Character. Solo effort against the clock. Standard club distances: 10 mile (16 km), 25 mile (40 km), 50 mile (80 km), and the hour record. Everything comes down to marginal efficiency — aerodynamics, position, pacing, and a chain that isn't costing you watts.
Conditions. Dry tarmac by design — events reschedule if the course is wet. Usually early-morning or evening starts to avoid wind and traffic. Short enough that weather variability rarely matters for lubricant choice.
Lube plan
If you wax — ZFC-recommended path. Total wear barely accumulates in a 40 km TT — what matters is the lowest-friction chain coating you can get. Freshly-applied top-tier immersive wax the night before and don't think about it again. Cost and faff are effectively zero factors for a sub-hour race.
If you're on oil — pragmatic equivalent. Friction matters here — even a few watts saved over a sub-hour effort moves the time. Best you can do without switching is a fresh, clean application of your oil the night before, with the excess thoroughly wiped down. For race-day-only optimisation, a hot-wax chain dedicated to TT use is a real upgrade — but that's a future conversation.