In the discussion of the topic “what bike to choose in Norseman”, it comes down to TT-bike VS road bike with clip-on. TT-bikes are more aerodynamic while road bikes are lighter. Then, what is the effect of weight in a course like Norseman?
Calculating the effect of weight in uphill can be done without fancy analytic tools. The length of the hills, average grade and a calculator is all that is needed. My low-tech calculations estimated an increased time in the five climbs to 2 min and 3 seconds using the metric for “Mr. Average-Joe”, weighing 75 kg + 8 kg bike and pushing 200 watts and a drag coefficient of 0,260 CdA which is a fairly good aero position. That did not account for the increased speed in the downhills, or the marginally decreased speed in the flats. The tool I used was Steve Gribble’s Interactive cycling power and speed calculator.
Like mentioned, that was low-tech calculation and a rough estimate of the effect of increased weight. Usually, that is good enough, but I wanted a better calculation and googled to find a better tool and ended up at a site called Best Bike Splits. The calculations are very complex and take account of everything, even the estimated weather on race day.
Inserting the weight of me and my bike, my FTP in the Norseman course they estimated that the time use with an average power of 252 watts would be 05:04:47. Then I could add 1 kg and do a new calculation. The added times was the following:
- 1 kg – + 1 min and 25 sec
- 2 kg – + 2 min and 51 sec
- 10 kg – + 13 min and 17 sec
I don’t know about you guys, but personally, I found the effect of weight to be smaller than I initially thought, and I think my estimates of the effect of weight is lower than average. How much money does it cost to reduce the weight 1 kg? Is it worth saving 1 min and 25 seconds? Could that money be used for taking an unpaid vacation for work to train better?
Knowing the effect of weight can put things into perspective, but knowing the effects of aerodynamic drag is another important part of the equation when you are putting things in perspective.
I cannot say the difference in aerodynamic drag from a high-end TT-bike to a high-end aerodynamic road bike with clip-on because I have not tested it and have not found any data on the difference. What I know is that my drag increased from a test best of 0,208 CdA to 0,303(!) going to a normal road bike with road helmet and medium deep wheels, from my Specialized Shiv with Zipp 808 front, Sub9 disc and aero helmet. Using that road bike setup would have cost you 15 – 20 min in Norseman (theoretically going from 0,208 to 0,303 would cost 30 minutes, but the deep 0,208 aero position cannot be maintained thru the whole race).
Finding good numbers of the differences in drag on TT-bike, aero road bike and a normal road bike was hard (any help is appreciated), but I would roughly estimate the following numbers:
- High-end TT-bike – 0,054 CdA
- Aerodynamic road bike – 0,077 CdA
- Road bike – 0,090 CdA
With an identical position the added time would be:
- High-end TT-bike – Baseline
- Aerodynamic road bike – + 6 min 39 sec
- Road bike – + 10 min 30 sec
I hope this set things in perspective regarding your choice of equipment for Norseman. If you have any comments or questions do not hesitate to share it in the comments field below.