What does it take to ride a sub 5hr bike split?
In this article Coach Alan focuses on answering the simple question “what does it take to ride that potentially elusive sub-five-hour IRONMAN/Long Distance triathlon bike split.” Read on to find out some of the factors that go into that performance and how you could overcome this.
Different course and conditions scenarios that make up the demands of executing a Sub 5hr Bike Leg.
If you’d like to know what it takes to ride that sub-5 hour split, you’ll need to start by breaking it down. Several factors go into the bike leg, and I’ve listed them below in order of significance. Ultimately we need to work if it is feasible and, even more importantly, sensible – well, unless you fully intend on walking the marathon!
The Five Factors
In the chart above, I have put together some information to demonstrate how different courses can present a different combination of challenges across the four factors with the truths below in mind.
Course, any rider in any weather on any bike can be unable to ride a sub 5hr split, for example, if it was entirely uphill.
Weather, any rider can experience conditions that make the split impossible even on a feasible course; wind, for example, could lead to this.
Equipment, at the extreme, even the world’s strongest cyclist on the most straightforward course in the best conditions can’t complete the ride on unsuitable equipment.
Rider, ultimately, even if the course, the weather and the equipment are all perfect, the rider can undo things.
Bike handling
IRONMAN Wales is a challenging course for climbing and often has harsh weather conditions: cold, wet and windy. This means the rider and their equipment need to ride to match that challenge. I would add that in my opinion, I believe that the IRONMAN UK course is more challenging due to often similar weather conditions being combined with poor/heavy road conditions and the technical nature of this course. All too often, the effect of corners, bike handling and carrying speed on a course is overlooked when looking at the level of challenge. Having coached athletes and raced personally at both events myself, I would say that it is easier to carry speed in Wales. On this course, the top male pros ride around 4h50 - 5hr and top female pros 5hr20 - 5hr30. However, riding well on a course of this type can also be undone by lacking confidence in or poor bike handling skills and experience. Luckily technical courses can be avoided if this isn’t a personal strength. IRONMAN Portugal, for example, is a surprisingly technical one. Coach Jon raced there this year and reported this back to the coaching group. Furthermore, the coastal nature of this course leads to windier conditions. A rider must be able to meet this challenge as well.
During the IRONMAN Frankfurt in 2019, temperatures were above 40’C and the rate of DNFs on this day totalled 700. In comparison, the DNF rate was 288 and 105 in 2018 and 2021, respectively. A significant proportion of the 2019 DNFs occurred before T2; this demonstrates that the weather can throw things off regardless of the ease of a course. To put some perspective on the course conditions, Sebastien Kienle has ridden the course in 4h12min – a significant chunk faster than the pros in Wales – yet the average age-grouper completed the course in 5hr49 and 6hr23 for the male and females respectively in 2019.
The other favourably quick courses are in Switzerland and Italy. However, the average age group times remain relatively slow. It is important to remember that the data covers all age groups (into the octogenarians), skewing the data. It is also important to remember that these events are likely to attract athletes that sensibly may choose to complete on a favourable course compared to a DNF at an event like Wales by missing the cut-off time. When looking at the overall general picture, you must consider your age group. Ultimately to even consider riding Sub-5, both the course and conditions need to be in your favour.
Course
So let’s assume you have picked a favourable course. Can you still do it? You need to look at yourself as an individual athlete to answer this. Looking at results may show it’s feasible, but it doesn’t tell you what it will take for you. I have used the TriRatings ranking page to select IRONMAN Tallinn for this article. It comes out as the fastest-rated course followed by IRONMAN Barcelona, although the notorious bunching of riders may somewhat influence this race on the lap course. IRONMAN Vitoria-Gasteiz and IRONMAN Florida also rate as quick if you are interested in other options.
Equipment and Rider
In swimming, the key metrics are buoyancy, drag and propulsion. For cycling, this neatly converts to CdA, rolling resistance, power, and drivetrain efficiency (though here perhaps we need to add biomechanical/pedalling effectiveness to swimming, a.k.a technique).
Let’s start with CdA and answer the question do you need a TT Bike? CdA can range from 0.16 to over 0.3; at about 0.28, getting lower becomes very difficult on a traditional road bike geometry. This is due to the rider not being able to pitch forward any further to reduce frontal area. That being said, riders with lower mobility may well be better served by trying to maximise a road bike set up than ride a poor TT position. Shorter cranks and getting the frame with the exact geometry, stack and height, in particular, to suit you personally can go a long way to optimise a position on either TT or Road Bike. It is also essential not to look at CdA as a constant when assessing your position or your performance. Any rider on any ride will experience a great range of CdA as they move around on the bike; it is likely the variable with the greatest degree of variation throughout a ride. With that in mind, we need to assess the average CdA from the real world as you ride, corner, drink, flex, relax, work hard and eat throughout an IRONMAN bike leg rather than the ultimate static position you can hold for minutes in a test environment.
