The Benefits of 160mm Spacing

THE BENEFITS OF 160mm SPACING

To withstand side-loads, increase spoke life and prevent rim failures, a tandem’s rear wheel requires the increased bracing angle created by widely-spaced flanges.

Next, Santana uses symmetric or “dishless” wheels to center the rim between the hub flanges. By equalizing spoke lengths, tensions and angles on both sides, dishless wheels distribute the load evenly instead of requiring half the spokes to withstand most of the force.

These two critical wheel strength considerations—wide flange separation and dishless symmetry—explain why Santana rejected the mid-’90s frame width compromise attempted by a few competitors who needed “just enough” space to equip their tandems with drum brakes and 8 cogs. Because 145mm—halfway between pre-existing single bike and tandem standards of 130mm and 160mm—was never wide enough to allow adequate spoke bracing and a dishless design, builders offering this cramped alternative can provide just one or the other. Meanwhile, Santana’s 160mm tandem standard will accommodate a wide array of advancements, including stronger and lighter wheels, additional gears and powerful disc brakes.

UNDERSTANDING WHEEL STRENGTH

While most people mistakenly count spokes, a wheel’s strength is actually determined by its geometry—best shown through a comparison of three rear wheels.

A traditional wheel is crippled by narrow right-side spoke bracing angles. Extra spokes are needed to oppose the stress allowed by a barely-adequate 17mm of lateral offset.

With Shimano’s innovative cross-over lacing, the right lateral spoke offset increases from 17 to 27mm. This seemingly small change allows spoke count to be halved—16 spokes can safely and reliably replace 32.

By increasing the right lateral offset to 43mm, Santana’s 160mm frame spacing permits an optimized version of cross-over lacing. Significantly, the right and left bracing angles are balanced—allowing spokes on both sides of the wheel to shoulder an equal share of the load. Thanks to the subtle optimizations allowed by 160mm spacing, Shimano’s tandem wheel empowers 16 spokes to do the work of 40.

SEE ALSO

Tandem Hubs
Shimano Sweet-16
Emergency Rim Included