Purple Triathlon / TT Bike Headsets

Measure the head tube top and bottom and the fork steerer crown to confirm inner diameters. Match those measurements to S.H.I.S. codes like ZS44/28.6 or EC44/40, and note that models like the Cane Creek 40-Series use a ZS44/28.6 upper cup to ensure proper seating and avoid binding.

Zero Stack works best on low-stack aero TT frames where a flush ZS44/28.6 upper keeps bars low and aerodynamic. External Cup offers a versatile replacement option using EC44/40 lowers, while Integrated headsets demand exact frame matching on seamless carbon TT frames for a clean look.

For paved, high-speed TT riding, sealed cartridge bearings keep rotation smooth under preload and resist contamination. Stainless steel 6902-sized cartridges paired with aluminum or carbon cups save weight, and high-end options like the Chris King DropSet use oversized cartridge bearings for ultra-smooth, low-play feel.

Stack height directly affects where your handlebars sit relative to the frame, so small stack changes noticeably alter an aggressive TT position. Integrated standards like IS41 have defined top/base stack dimensions (about 3.1–3.2mm top, 6.9–7mm base), and mixing a ZS upper with an EC lower is a common way to fine-tune stack without changing the frame.

Yes, many TT headsets include rotation limiters to prevent over-steer and semi-integrated cable routing designed for aero cockpits. Models such as the Funn Descend (ZS44/28.6 | EC44/40) emphasize robust sealing and routing compatibility, helping keep bearings protected during sustained aero riding.