Forumslader Pro V6: The DIY Legend Gets a Professional Overhaul For years, the "Forumslader" has been a cult classic among touring cyclists, randonneurs, and tech-savvy commuters. Born from an online forum discussion (hence the name), it was a DIY solution to a simple problem: most bike computers don't accurately measure low-speed climbing or account for headwinds. The Forumslader Pro V6 is the latest, most refined iteration—turning a hobbyist project into a legitimate, professional-grade cycling instrument. What Is It? At its core, the Forumslader Pro V6 is a wired cycling computer that measures speed, distance, altitude, and—most importantly— current power output (watts) . Unlike standard crank- or pedal-based power meters that cost $500+, the Forumslader calculates power using a different principle: measuring the force applied to the chain. It uses a custom-developed strain gauge integrated into the dropout (rear wheel mounting point) or a chain tension sensor. Combined with wheel speed and cadence, it computes your real-time wattage. Key Features of the V6 The "Pro V6" marks a significant leap from earlier versions (V3, V4, V5):
High-Resolution Color Display: The V6 replaces the old monochrome screens with a modern, sunlight-readable color LCD. Improved Power Accuracy: While not meeting the strict 1-2% tolerance of a $1,500 SRM, the V6 achieves roughly 3-5% accuracy —remarkable for its price and concept. No Calibration Drift: Early versions required frequent zero-offset calibration. The V6 introduces automatic temperature compensation. Integrated Lighting Control: A unique feature: the V6 can automatically control high-end hub dynamo lights (e.g., Supernova, Busch & Müller), switching between daytime running lights and full beam based on ambient light sensors. USB-C & Data Logging: Records rides to internal memory and exports as .fit or .gpx files.
Who Is It For? This is not a device for racers chasing every single watt. It is built for:
Long-Distance Randonneurs (e.g., Paris-Brest-Paris): Battery life is phenomenal (months on two AA batteries, or runs directly off a dynamo hub). No charging stops needed. Touring Cyclists: The display is large, simple, and shows remaining range based on current power consumption. DIY & Open-Source Enthusiasts: The firmware is often open-source, allowing users to tweak algorithms or add new features. Budget-Conscious Power Users: You get power data, navigation cues, and light management for roughly €250–350 (assembled), far less than a Garmin + power meter combo. forumslader pro v6
Installation: The Catch Unlike a Garmin or Wahoo, the Forumslader Pro V6 is not an out-of-the-box solution.
Tools Required: You need basic wheel-building skills or a cooperative bike shop. The strain sensor often requires replacing a wheel axle or modifying a dropout. Wiring: It uses thin, durable cables along the chainstay and down tube. Clean routing is essential. Compatibility: Works best with dynamo hubs (SON, Shimano) and rim brakes. Disc brake compatibility exists but requires specific adapters.
How to Buy One The Forumslader is still a grassroots product. You won't find it on Amazon or REI. Forumslader Pro V6: The DIY Legend Gets a
Primary Source: The official forum at forumslader.de (German language, but Google Translate works). Assembly Options: You can buy a PCB + sensor kit (solder yourself) or a fully pre-assembled "Pro" unit. Lead Times: Because they are batch-produced, expect 4–8 weeks for delivery.
Forumslader Pro V6 vs. The Competition | Feature | Forumslader Pro V6 | Garmin Edge 540 + Power Meter | |---------|--------------------|--------------------------------| | Price | ~€300 | ~€800+ | | Power Accuracy | 3-5% | 1-2% | | Battery | Months / Dynamo | 20-30 hours | | Light Control | Yes (dynamo) | No | | Navigation | Basic (breadcrumb) | Full maps | | Ease of Install | Advanced | Easy | Verdict: A Niche Masterpiece The Forumslader Pro V6 is not for everyone. If you want turn-key simplicity, buy a Garmin. But if you enjoy the intersection of engineering, cycling, and self-reliance , this device is a joy. It offers something no other computer does: permanent power measurement without ever charging a battery, integrated light management, and a direct connection to the soul of your bike. For the dedicated long-hauler, the V6 is less a tool and more a companion. Rating: ★★★★☆ (4.5/5) Deducting half a star only for the installation complexity.
Disclaimer: Forumslader is a community-driven project. Specifications and availability change frequently. Always check the latest threads on forumslader.de before purchasing. What Is It
The Forumslader Pro V6 is widely considered one of the most powerful bicycle dynamo chargers available, specifically designed for high-efficiency energy harvesting. It is a semi-custom product developed by Jens Düring in Germany, often favored by long-distance tourers and ultra-cyclists for its massive power output. Key Features High Power Output: Uses "staged impedance matching" to pull up to 10W from a standard hub dynamo, significantly more than many commercial competitors. Buffer Batteries: Features integrated buffer batteries (e.g., 3 x 700mAh cells) that ensure a stable 5V/3A USB output even when stopped or at low speeds. Smart Connectivity: Includes a Bluetooth module that interfaces with a smartphone app to display real-time data like speed, altitude, battery state, and dynamo power. Versatility: Offers 12V outputs for specialized lighting or other electronics and can even accept solar panel input. Pros and Cons Pros Efficiency: Unmatched energy harvesting at both low and high speeds. Availability: Often involves long wait times and must be ordered via email from the developer. Stability: Buffer batteries prevent "charging start/stop" errors on sensitive smartphones. Weather Resistance: Some users report corrosion if not properly enclosed; an aftermarket water-resistant cap or housing is recommended. Statistics: Detailed data tracking via the dedicated Forumslader app. Complexity: Website and purchasing process can be difficult to navigate for non-German speakers or those unfamiliar with the project. Review Summary
Forumslader Pro V6 is a high-performance bicycle dynamo USB charger designed for long-distance cyclists who need reliable off-grid power. Manufactured in small batches in Germany, it is widely regarded as one of the most efficient and powerful charging solutions on the market. CYCLINGABOUT.com Key Features & Performance Integrated Buffer Battery : Unlike many "direct" chargers, the includes built-in batteries (available in 1.5Ah to 3Ah capacities) that store energy while you ride. This ensures a stable, continuous charge to your devices even when you stop or slow down for steep climbs Efficiency at Speed is optimized for high-power output at higher speeds. For instance, at 25 km/h, it can deliver roughly 7.1W of power, reaching near-peak efficiency of the dynamo hub Form Factors Pro V6 (Inline) : A budget-friendly, standalone version typically housed in a small tube, designed to be tucked into a handlebar bag. : A specialized version designed to fit inside your bike's steerer tube for a clean, integrated look. Note that it requires significant steerer tube length (up to 290mm depending on battery size). Smart Connectivity : It features Bluetooth integration, allowing you to monitor real-time charging statistics, battery levels, and dynamo performance via a smartphone app. Comparison Table: Power Output (approximate) Hub Potential (MPPT) Forumslader V6 Data sourced from CyclingAbout hub power testing. CYCLINGABOUT.com Considerations for Buyers Availability : Because they are produced on a small scale, they can sometimes be difficult to source outside of Europe, and the official website is primarily in German. Installation : The "Pro" version is relatively "plug-and-play," but the "Ahead" version requires specific mechanical dimensions for your bike's fork. Low Speed Trade-off : While highly efficient at cruising speeds, it extracts a lower percentage of available power at very low speeds (walking pace) compared to some specialized low-speed chargers. CYCLINGABOUT.com Are you planning to install this inside your steerer tube , or would you prefer the external bag-mounted
