2026 Principia Gravel 20 Base

	45cm	50cm	55cm	61cm
Stack	575.8mm	598.8mm	624.5mm	663.9mm
Reach	397.3mm	399mm	397.4mm	410.9mm
Stack to Reach Ratio	1.45:1	1.5:1	1.57:1	1.62:1
Seat Tube Length, C-T	450mm	500mm	550mm	610mm
Top Tube Length, Effective/Horizontal Center	557mm	565mm	570mm	595mm
Top Tube Slope	15.4deg	12.4deg	9.9deg	7.6deg
Head Tube Angle	70deg	71deg	71.5deg	73deg
Seat Tube Angle	74.5deg	74.5deg	74.5deg	74.5deg
Head Tube Length	135mm	155mm	180mm	215mm
Bottom Bracket Drop	67mm	67mm	67mm	67mm
Bottom Bracket Height	289mm	289mm	289mm	289mm
Chainstay Length	435mm	435mm	435mm	435mm
Chainstay Length Horizontal	429.8mm	429.8mm	429.8mm	429.8mm
Front-Center	633.7mm	633.7mm	634.8mm	644.3mm
Front-Center Horizontal	630.7mm	630.7mm	631.8mm	641.4mm
Wheelbase	1060.5mm	1060.5mm	1061.6mm	1071.2mm
Fork Offset/Rake	45mm	45mm	45mm	45mm
Fork Length, Unknown	425mm	425mm	425mm	425mm
Trail	81.7mm very high	75mm high	71.7mm high	61.8mm mid/neutral
Mechanical Trail	76.8mm	70.9mm	68mm	59.1mm
Wheel Flop	26.3mm	23.1mm	21.6mm	17.3mm
Tire to Pedal Spindle	107.7mm 170 mm cranks	107.7mm 170 mm cranks	108.8mm 170 mm cranks	118.3mm 170 mm cranks
Pedal Spindle to Ground Clearance	119mm 170 mm cranks	119mm 170 mm cranks	119mm 170 mm cranks	119mm 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://principiabikes.com/gravel/gravel-aluminium/gravel-20---grey-pg-2591

Geometry