When you’re setting up a forecast in order to analyse a course on myWindsock, there are a couple of things you can do in order to make it a touch more accurate as well as model the difference that equipment choices might make and calculate a pacing plan. Rolling resistance, drivetrain efficiency and a number of other things can impact the accuracy of a forecast and many of these assumptions can be tightened using our advanced settings.

Let’s check out a forecast… 

From the main page of the forecast, scroll down the margin on the left until you get to the bottom…

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How does a change in rolling resistance impact the overall time in an Ironman? 

Let’s, for example, imagine we want to ride an Ironman bike split under 5 hours, that’s pretty good going for most amateur athletes. We are at Ironman Texas and are able to hold an average power of around 210W with a cda just over 0.25. These sort of numbers are typically what you might find in an amateur Ironman field. Our rolling resistance coefficient is set to 0.005, this is typical of what you might find in a training tyre – but what if we change rubber?

Rolling resistance – typical values and what to buy?

Helpfully, Aerocoach have compiled a list of rolling resistance data here which you’re able to see how various tyres performed on their test. Databases like this are how I decide which tyres to buy, but beware – there’s a payoff between puncture protection and rolling resistance! 

If we move from a tyre with a crr of 0.005 to something like a GP5000 TT, which Aerocoach measured at 0.002216 for their tubeless version, how much time do we save on our Ironman from the original 5 hours, 1 minute and 38 seconds? This is a saving of around 30W which equates to a whopping 13 minutes and 55 seconds – that’s huge!

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If you want to model your next race, training ride or KOM you can check out myWindsock here.