So the question was posed on episode 532 of the popular triathlon podcast IM talk and it went something like this… “The top marathon... Part 1: The run vs bike leg at Ironman. How do they compare to solo efforts?

So the question was posed on episode 532 of the popular triathlon podcast IM talk and it went something like this…

“The top marathon runner runs about 2hrs 4min/2hrs 5min for his marathon, whilst the Ironman equivalent (ie major event with top Ironman athletes) is Kona where the run (following 180k bike) is around 2hrs 45min, so the top marathon run is about 25% faster than the top Ironman run. What would the top Tour de France rider do for a 180k solo bike and what’s the difference between those top riders at Kona and the Tour de France rider…does it also equal 25%?

It ‘s an interesting discussion, full of other factors which we can bring out but nevertheless, are the differences between the best solo runs and best Ironman runs the same as the best solo TT’s and Ironman TT’s?

Let’s begin with getting a bit more accurate with the numbers.

If we take the current marathon world record it’s 2.02:57. We’ll call it 2.03  (123 minutes). Mark Allen currently still holds the fastest run split at Kona in 1989! A 2:40:03 which apparently included transition times. In this case we’ll conservatively estimate 2:38 or (158 minutes).Kona course measurements are usually accurate, a lot of other courses have not been. There are quicker Ironman runs. Peter Reid did 2:35:21 at Ironman Austria in 1999 and Luc Van Lierde ran a 2.36.49 at Roth. Both of these courses are quicker than Hawaii due to temperatures alone. However, let’s stick to Kona for now and take 2.03 vs 2.38 which gives us 35mins difference so 35/123*100 = 28% increase.


Mark Allen (yellow shorts) being pushed by Dave Scott to the fastest Ironman run split of 2:40:03 including transition time !

We don’t really have any Tour de France riders with recent competitive 100 mile TTs. However, we do have the record books and there’s some serious riders who hold the all time best records.  The 100 mile TT record is currently held by Richard Bideau 3:18:54 (2015) which equates to an average of 30mph.

Richard Bideau - by Ellen Isherwood

Richard Bideau – by Ellen Isherwood

“I ride on power; I rode the race at 290 watts average but lifted that to 300 in the last 10 miles because I wasn’t really feeling tired” (Richard Bideau)

Even more amazing, it was Bideau’s first attempt at a 100 when he broke thje record. He added that he would probably ride 305 watts if he was to do another 100.  Incase you’re wondering about that chainring, it’s a 65-11 ! Click here to read the interview

Clearly Froome, Wiggo, Cancellara or Martin etc would smash this time on a similar course, but this is the best data I’ve got to work with until we can convince once of them they should have a pop at a 100 miler. Alex Dowsett might be a better chance.

Interestingly Ian Cammish in 1993 rode a straight out 100 mile TT (Road Records Association) record in 3:11:11. That tailwind must have felt good! The British time trialler also rode a 3:31:53 in 1983 on a standard flat road course without using TT bars – here’s a pic of the bike he rode that on…


Kona bike splits have been hotting up and the modern technology must help a little but we still need to go back a few years fo the record. Norman Stadler in 2006 rode 4:18:23 (26 mph).


Stadler at Kona (2006) setting the bike course record of 4:18:23

We have to remember that The Ironman bike is 112 miles. If we adjust this time for 100 miles, it would be good for 3.50.45. Of course, Stadler would likely have gone faster if he knew he was riding 100 miles and not 112! Kona, with its howling winds and high temperatures is also far from the quickest course. Andrew Starykowicz rode a 4.02,17 at the 2013 Ironman Florida. Starykowicz had an average power of 325 or 327 normalized which is higher than Bideau’s effort (which I can’t get my head around).

Still, lets’s take a step back to the record time and the Kona record time (adjusted from 112 to 100 miles).

Bideau’s 100 mile record 3:18:54 (199 mins) vs Stadlers 3:50:45. = 16% increase.

There’s another interesting comparison we can quickly make if we use some recent data from Challenge Roth. Roth is one of the fastest Ironman courses and unlike official Ironman events, the organiser, ‘Challenge’ offer a relay option. It just so happens, that in 2009 when Norman Stadler rode a 4:14:42 Ironman split, there was a former UCI pro cyclist, Tobias Erler,  riding the course as part of a relay team. He is the only guy to have ridden a sub 4hr Iron distance bike split – 3:59:11. The difference between Erler and Stadler that day equated to a mere 6% increase.

So it’s pretty clear, even with this less than accurate analysis, that the Ironman marathon is the leg which shows the suffering – the difference to fresh marathon runners is a lot larger than what we see in the bike times. There’s many reasons why you’d generally expect this. The run leg comes after the bike leg in an Ironman, so you are more tired and have a bigger calorie deficit. Making up calories on the run is a lot harder and impacts the speed you can go. The impact of this is far less when making up calories on the bike. There’s also the fact that the faster you go, the more effort you have to put in; It’s diminishing returns on a bike, which is why if you want to pace the best effort on a solo Ironman you would back off the power slightly on a descent and add a bit more power on a climb. These diminishing returns are seen on a bike due to the wind resistance – they’re not really a big factor when it comes to running. I’m sure we can bring some of this difference down when we get a Brownlee/Gomez shoot out on Ali drive which I’m sure which break Kona run records.

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