Theory Threadless Cup Headset

This headset is designed specifically for non-integrated headtube frames that use an external cup (EC) standard. It is compatible with 1 1/8 inch steerer tubes, so please verify that your frame is not an integrated or tapered setup before purchasing.

External Cup (EC) refers to a design where the headset bearings sit outside the headtube of the frame, rather than being pressed inside. This is the traditional standard for many steel and aluminum frames and is generally easier to service or replace than integrated systems.

Yes, you will need a headset press to properly install the cups into your frame without damaging them. While some home mechanics use DIY methods, a dedicated press ensures the cups are seated perfectly square, which is critical for smooth steering.

No, this headset is strictly for 1 1/8 inch straight steerer tubes. It will not accommodate the larger diameter found on tapered forks.

Yes, the headset includes the necessary crown race that presses onto your fork's steerer tube. You will need to ensure your fork is clean and free of old race residue before installing the new one.