If you're heading to Busselton this December, you're racing one of the flattest 70.3 courses anywhere in the world. The bike has nothing you'd call a climb and the run barely leaves sea level. That's the appeal, and it's also the trap. With no hills to slow you down, the only thing setting your effort on the bike is you. The other thing worth knowing before you go: the afternoon sea breeze that rolls in off the Indian Ocean in early summer doesn't care how fast you rode. If you're still out on the run when it arrives, you'll feel every watt you spent chasing a bike split.
Race Overview
IRONMAN has been racing in Busselton since 2004, when the full distance IRONMAN Western Australia joined the calendar. The 70.3 was added in 2016, first raced on December 4 that year alongside the full distance event as an age group race with 30 qualifying slots for the 70.3 World Championship in Chattanooga. The 2026 edition is the tenth.
The race has grown well beyond its age group roots. In 2024 it ran as the IRONMAN 70.3 Western Australia Asia-Pacific Championship and served as the penultimate stop on the IRONMAN Pro Series, drawing nearly 80 professionals racing for a US$75,000 purse. Italy's Gregory Barnaby and Spain's Marta Sanchez took the wins, and more than 3,400 athletes raced across the 70.3 and full distance events, the biggest field in the weekend's history.
For 2026, the race is set for Sunday, December 6, on the same morning as IRONMAN Western Australia, which carries the Asia Pacific Championship title this year. The race village and transition sit at Signal Park on the Busselton foreshore, and the full distance race is already sold out. With both fields sharing nearly identical courses, expect busy roads and a lot of energy along the water from start to finish.
Course Description
The swim covers 1.9km in Geographe Bay, starting from the Busselton Foreshore. The current layout keeps swimmers close to shore, which cuts down exposure to wind and chop, and the course takes athletes under the Busselton Jetty, the longest timber jetty in the Southern Hemisphere. Water temperature in early December usually lands around 66°F (19°C), so plan on a wetsuit swim. The bay is known for flat, clear water, but it isn't guaranteed. The pros raced through chop in 2024, and a morning wind out of the wrong direction can turn a fast swim into a rough one.
The bike is a single 90km lap. It starts along the coast before heading inland into the Tuart Forest, a stand of tall native tuart trees that gives riders some shelter from the wind that the coastal sections don't. Training route data puts the steepest pitch on the course around 3 percent, which tells you most of what you need to know about the terrain. Aid stations sit at roughly 23km, 44km, and 66km. One lap also means one look at everything. There's no second loop to correct a pacing mistake or adjust to what the wind is doing, so the number you start with is the number that shapes your day.
The run is two laps along the Busselton foreshore, heading east first before turning back west to run past the jetty. It's flat and fast, with big crowds on every lap, but much of it runs in the open along the water. The second lap is where the timing of the sea breeze starts to matter, and where a bike leg ridden on feel tends to show up.
Forecasted Weather
Early December in Busselton is the start of the Australian summer, and conditions are usually dry and mild. Average highs run around 73°F (23°C) with overnight lows near 57°F (14°C), though hotter days are always possible this time of year. Rain is rare, with fewer than two wet days in a typical December. The 2025 race ran in what local race coverage described as near perfect conditions.
Wind is the variable that matters. December is peak season for the southwest coast's afternoon sea breeze, known locally as the Fremantle Doctor, which typically arrives from the south to southwest sometime between late morning and mid afternoon and can build to 15 to 25 knots. Faster athletes may be off the course before it fills in. Most age groupers won't be. Check the forecast in race week for when the breeze is expected to arrive, since that's what decides how much the back half of your bike and your second run lap will cost.
Why This Course Rewards a Best Bike Split Plan
Busselton's reputation for personal bests is earned, but a flat course only rewards the athletes who pace it like a triathlon instead of a time trial. A BBS race plan for IRONMAN 70.3 Western Australia 2026 will:
- Give you a ceiling on a course with no natural brakes. With no climbs to force you to ease off, the most common mistake here is riding a number that feels easy for 90km and paying for it on the run. A target set before race day keeps your effort honest when the road won't.
