CSK BMW 1 Series M135i F20/F21 N55 Axle-Back Exhaust Straight Pipe – Rear Box/Back Box/Muffler/Rear Silencer Delete Rear Section – 304 Stainless Steel, TIG Welded – Performance Axleback Tailpipe – CSK001

CSK CSK001 Axle-Back Straight Pipe for BMW 1 Series M135i F20 F21 N55

Give your N55-powered M135i the soundtrack it deserves. The CSK CSK001 axle-back straight-through tail section replaces the restrictive factory rear can on the F20 and F21 1 Series M135i, unlocking a deeper, louder, motorsport-style note with crisp turbo presence and addictive overrun character. Built from 304-grade stainless with fully back-purged TIG welds, it is a durable, great value sound upgrade that looks as good as it performs.

We have installed this rear section for customers and the response has been consistently positive on tone, quality and fit. If you want your M135i to sound purposeful without committing to a full cat-back, this is the sweet spot.

Why enthusiasts choose CSK CSK001

• Direct replacement tail section for BMW 1 Series M135i F20 and F21 with the N55 engine
• 304 stainless steel for long-term corrosion resistance
• Back-purged TIG welding for clean, strong, reliable joints
• More volume with a richer tone and enhanced turbo spool and lift-off character
• Excellent value compared to full systems while retaining OE tips and simplicity
• Made to order by CSK Exhaust with a 12 month manufacturer warranty

Key details

• Product: CSK axle-back straight pipe for M135i
• Compatibility: BMW 1 Series M135i F20 5 door and F21 3 door, N55
• Part number: CSK001
• Material: 304 stainless steel
• Manufacturing: TIG welded, back purged
• Dimensions: 97 x 22 x 50 cm
• Weight: 6.35 kg
• Warranty: One year CSK manufacturer warranty
• Made to order. Please allow manufacturing time

Vehicle fitment

• BMW 1 Series F20 M135i 5 door hatchback N55 from April 2011 to present
• BMW 1 Series F21 M135i 3 door hatchback N55 from December 2011 to present

Hear it

Factory system vs CSK CSK001 axle-back

Fitting and support

Professional installation is strongly recommended. MJ Modifications offers fitting in Warwickshire. To request a quote, email info@mjmodifications.co.uk.

We perform a compatibility check before dispatch. Add your UK registration or the last 7 digits of your VIN at checkout.

Please ensure the part is fitted by a professional. If it does not fit perfectly, remove and return it before starting the vehicle.

Search-friendly terms

BMW M135i axle back, M135i straight pipe rear section, BMW 1 Series M135i sound upgrade, F20 M135i tail section pipe, F21 M135i tailpipe section, N55 M135i exhaust mod UK, stainless 304 M135i axleback, CSK exhaust pipe M135i, M135i louder exhaust option, hot hatch performance exhaust M135i, direct fit rear section M135i, UK supplier BMW M135i exhaust pipe, M135i turbo spool sound, M135i pops and crackles rear section, performance tail section BMW 1 Series M135i.

Manufactured by

CSK Exhaust