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The stack-to-reach ratio is one of the most valuable — yet overlooked — tools in bike fitting. It tells you how upright or aggressive your position will be on a given frame and helps compare geometries across bikes of different sizes, styles, and brands.
Stack = Vertical distance from bottom bracket to top of head tube
Reach = Horizontal distance from bottom bracket to top of head tube
Stack-to-Reach Ratio = Stack ÷ Reach
This gives a normalized indicator of a bike's fit posture — useful across brands and frame sizes.
✅ Higher ratio → More upright, comfort-oriented geometry
✅ Lower ratio → Lower, aggressive, race-style fit
✅ Great for comparing road, gravel, endurance, or touring bikes
✅ Eliminates confusion between inconsistent size labels (like "54 cm" or "M")
Bike Type | Stack-to-Reach Ratio | Fit Style |
---|---|---|
Aero Race Bike | 1.35 – 1.45 | Low, stretched, aggressive |
Standard Road Bike | 1.45 – 1.55 | Balanced performance |
Endurance Road Bike | 1.55 – 1.65+ | Upright, comfort-focused |
Gravel / Touring | 1.60 – 1.75+ | Relaxed and upright |
Flat Bar / Hybrid | 1.70 – 1.90+ | Maximum upright comfort |
💡 For long-distance comfort, aim for 1.55 or higher — ideally 1.60+.
Stack: 580 mm
Reach: 370 mm
S:R = 1.57 → Comfort-oriented for long rides
Stack: 520 mm
Reach: 390 mm
S:R = 1.33 → Aggressive, efficient but less forgiving
Stack: 610 mm
Reach: 360 mm
S:R = 1.69 → Ideal for relaxed posture and long touring days
🔎 Check geometry charts before buying — don’t rely only on frame size labels
📊 Use S:R ratio to compare bikes across brands
🔧 Helps guide decisions on stem length or bar height adjustments
🚲 Especially important for gravel, endurance, and touring riders
If comfort is your top priority — whether for commuting, endurance rides, or multi-day touring — aim for a stack-to-reach ratio of 1.55 or above. It promotes a more upright position that reduces strain on your neck, back, and wrists, especially over long distances.
⚙️ While low-ratio frames work for racing, most riders benefit from a fit that balances performance with all-day comfort — and S:R ratio is the key.