The Weymouth Bike Leg: 90km of Dorset Hills, Not a Steady-Watts Course

The big picture

The bike leg at IRONMAN 70.3 Weymouth measures 90.8km on a single anti-clockwise loop: you start on the seafront, head north into the Dorset countryside as far as King's Stag and come back. The official elevation gain is 1,043m; other measurements, like PJAMM Cycling's, put it lower, around 740-800m. Sources disagree, so don't get hung up on the exact number. The real point is this: the course is hilly, almost never flat, and it won't let you hold steady power.

The key points on the profile

Two segments deserve specific attention:

• Around km 43: a punchy climb of roughly 3km with ~150m of ascent. It comes mid-leg, just when you're tempted to push. Don't.
• Around km 84: a ~1.5km kicker when the legs are already loaded. Reported gradients hit ~12%.

Between those two points, lots of false flats and rolling countryside. This is where age-groupers burn their race: pushing 30-40 watts over threshold on every roller costs you dearly on the half marathon.

Pacing: manage the spikes, not just your FTP

On a course like this it's normalized power that matters, not average. A concrete strategy:

1. First 40km: conservative, stay below your target even if you feel good. The early false flats invite you to overdo it. 2. The km 43 climb: set a power ceiling BEFOREHAND (e.g. 110-115% of race target) and stick to it. Better to lose 60 seconds here than 10 minutes on the run. 3. The km 84 kicker: easy gears, out of the saddle if needed, but no sprinting. T2 is only a few km away.

If you don't ride with a power meter, go by feel: on the climbs you should always be able to talk.

Gearing and kit

With reported gradients up to 12%, a generous cassette is not a sign of weakness: an 11-32 or 11-34 with a compact lets you climb seated and save your legs. Mid-depth wheels (40-50mm) are a good compromise if the wind is strong, but the variable here is unpredictable: the 2022 race report describes near-windless conditions, while other editions have seen gales. Prepare for both scenarios and decide at the last minute if you have two wheelsets.

Punctures: in 2019 the narrow, wet roads caused plenty of punctures, as the report from that year notes. Two spare tubes or sealant, CO2 or a mini pump: this isn't a course to travel light on spares.

Cold and roads

The start can be cold: lows around 7°C in September, and the first km on the bike come straight out of a wet swim. In 2022 several athletes found arm warmers or a gilet picked up in T1 useful. Put them in your bag: taking them off costs nothing, not having them can ruin your first hour.

The roads were closed to traffic in 2022, but they're still narrow country lanes: hold your line on the descents, watch out when overtaking and mind the surface, which can be slippery in the rain.

What to do now

• Train over-threshold surges on climbs followed by settling back to race pace: 3-5 minute efforts on 6-10% gradients.
• Fit your final cassette at least a month out and test it on hilly routes.
• Simulate the leg: 90km with 1,000m of climbing followed by a 20-30 minute run at race pace. If the run falls apart afterwards, your bike pacing was wrong.
• Study the profile on PJAMM and memorise km 43 and 84: knowing when to hold back is worth as much as any training session.