Aheadset is a headset structure in which the thread on the headtube has expired.
The bearing clearance is adjusted by moving the steering wheel.
The advantage of aheadsets are quick installation and adjustment with only an Allen key, but the downside is that the stem can not simply be higher or lower.
A relatively recent development, integrated headsets do away with the upper and lower cups on threadless headsets and instead seat the bearings directly against the head tube of the frame. Favored sometimes for their aesthetic appeal, integrated headsets reduce the number of parts involved in the headset assembly. Prominent standards for integrated headsets include Cane Creek’s “IS” and Campagnolo’s standard, which is nameless apart from the manufacturer name.
Chris King, a leading headset manufacturer, offers a vehement argument against the implementation of integrated headsets. The basis of King’s argument is that headtubes with bearing “seats” are far from being machined with reasonable precision. The headset cartridge bearings therefore sit somewhat loosely in the headtube of the bicycle (as opposed to being press fit). During use, the bearings, under thrust loads, will rock in their seats and will easily damage the softer frame material (often aluminum, although some titanium frames are manufactured for integrated headsets). Given enough damage to the frame, there would be no choice but to replace the frame, especially if the frame is made of an aluminum alloy (titanium and steel can potentially be repaired, but usually at great cost to the consumer). King also argues that the integrated headset is largely a cost-cutting measure for many of the larger bicycle manufacturers, since integrated headsets are somewhat cheaper and take less time to install.