Episode Details

Featuring: Mike Levy, John Karrasch, and Jan Heine

Does a 32-inch wheel actually save watts, or is the testing methodology broken? We put Chung Method advocate John Karrasch and vocal critic Jan Heine in the same room to hash out the reality of rolling resistance.

This week, the usual crew steps aside to host a direct debate between two of the most outspoken voices in tire tech. John Karrasch (aka flexfitbyjohn) has generated massive datasets using the Chung Method, recently claiming that adopting 32-inch wheels can improve rolling resistance by up to 10%. On the other side, Rene Herse CEO Jan Heine—a pioneer of supple gravel tires—argues that wheel size ultimately doesn't matter for speed, pointing to historical roll-down tests and potential flaws in the Chung Method's precision.

After a long series of online blog posts and rebuttals, we brought them together to debate the physics, the testing protocols, and the future of gravel geometry face-to-face.

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Episode Timestamps

00:00:00 - Episode Intro & Guest Backgrounds

00:07:51 - Setting Up the 32-Inch Test Bikes

00:12:12 - Understanding the Chung Method for Tire Testing

00:16:18 - The Results: Do 32-Inch Wheels Roll Faster?

00:25:01 - Analyzing the Physics and Approach Angles

00:29:32 - Jan Heine's Counterargument: Wheel Size Doesn't Matter

00:36:58 - The Debate: Is the Chung Method Too Precise?

00:42:36 - Defending the Data and Real-World Variables

01:03:15 - Tire Design Priorities: Casing, Compound, and Pressure

01:17:11 - Tire Inserts and 36-Inch Wheel Possibilities

01:18:57 - 2030 Gravel Bike Predictions & Outro