No. 25: [Transmission & Structure] The Inconvenient Truth of Chainlines—The Price of the 'Multi-Speed' Propaganda

​“I just can’t get rid of that gritty feeling transmitted to my feet when I shift into the big ring and the largest cog...”

​Even with a perfectly adjusted front derailleur, you cannot cancel out the friction caused by the physical 'cross-chaining' of the chain. While many cyclists pour their hearts into weight reduction and bearing performance, are they not overlooking the greatest energy loss of all: “chainline distortion”?

​In this modern era of increased gear counts and wider cassettes, the diagonal path traced by the chain has become a physical cost that can no longer be ignored. How you incorporate this “distortion” into your calculations is the dividing line between the longevity of your drivetrain and its efficiency.

​1. The wattage stolen by the 'diagonal' and the limits of dish

​When chain links twist to engage with the sprocket, immense lateral friction is generated. This is not merely drivetrain resistance. It is a “self-consuming action” where the plates shave the tooth tips and the pins wear down the links from the inside.

​Even more serious are the limitations of hub design that accompany the increase in rear gear counts. As the number of speeds grows to 11 or 12, the freehub body bites further inward, and the wheel’s “dish” (the difference in spoke tension between left and right) increases.
Disc brake models are overcoming this through greater rim design freedom and adjustments to strength and balance. On the other hand, those riding rim brake models are facing a grave situation.

​Returning to the point: are we not sacrificing the structural rigidity of our wheels and our drivetrain efficiency—the very foundation of a road bike—just to gain a few “unused easy gears”?

​2. The rationality of 14-28T sprockets and doubts about multi-speed systems

​How many times does a non-professional rider actually need an ultra-small 11T or 10T top gear? A configuration like “14-28T,” which prioritizes a close-ratio setup in the frequently used range, makes it easier to keep the chainline near the center, resulting in far higher drivetrain efficiency.

A masterpiece known to those in the know, balancing close ratios in the frequently used range with an optimized chainline.

​The increase in rear gear counts cannot be denied as a facet of clever strategy by manufacturers. As the number of gears increases, the chain becomes thinner, and adjustments require sub-millimeter precision.

​The oversized pulley wheels that have become a hot topic in recent years are logically correct in their goal of easing the chain’s bending angle, but if you seek high-precision customization, you face the trade-off of increased weight and reduced shifting accuracy.
In actual practice, physical “straightness” is far more valuable than the numbers on a spec sheet.

​3. The correlation between vibration correction and 'fatigue'

​Disturbance in the chainline is directly linked to riding stability. If the chain picks up road gaps while stretched diagonally, it will thrash violently both vertically and horizontally, accumulating mental fatigue for the rider.

​The fact that Shimano’s GRX series is equipped with a stabilizer and is obsessed with vibration correction is because the loss caused by this “thrashing” cannot be ignored. The fatigue brought on by the shifting operation itself also accumulates as the distance increases.

​Devoting the brain resources that would otherwise be spent constantly calculating the “optimal chainline” to pure leg-power competition—is that not what it means to have your equipment completely under control?

A trusted standard for an 11-speed environment. Always aim for straight operation.

A structure that allows anyone to perform precise trim operations. Essential equipment for mitigating “distortion” in the chainline.

​4. A record of failure: The thing that 'dropped' the most was my spirit

Once, when my thinking had stopped due to the fatigue of a long-distance ride, I forced a shift into the big ring and the largest cog while applying high torque.With a merciless metallic 'clunk'the chain dropped, anda deep, permanent scar was carved around the bottom bracket.

The damage to the frame hurt, but I felt most depressed by my own 'immaturity in operation.' It is a lesson that power plays ignoring the limits of a system always lead to the worst results.

Before investing in things like expensive bearings to increase drive efficiency, I want you to build a mental map that keeps the chain as 'straight' as possible.
Bring invisible friction under control. Beyond that lies the'true freedom'where you can immerse yourself in just riding without fearing equipment trouble.

Conclusion: Stop the 'Betrayal' of Precision Machinery

The physiological disgust toward that unnatural bending when looking down at the chain from directly above. Continuing to turn the pedals while ignoring that isan act of betrayal against a delicate machine.

Trust the parts, understand their design philosophy, andtrace the most 'optimal' line. Isn't that intellectual maneuvering the very abyss of the road bike hobby?