Importantly you may also want to improve your output in terms of watts relative to your drag: your average W/m2. It is commonly understood that watts per kilo make a significant difference uphill; watts per gram of drag (W/m2) make a substantial difference on the flat.
I have used BestBikeSplit to model the information in the table below to show what it takes to ride a sub 5hr bike split on the Tallinn course. Each example only varies by the bike ridden and thus the likely average drag of the rider. As you can see on a simple road bike, it is challenging for the rider to even get under 5hrs, let alone run off the bike. Even with a basic clip-on setup, it is difficult but perhaps not impossible with a strong enough rider. An increase in FTP from 290W to 329W for this rider would be sufficient to make a road bike clip-on setup undoubtedly feasible. A 39W increase or a 13.4% increase is unlikely but not impossible for a relatively young athlete in their ‘training age’. So do you need a TT bike? No, not necessarily.
Even with a basic TT Bike setup, the required work or stress in TSS is a little high to enable the example athlete to run well. Still, a modest improvement in FTP of 7W is certainly feasible, as is a modest improvement in aerodynamics. So does a TT Bike potentially help? Yes! But only if you can ride it well and maintain a good average CdA. A rider that isn’t confident on a TT bike will likely hold a much better average CdA with a set of clip-on bars if they are comfortable with this setup.
A TSS of around 250 - 280 will allow for a good marathon, with the required FTP. (Above based on 80kg Rider with 290W FTP)
Rolling resistance and drivetrain efficiency can be assumed for all riders. Even for those riders unable to change a tyre/tube, tubeless can now allow riders not to resort to slower, more resilient tyre choices. Everybody can clean their bike and ensure they have a smoothly operating drivetrain. But even though assumed in this article, this still means every rider has to pay attention to tyre selection, chain wear and lubricant, gear selection and jockey wheel and bottom bracket condition.
Weight can be assumed with this course, but it will have a minor effect on CdA with significant changes in body composition. More notably, those athletes carrying fat tissue around their abdomen may be restricted in how much they can reduce frontal area due to their stomach hitting their thighs. A reduced crank length in this area may help on the bike, but ultimately, it would be wise to work on improved body composition for health and performance. Importantly this may not mean weight change but rather a conversion of fat mass to heavier muscle mass.
CdA Coaching
Aerodynamic testing can give the impression that you need to get tested and get in a tunnel to make aero gains and spend lots of money. In reality, a lot of CdA can be coached and learnt by a rider. After all, it is true that a rider can go to a wind tunnel and achieve an amazingly low CdA but then significantly underperform out on the road! The reason why is where the coaching can come in.
Discipline and awareness are critical to achieving a low average CdA throughout a ride. A mirror alone in front of your turbo can help you achieve this!
What does it take
According to this BestBikeSplit model, to break 5-hours, you will need more than 780 W/m2 in terms of average aerodynamic efficiency to absolute wattage at race pace or over 3.2W/kg at FTP should make Sub5 feasible. Still, if your aerodynamics are terrible, you don’t stand a chance!
It is crucial to take these numbers in a modelled and theoretical context; they are not absolute and are by no means perfect predictions. However, they demonstrate the prioritisation of importance, and it is this hierarchy that should be heeded when trying to assess if your Sub 5 goal is feasible:
Pick the right course
Make a sensible choice regarding likely conditions (and then don’t have some bad luck on the day!)
Ride a good average CdA
Pay attention to your rolling resistance and drive chain efficiency
Ensure your bike handling is well-practised in your race position and setup
Train well
Execute a good race
Alan has worked with Tri Training Harder since 2014. During this time working with a wide spectrum of athletes from beginner, to youth and junior elite athletes through to 70.3 and Ironman AG winners and Ironman Kona Qualifiers.
An active Triathlon coach since 2007 Alan has been fortunate enough to work with athletes, peers and support staff who have continutally challenged him to evolve and develop. Building on a solid foundation in swimming teaching, Alan has specifically developed swimming coaching experience having worked in High Performance Swimming environments. Alan's other passion is all things fast on a bicycle!
Since 2015 Alan has worked in conjunction with the other Tri Training Harder Coaches to significantly develop collective coaching practice both on camp and online.
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