The Fastest Bike Courses in Ironman 70.3 Racing (Ranked by Real Data)

How I ranked them

For each race I took the median bike split from everyone who finished and turned it into an average speed over the 90 km bike. I went with the median instead of the average because a handful of very fast pros or a few people with flat tires can pull the average around, and I didn't want that deciding where a race landed.

Once the list was sorted, I wanted to know why some courses sit near the top and others near the bottom. A few things kept coming up.

What seems to make a bike course fast

• Climbing. Not a surprise, but it was bigger than I expected. A course with a lot of climbing is a different race from a flat one, even though the distance is the same.
• Wind. I used to assume flat and coastal meant fast. Then I looked at a few of those and the splits were slower than I'd have guessed. A headwind can feel as bad as a hill, and a loop that gives you some tailwind back seems to treat people better than a long stretch straight into it.
• Roads and corners. Rough pavement, tight turns and narrow lanes make everyone brake and speed up again. Wide, smooth roads let people just ride.

A course that feels easy isn't always fast

This was the part I found most interesting. A course can look gentle, with no real hills, and still produce slow splits because of the wind. And a course with one big climb can come out quick if the descent is long and smooth enough to ride hard.

It's why I trust what people actually rode more than the course map or the race website. The splits already include the wind, the road and the weather on the day.

So what do I do with this?

If I wanted a personal best, I'd pick a fast bike course. Getting off the bike with fresher legs is probably the best thing you can do for the run.

Qualifying is a different question. A fast course doesn't help much if everyone else rides faster on it too. What matters there is how tight the cut-off is for your age group, not how fast the bike is. I put that together in the easiest qualifier rankings.

If you're after a PR, or you want a first race where the bike goes well, have a look at the fastest bike course rankings and see how the courses stack up.

About the data

• I use the median bike split from finishers, converted to average speed over 90 km.
• Rankings come from the most recent edition of each race that has enough finishers. One windy or rainy day can push a course down the list, so a single year doesn't tell the whole story.
• I haven't measured how much each of climbing, wind or road surface costs in minutes. What I describe above is what I noticed in the results, not a precise formula.