There are two note worthy rim makers in Japan, Araya and Ukai. They are note worthy because each of them has had their rims sold as original equipment on new bicycles and at one point both had their rims sold in the US as after market replacement parts. Both are well known for excellent quality and workmanship, however, at the moment, only Araya seems to have rims available in the US for after market replacements.
Ukai's participation in the United States parts distribution system dropped off beginning in the fall of 1987, after the G7 meeting drove the value of the dollar down and Japanese goods edged their way toward double the Yen price. Ukai is reported to have been the maker of the Specialized and also made the Ritchey rims that are sold on new bikes as original equipment. The Ukai manufactured Ritchey rims can be identified bt their welded rather than sleeved joint.
Right: Sectional View of Araya joint.
Both of these rim makers sell their goods through importer/distributors who have to make a value judgement in terms of what they think will sell to retailers in a reasonable period of time. The importer/distributor then places an order through a Japanese export trading company for delivery 90 to 120 days in the future. If they predict wrong they will have an overstock, tying up their capital. By nature, these organizations, when it comes to bulky items like rims, buy very conservatively which leads to occasional stateside shortages of either models, colors, or drillings.
The RM-17 uses a Box shape extrusion of aluminum alloy as the basis for the rim. The series of aluminum alloy used isn't known. The double walled rim doesn't use steel eyelets to relieve spoke nipple stress and possible nipple pull through, but instead relies on added aluminum thickness in the spoke bed wall. The sidewalls of the RM-17 has a slight concave shape to it in the area of brake pad contact.
Once the extrusion has been rolled into the rim's hoop shape the ends are TIG welded together. The extra aluminum material, from the weld, inside the rim between the sidewalls is stripped away with a grinder. The exterior three sides, the outer sidewall and hub facing side are machined then polished removing all physical trace of the weld on the surface, leaving just smooth continuous rim sidewall for brake pad contact. Like the RM-20, the only evidence of the weld, is a slight, almost imperceptible, discoloration, within the smooth surface, at the joint from either the heat or the wire feed's alloy composition. After the hoop has been polished, it's drilled for the spoke nipple and valve holes, then anodized.
The rim is Clear anodized to leave it in a Silver color or hard anodized to the customary Grey color. We sell the 26" diameter RM-17 in either a 32 or 36 spoke hole drilling to accommodate a Schrader valve. For more specifics, please consult the Rim table.