Sam Calder from Rule 28 reveals how a 4-hour wind tunnel session saved Dylan Johnson 13 minutes on his Unbound finish time—without touching his bike. We dig into the specific fabric upgrades, sock choices, helmet selection, and hydration pack placement that made the biggest difference, plus the practical aerodynamic gains you can actually apply to your own racing.
Key Takeaways
- Upgraded socks alone saved Dylan 3 watts at his race speed (35 km/h), with woven fabrics and inverted texture patterns delivering measurable gains over knitted alternatives
- Helmet size matters more than aero helmet choice in gravel positions—a smaller Metander medium was 4-5 watts faster than large, because head position is above shoulders rather than in line with torso
- Larger hydration reservoirs (3L) are faster than smaller ones (1.5L) in gravel positions because they fill the low-pressure void behind your helmet, creating a cleaner airflow curve to your hips
- Budget-conscious riders get the best return from socks and tubeless setups; a complete optimization (suit, socks, helmet, gloves) can yield around 20 watts for a reasonably sized rider at 35 km/h
- Tire choice is context-dependent—wider mountain bike tires (2.2") reduce puncture risk and rolling resistance on rough gravel despite slightly higher aerodynamic drag, making them worth the tradeoff in competitive racing
- Custom tailoring an off-the-shelf suit to your body proportions (via a tailor) is more cost-effective and accurate than ordering custom-made kit, and delivers aerodynamic benefits that matter more than buying marginally faster new products
Expert Quotes
"If you're leaving even five watts on the table, you're handing your rivals a five-minute head start at your next race."
"The biggest takeaway really for gravel is helmet size. With a more upright position, helmet being above shoulders and torso... the helmet itself can be bigger, but it can still be faster."
"You could be looking at sort of 20 watts in total. Like we had Alex Patton from GCN in the wind tunnel to optimize him for unbound... just by itself is about 16 and a half watts."
"To double your speed requires eight times more power to overcome the aerodynamic drag... different fabrics perform differently at different speeds."