Smashing the Sub 6 hour IRONMAN Bike

For many people, doing an IRONMAN is an effort in itself. Putting in a fast time is one step too far! However, for the rest, they want to nail a time as well as get round. The six hour bike split is a very worthy goal to have and for many people on their way to breaking 11 or 12 hours, breaking 6 hours on the bike is an important milestone. Here we discuss how to get below six hours and still run off the bike!

Riding six hours for an IRONMAN bike split is tough, it takes a lot of work and there are several factors that go into making it possible. Firstly, it is important to consider what the implications are. Riding 180km in six hours means holding 30km/h or faster for the bike leg. It implies you can ride an IRONMAN 70.3 in less than 2hrs 30mins. Along the same logic, 30km/h means 40km is completed in 1hrs 20mins and 20km in 40mins. Clearly that is if the speed is the same then the intensity is always IRONMAN intensity, so in reality, you would need to be faster than all those time checks above.


It is also really important to remember that you still need to run off the bike. Therefore, this whole discussion is on the premiss that you get to T2 in a state to be able to continue on and race as best you can in the marathon (see the article about running sub 4 hours off the bike). No one remembers the first person into T2, everyone remembers the first to the finish line!

Firstly you must consider the course selection. Not only does it need to be a fast course, it needs to suit your riding style. If you are 95kg, then choosing a hilly course won't help. If you are not good at descending, then choosing a technical course, won't be wise either. If you feel the cold, racing in conditions that are traditionally colder, is a poor choice too. So the first tip on riding a fast bike time is to choose a fast course that suits you!

Secondly, we need to look at you and your bike. This is not an exercise of draining the savings account to ensure you have the most aerodynamic bike out there. However, it is worth considering what time savings you can make within your budget. The obvious considerations are:

  • Bike fit – have you had the bike fitted to you? You may be able generate more power and be placed in a more aerodynamic position with a proper fit. (double win!)

  • Aerobars or no aerobars?

  • Comfort of position (as above) can you hold an aerodynamic position for sustained periods? Can you hold your head in the right place? What type of helmet suits you? Can you ride technically from this position?

  • Clothing - is your clothing comfortable for riding? Is your clothing suitable for the race conditions? Does your clothing flap or catch wind at all?

  • Tyre types – are your tyres in good condition for racing? What pressure do you have in them? Are you riding normal butyl inners or the faster latex? Are your tyres (and inners combination) the fastest?

  • Is your bike clean and well lubed before starting to reduce mechanical drive chain losses (regularly estimated at 12-14% of the power you put into the pedal)?

  • Then you can start looking at things like wheel types, expensive frames etc etc.

To put some figures on this, your CdA the coefficient of drag multiplied by your area makes a significant difference over IRONMAN distance. For en elite athlete with a CdA of between 0.18–0.25, they could be riding up to 30-40 mins faster purely from aerodynamic savings. As we mentioned above, this can be quite an expensive gain to purchase, so you need to consider what your best bang is going to be for your buck. An amateur on a road frame would have an approximate CdA of between 0.33-0.45, or 0.25-0.3 if they were on a TT bike. Though a bike fit wouldn't highlight those differences on their own, it would give you a good idea of improving your 'slippiness' through the air. Nevertheless, the bottom line is that you need to be able to ride whatever position you have...for less than 6 hours so there is no point in having a CdA of 0.18 on the aerobars, but then spending the whole time sat up! You need to train yourself to hold your position.


Finally, we start considering the the actual training: the physiological training to get round in less than six hours. Clearly 30km/h is the race goal. However, you need to be holding about a 75% intensity when riding at that speed. In terms of power numbers, that is 70-75% of FTP, or about 78-84% Lactate Threshold heart rate or an RPE of 2.5-3 out of 10.

If you have a power meter, you can fine-tune this effort even more by using Joe Friel's "How to Cheat by using a Power Meter in an IRONMAN" blog. Using his table you will notice to keep the right side of a successful IRONMAN run, you may need to drop below the 70% FTP depending on how strong you are on the run. As he says in his article, its about budgeting about 250–300TSS for the ride and not going above that. If you want to go for 6 hours, then you can only change the intensity, which means you need to train for that effort.

When considering the actual training, it is also important to consider what fuel you are taking. Not only do you need to be confident that you are getting enough fuel, it is also about being able to take on the fuel when riding at the intensity that you are going to race at. Therefore, not only do you need to practice your nutrition plan, you also need to practice your nutrition plan at 'race pace' and if possible in race conditions.

In conclusion, there are clear ways to help yourself get under the six hour mark at an IRONMAN and in many ways when linking that up with the sub-one-hour swim and sub-four-hour run, this could be you on your way to break 11 hours, or it may be a big part to helping you have time for the marathon if running isn’t your strength. Either way, this article lays them out in a process of stationary to movement: from computer (choosing your race); to you and your bike; to training and racing tips. That is not always the way you need to look at it, so it certainly isn't sequential. If you plan on sticking in the sport for a long time, it may be best to focus on training your body up and then getting a significant peak in improvement as a result of training and only after you complete the race and have nailed your nutrition strategy you make bold purchases of new bike parts and wheels to go fast at (e.g.!) Roth – who knows, then you may be focussing on a sub 5 hour bike!

Good luck!