Mastering Col d’Eze: The Critical Climb of Ironman Nice 2025
Col d’Eze: The Climb That Defines Your Ironman Nice 2025 Marathon
How to bank ~50 seconds on the first long ascent without adding watts—by dialing your aero and pacing where it matters.
TL;DR — 11 km at 5% + Masamune aero adjustment = –50 s without increasing power.
The Col d’Eze around km 25 is the first long climb of the Ironman Nice 2025 bike course. You arrive “fresh” but flooded with adrenaline. Spend glycogen too early here and you’ll pay it back with interest on the Promenade des Anglais marathon. This guide shows you how to combine aero efficiency and smart pacing to leave the summit ahead—without burning matches.
1) Location & Why It Matters
| Metric | Value (2025) |
|---|---|
| Distance | 11.0 km |
| Average gradient | 5.1% (max ~8%) |
| Elevation gain | ~495 m |
| Altitude | ~50 → ~510 m |
| Typical wind | W–NW 8–12 km·h⁻¹ (crosswind sections) |
A single poor pacing decision here can translate into minutes lost during the marathon. Expect noticeable crosswind around km 6–7. Aero stability rules, and—on this climb—your cockpit is king.
2) Free Lead Magnet: “Masamune Aero Lite — Video Setup + Cheat Sheet”
- 4-minute setup video: stack, reach, and bolt torque at 6 Nm.
- PDF cheat sheet: 3 tested configurations + measured ΔCdA.
Grab it here: Masamune Assembly & Setup
3) 90-Second Masamune Aero Tune (Do This Before the D6204 Sign)
| Step | Action | Gain |
|---|---|---|
| 1 | Lower stack by 5 mm just before the D6204 / “La Turbie” sign. | ~–2 W drag |
| 2 | Close the outside wrist by 5° in crosswind. | Improved lateral stability |
| 3 | Set elbow angle to 92° → roughly –0.004 CdA. | ~–3–4 W @ 14 km·h⁻¹ |
| 4 | Tighten cockpit bolts to 6 Nm. | Safety under gusts |
| 5 | Power plan: 95% FTP for the first 4 km → then 90% FTP to the crest. | Protects glycogen for the marathon |
Field data: outdoor tests (power meter + differential pressure sensor, Jan 2025) confirmed average savings of ~24 W at 45 km·h⁻¹ and ~4 W at 14 km·h⁻¹. On Col d’Eze, that aggregates to about ~50 seconds “free” at the summit, strictly from aero optimization plus steadier handling.
Gear note: If you’re using the Masamune cockpit, these micro-changes are quick and repeatable. If not, consider the Masamune Aero Lite—it’s designed for fast stack micro-adjustments and stable forearm support in crosswinds.
4) Pacing Targets by Finish Goal
Assumptions: 75 kg rider, CdA 0.23, Masamune cockpit, dry roads.
| Goal | Climb Power | Indicative W·kg⁻¹ | Result |
|---|---|---|---|
| Sub-10 h | 290–300 W | ~3.9–4.0 W/kg | +1–2 min buffer at the crest |
| 10–11 h | 250–260 W | ~3.3–3.5 W/kg | Avoid spikes; protect glycogen |
| 11–12 h | 220–230 W | ~2.9–3.1 W/kg | Save legs for Col de Vence & the run |
Keep cadence in your preferred aerobic band and avoid >105% FTP surges when overtaking. Your only “green light” for brief spikes is exiting hairpins or when you must bridge to legally draft distance (12 m rules still apply).
5) Crosswind Technique for km 6–7
- Press the inside knee lightly against the top tube to reduce yaw-induced wobble.
- Eyes 15 m ahead—not at the side gusts.
- Relax the shoulders; stiff traps = higher drag + twitchier steering.
GoPro + IMU tests (Feb 2025): this combo reduced fore-aft oscillation by approximately 10% in gusts, which translates into steadier power and fewer aero losses.
6) Playbook: How to Ride the 11 km
- km 0–1.5 (roll-in): Ease to ~90–92% FTP, settle breathing, check hand/wrist angle.
- km 1.5–4: Rise to ~95% FTP on the steadiest pitches. Stay seated; micro-stand only to keep cadence from dropping below your aerobic floor.
- km 4–6: Back to ~90–92% FTP. Re-center aero pads; keep elbows narrow and angle ~92°.
- km 6–7 (crosswind): Wrist closed 5°, knee to top tube, eyes forward. Don’t fight the gusts—flow with them.
- km 7–9: Return to ~90% FTP. Small sips every 10–12 minutes, gel if needed (see nutrition below).
- km 9–11 (crest): Stay smooth; no victory surges. Think: heart rate down before the descent.
7) Rapid Pre-Climb Checklist
- ✔ 30 g CHO gel ~km 20 (with a small water rinse).
- ✔ Tire pressure ~95 psi (25 mm) for dry conditions.
- ✔ Masamune alignment marks double-checked.
- ✔ Helmet vents closed for the climb (≈ –1 W drag benefit, marginal but free).
- ✔ Bolt torque verified at 6 Nm.
8) Nutrition & Thermoregulation
- Fuel rate: target ~10 g CHO per km during the climb via small gels or chews—prevents a glucose dip on the descent.
- Cooling: a brief splash of cold water to the nape at ~km 7 can lower core ~0.3 °C.
- Sodium: ~300 mg/h mixed into the aerobar bottle so you can drink without breaking aero (keep the head steady).
9) Join the Weekly Col d’Eze Challenges
Be part of the TetsuoPerformance Strava Club: strava.com/clubs/tetsuoperformance
| Weekly Challenge (AUG–SEP) | How to Join | Prize |
|---|---|---|
| Col d’Eze Split Hunt | Tag your activity #ColDEzePower. Our club bot extracts your best time on the official segment. Top-10 consistent efforts (Δ ≤ 5%) enter Monday’s raffle. |
1 Masamune foam kit weekly |
| Aero-Stack Photo Friday | Post your cockpit photo with stack in mm. Most 👍 in 24 h gets featured on @tetsuo_tri. | Tetsuo merch |
Community target: 300 active members before 1 SEP + steady UGC for Reels.
10) Quick FAQs
- Best gearing for a 75 kg athlete?
- 50/34 with 11–30 cassette (or 11–32 if you prefer higher cadence on 7–8% ramps).
- Is a full disc wheel allowed?
- Yes, but skip it if average wind > 25 km·h⁻¹ or gusts are strong in the 6–7 km crosswind zone.
- What about the bike cut-off buffer?
- Plan for the overall event cut-off at 10 h 30 min. Don’t bleed time on the descent—arrive at the run calm, not cooked.
11) Common Mistakes to Avoid on Col d’Eze
- Starting too hard: burning >100% FTP for the first 5–7 minutes amplifies drift for the rest of the climb.
- Ignoring aero in crosswinds: wide elbows + shrugged shoulders = higher CdA and twitchier steering.
- Fueling too late: waiting until “you feel it” is always too late on long climbs.
- Over-braking on the descent: set up inside-out lines early; feather brakes while maintaining aero head position.
