW 1 Series F20 F21 M135i and M140i with twin 80 mm tips

Give your 1 Series the soundtrack it deserves with this Supersprint valve‑operated rear silencer. Designed as a direct replacement back box for the F20 F21 M135i and M140i, it delivers an assertive, richer tone under load while remaining refined on the motorway. The twin 80 mm outlets complete the OE‑plus look and the fitment is plug‑and‑play on the original hangers.

• Rear section back box for BMW F20 F21 M135i and M140i with valve control
• Twin 80 mm tailpipe finishers for a clean, factory‑style appearance
• Deep, sporty sound without intrusive cabin boom
• Uses OE mounting points for a straightforward bolt‑on swap
• Premium European stainless steel construction in AISI 304 and AISI 409
• Carefully routed for thermal protection around nearby components
• Meets stringent safety guidance similar to JASO fire‑risk criteria
• 3‑year warranty with unlimited mileage
• Supersprint part number: 522324

Why enthusiasts pick this rear silencer

Supersprint tunes the rear section first to unlock the character of the N55 and B58 engines while keeping day‑to‑day manners. The bespoke internals and tubing profile are tailored to the F20 F21 chassis so you get a purposeful growl when you want it and calm cruising when you do not. The polished twin outlets in 80 mm size sit perfectly in the diffuser for a subtle, performance‑led finish.

Build quality you can trust

Using selected gauges of AISI 304 and AISI 409 stainless steel, this rear muffler is engineered for long service life in UK conditions. Attention to routing, bracketry and heat management mirrors OEM standards, helping protect sensors, trim and ancillaries. It is a premium European‑made upgrade backed by a 3‑year warranty.

Compatibility

• BMW 1 Series F20/F21 M135i 2012 to July 2013
• BMW 1 Series F20/F21 M140i

To be installed as a kit with: 524212 and 988603 or 988613.

Installation and support

This axle‑back section is a simple bolt‑on using the factory hangers. No chassis cutting and no changes to mechanical components are required. For professional fitting and advice, book with MJ Modifications in Warwickshire. Request a quote at info@mjmodifications.co.uk.

Proven in our workshop

We have fitted this Supersprint rear box on customer M135i and M140i cars and feedback has been consistently positive for tone, finish and fitment. Owners love the valve‑controlled character, the quality welds and the perfect alignment of those 80 mm tips.

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