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Dropout – No 40: The Ultimate Guide to BMC’s Reliable Derailleur Hanger for Peak Performance

If you’re a cycling enthusiast who owns a BMC bike, you’ve likely encountered the need for reliable spare parts to keep your ride smooth and efficient. One such essential component is the Dropout – No 40, a specialized rear derailleur hanger designed specifically for select BMC models. In this comprehensive guide, we’ll dive deep into everything you need to know about the Dropout – No 40, from its features and compatibility to installation tips and maintenance advice. Whether you’re a seasoned mechanic or a weekend rider looking to upgrade your setup, this article will help you understand why this part is crucial for maintaining optimal gear shifting and frame protection.

Understanding Derailleur Hangers: Why They Matter in Cycling

Before we zoom in on the Dropout – No 40, let’s take a step back and explain what a derailleur hanger is and why it’s so important. A derailleur hanger, often called a dropout or gear hanger, is a small but vital piece of metal that attaches the rear derailleur to your bike’s frame. It’s designed to be the “weak link” in your drivetrain system – meaning it’s meant to bend or break in the event of an impact, protecting your more expensive frame and derailleur from damage.

In the world of high-performance cycling, especially with brands like BMC known for their precision engineering, having the right hanger ensures smooth gear changes, proper chain alignment, and overall bike longevity. Without a properly functioning hanger, you might experience skipping gears, noisy shifting, or even complete drivetrain failure during a ride. That’s where specialized parts like the Dropout – No 40 come into play, offering a perfect fit for BMC’s innovative bike designs.

Bicycle dropouts | The different types and features explained | BikeRadar

This image shows a typical bicycle rear dropout in action, highlighting how the hanger integrates with the derailleur and chain for seamless performance.

What Is the Dropout – No 40? A Detailed Overview

The Dropout – No 40 is an official spare part from BMC Switzerland, cataloged under SKU 212486. It’s a black anodized rear derailleur hanger crafted for durability and precise fitment. Typically made from high-strength aluminum alloy (though BMC doesn’t specify the exact material in public listings, it’s standard for such components to use 6061-T6 aluminum for its balance of strength and lightweight properties), this hanger is engineered to withstand the rigors of road and time-trial cycling.

Key features include:

• Compact Design: The Dropout – No 40 has a sleek, minimalist shape that aligns perfectly with BMC’s aerodynamic frames.
• Threaded Mounting Points: It includes pre-threaded holes for easy attachment of the derailleur, often coming with or requiring M3x10 flat-head screws.
• Protective Role: As a sacrificial part, it absorbs impacts from crashes or debris, preventing costly frame repairs.
• Color and Finish: Available in black, which matches the aesthetic of many BMC bikes for a seamless look.

Priced affordably at around CHF 19.00 (approximately $22 USD, depending on exchange rates), it’s an accessible replacement that doesn’t compromise on quality. According to BMC’s official site, the package includes one rear derailleur hanger, and it’s readily available in stock for quick shipping. This makes it a go-to choice for riders who prioritize original equipment manufacturer (OEM) parts over aftermarket alternatives.

Dropout – No 40 Black – BMC Switzerland AG

Here’s a close-up of the Dropout – No 40 itself, showcasing its precise machining and black finish.

Compatibility: Which BMC Bikes Use the Dropout – No 40?

One of the most critical aspects when shopping for bike parts is ensuring compatibility. The Dropout – No 40 is specifically designed for certain BMC models, focusing on their time-trial and road-oriented lineup. Based on official documentation, it’s compatible with:

• MY15-18 Timemachine TMR01
• MY15-18 Timemachine TMR02
• MY16 Speedfox 02 (noted in some retailer listings for additional versatility)

These models are part of BMC’s high-end range, known for their carbon fiber frames and aerodynamic profiles. The Timemachine series, in particular, is favored by triathletes and time-trial specialists for its speed-focused geometry. If you own one of these bikes, the Dropout – No 40 is the exact match to restore your shifting precision.

For a broader context, similar hangers (like those labeled #40 in other brands) might fit Marin or Polygon bikes, but for BMC owners, sticking with the original ensures perfect alignment. Always check your bike’s model year and serial number against BMC’s mechanical support resources to confirm fitment.

