A spoked wheel relies on having all of the spokes in constant tension. A highly dished rear wheel starts with very light tension on the left side spokes. The torque of hard pedaling combined with cyclical weight loading can cause the left side "leading" spokes to occasionally go completely slack momentarily.

Repeated cycles of tension and slackness cause these spokes to fatigue at the bends, and ultimately break.

With half-radial spoking, the amount of dish is very slightly less to begin with if you run the radial spokes up along the inside of its flange ("heads out.") In addition, since there are no "leading" spokes, no amount of torque on the hub can reduce the tension on any of the spokes. In fact, if you have an old wheel that has been breaking left side spokes, "half rebuilding" the wheel into a half radial will solve the problem once and for all.

Wrong-way Half Radial

Sometimes, rear wheels are spoked half-radial with the radial spokes on the right. This is generally done for reasons of improving derailer clearance, particularly on wheels with unusually thick spokes or unusual flange designs. Such wheels require hubs with greater torsional stiffness since most of the driving torque must then be transferred by the left side spokes.

A radial lacing has the highest lateral strength of any lacing pattern. This is covered in the RADIAL LACING INFORMATION chapter. A multi-speed rear wheel that is half radially laced, with the non drive side being the side with the radial lacing, can only have increased imbalance in the lateral strengths of the two sides of the wheel. The radial spokes on the non drive side will also need a lower build tension when compared to a standard wheel. Since radial lacing has the highest lateral strength, the spokes do not need to be as tight to counter the lateral forces from the drive side in order to achieve a true wheel. Also, with the non drive side spokes even looser than normal, the likelihood that the wheel will go out of true from road shock is increased.

A properly built half radial rear wheel will be radially laced on the drive side. It would also be best to lace the drive side so the spoke heads are on the inside of the flange.

A mixed lacing pattern I discovered that works very well for balancing rear wheel lateral strengths is the 2-cross/3-cross lacing. This pattern uses 2-cross lacing on the non drive side and 3-cross lacing on the drive side. The non drive side spokes end up being shorter than the drive side spokes, a condition that causes theoretical force vector triangles that counteracts the dish offset of the wheel. This theoretical triangle is comprised of the real force vectors of the spokes and a theoretical force vector across the hub.

The figure to the right is a simplified version of the theoretical force vector triangles created by this lacing. The RED lines represent the force vectors of the spokes, and the BLUE line represents the force vector of the theoretical third side of the triangle. The location of a 3-cross length spoke on the non drive side is indicated by the GREEN spoke head for your reference. The PURPLE line, which is perpendicular to the BLUE force vector, indicates that the rim is closer to the non drive side of this theoretical force vector triangle.

Having a theoretical force vector triangle with the opposite circumstances of the actual triangles formed by drive and non drive spoke pairs works against the imbalance caused by the dish offset. A wheel built like this still has the drive side spokes under greater tension, but the difference in the tensions is not as great as they would be if the wheel was laced conventionally. Since the spoke tensions do not vary as much, the wheel has lateral strength characteristics that are more balanced than typical. It has been my experience that these wheels do hold true much better than conventionally laced (all 3-cross) multi-speed rear wheels.