Add Bike Geometry
Target Handlebar Height
Adjust to your preferred handlebar height to see how effective reach changes
Understanding Bike Geometry
Why Head Tube Angle Matters
The head tube angle determines how the front end of your bike is positioned. As you raise your handlebars (increase stack) by adding spacers or using a higher-rise stem, the angled head tube causes the horizontal distance to the bars (reach) to decrease.
The Math Behind It
For every 10mm of added stack height above the frame's stack measurement, you lose approximately 4-5mm of reach on most mountain bikes (with head tube angles between 65-67°). The exact amount depends on the head tube angle: slacker angles cause more reach reduction per unit of stack increase.
Sizing Tips
When comparing bikes, always consider the effective reach at your preferred handlebar height. A bike with longer frame reach but lower stack might actually feel shorter than a bike with shorter frame reach but higher stack, once you set both to the same bar height.
Typical Geometry Ranges
XC (Cross Country)
Head Angle: 67-71° | Reach: 430-460mm | Stack: 600-630mm
Steep angles for efficiency and climbing
Trail
Head Angle: 65-67° | Reach: 450-470mm | Stack: 620-640mm
Balanced geometry for climbing and descending
Enduro
Head Angle: 64-66° | Reach: 460-490mm | Stack: 630-650mm
Slack angles for stability on steep descents