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From the pages of Velo: Performance Quantified

Torsional Stiffness Results

The torsional stiffness test we co-developed with Microbac Laboratories, Inc. measures how a bike moves at three different points while subjected to a simulated pedaling force. Here’s how it works.

The front fork is fixed. The rear dropouts are mounted to a dummy axle that pivots on an eyebolt, allowing the rear of the bicycle to twist and move laterally. A chain is connected from the large chainring to the dummy rear axle to transfer the pedaling force through the rear triangle.

Dial indicators contacted the bike at the center of the drive crankarm’s face, at the top of the head tube and at the top of the seat tube. Two 50-pound dumbbell weights were hung on a spindle screwed into the left crank positioned horizontally forward and the values were recored on the three dial indicators.
—LENNARD ZINN