For those of you who did IM Texas in 11, 12 or 13:
What was your bike split and what did was your effort in watts per kg (not your FTP but your NP per kg for the bike)
Thanks
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2013 , 5:01:51 , 3.21
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For those of you who did IM Texas in 11, 12 or 13:
What was your bike split and what did was your effort in watts per kg (not your FTP but your NP per kg for the bike)
Thanks
I don’t think watts per kilo is a good gauge for that course. Brute watts matter. Someone who weighs 58 kilos has a 230W FTP will ride at around 170W. Someone who is 90 kilos with an FTP of 300W will ride at around 225W. I bet you the big guy goes much faster off the 225W even though his watts per kilos is only 3.3 vs the little guys who is more like 4W.
I would say watts and cda matter most 
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I went 5:21 in 2013 on 155 watts weighing about 158lbs on race day. I know time and watts are correct but weight is my best guess but win my usual IM race weight +/- 2lbs.
I would say watts and cda matter most
Topline watts matter as you said. take two guys both 4W per kilo, one at 250W, the other at 325W. A larger proportion of the former’s top line watts go towards moving the same 700c wheel (assume same rubber) at the same speed. The guy with less brute watts has less “leftover watts” to push his smaller frame and smaller body through the wind. Generally the bigger rider will go much faster for similar aero positions. IM Texas bike course will favor the guys with big top line watts…well, until you get to the run when for every watt you produce, you generate 4 more as heat and the big runner generates a ton more heat. What you want is to be like Rapp…weigh nothing and generate a ton of watts and be super aero…win win win.
Agree. Small, Aero, and Tons of watts is best. Aero, tons of watts is next (unless it’s cool in which it’s probably tied), but being from Texas we know in mid-late may that’s not the case typically. Case in point did a case study on a young pro from Australia pushing 300 watts for 70.3 at 145lbs he is now at ~138lbs still pushing 300 watts with the same bike time, but much faster run times.
I have 9 weeks or so go get from 145 down to 138…sadly there is no chance on earth to get up to 300W !!!
I have a feeling you will do fine as always!
I have 9 weeks or so go get from 145 down to 138…sadly there is no chance on earth to get up to 300W !!!
I’m aiming to drop 5lbs to get to 145 on race day…and no way i’m getting to 300W, either. Not even close.
I have 9 weeks or so go get from 145 down to 138…sadly there is no chance on earth to get up to 300W !!!
I’m aiming to drop 5lbs to get to 145 on race day…and no way i’m getting to 300W, either. Not even close.
I think we need to contact Macca and get him to put us on the carrots, cabbage and broccoli diet. That still won’t get us to 300W…but maybe it will get us to 300W for the obligatory 1 min “hero surge” out of T1!!!
Dev
@Dev…
The only reason I responded to this thread was because I liked the way the question was worded… Asking the w/kg relative to the known power ridden, on a known course, with a known weight…These numbers are not debatable(its what you did that day with that weight on that course) so wouldnt they be more appropriate?.. Rather than the typical what IF of your estimated FTP did you ride for IMxx???
I certainly understand your Absolute power theory and the 90kg guy vs the 58kg guy and also understand that CDA is huge in this picture but not in the original question…The other thing that never gets discussed is that both of those guys pretty much have the same weight bike which is also never calculated into the picture… Shouldn’t track w/kg relative to the watts ridden for the bike leg , to the weight and rider combined? watts for bike / kg of rider/bike
90kg/198lb guy rides 225 for an IM , that is w/kg of 2.51 for that ride , add a 20lb bike and that is w/kg 2.28 , loses .23 when adding bike
58kg/128lb guy rides 170 for an IM , that is w/kg of 2.93 for that ride , add a 20lb bike and that is w/kg 2.53 , loses .40 when adding bike
On most IM course, actually 95+% of all triathlon bike courses in the world, your power/Cda ratio is more important than your p/wt ratio.
p/wt ratio is good for comparing a lot of things but it’s only half of what you need to know especially in triathlon.
The OP would have ben smart asking what was your p/wt ratio, your p/Cda ratio and your time. That would give you a much, much better picture of how faster someone truly is or isn’t.
@Dev…
The only reason I responded to this thread was because I liked the way the question was worded… Asking the w/kg relative to the known power ridden, on a known course, with a known weight…These numbers are not debatable(its what you did that day with that weight on that course) so wouldnt they be more appropriate?.. Rather than the typical what IF of your estimated FTP did you ride for IMxx???
