Summary
Reach is a fundamental bicycle geometry measurement that captures the horizontal distance from the center of the bottom bracket to the top-center of the head tube. It directly affects how stretched out a rider feels when standing and is one of the most reliable predictors of how a bike will handle—especially on technical terrain or at speed. Alongside stack, reach defines the spatial layout of a frame’s fit, and plays a major role in bike sizing, handling dynamics, and cockpit setup.
Key Facts
- Introduced: Entered common usage in geometry charts in the early 2010s
- Category: Concept
- Also known as: Front-center reach, BB-to-head reach
- Used by / Found on: All modern mountain, gravel, and road bikes
- Unit: Millimeters (mm)
- Measured on: Frame only, as a static dimension
- Influences: Fit while standing, cockpit length, bike stability and maneuverability
Overview
Reach measures how long a bike feels when you’re standing up on the pedals, rather than sitting in the saddle. It is defined as the horizontal distance from the center of the bottom bracket to an imaginary vertical line that runs through the center of the top of the head tube. This makes it one of the most direct and consistent ways to assess frame length, unaffected by angles or rider position.
The term rose to prominence in mountain biking as geometry trends evolved—particularly with the shift toward longer frames, slacker head angles, and shorter stems. As riders pushed into steeper terrain and higher speeds, traditional measurements like top tube length became less useful for describing ride feel. Reach provided a more accurate metric for determining whether a bike would feel roomy, cramped, stable, or twitchy.
While reach began as a mountain biking metric, it has steadily gained relevance in gravel, cyclocross, and even road bike design, especially as riders demand more clarity in fit across increasingly diverse platforms. It now plays a central role in sizing decisions and cockpit setup, particularly for performance and off-road-oriented riding.
How It Works
Reach describes how far forward the bike’s head tube—and by extension, the handlebars—sit in relation to the bottom bracket. Unlike effective top tube length, reach is not influenced by seat tube angle or saddle setback, and provides a stable reference across different frame shapes and use cases.
1. Measurement Method
To measure reach:
- Draw a vertical line upward from the center of the bottom bracket
- Then measure the horizontal distance from that line to the center-top of the head tube
This forms a right triangle with stack as the vertical leg and reach as the horizontal leg. The result is a geometry value that is unaffected by the slope of the top tube, stem length, or saddle position—making it an especially reliable frame measurement.
2. Fit Relevance
Reach is crucial for understanding how a bike fits when the rider is out of the saddle, such as when climbing steep terrain, descending, or sprinting. This makes it especially valuable for disciplines where rider movement is dynamic and weight distribution is critical.
In contrast to top tube length—which can change depending on seat angle or rider setup—reach provides a fixed measurement of how far forward the cockpit sits in relation to the rider’s feet.
3. Frame Sizing Implications
Reach values increase with frame size, though the actual numbers vary depending on brand and category. Typical examples:
| Frame Size | Trail/Gravel | Enduro/Downhill |
|---|---|---|
| Small | 400–430 mm | 420–450 mm |
| Medium | 440–460 mm | 460–490 mm |
| Large | 470–490 mm | 490–520 mm |
| XL | 500–530+ mm | 520–550 mm |
While not a complete sizing tool on its own, reach helps riders decide whether a frame will allow enough room to move, or whether it will feel too short and cramped, especially in aggressive riding scenarios.
4. Relationship to Other Geometry Metrics
Reach should always be considered in relation to:
- Stack: The vertical partner to reach; together, they define how upright or aggressive the frame is
- Head Angle: Slacker head tubes reduce effective reach unless top tube length compensates
- Seat Tube Angle: Steeper seat angles bring the saddle forward but don’t affect reach
- Stem and Bar Setup: Although reach is measured at the frame level, stem length and bar sweep influence actual reach to the grips and can be tuned post-purchase
Impact on Fit & Handling
Fit and Comfort
- Longer reach provides more space for the rider’s upper body to move forward and back, enhancing comfort, control, and front-rear weight balance
- Shorter reach puts the handlebars closer to the rider, often resulting in a more upright stance but potentially reducing maneuvering space
It affects how stretched a rider feels especially while standing—which is key in mountain biking and gravel, but increasingly important in road fit as cockpit setups get more integrated and sizing needs become more nuanced.
Handling Dynamics
- Long Reach = Stability: Extends the wheelbase, improves balance at high speed, and helps riders stay centered on steep descents
- Short Reach = Agility: Allows for quicker weight shifts and tighter cornering, but may feel unstable on fast or steep terrain
- Reach + Stack balance allows riders to match posture to purpose—whether that’s tucked for racing, upright for comfort, or neutral for all-round control
Notable Use Cases
- Trail Bikes (e.g., Trek Fuel EX, Santa Cruz Tallboy): Mid-range reach (~440–470 mm in M/L sizes) for a balanced mix of climbing comfort and descending confidence
- Enduro Platforms (e.g., Specialized Enduro, Canyon Strive): Longer reach (~470–510 mm) supports high-speed descending and modern short-stem setups
- Downhill Bikes (e.g., Commencal Supreme DH): Extremely long reach (~510–540 mm) for stability on aggressive terrain
- XC Bikes (e.g., Orbea Oiz, Scott Spark): Slightly shorter reach for nimble, race-oriented handling and in-the-saddle pedaling efficiency
- Gravel Bikes (e.g., Salsa Warbird, Open U.P.): Reach values tuned to maintain comfort and control across varied terrain, often combined with high stack for upright posture during long rides
Related Terms
- Stack
- Wheelbase
- Top Tube Length
- Head Tube Angle
- Rider Position
References
- Trek Bikes Geometry Glossary
- Specialized Geometry Tech Sheets
- Pinkbike: “Geometry 101: What is Reach?”
- BikeRadar: “How Reach Affects Handling”
- Santa Cruz Bicycles Fit Guides
- Transition Bikes Geometry Comparison Tool
- Norco Ride Aligned Fit System