If your bike isn’t listed, BMC offers a spare parts list PDF for MY2020 and beyond, which can help identify alternatives. For older models, consulting a local BMC dealer is recommended.

BMC Teammachine R 01 Five Bike Cool White / Black / 56cm

An example of a BMC Teammachine bike, which shares design ethos with the compatible Timemachine models.

Why Replace Your Derailleur Hanger with the Dropout – No 40?

Derailleur hangers don’t last forever. Common reasons for replacement include:

• Accidents and Impacts: A fall or hitting a rock can bend the hanger, leading to poor shifting.
• Wear and Tear: Over time, constant chain movement can cause fatigue.
• Upgrades: If you’re switching to a new derailleur, a fresh hanger ensures compatibility.

Opting for the Dropout – No 40 provides several benefits:

• Improved Shifting Accuracy: Its precise design maintains chain line, reducing ghost shifting.
• Frame Protection: By sacrificing itself, it saves your expensive carbon frame from cracks.
• Cost-Effective: At under $25, it’s cheaper than repairing a damaged frame.
• OEM Quality: BMC’s engineering standards mean it’s built to the same specs as your original part.

Riders often report smoother performance post-replacement, especially on demanding terrains like hills or sprints.

Step-by-Step Guide: How to Install the Dropout – No 40

Installing the Dropout – No 40 is a straightforward DIY task if you have basic tools. Here’s a detailed guide:

1. Gather Tools: You’ll need a 4mm or 5mm Allen key (depending on your bike), threadlocker (like Loctite blue), and possibly a torque wrench.
2. Remove the Old Hanger: Shift to the smallest cog, remove the rear wheel, and unscrew the derailleur from the hanger. Then, remove the hanger bolts from the frame.
3. Clean the Area: Wipe down the frame’s mounting points to remove dirt or old threadlocker.
4. Attach the New Dropout – No 40: Align the hanger with the frame’s slots. Apply threadlocker to the bolts and tighten to 5-7 Nm (check your bike’s manual for exact torque).
5. Reattach the Derailleur: Screw the derailleur back on, ensuring it’s straight. Reinstall the wheel and test shift through all gears.
6. Adjust if Needed: Use barrel adjusters to fine-tune shifting.

Safety tip: If you’re unsure, visit a professional bike shop to avoid misalignment issues.

Rear dropout with adjustments screws of a single speed bicycle – Bicycles Stack Exchange

This image illustrates a rear dropout during installation, with adjustment screws for precise chain tension.

Maintenance Tips for Longevity

To get the most out of your Dropout – No 40:

• Regular Inspections: Check for bends or cracks after every few rides, especially off-road.
• Cleanliness: Keep the area free of mud and grime to prevent corrosion.
• Lubrication: Lightly oil the pivot points, but avoid over-lubricating to prevent attracting dirt.
• Storage: When not riding, store your bike in a dry place to minimize wear.
• Professional Tune-Ups: Schedule annual servicing to catch issues early.

Following these practices can extend the life of your hanger and overall drivetrain.

2024 BMC TeamMachine R 01 Three 12 Speed Disc Road Bike

A full view of a modern BMC road bike, emphasizing the integrated design where the Dropout – No 40 plays a key role.

Where to Buy the Dropout – No 40 and Alternatives

You can purchase the Dropout – No 40 directly from BMC’s online store or authorized dealers. Prices hover around CHF 19.00, with shipping available worldwide. For alternatives, third-party manufacturers like Wheels Manufacturing offer compatible hangers (e.g., Dropout-444 for similar fits), often at similar prices but with CNC-machined precision.

If you’re looking on marketplaces like eBay, ensure the seller specifies BMC compatibility to avoid mismatches.

Conclusion: Elevate Your Ride with the Dropout – No 40

The Dropout – No 40 might seem like a small part, but it’s a cornerstone of your BMC bike’s performance. By understanding its role, compatibility, and maintenance, you can keep your rides enjoyable and trouble-free. Whether you’re prepping for a triathlon or daily commutes, investing in quality spares like this ensures reliability. If you have experiences with the Dropout – No 40 or questions, share them in the comments below – happy cycling!