After I finished yesterdays article about Triathlete Magazines Windtunnel Testing it occurred to me that there were additional elements worth considering. So today I’ll look at the effect of different bikes at IMNZ and consider the impact of adding a water bottle to the frame – which works in the favour of the Specialized Shiv Tri.

Firstly – Ironman New Zealand. Much colder and a bit hillier than Kona. Much colder and very much hillier than Florida. Also a hideous road surface.

For 2011 conditions (the last time there was a full Ironman) we get the following differences.

Windtunnel Testing Performance Comparison






You can see why I’m so fond of recommending Speed Concepts to my clients for the conditions we often face in major events here.

However – the long range forecast for Ironman New Zealand 2013 is light winds and getting quite warm midway through the bike (as opposed to 2011 which stayed cool). So the predicted conditions would lead to the differences shown in the next table.

Windtunnel Testing Performance Comparison






Light winds means low AoA and we’re back into Cervelos territory.

Based on the above you would be cursing if you had sold your Cervelo P4 or Trek Speed Concept to get a Specialized Shiv for this years Ironman New Zealand. Or would you…?

Effect of bottles

A couple of years ago Cervelo shared some test data for different superbikes – showing how the relative performance changed as you added bottles and a rider. Why this is relevant now is because the Specialized Shiv has the capability to carry a bladder in the downtube – effectively meaning you can carry hydration without changing the aerodynamics of the frame.

The P5 and Ordu did not exist at that point. But the Speed Concept did. So I’ve taken the effect of adding an Arundel Aero Bottle to the Speed Concept and added it to the Triathlete Magazine Data. From the Kona model:

Windtunnel Testing Performance Comparison






So even putting an aero bottle on negates much of the advantage the Speed Concept has in the Triathlete Magazine testing. And the figures on a round bottle sway the table in favour of the Shiv. However – the Magazine did not test with the straw sticking out (and I’ve seen straws looped out into the wind that would definitely be costing speed) so that would alter the above chart a little back in favour of the Speed Concept.

This serves as a useful illustration of the number of elements that need to be considered in performance. A ‘fast’ bike can be ruined by poorly thought out hydration or nutrition carrying systems. Likewise the benefit of deep section wheels disappears pretty quickly when you put the wrong tyres on. Which is why Speedtheory is here – to deal with the details for you.


  1. Robin says:

    And that is why we love our speed theory web site. Definitive and cuts through marketing hype.