Bike Forums - View Single Post - So why does Cinelli not make quill stems (again)?

01-13-11 | 09:45 AM

#11

SJX426

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Joined: May 2008

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From: Fredericksburg, Va

Bikes: ? Proteous, '65 Frejus TDF, '73 Bottecchia Giro d'Italia, '83 Colnago Superissimo, '84 Trek 610, '84 Trek 760, '88 Pinarello Veneto, '88 De Rosa Pro, '89 Pinarello Montello, 'Litespeed Catalyst'94 Burley Duet, 97 Specialized RockHopper, 2010 Langster

No.
I really don't see a difference functionally. The expander nut is probably less expensive to make and allows for the bolt to be axially aligned. The expansion is nearly 360 degrees minus the slots providing a uniform distribution of force against the steerer. Also the force tends to be a radial line normal to the axis of the tube. This may allow for a higher force applied to the steerer. It also may cause deformation to the edge of the stem opening. The stem can be cut normal to the axis and the slots easily cut into the tube.

The wedge and the tube have to be at the same angle, or nearly so for distribution of mating surface. This requires two surfaces to be created not at 90 degrees (fixturing required to create angle - $). The forces are opposite each other and along the axis of the tube resulting in a force vectors parallel to the axis and a longer line of force compared to the cylindrical one of the expander nut. The axis of the bolt is retained but the cylindrical shape becomes much like an ellipse. The overall length of the tube needs to be longer to account for the angle, requiring more material - $.

In either case, if the stem OD is off slightly from the ID of steerer, creaking can occur. I have not had that problem with Cinelli's but with 3TTT to the point of significant deformation at the end of the steerer tube.

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