2021 Bird Bikes Zero 29 Base

	Medium	Medium Long	Large	Extra Large
Stack	637mm	646mm	655mm	664mm
Reach	437mm	460mm	482mm	504mm
Stack to Reach Ratio	1.46:1	1.4:1	1.36:1	1.32:1
Seat Tube Length, C-T	395mm	420mm	445mm	470mm
Top Tube Length, Effective/Horizontal HT Top	606mm	631mm	656mm	681mm
Head Tube Angle	63.9deg	63.9deg	63.9deg	63.9deg
Effective Seat Tube Angle, ETT HT Top	73.6deg	73.6deg	73.6deg	73.6deg
Head Tube Length	110mm	120mm	130mm	140mm
Bottom Bracket Drop	67.8mm	67.8mm	67.8mm	67.8mm
Bottom Bracket Height	306.7mm	306.7mm	306.7mm	306.7mm
Chainstay Length	435mm	435mm	440mm	440mm
Chainstay Length Horizontal	429.7mm	429.7mm	434.7mm	434.7mm
Front-Center	747.4mm	774.3mm	801.1mm	828mm
Front-Center Horizontal	744.3mm	771.3mm	798.3mm	825.3mm
Wheelbase	1174mm	1201mm	1233mm	1260mm
Fork Offset/Rake	42mm	42mm	42mm	42mm
Fork Length, Unknown	541mm	541mm	541mm	541mm
Trail	136.7mm very high	136.7mm very high	136.7mm very high	136.7mm very high
Mechanical Trail	122.8mm	122.8mm	122.8mm	122.8mm
Wheel Flop	54mm	54mm	54mm	54mm
Tire to Pedal Spindle	202.9mm 170 mm cranks	229.8mm 170 mm cranks	256.6mm 170 mm cranks	283.5mm 170 mm cranks
Pedal Spindle to Ground Clearance	136.7mm 170 mm cranks	136.7mm 170 mm cranks	136.7mm 170 mm cranks	136.7mm 170 mm cranks

Very Upright

Somewhat Upright

Average

Somewhat Aggressive

Very Aggressive

The Bike Insights Upright/Aggressive scale is based on analysis of a bike’s proportions relative to similar sized bikes in the same category.

Category Trend

Source:https://www.bird.bike/wp-content/uploads/2021/09/Zero-29-Mk2-Tech-Sheet.svg

Geometry