Bicycle Mechanics - Stem sizing question

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Frankie Fixed
05-02-06, 04:34 PM
I would like to buy a track stem for my pista but I am confused about size. I am told I need a 1" threadless stem, but a stem that I have used successfully in the past measures 3/4" where it fits down inside the head tube. I double checked that I was reading the outside scale not the inside scale on my calipers. Can anyone explain this contradiction?

AnthonyG
05-02-06, 04:49 PM
If the stem fits inside the head tube then its the old fashioned threaded system and that's called a quill stem with the fork steerer being attached to the frame without the stem being attached. With a threadless system the fork steerer protudes past the top of the headset and the steerer clamps to the outside of the stem and with this system the steerer/fork isn't attached to the frame without the stem being in place.


Regards, Anthony
HillRider
05-02-06, 05:01 PM
The standard OD for a 1" threaded stem's quill is 22.2 mm. As noted, the 1" dimension (25.4 mm) is the OD of the steerer tube and the quill has to go inside it.