Wheel Technology

WHEEL TECHNOLOGY

The wheels that come on many new tandems will last for only a year or two. And when you need to replace them with a capable pair of wheels, be prepared to shell out $300–$900. Because wheels are the most important (and expensive) item on any new bicycle, and wheels work twice as hard when used on a tandem, every Santana includes a strong pair of wheels that combine innovative design elements, tandem-specific materials, and high-quality workmanship.

TWO CRITICAL DESIGN ELEMENTS
The wheels on every Santana feature symmetric “dishless” design and widely-spaced hub flanges. Dishless wheels, a design pioneered by Santana back in the ’70s, allow spokes on both sides of a tandem’s rear wheel to carry the same load. Wide flange separation, a related characteristic, improves the spoke bracing angle to provide additional lateral strength while preventing “dynamic transfer”—momentary spoke-tension overloads that eventually will cause a rim to fatigue, crack and fail.

THE BENEFITS OF 160mm SPACING
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
Hadley/Velocity wheels
Shimano Sweet-16
Spinergy PBO