- Set your power around the wind, not the elevation profile. The coastal sections and the more sheltered forest roads don't ride the same, even when they look identical on paper. A plan built on your actual CdA and the forecast wind shows you where extra watts buy real time and where they just burn matches.
- Get one lap right the first time. A single 90km loop means no chance to recalibrate on a second pass. Knowing your target for each section ahead of time is the only way to adjust for conditions you'll only see once.
- Protect a run that may be heading into the sea breeze. The half marathon is flat, but the second lap often lines up with the afternoon wind building off the bay. A plan built for the full 70.3, not just the bike split, keeps enough in your legs to run that lap instead of grinding through it.
Interactive Race Plan and Course Map
This power plan was modeled for an athlete with an average CdA of 0.2579, an FTP of 250 watts and weighing 165 lbs. Want to see what your time would be on the 2026 IM 70.3 Western Australia course? Try the Time Analysis feature below, where you can quickly adjust Drag, Power, Weight and Crr to your own values. Check out our demo race plan to see what a premium race plan looks like.
Alert!
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Read more about the Advanced Surface Conditions chart on the FAQs page.
| Interval | Int. Time | Total Time | Int. Dist. | Total Dist. | Grade | Speed | Power |
|---|---|---|---|---|---|---|---|
| #1 | 00:17:18 | 00:17:18 | 6.47 mi | 6.47 mi | -0.02 % | 22.44 mph | 201 w |
| #2 | 00:00:08 | 00:17:27 | 0.05 mi | 6.52 mi | -1.63 % | 21.13 mph | 62 w |
| #3 | 00:05:52 | 00:23:19 | 2.22 mi | 8.74 mi | +0.03 % | 22.71 mph | 203 w |
| #4 | 00:00:26 | 00:23:45 | 0.16 mi | 8.90 mi | +1.93 % | 21.75 mph | 312 w |
| #5 | 00:02:01 | 00:25:47 | 0.75 mi | 9.65 mi | -0.23 % | 22.14 mph | 183 w |
| #6 | 00:00:16 | 00:26:03 | 0.08 mi | 9.73 mi | -1.69 % | 18.15 mph | 57 w |
| #7 | 00:01:40 | 00:27:44 | 0.63 mi | 10.36 mi | +0.26 % | 22.54 mph | 224 w |
| #8 | 00:00:20 | 00:28:04 | 0.13 mi | 10.49 mi | -2.22 % | 22.70 mph | 14 w |
| #9 | 00:06:02 | 00:34:07 | 2.29 mi | 12.78 mi | -0.04 % | 22.70 mph | 198 w |
| #10 | 00:00:08 | 00:34:15 | 0.05 mi | 12.83 mi | +1.58 % | 22.43 mph | 312 w |
| #11 | 00:27:38 | 01:01:54 | 10.50 mi | 23.33 mi | +0.02 % | 22.80 mph | 200 w |
| #12 | 00:00:08 | 01:02:02 | 0.04 mi | 23.37 mi | -3.13 % | 15.89 mph | 0 w |
| #13 | 00:10:57 | 01:13:00 | 4.06 mi | 27.43 mi | +0.12 % | 22.24 mph | 221 w |
| #14 | 00:00:33 | 01:13:33 | 0.19 mi | 27.62 mi | -1.80 % | 20.72 mph | 28 w |
| #15 | 00:00:15 | 01:13:49 | 0.10 mi | 27.72 mi | +1.16 % | 23.08 mph | 289 w |
| #16 | 00:00:06 | 01:13:56 | 0.05 mi | 27.77 mi | -5.43 % | 25.42 mph | 0 w |
| #17 | 00:00:23 | 01:14:20 | 0.16 mi | 27.93 mi | +2.83 % | 23.33 mph | 286 w |
| #18 | 00:14:43 | 01:29:04 | 5.59 mi | 33.52 mi | -0.07 % | 22.78 mph | 192 w |
| #19 | 00:00:06 | 01:29:11 | 0.04 mi | 33.56 mi | -1.01 % | 22.61 mph | 129 w |
| #20 | 00:12:32 | 01:41:43 | 4.72 mi | 38.28 mi | +0.11 % | 22.57 mph | 213 w |
| #21 | 00:00:12 | 01:41:56 | 0.07 mi | 38.35 mi | -1.38 % | 19.12 mph | 94 w |
| #22 | 00:00:12 | 01:42:08 | 0.04 mi | 38.39 mi | +5.04 % | 11.45 mph | 289 w |
| #23 | 00:00:24 | 01:42:33 | 0.11 mi | 38.50 mi | -1.91 % | 16.35 mph | 30 w |
| #24 | 00:17:11 | 01:59:45 | 6.69 mi | 45.19 mi | -0.08 % | 23.34 mph | 184 w |
| #25 | 00:00:32 | 02:00:17 | 0.21 mi | 45.40 mi | +1.06 % | 23.80 mph | 278 w |
| #26 | 00:07:19 | 02:07:36 | 2.74 mi | 48.14 mi | 0.00 % | 22.47 mph | 202 w |
