Q. What’s the deal with 44mm headtubes?


44mm head tubes have been around for quite a while- they’re commonly called Zero Stack (ZS) or Semi-Integrated (SI). Its only since around 2013 that headset manufacturers have taken full advantage of their versatility, offering external cups to accommodate straight 1 1/8″, 1 1/4″, tapered, and straight 1.5″ steerers. On a straight 1 1/8″ steerer you can even run an offset headset. Its become particularly popular on steel framed bikes because of its versatility, and it fits the frame tubes much better than a 1.5″ or larger head tube does.

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