The Mavic Open 4 CD is an extremely popular 700c clincher rim used by many, many road bike riders including a few that work here. The Open 4 is a "U" shape with sidewalls sloping out and upward from a narrower spoke bed wall achieving a flat sidewall for a braking surface for the upper third of the wall height. Each of the walls for this extrusion including the cross-tie wall exhibit a thin, delicate stability. Again, this rim's metallurgical composition remains a Mavic kept secret.
The Open 4 CD has Mavic's "couche dure", hard anodized Grey finish for a surface treatment. The hard anodizing is done after the rim has been rolled and joined into its hoop shape, and after it has been drilled for the spoke and valve holes. The ends of the rolled hoop are joined using an aluminum insert into the cavity between the cross-tie and spoke bed walls of the rim. It uses the rim ends as a "sleeve" to hold and retain the inner aluminum core. The joint holds the ends rigidly together, though we have noticed an occasional, small misalignment, raising one edge slightly, just a tiny bit, that the brake pad may grab.
The Open 4 CD uses two-piece, double wall stainless steel eyelets to prevent spoke nipple pull through rim failure. Both eyelet pieces are stamped from sheet stainless steel, the upper eyelet piece is cup shaped, while the lower eyelet piece takes the form of a hollow rivet.
The upper cupped shaped piece is taller in the Open 4 than other rims because of the section height of the rim and the distance between the cross-tie and spoke bed walls. The upper piece, having an oval flange, is inserted into the spoke hole from the interior, or tire side. The lower piece is set into the upper cup piece, with the lower piece protruding though the spoke bed wall. Force is applied to the top of the lower piece so a mandrel at the hub facing side of the spoke bed wall can flare the lower piece into a smooth round blossom that now holds both eyelet pieces firmly within the outer walls of the cross-tie and spoke bed walls. The spoke bed wall on the Open 4 CD showed no post machining distortion from this peening process. More specifics about the Open 4 CD are available in the Rim Table.
Open 4 CD 700c (Hole-28-32-36) MAVIC MODULE 3 CD
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