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Race IntelligenceRio de Janeiro, Brazil

IRONMAN 70.3 Rio de Janeiro

Know your day before you race it.

Enter four numbers you already train with. You get a likely finish range, target paces and watts, and how I would race this course.

Race day
8 August 2027
Swim
1.9 km
Bike
90 km
Run
21.1 km

Published route evidence. Final 2027 route pending. Checked 14 Sept 2026.

01 Race Card

Build my Race Card

Your first range uses conservative assumptions. Add optional evidence to make it more specific. It is calculated in your browser and saved only on this device.

Your numbers
Distance unit
Weight unit
You and this race
Sharpen your range with more detailOptional. Recent swim, bike and run results, equipment and transitions.

Add only the evidence you have. Every control changes a discipline range, its uncertainty, or an execution-risk explanation.

Swim evidence

Replaces the broad pool-to-open-water assumption.

Bike and equipment

These replace broad mass, aerodynamics, tyre, and power-to-speed assumptions.

Run evidence

A recent effort and honest durability/acclimation answers refine the post-bike run.

Race execution

Transition proficiency changes the T1/T2 range and how wet conditions are treated.

02 The course

What Rio de Janeiro actually gives you

You swim off one of Rio de Janeiro's iconic beaches, ride a flat 90 km route around the city, then run a scenic half marathon through Rio's iconic scenery. The flat bike tempts overriding; hold your number and the run stays available. The organiser's own course page for this edition is still light on route detail, so treat specifics as provisional until maps are published.

Show distances in

Swim

1.9 km

Ocean Swim

Setting
one of Rio de Janeiro's iconic beaches

An iconic-beach ocean swim gives a controllable opening with real conditions to respect.

Source: Current published route

Bike

90 km

Flat Route

Setting
roads around Rio de Janeiro

A flat bike course removes any terrain reason to hold back, so pacing discipline has to be self-imposed.

Source: Current published route

Run

21.1 km

Scenic City Route

Setting
Rio de Janeiro's iconic scenery

A scenic city run rewards legs that didn't override the flat bike.

Source: Current published route
Where these course facts come from

These facts come from the organiser’s latest published material: swim, Current published route; bike, Current published route; run, Current published route. They describe the character of the course. They do not confirm the final 2027 route.

03 Race plan

How I’d want you to race it

One job for each part of this course. The distance markers tell you when the job changes. The course tells you why.

Swim

Respect the ocean conditions

  1. 0–300 m

    The start

    Respect real ocean conditions

    An iconic-beach ocean swim rewards a controlled, honest opening rather than fighting for position.

    • Seed honestly
    • Settle into rhythm

Bike

Ride the flat by number

  1. 0 km–45 km

    First half

    The flat is a trap, not a gift

    With no hills to force pacing discipline, it's easy to override on this flat course. Hold your number regardless of how easy it feels.

    • Cap opening effort
    • Fuel early

  2. 45 km–90 km

    Second half

    Protect the run

    Finish planned nutrition and hold effort before the scenic run.

    • Stay patient
    • Finish planned nutrition

Run

Use the iconic scenery

  1. 0 km–10.5 km

    First half

    Start controlled

    Let the scenic opening feel easy, not fast.

    • Easy first aid station
    • Check posture

  2. 10.5 km–21.1 km

    Second half

    Earn the finish

    Only progress once the first half has held together.

    • Stay tall
    • Choose the last move late

04 Race week

What I would keep an eye on

There is no useful 2027 forecast this far out. For now, past race dates give us a point of reference. Closer to the race, the forecast will tell us whether the plan needs changing.

Forecast statusToo early for a forecast

A race-day forecast is not meaningful yet; check back closer to the event.

Temperature
17.8–26.7°CDew point centred on 16.6°C
Wind and gusts
9.0 km/hGusts up to 48.2 km/hPrevailing direction NE
Rain likelihood
Up to 55%Wet-surface uncertainty retained

Historical baseline, 2019–2025 · Open-Meteo historical archive · Updated 2026-09-14.Historical comparison only. This is not a forecast for 2027.

05 Method

What goes into your range

Your CSS, FTP, weight and run threshold create the first range. Open-water, bike, run and execution evidence can replace broad assumptions. Course data and the historical conditions baseline shape every simulation.

  1. Your numbersCSS · FTP · weight · run threshold
  2. This raceDistance · water type · elevation · exposure
  3. Your Race CardFinish and discipline ranges, with target paces and watts

Confidence is built from four inputs

Athlete evidence
Builds with recent open-water, bike and run efforts
Bike setup
Builds with equipment, mass, aero and tyre detail
Course evidence
Partial while the 2027 route is unconfirmed
Race-week conditions
Historical baseline until a forecast is useful
How the model works

It starts with the targets in your Race Card, then samples the parts of a 70.3 that vary: open-water pace, transitions, bike speed at the planned power, and the drop in run performance after the swim and bike. Repeating that calculation produces a likely range rather than a single heroic number.

The current time calculation uses this race’s published distances, or standard 70.3 distances where none are published, with the available course headings, elevation and exposure evidence. Weather scenarios vary temperature, dew point, wind, gusts, rain and water conditions together. Unknown route detail stays visible as uncertainty rather than false precision.

It is not predicting your exact finishing time, placing, or race-day weather. It answers a narrower question: given the plan and the information we have, what range of day is plausible, and where is the uncertainty coming from?

Confidence is not a permanent “low”. It is recalculated across four separate inputs:

  • Your evidence: consistent inputs and recent race-like swim, bike, and run results.
  • Bike setup: measured or specified aerodynamics rather than a broad prior.
  • The course: verified distance and route character, including elevation and technical sections.
  • The conditions: a current forecast is more useful than a historical comparison.

It starts low when those inputs are broad. It can become moderate or high as the evidence improves. A narrower range means better information, not a guarantee.

06 Next steps

If Rio de Janeiro is your race

Your range is built on today’s numbers. The months of training before race day decide what those numbers become.

The work from here.

Self-guided routeHalf-distance training plansTraining plans for the durability this course asks for.See the plans Personalised routeWork with me on the whole buildCoaching when you want the plan and race decisions joined up.See coaching

Further reading

ArticleHow to pace a 70.3 so you can still runThe longer version of the pacing logic behind this Race Card.ArticleFix the first ten minutes off the bikeUseful when an overridden flat bike needs to become controlled running.

Evidence

Sources and verification

Course status: Partially verified. The organiser’s descriptions and latest published route profiles are in use. The final 2027 route is not yet confirmed. Last checked 2026-09-14.