Road TT athlete targeting hilly 24 mile TT. Need to assess aerodynamic impact of positional changes, specifically around cockpit stack and reach, which can then be physiologically assessed on road to arrive at the optimal setup from all tested configurations.
Adjust the inputs to recompute aerodynamic power at your chosen speed and the
time saving over the course. Time saving is each run's weighted CdA vs the baseline run,
scaled by the sensitivity.
Watts @ km/h ·
s per m²
CdA plots
Accepted changes
Config
Change
Weighted CdA (m²)
Time saving (s)
O
Config N & narrow q factor
0.2107
-55.4
Post-session debrief
Legalising the saddle saved 4w. Reach changes (+/-20mm) were within repeatability. Stack up 10mm was significantly worse, however the two steps lower of 10mm and 20mm found good improvements. 20mm lower found 4w. Helmets were all slower, however Specialized TT5 was the closest so was reserved for later field testing with Streamlines Cirrus. In best set up repeat, drag had drifted up by 5-6w (0.003-0.004m^2). Switching to the WattShop Cratus narrow spindle crankset with 68T (also removing front mech) found 8w. 160mm crankarms were neutral. Shorter pedal axles (6mm total) was 2w better, so within repeatability but taken based on previous testing and the benefit the crankset brought. Removing the aero bottle cost 3w. Narrower pad width was neutral so reverted on. Aggressive shrug was 4w worse, so stick with natural baseline position. Final baseline repeat came in 4w higher, which reflected the general trend of drifting baseline throughout the test. This reinforces the total gains you found of ~24w, 0.012m^2 or 65 seconds for the course. The Impsport skinsuit was neutral.