How To Pace An Ironman Bike

Your IRONMAN bike pacing strategy will make or break your race. Here’s how to get it right…

Ironman is an endurance trial, not a race. The most successful Ironman athletes know exactly how to pace themselves and have the mental strength to execute their pacing strategy on race day.

​The bike section is where pace judgement is most vital. There are three big mistakes that people make here.

  1. Attempting to ride at a constant power output that is slightly too high.
  2. Riding in bursts, ranging from easy to hard – without realising.
  3. Riding too hard on the hills, due to inappropriate gearing.

All three of these mistakes cause fatigue with no overall benefit. They make you tired, they make your stomach feel crap and they make you want to quit. Get it wrong and you’ll struggle to ride 112 miles and run 26.2 miles.

Why I’m Passionate About Ironman Pace Strategy

In 2015 I did Ironman Barcelona, having recently become a new Dad. With a full time job I could only average 7-hours per week in training.  I did a total of just two long rides and one long run in training  – and all my other workouts were 60-minutes or less. I was therefore very nervous about the Ironman and knew I’d have to get my pacing right to stand any chance of surviving.

On race day I followed the pacing strategy below and I actually set a new personal best of 8 hours 55 minutes. I was pretty shocked. I don’t even consider myself a natural endurance athlete – before I discovered this pacing strategy I’d always bombed at long distance events.

It was like a revelation to me and I believe anyone can benefit from this approach. Lesson one is to not base your pace-strategy on the bike split you’d ‘ideally like to do’. Instead, follow the advice below and your speed will take care of itself.

What You Need

You need a power meter to get your pacing right. If you don’t have one already, I recommend you buy one now. You might not want to fork out money on more equipment but trust me – it’s one of the best purchases you will ever make. A power meter will massively increase your chances of success at Ironman. I used a Stages Shimano Ultegra, costing around £500.

Note: For Heart Rate and Feel guidelines, I created a more recent blog. But don’t stop reading this one yet.

Test Your Power Output

Once you have a power meter, you’ll need to get an accurate idea of your own power output. To do this, you should conduct a 20-minute time trial, known as a “CP20” test. It’s REALLY SIMPLE to do. You simply ride as hard as you can for 20-minutes and record your average power output. See our video on this page for more guidance.

Once you know your CP20 power output you can work out your Functional Threshold Power (known as your FTP). It is a common measure of cycling ability and it’s SUPER EASY to estimate…Simply multiply your CP20 power output by 95% to get your FTP. 

Example:
If your CP20 power = 200 watts
You would multiply it by 95% to get your FTP.
Therefore, your FTP would be 190 watts.

Once you’ve done that, you can use the Ironman pacing guidelines below:

Ironman Power Output Guidelines
Research shows that Ironman bike race pace should be 65-80% of your FTP.  The faster you are, the higher the percentage you should aim for. Top pro’s can maintain 80% of their FTP because they are only racing for around 8-hours. Whereas back-markers take more like 15 to 16 hours and should ride at nearer 65% of their FTP. Everyone else should be somewhere in between.
TIP: Don’t be over optimistic, especially if it’s your first Ironman.

IRONMAN POWER OUTPUT GUIDE
  • 8 to 9 hour Ironman athletes aim for 78 to 80% of FTP
  • 9 to 10 hour Ironman athletes aim for 76-78% of FTP
  • 10 to 11 hour athletes aim for 74-76% of FTP
  • 11 to 12 hour athletes aim for 72-74% of FTP
  • 12 to 13 hour athletes aim for 70-72% of FTP
  • 13 to 14 hour athletes aim for, 68-70% of FTP
  • 14 to 15 hour athletes aim for 66 to 68% of FTP
  • 15 to 17 hour athletes aim for 64-66% of FTP

Conclusion

Riding at the right intensity takes discipline and courage, especially when other people are overtaking you. But it really works. At around the 80-mile point you’ll notice people starting to drop off, while you continue to ride strong.

​You’ll also find that you can digest your energy drinks and energy snacks far easier, which helps you maintain your energy levels going into the run. Therefore, you’ll actually RUN FASTER as a result of pacing yourself properly on the bike, and you’ll feel fresher and more energised.

Intelligent pacing leads to faster, more consistent Ironman results – and yet hardly anyone gets it right. I just hope this triathlon coaching blog helps you make the right pacing choices at your next Ironman. Good luck!

By Phil Mosley.
Triathlon Plus Coaching Editor & Ironman Certified Coach.
Founder of My Pro Coach.

​Copyright © 2016 Philip Mosley

P.S: For an updated version of this blog, including Feel and Heart rate guidance, click here.
P.P.S. Preview my IRONMAN 140.6 programs here, with email coach support.
P.P.S. For more guidance from our coaches, follow us on Instagram.
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Phil Mosley (Coach & Founder)
Phil Mosley (Coach & Founder)

Phil is a recognised expert in the field, having featured on many endurance sports publications. He founded MyProCoach in 2010 to sell premium training plans complete with email coach support for triathlons, duathlons, running & cycling.

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