Professional Bike Fit
Reference models: Retül Fit, Guru Fit System, Shimano Dynamics Lab
CWPM vs Sustained bike power
Cost per minute saved across the full slider range, all other parameters held at your current profile.
FORMULA CWPM = cost ÷ Δt, where Δt = (min/h at your speed) × κ(slider) × Tbaseline(slider). Curve direct-aero sets the empirical κ bump; Tbaseline is the leg duration at your profile.
Time saved vs Sustained bike power
Minutes shaved at the 140.6 Full format as your slider value varies.
FORMULA Δt = (min/h at your speed) × κ(slider) × Tbaseline(slider). Curve direct-aero sets κ; Tbaseline is your 140.6 Full bike leg duration.
Time saved across race formats
Minutes shaved if you raced each distance at your current profile.
FORMULA For each format f: Δtf = (min/h at your speed) × κ(profile) × Tbaseline(f). Only the leg distance — and therefore Tbaseline — varies between bars; κ is held constant from your profile.
Cost vs time saved — bike alternatives
Every bike upgrade in the catalog plotted at your current profile. The line is the Pareto frontier: anything above it is dominated by a cheaper item that saves the same or more time.
HOW TO READ Each dot is one upgrade. Its horizontal position is the time it would save you at your current profile — the same Δt computed in the charts above. Its vertical position is the upgrade's cost. The green dashed line is the Pareto frontier: items where no cheaper alternative matches or beats them on time saved. Anything floating above the line is dominated — somewhere down-and-to-the-right sits a frontier item that delivers the same or more minutes for less money, so it's the better buy.
Why it works
Your body makes up roughly 70% to 80% of all aerodynamic drag on the bike. A professional biomechanical fit manipulates your cockpit geometry to minimize your frontal surface area ($CdA$) without sacrificing power generation.
Direct aero — watts saved scale with $v^3$ (flat in power); an empirical $(P/225)^{0.15}$ bump on top.
Source basis for the savings estimate
3 referencesThe ΔCdA = 0.01701 m² primitive is a calibrated midpoint drawn from the literature below. Peer-reviewed studies are weighted most heavily; independent / industry labs fill gaps where peer review is sparse for this gear category.
- Aerodynamic study of different cyclist positions: CFD analysis and full-scale wind-tunnel tests.Journal of Biomechanics, 43(7):1262–1268.Quantifies CdA changes across upright, dropped and TT positions — the canonical position-drag reference.doi.org/10.1016/j.jbiomech.2010.01.025
- Validation of a mathematical model for road cycling power.Journal of Applied Biomechanics, 14(3):276–291.The standard P = f(CdA, Crr, v, slope, mass) model used to convert drag/friction deltas into watts and minutes.doi.org/10.1123/jab.14.3.276
- Riding against the wind: a review of competition cycling aerodynamics.Sports Engineering, 20(2):81–110.Comprehensive review of CdA contributions from rider position, helmet, frame, wheels and clothing.doi.org/10.1007/s12283-017-0234-1
How the savings estimate was built
ΔCdA 0.01701 m²Published CdA reduction → watts saved at your equilibrium speed → minutes per hour.
- Pull reported ΔCdA (m²) from wind-tunnel / velodrome data for items in this category and price tier.
- Solve the power balance for your equilibrium speed v*, then watts saved there: ΔP = ½·ρ·v*³·ΔCdA.
- Convert via the component-aware multiplier ΔM/h = 60·ΔP/(3·P_aero+P_roll), then apply the empirical (P/225)^0.15 bump.
- Round to a conservative midpoint of the observed range to avoid manufacturer bias.
This is a calibrated model number, not a measurement of your equipment. The value reflects published delta-ranges for the Foundations category with a direct-aero response, biased toward independent rather than manufacturer data. The slider sweep above shows how watts-saved at your speed and the curve κ reshape it across athlete profiles.