Project 32: Testing a 32-Inch Gravel Bike Prototype

Stephen Fitzgerald Builds Prototype 32-Inch Gravel Bike for Rodeo Labs

In a column for bikepacking.com, Stephen Fitzgerald of Rodeo Labs argues that despite initial skepticism and industry hype, testing a 32-inch wheel build provides tangible data on endurance efficiency.

Fitzgerald explored the history of large-wheel bicycles and constructed a prototype 32-inch gravel bike after realizing he had dismissed the trend without personal testing.

The Tech TL;DR:

• Stephen Fitzgerald of Rodeo Labs built and tested a prototype 32-inch gravel bike after initially dismissing the wheel size as industry hype.
• Data from tire tester John Karrasch suggested a 160-rider could save roughly 25 minutes over a 350-mile gravel race using 32-inch wheels.
• Major brands including Salsa, Mason, Trek, and Scott have expanded production options as component availability for 32-inch setups grows.

Unicycles and Cruisers Preceded Mountain Bike Trends

Thirty-two-inch wheel development did not originate in modern mountain biking, bikepacking.com reported. Unicyclists adopted 36-inch rims in the early 2000s, while 32-inch setups emerged around 2010. Cruisers also contributed to the lineage, with David Folch of Dirty Sixer noting a 36-inch Coker from 25 years prior, and Black Sheep in Fort Collins undertaking early work on the 36-inch ZAMer in 2009.

Focus Bikes ran an April Fools joke about a “Big Bird 36” bike in 2016, and Leonard Zinn adapted frames for taller riders. Walmart offered a $229 32-inch cruiser in 2015, according to the same report.

Industry Warnings Spark Prototype Development

Fitzgerald wrote that ignoring the universal derailleur hanger (UDH) standard previously cost his company between $100,000 and $200,000. After walking the aisles at the Sea Otter Classic and observing widespread industry attention toward 32-inch equipment, Fitzgerald reassessed his position and decided to build a prototype gravel platform.

Larger Wheels Save Time Through Lower Rolling Resistance

Fitzgerald consulted tire testing data from John Karrasch, known online as FlexFitByJohn, who utilizes the Chung method to measure rolling resistance. Karrasch calculated that a 160-pound rider maintaining 200 watts over category 2 gravel could finish a 350-mile race like the Unbound XL roughly 25 minutes faster on 32-inch wheels. Maxxis introduced the Aspen ST tire in 2024 and 2025, providing cross-country racing credibility to a component category that previously lacked tire options.

# Example conceptual rolling resistance calculation loop
def calculate_time_savings(power_watts, distance_miles, resistance_delta):
    base_speed_mph = power_watts / 12.5
    adjusted_speed = base_speed_mph + resistance_delta
    time_base = distance_miles / base_speed_mph
    time_adjusted = distance_miles / adjusted_speed
    return (time_base - time_adjusted) * 60 # minutes saved