| #27 | 00:00:20 | 02:07:57 | 0.12 mi | 48.26 mi | -1.40 % | 21.90 mph | 106 w |
| #28 | 00:20:26 | 02:28:23 | 7.91 mi | 56.17 mi | -0.02 % | 23.21 mph | 191 w |
| Totals/Avg | 02:28:23 | 02:28:23 | 56.18 mi | 56.18 mi | -0.28% | 22.72 mph | 197.56 w |
No Categorized Climbs Found
To determine the category of a climb, we check if the grade is greater than or equal to 3.0% and if the climb distance is greater than or equal to 300 meters. If these conditions are met, the climb is considered significant, and its score is calculated.
Build your own personalized 2026 IM 70.3 Western Australia power plan today! Sign up for a free Athlete Basic account to get started with your athlete profile and bike setup, then grab the 2026 IM 70.3 Western Australia course to model your own race plan.
2026 IM 70.3 Western Australia FAQs
Your target power depends on your FTP, body weight, bike setup, and finish time goal — not a generic number that applies to every rider. The variables that matter most are your current fitness, your aerodynamic position, and the specific demands of the 2026 IM 70.3 Western Australia course. The best approach is to build a personalized plan in Best Bike Split using your actual athlete profile — you'll get a segment-by-segment power target based on your specific inputs rather than a one-size-fits-all recommendation.
Every course is different and requires its own unique pacing plan. On a multi-loop course, fatigue and wind shift between laps and what felt comfortable early can become unsustainable later. On an out-and-back, headwind in one direction becomes tailwind in the other — an asymmetry a flat power target can't account for. On a point-to-point or single-loop course, you only get one pass at every section with no opportunity to recalibrate. When you create a Best Bike Split race plan for 2026 IM 70.3 Western Australia, we model the specific demands of that course so your pacing strategy reflects the race you're actually doing.
Significantly — and the effect varies depending on the course profile. On flatter courses, wind and aerodynamics become the dominant variables in your speed equation, more so than on courses where gradient naturally dictates effort. On climbing-heavy courses, your power-to-weight ratio and how you manage the descents matter most. A Best Bike Split race plan lets you model the specific conditions forecasted for 2026 IM 70.3 Western Australia, so your targets reflect what you'll actually face on race day rather than what the course looks like on paper.
It depends on the course and how well you pace it. Flat, fast courses offer genuine PR potential but only if you execute correctly — without terrain to naturally regulate your effort, going out too hard early is easy and costly. Technical or hilly courses reward smart segment-by-segment pacing over raw fitness. Either way, a physics-based race plan from Best Bike Split gives you a realistic split prediction based on your actual profile so you know before race day what a well-executed bike leg looks like for you specifically.
Yes — and this is one of the most underused features. Once you've built your 2026 IM 70.3 Western Australia race plan, you can export it directly to Zwift, TrainerRoad, or any ERG-mode trainer for indoor sessions, or push it to your Garmin, Wahoo, or Karoo for outdoor rides. Training on your actual race plan means you arrive at 2026 IM 70.3 Western Australia already knowing what your target effort feels like at every section of the course — not just what the number says on paper.