I certainly understand your Absolute power theory and the 90kg guy vs the 58kg guy and also understand that CDA is huge in this picture but not in the original question…The other thing that never gets discussed is that both of those guys pretty much have the same weight bike which is also never calculated into the picture… Shouldn’t track w/kg relative to the watts ridden for the bike leg , to the weight and rider combined? watts for bike / kg of rider/bike
90kg/198lb guy rides 225 for an IM , that is w/kg of 2.51 for that ride , add a 20lb bike and that is w/kg 2.28 , loses .23 when adding bike
58kg/128lb guy rides 170 for an IM , that is w/kg of 2.93 for that ride , add a 20lb bike and that is w/kg 2.53 , loses .40 when adding bike
Desert dude did a good job on this, but I want to stress one point: weight doesn’t decide how fast you go on a flat course.
Therefore,
-watts per kilo don’t matter on a flat course
-watts per CdA becomes way more important
Let’s break that down using your examples:
90 kg @ 225 w, 2.51 w/kg.
58 kg @ 170 w, 2.93 w/kg. Let’s add weights of bikes
Big: 2.28 w/kg
Little: 2.53 w/kg.
What eats your power on the bike? Assuming these guys are riding equal bikes (not in any order)
Drivetrain losses. These will be the same ~2% of whatever for both guys.**Rolling resistance. **This will be the same order of magnitude, but will probably only be a few watts higher for Big Guy. Effectively same for both.**Uphills. **Well, there are very few uphills on a flat course! Same for both.Therefore, aerodynamic drag becomes the big one. If they’re both riding equivalent frames and wheels, then body position becomes the deciding factor.Let’s think about it - if big guy is riding 225w, that’s 1.33x as much as little guy. But what if Big Guy’s surface area is only 1.2x as big? Well, that means that he’s putting out MORE power per surface area. So, he has to push less air out of the way, so he goes faster.
This is why time trialists are rarely small guys - Fabian’s 6’1", so is Tony Martin. Rapp is above 6’1", as are Weiss and Thorbjorn Sindballe, to name a few strong cyclists.
Obvious exceptions are TdF time trialists - guys like Contador and Froome. They just tend to have absolutely absurdly high FTPs (400w+) so their power/ CdA is right up there with the big time trialists.
If this interests you, you can play around with this:
http://www.gribble.org/cycling/power_v_speed.html
Did it last year. First IM.
184W ave, 187NP, 2.67 W/kg, estimated cDa of around .22-.23, very hot temps, 10ish mph winds. Went 4:58.
Bike setup is here http://journeytogopro.blogspot.com/2014/03/the-bike-setup-matters.html
And there are more posts about my race in Texas. I made a lot of mistakes, which I later pointed out how I fixed them at Louisville.
For fun I used Bryan’s Numbers to do a quick simulation. I then modeled a bigger dude (assuming the same CDA) to determine what he/she would need to ride for a 4:58 split? Results are below (I know I need to add W/Kg to the outputs not sure why I don’t have that already)
Bryan’s Numbers (154 lbs) 2.67 W/Kg
New Dude (170 lbs) 2.5 W/Kg (assuming same CdA … a potentially big assumption carrying an extra 16 pounds)
2012 - 5:33 AP-165 NP-181
2013 - 5:27 AP-166 NP-182
Weight both years was 175lbs, so about 2.34 w/kg NP
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I forgot my point in the post earlier. Get your CdA as low as possible and push as many watts as you can (while still giving yourself enough for the run). Simple right… As a side note I have low watts and high CdA a horrible combo!
On most IM course, actually 95+% of all triathlon bike courses in the world, your power/Cda ratio is more important than your p/wt ratio.
p/wt ratio is good for comparing a lot of things but it’s only half of what you need to know especially in triathlon.
The OP would have ben smart asking what was your p/wt ratio, your p/Cda ratio and your time. That would give you a much, much better picture of how faster someone truly is or isn’t.
I don’t doubt that W/CdA is a better predictor of bike performance in almost all cases. But I bet that W/kg on the bike explains more of the variance in bike+run performance, given the greater importance of weight in running. Of course, they aren’t mutually exclusive and the goal should be to optimize both. But W/kg might be a little more important for overall triathlon performance.
It would be cool to do a regression analysis to find out. Art Hare plotted up self-reported power/weight and raw power vs speed. But I doubt that enough STers know their CdA to get a big enough dataset.
A couple of results for you…
4:50 @ 3.5w/kg
4:53 @ 3.05w/kg
David