Hey,
I was 3.8 for both Kona/ and IMWI → 4:46 in both races. 31 & 1st fastest bike splits respectively. Steve HED. has given me some feedback on bike positioning, so I should be faster with the same output for '08
That was with a power tap which looses 2-3 % over the drive train vs Quarq/ other crank systems.
Nat
I had 3.17 watts NP/kg but only a bike time of 5:17 at IM Japan. What am I doing wrong? Or am I ok?
"Considering nobody knows their CdA and the fact that there’s a correlation between CdA and mass then I’d say W/kg is fine.
To generalize, you’d probably see a lot of top AGers (top 10 in their AG) be around 3.0 W/kg. More specifically, that would mean an NP (normalized power) of 200w for someone who weighs 65kg and has an FTP of 270w."
Chris, I know you’ve been using power about as long as I have…so I’m surprised to read the above. W/kg is a ballpark measure at best. 3.0W/kg isn’t going to mean much if the CdA is sky high. And its easy to drop 2-3 kilos of weight, thereby improving W/kg…and not have done a damn thing to improve on-road speed because the position is the same. You might motor uphill better, but that’s about it.
And it isn’t really all that hard to do a decent road test for CdA. You don’t have to spend a fortune at a tunnel to get a reasonable number. But you DO have to spend a little time and understand a little math. And pay attention to quite a few details.
I like the W/kg number to compare general power output improvements over time. If I want to have a good estimate of my race capabilities…I need a good aero test on the road.
i believe lighter riders wll have to ride with higher W/kg, since your CdA probably does not grow by 20% if your body weight is 20% higher and W/kg remain the same.
You phrased your question incorrectly to get maximum ST response.
To get maximum response - you need to tell YOUR watts/kilo…then you get a flood of people
telling you that you’re pathetic and doing it all wrong. They still won’t tell you their own numbers…but
at least you get a lot of responses 
FWIW I have ridden at about 2.5 W/k in two races - and both times had a top 20% finish in 40-45. To place
higher, I guess you need more…
.
+1
And, it really helps if the post’er states their weight since a 30lb difference in body weights can produce one helluva different W/KG #.
Also, most, but not all ST’ers are smart enough to answer this post with their WKG for the 112 miles, but then there are those people who will post up their 1HR W/KG thinking that is the ONLY WKG (like MAP).
I was having a conversation yesterday on the whole W/KG subject with a rider who stated that he’d bumped up his W/KG to 4.1 on a ride over the weekend. I asked him to send me his file and when I dropped it into WKO I noticed that he’d set the chart to sample for 60 seconds, but assumed he was looking at a figure that represented 1 HOUR. DOH!!!
Anyway, poor guy was pretty bummed, but it shows that WKG really isnt a good marker for Triathletes since CDA and NP would be much more telling for either a full dist IM, or an HIM. A 3.75 WKG for a 150lb/68KG rider would be 255 watts for 112 miles, and that’s a pretty stout number to hold for 4+ hours. For someone who’s perhaps a Clydesdale that’s dropping 20lbs to say 190lbs/86KG, a 3.75W/KG would be 322.5 watts for 4+ hrs. For my CDA (which I do have) That’d have me averaging 27mph on flat ground/no head or tailwind, and that’s just not gonna happen.
At the VineMan HIM last year I dropped an easy bike split of 2:37 with lazy 209/225 avg/np at 214lbs/97kg. So that’s a WKG of 2.15 which is very very laid back for an HIM.
For IM this year, I have dropped down to 85kg and will be looking for a W/kg of 2.2, and if I can keep my VI down then I should have an NP that is only 12 watts higher.
So, if you stayed with all that nonsense above, then great…but wouldnt it all be a LOT simpler if we just skipped the WKG foolishness, and just went with NP and dist. ?
Yes-
Watts/CDA is a great measure for triathlon. Roadies use watts/kg since most of their key races have huge hills. But for flat courses, watts/cda is a much better metric.
Since CdA seems to go up roughly with the cube root of rider weight (roughly), or at most the square root (depending on who you ask), this gives a huge advantage to bigger riders- for a given watts/kg, they naturally have a much higher watts/cda.
As an example of this- take a falt, windy course like IMAZ- i got off bike <5 hours, i didnt see any AG’ers around me who were any smaller than i was (6’2", 195lbs)- ie those big flat courses are big advantages to the big guys.
Another way to think about it- watts/kg is basically a measure of your Vo2max. As you get bigger, even though peoples vo2max (which is measured per kilo) tends to drop a bit , they get a lot more total watts, to spread over a largely unchanged cda.
I had 3.17 watts NP/kg but only a bike time of 5:17 at IM Japan. What am I doing wrong? Or am I ok?
I was 3.08 at IMC with a time of 5:19 in '07 and 2.95 at IMC with a time of 5:18 in '08. These are all just examples of how course, conditions and many other variables can play a part. It’s a ballpark # so I wouldn’t worry about it. You’re fine, imho.
Thanks, Chris
Come on dude – it’s a ballpark #. You guys seem like you’re getting all bent out of shape debating the details of something you’re can’t fine tune across a wide range of people. Even the OP was careful enough to phrase his question accordingly.
Just go with what we all have observed in practice and over the course of many discussions on this subject. The fact is that almost nobody knows their CdA. You can tell me that it’s really not that difficult to figure out and then I suggest you go ask 100 people if they know their CdA. You’d be lucky if you found 5 people who know it. Secondly, we all know our weight and it’s also a fact that there’s a correlation between mass and CdA. AC has been trying to educate people about this fact for years with little success apparently. Just go search on “CdA correlation” and “Andrew Coggan.” Given that information, when someone asks for a ballpark W/kg # then we can safely provide one, imho.
I’m a bit shocked at how anal people are attempting to get in answering this guys question. If we want to debate something then I’d debate the usefullness of using your W/kg or W/CdA for anything truly meaningful. Personally, I think it’s a waste of time. I say you spend general prep focusing on increasing your FTP as high as you can get it without frying or injuring yourself and then turn your attention to impeccable race execution during race prep. Everything else will take care of itself (including your time and your place within your AG). Control the variables you can control and ignore everything else.
Knowing W/CdA or W/kg isn’t going make you go faster, imho. Honestly, I don’t think I even bothered to ever know what mine was until this subject came up on ST a few times over the last year.
Thanks, Chris