Ironman Cozumel 2013: Full Results and Analysis

In last week’s pre-race analysis I noted that while Ironman Cozumel appeared to be very slightly faster than the average North American race it also had the capacity to be slower under the right (or wrong, depending on your perspective) conditions. A good example of the challenge of attempting to guess performance requirements on the basis of historic results. Sure enough where last year’s race was most notable for a slower than normal swim, this year’s event produced much quicker times on a shortened course. Wind conditions resulted in the swim being reduced to 3.1km resulting in fast swim splits and a faster year in Cozumel.

Distribution of Finisher Splits at Ironman Cozumel

Comparing the split distribution among finishers from 2013 with previous years (above) it’s clear that the swim is the major difference. Bike and run are broadly similar, particularly when using the dotted percentile markers to compare, and the faster overall times in 2013 are a natural consequence of quicker swims. The impact of the shorter swim course, and presumably conditions on the day, is significant with well over 50% of the field finishing in under an hour.

Adjusted Distribution of Swim Times from Ironman Cozumel 2013

Knowing the swim was 3.1km long I can attempt to scale swim times to reflect on how they might have looked over a full length course. The graph above shows that simply scaling the times still results in a much faster distribution than previously seen. Assuming the 3.1km is accurate conditions were likely also favourable. The impact of a course change is much more complicated than a simple linear transformation.

Finisher Distributions by Male Age Group at Ironman Cozumel 2013
Finisher Distributions by Female Age Group at Ironman Cozumel 2013

For those interested in their own age groups and how the results shaped there the two graphs above offer a little more insight and indicate times for the top 5, 10, 25 and 50 percent of the field.

Median Splits by Category at Ironman Cozumel 2013
Median Splits by Category at Ironman Cozumel 2009-2012

We expect the median splits to follow the same pattern as the distributions. Skipping over the swim, both bike and run times are generally comparable, with bike times being a touch faster among the male age groups in 2013. The pattern is less clear among the female field with bike times often slower and run times mainly faster.

Top 20 Male Age Group Performances and Kona Qualification at Ironman Cozumel 2013
Top 20 Female Age Group Performances and Kona Qualification at Ironman Cozumel 2013

It goes without saying that the top 20 age group performers are generally – but not universally – faster than in previous years. Qualification times this year are well ahead of the average. Slot allocations are based on my estimates prior to the race and did vary on the day based on lower starter numbers. I’m told that a number of slots also rolled with both the M70-74 and M75-79 slots moving to the largest age category, M35-39, taking their total up to 8. It’s not often you see that much gain, but it’s the reason you should always go to the roll down.

So Cozumel hammers home the point that whatever has happened before it’s what happens on the day and how you perform under those conditions that counts. This year’s race was faster, but this can be attributed to the shortened swim, had that not been the case we might expect results a little closer to the norm.

I’ve uploaded a spreadsheet of the full results and splits from Ironman Cozumel 2013 to Google Drive.

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  • Rob Knell

    Hi Russ

    Greetings from Cozumel. A few comments: firstly, the swim was very fast indeed: not just short, but also with a current. Secondly, the bike was quite a bit harder this year, with exceptionally strong headwinds on the Western side of the island which get stronger during the morning – wind speeds at Cozumel airport, which is on the sheltered Eastern side, were up to 27kph with gusts up to 40, and we were getting that full in our faces for 20 km on each lap. The median bike splits reflect that with slower times for most of the male age groups, and you can also see the effect in the very fat positive tail on the frequency distribution of bike times this year. I rode harder than last year and was 10 minutes slower.

    Unfortunately the strong effect of the wind was negated for the large number of competitors who drafted shamelessly: the drafting was much worse than last year with lots of big packs forming and making life difficult for those of us who chose to put our noses in the wind and try to keep it clean. I finished in the 400s this year as opposed to the 200s last year but this year I was passed by several hundred people in tight draft packs so I’m claiming a moral victory 🙂

    Finally the run started very hot and humid and then had torrential rain and flooded roads by about 4 pm. All in all a very hard but good day.



  • Ryan Collison

    I was looking through the raw data on the google drive link. It appears there was a ~26% DNF rate (just over 1,800 finishers out of a starting field of ~2,485)! Am I reading this right? Is this unusually high? I have heard that the DNF rate is normally ~10%, but have not seem any data around that. From your perspective, what would a high, normal and low DNF rate be?

