The Subsonic Ergo 39a is a low-stack clip-on aerobar built around Profile Design’s Subsonic bracket to help riders achieve lower, narrower positions than typical clip-on systems. The design is intended to improve aerodynamics by keeping stack height low without the added frontal area associated with below-the-basebar extension clamping. Paired with Profile Design’s Ergo armrests and 39a extensions, this system is geared toward fine-tuning fit while maintaining a consistent pad-to-grip relationship as stack height is increased.
Key Features
Low-stack Subsonic bracket designed to achieve a lower arm-pad height than standard aerobars
Designed to avoid the added frontal area of a below-the-basebar extension clamping system
Bracket is compatible with Profile Design riser kits to increase stack without changing the pad-to-grip relationship
Ergo armrests are designed to tightly cup the rider’s arms to facilitate a narrow position and increase control at speed
39a extensions described with a 39 degree angle and 87 mm rise
Extension rotation is adjustable using the shaft bolt
After cutting the extensions, there is a stated 40 mm range of extension length adjustment
Stated adjustability includes 80 armrest-position options, and 1200 possible configurations when combined with risers
Clip-on format also allows extension width and tilt to be adjusted
Specs
Bracket: Subsonic
Clamp Diameter: 31.8 mm (26.0 mm with Shim Kit; Shim Kit is sold separately)
Armrest: Ergo / 10 mm Pads
Extension Length: 340 mm
Width: 142 mm to 272 mm
Weight: 590 g
Color: Black
Fit Data
Armrest offset: -85 mm to -17.5 mm in 7.5 mm steps
Armrest width: 142 mm to 272 mm in 18.5 mm steps (with extensions at 100 mm)
Armrest stack: minimum 40 mm; compatible with existing risers adding up to 70 mm of stack in 5 mm increments
Compatibility/Fit Notes
Designed for 31.8 mm handlebar clamp diameter
26.0 mm compatibility requires a Shim Kit (sold separately)
Compatible with Profile Design riser kits as noted above
Notes
Manufacturer torque settings: Bar Clamp 6 Nm, Extension Clamp 5 Nm, Armrest Bolts 4.7 Nm
Weight breakdown (manufacturer): Bracket 304 g, Armrest 148 g, Extensions 186 g, Total 590 g
