The Challenging Journey of Transforming a Chinese MTB Frame into a Gravel Bike

Unveiling the DIY Gravel Bike: A Journey of Conversion and Compromise

The Evolving Landscape of Gravel Biking and a DIY Experiment

Gravel cycling is experiencing a dynamic transformation, with a growing emphasis on wider tires and diverse geometries, catering to both speed-focused racing and adventurous exploration. Amidst rising prices for pre-built gravel bikes, some enthusiasts believe that modern gravel designs share characteristics with older hardtail mountain bikes. This article recounts an ambitious project to construct a gravel bike from a Chinese mountain bike frame, aiming to create a capable machine at a reduced cost.

Initial Vision and the Foundation of the Build

The primary objectives for this custom build were to achieve a lightweight bicycle with a comfortable yet agile geometry, all while adhering to a strict budget. The project's cornerstone was a carbon XC frame, the Airwolf T1100, directly acquired from a Chinese supplier. This frame, along with a rigid fork and carbon seatpost, formed the base. While the frame itself was remarkably light, weighing only 990g, some of the accompanying hardware, such as bolts and seatpost clamp, proved to be of lower quality, posing early challenges.

Early Successes and the Quest for a Drop-Bar Machine

Initially assembled with standard mountain bike components, including XC tires and a narrower flat handlebar, the bike demonstrated impressive performance in local cyclocross races, securing respectable finishes. This early success fueled the ambition to transform the setup into a dedicated drop-bar gravel machine. The author embarked on this conversion with the hope of achieving a high-performance bike at a lower cost than purchasing a complete, off-the-shelf option, though acknowledging the potential for significant effort and unexpected complications.

Addressing Chainring Size and Clearance Limitations

A significant hurdle encountered was the compatibility of chainring sizes. While most gravel bikes accommodate 38-tooth or larger chainrings, the 73mm bottom bracket shell of the chosen mountain bike frame restricted options to mountain bike chainsets. The maximum chainring size that could be fitted was 36-tooth, a limitation that even some XC mountain bike frames might face. This presented a compromise for achieving higher gears, prompting considerations for alternative cassettes to optimize gearing ratios.

The Impact of Fork Height on Bike Geometry

Fork height, measured as axle-to-crown, plays a crucial role in a bike's geometry. The Airwolf frame's design was based on a 506mm axle-to-crown fork, typical for a 100mm suspension fork. However, the carbon fork supplied with the frame had a shorter axle-to-crown of 485mm, accounting for suspension sag. A further reduction to 470mm with a second-hand ENVE rigid fork intentionally altered the bike's geometry. This change resulted in a steeper head angle, seat tube angle, increased reach, and a lower bottom bracket, significantly affecting the bike's handling characteristics.

Navigating the Labyrinth of Component Standards

The cycling industry is notorious for its myriad of non-standardized components, a complexity amplified when attempting to blend mountain bike and gravel parts. Issues arose with axle widths, brake mounts, and gearing systems. Adapters were necessary for wheel compatibility, and post-mount brakes on the frame and fork clashed with the flat-mount standard of most modern gravel groupsets. The solution involved sourcing older, compatible components and carefully considering fluid types for hydraulic brakes. SRAM AXS components offered a more straightforward approach to mixing drivetrain parts due to their modular design.

Optimizing Reach for an Ergonomic Riding Position

Beyond numerical specifications, the actual feel and fit of the bike are paramount. Mountain bikes typically feature longer reach and top tube lengths due to their design around flat, wide handlebars and shorter stems. This necessitated considering a smaller frame size as a starting point for the gravel conversion. Additionally, the specific brake and shifter units influence reach, with newer models potentially having longer dimensions, requiring careful selection to achieve an optimal riding position.

Assessing Frame Space for Bikepacking and Adventures

For riders planning bikepacking trips or extended adventures, internal frame space for bottles and bags is a critical factor. Mountain bike frames generally offer less internal volume compared to dedicated gravel framesets, a characteristic that becomes even more pronounced when opting for a smaller frame size to achieve desired geometry for a gravel build. This limitation impacts the capacity for carrying essential gear on longer journeys.

The Cumulative Costs of Customization

What might initially appear as a cost-effective starting point with a cheap frame can quickly escalate due to the myriad of necessary modifications. Brake adapters, axle spacers, and new hydraulic cables and fittings all contribute to the overall expense. Even with a collection of spare parts, smaller, specific components are often required to complete the build, potentially negating some of the initial cost savings.

Evaluating the Ride Experience of the Converted Bike

After extensive adjustments and numerous false starts, the converted bike presented a distinct, albeit compromised, riding experience. While it could serve certain purposes, it fell short of the performance offered by purpose-built gravel alternatives. The front end remained noticeably high, even with a shorter fork and aggressive stem, leading to slower handling in corners. Despite efforts to optimize weight distribution, the reach and front-center remained long, resulting in a unique, somewhat unconventional feel. However, one benefit was the complete absence of toe-overlap, an issue often encountered with gravel bikes using wider tires.

The Role of Tire Quality in Gravel Performance

The effectiveness of wider tires in gravel riding is heavily dependent on their quality and construction. The article highlights that merely having wide tires is insufficient; premium models with supple carcasses, fast rubber compounds, and reasonable weight are crucial for optimal performance. Basic or cheaper mountain bike tires will not yield the same benefits. As gravel tire trends lean towards wider options, and some mountain bike tires are adapted for gravel use, the emphasis remains on high-quality construction for speed and efficiency.

Comparing DIY to Off-the-Shelf Options

For those who relish the intricate process of building and fine-tuning a bike, the DIY conversion can be a rewarding experience. However, for most riders, purchasing a complete, purpose-built gravel bike is likely more cost-effective and less time-consuming. While a custom build from a Chinese MTB frame can be assembled for around £1,100 (excluding some components), the Whyte Verro, a well-regarded gravel bike, costs £1,799 and offers a comprehensive, integrated package without the inherent compromises of a conversion. The author concludes that for adventure-oriented riding, a DIY project might suffice, but for racing or performance-driven cycling, a dedicated gravel bike remains the superior choice.

Reflections and Future Considerations for DIY Builds

If embarking on a similar project again, the author suggests starting with a 29er hardtail frameset featuring a 142x12mm rear end and a geometry that was considered slack for its era. This approach would mitigate the risk of an overly steep head angle when using a shorter fork. The importance of flexible wheel hubs, such as the DT Swiss 240, which can be adapted to various setups, is also emphasized to avoid the inconvenience of axle spacers. Diligent searching for older, discontinued products can yield suitable components. The overarching advice is to anticipate challenges and accept that some compromises are inevitable in a custom build.

Identifying the Ideal Candidate for a Custom Gravel Bike Project

This type of DIY project is best suited for individuals with a strong understanding of bike geometry and mechanics, coupled with the confidence to build a bike from scratch. It requires a willingness to invest time in sourcing specific parts and a patient, iterative approach to tweaking and adjusting components. Such a project is particularly appealing to riders prioritizing adventure, exploration, and general riding over competitive racing, especially those adept at finding bargains in the second-hand market. Ultimately, it caters to those who value the process of customization and are prepared to manage the inherent compromises to achieve a personalized riding experienc