  • Hi Ryan,

    You’re right in that there are 2,485 athletes listed in the results of which 1851 recorded finish times. However this doesn’t actually mean that 26% DNFed because the 2,485 athletes also includes those who registered for the race, but never turned up/started. So while 2,485 athletes registered for Cozumel not all of them made it to the start line on the day and the effective DNF rate from those who did start will be lower. Unfortunately it’s very hard to tell what that rate would be because the Ironman results don’t indicate DNS if an athlete has no swim time they may have been a DNS or perhaps a DNF in the swim. IF i take the count at T1 there were 1915 athletes exiting T1 and given DNF rates in the swim are typically fairly low, especially when it’s shortened with the current we might estimate say 1930 starters and then get an overall DNF rate of around 4%.

    I’ve written something about DNF in Ironman before: The Reality of the Ironman DNF. That talks through these numbers for a range of Ironman races. From what I’d seen I’d consider anything below 5% to be a low DNF rate, 5-10% to be the normal range and over 10% to be high. Once a race crosses 15-20% DNF rate I ‘d consider that exceptional and indicative of some significantly tough conditions. Lake Tahoe is the most recent examples that springs to mind for extreme DNF rates: Ironman Lake Tahoe 2013: Full Results and Analysis.

    Hope that’s clear


  • Rob,

    Thanks for the feedback on the race again. Useful to know and makes more sense of my hurried look over the graphs I generate. I need to get more people to comment when they race. Drafting seems to have been a common theme fro what I’ve seen on the forums and if reports are accurate it was particularly bad here. Presumably the strong winds helped -reducing the speed difference and upping the temptation to take shelter. Not that there’s ever an excuse and good on you for keeping clean. Other than the benefits of a shortened swim with the currents sounds like conditions tended towards the worst.


  • Bob McRae


    This is excellent analysis; I am grateful to have found it. As I started to dig in, I found that the raw data is affected by the timing issues that seem to persist in the original data. Specifically, many racers’ bike splits include the swim split and T1 times. So, just be aware that the analysis based on that data — of course — will reflect slower bike times.

    Thanks again for the excellent analysis and discussion.

    Yes, the draft packs were astoundingly numerous and seemingly un-policed. Shameful.

  • Bob,

    Good point. Checking the results data it seems approximately 13% (250) finishers have missing swim times merged into their bike time. Small enough that I didn’t notice, but big enough to have some influence on distributions and medians (likely a matter of minutes). I occasionally see this in race results, but checking through the database this is the worst example by quite a margin. I’ll flag this to remove the merged splits from future group comparisons to avoid any further skew. Thanks for pointing it out.

    Anecdotally complaints of drafting packs are on the increase suggesting the drafting problem is getting significantly worse. Reports, if an accurate reflection of the situation, make me suspect it’s becoming one of the major determiners in age group races. Not necessarily at the very front-of-the-pack for age group winners, but not far behind at all and certainly having some influence of Kona qualification. Unfortunately there’s no good way to test this out in the results data.



  • Ron

    Thanks Russ,

    Your analysis of the race is very useful. This was my first 140.6 so I don’t have a real comparison but I can attest to the increasingly strong headwinds on the windward side of the bike course and a surprising number of draft packs. As I was not challenging for an age group win I wasn’t offended by the drafters but it seems it would not be such a hard problem for Ironman to solve. The bike took more out of me than I expected due almost entirely to the headwinds (it’s hard to train for that in Michigan).

    My swim split was a solid 20 minutes faster than expected and I felt like I spent very little energy — I was surprised how quickly the changing tents appeared on my left.

    The flooded streets from the second loop on of the run were a challenge but at least the rain cooled things off – my bike computer showed temps as high as 92 toward the end of the ride.

    Thanks again for taking the time to provide this anaylsis, I found your site helpful before and after the race.


  • Writingprincess

    Thanks so much for this analysis. After looking at this I feel MUCH better about my 15:25 finish and 7:23 bike. The winds were horrendous and as this was my first completed Ironman I was feeling a bit down about the shortened swim but then the bike was long. I really took my time on the bike and I, like Rob, did not draft. It wasn’t easy. I mean there were PACKS of cyclists together it felt like another wind tunnel out there. LOL. Still, me being a back of the packer I guess I had to ride it alone so to speak. but I took my time and was able to finish before the cutoff. The run was indeed super hot and I got caught in the torrential rains that followed. (Thank the Lord for clean, new socks in my SN bag)…all in all this race was tougher than people give it credit for. And Im glad I survived. Woo hoo. Can’t wait to do another one.

  • Frederic

    I did IM Coz in 2013 and relate to experiences posted prior. The east side had stronger winds, more drafters and less refs. I saw several small groups of drafters (6 each?) not huge packs. Risking a 4min penalty is pretty puny compared to the draft gains in the strong winds for cheaters who can do the math. I’m curious whether the winds typically are like 2013’s since we had a weird weather pattern which closed the beaches & the scuba for days, shortened the swim and threatened to cancel it.