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Race IntelligenceThun, Switzerland

IRONMAN Switzerland Thun

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
4 July 2027
Swim
3.8 km
Bike
180.2 km
Run
42.2 km

Published route evidence. Final 2027 route pending. Checked 15 Sept 2026.

Official course routeThe real GPS route for each discipline with official GPX data available, drawn in one shared coordinate space.

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 Switzerland Thun actually gives you

You swim one loop in Lake Thun, ride two demanding Alpine loops, then run three loops through Thun and across its bridges. The first bike loop is not a chance to bank time: the climbs repeat, and the run still has its own changes of rhythm.

Show distances in

Swim

3.8 km

Alpine Lake Loop

Layout
1 loop
Setting
Lake Thun

A calm alpine lake loop gives a measured start before the climbs.

Source: 2026 current route

Bike

180.2 km

Hilly Alpine Roads

Layout
2 loops
Setting
the countryside around Thun

Two loops through the Alps repeat the steepest question of the day, making lap-one restraint decisive.

Source: 2026 current route

Run

42.2 km

Lakeside and City Course With Bridges

Layout
3 loops
Setting
Thun and Lake Thun

Three loops through Thun and across its bridges reward a bike that protected the final third.

Source: 2026 current route
Where these course facts come from

These facts come from the organiser’s latest published material: swim, 2026 current route; bike, 2026 current route; run, 2026 current 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

Use the alpine lake

  1. 0–300 m

    The start

    Settle in Lake Thun

    Find a calm rhythm in the alpine lake before the demanding bike.

    • Seed honestly
    • Settle early

Bike

Ride both loops evenly

  1. 0 km–90 km

    Loop one

    Cap the Alpine climbs

    The climbs return on lap two. Ride the first loop to a power ceiling rather than a speed target.

    • Cap power uphill
    • Fuel before the climbs

  2. 90 km–180.2 km

    Loop two

    Match lap one

    Repeat the effort and finish nutrition before the three-loop run through Thun.

    • Stay patient
    • Finish planned fuel

Run

Protect the bridges

  1. 0 km–14.07 km

    Loop one

    Start beneath your ceiling

    The bridges and lake views can make the opening feel easier than it is. Keep it controlled.

    • Easy first aid station
    • Stay tall

  2. 14.07 km–42.2 km

    Remaining loops

    Use what the Alps left

    Let each repeat be an honest check before making the final move.

    • Shorten stride on bridges
    • 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
15.4–26.7°CDew point centred on 14.8°C
Wind and gusts
4.0 km/hGusts up to 25.9 km/hPrevailing direction N
Rain likelihood
Up to 85%Wet-surface uncertainty retained

Historical baseline, 2019–2025 · Open-Meteo historical archive · Updated 2026-09-15.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 full distance 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 full distance 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 Switzerland Thun 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 routeFull-distance training plansPlans for climbing durability.See the plans Personalised routeWork with me on the whole buildCoaching for the complete build.See coaching

Further reading

ArticleFull-distance race strategy: calm execution beats chaosPacing logic for a repeated Alpine bike.ArticleFix the first ten minutes off the bikeUseful before a three-loop run.

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 2026-09-15.