Wheelbuilding Notebook: Sun CR-18 Rims (26 inch, 590mm) for Schwinn Three Speeds

 Several times in the past, I've written about using Sun CR-18 rims to spice up vintage Schwinn three speed bikes. Vintage Schwinn bikes usually use 597mm rims (S5, S6 sizes), a different size from the normal 590mm  (26 x 1-3/8) rims used by English bikes.

However, many Schwinn three speeds have calipers that will reach far enough to use the slightly smaller and more common 590mm 26 x 1-3/8 rims. 

For example, I used CR-18s previously on a pre-war Schwinn New World. See HERE.

And I built a bike for my wife using Sun CR-18 rims and a 1946-47 Schwinn New World. See HERE.

In the case of the pre-war New World, the "Schwinn Built" steel calipers were able to reach the slightly smaller Sun rims. In the case of the post-war New World, a set of Weinmann 810 "Schwinn Approved" calipers also were able to reach.

So what size spokes should you use? Here is what I use:

• Front wheel: Schwinn or Schwinn "Approved" hourglass hub (sometimes called the "Schwinn script hub"). 36 holes, cross 4 pattern. Rim is Sun CR-18, 36 hole, 26 x 1-3/8 (590mm). Spoke length is 288mm. 

 

• Rear wheel: Sturmey Archer AW three speed rear hub. 36 holes, cross 4 pattern. Rim is Sun CR-18, 36 hole, 26 x 1-3/8 (590mm). Spoke length is 286mm. 

 

Below are my results using a spoke calculator. These spoke lengths filled the spoke nipples to their ends without going over.