My Tacx wattage was low. I now think it was because I had the tension too tight. I have a CT now and the wattage can be + or - 25w depending on tension but at least with the CT you can calibrate it. With the Tacx it’s just a guess
I calculated myself as needing a 325w avg. to go 54 minutes in a 40k.
Have you seen www.analyticcycling.com?
You can calculate it there.
Gary, I’m curious: when you calculate this figure of 325 W, are you just using the 0.5 m^2 effective frontal area (the default value) for a reason, or is this something you have estimated/calculated as being correct?
ric
Yes, I have no idea if this is correct, my position is pretty good, I left the default.
As I start testing and racing again this month I will be able to better validate the wattage requirements for the event, however the 325 is a rough estimate and training goal for now.
For those who own a tacx trainer (I’m not sure if this will work for other trainers) - there was a calibration protocol described on the wattage forum:
Spin your bike up to 25mph and stop pedaling. The wheel should come to a stop in exactly 10 seconds. Adjust roller pressure up or down to achieve this, and wattage shown should be pretty accurate (or at least repeatable). I like to do this after warming up for 5 minutes.
I know a guy who has a power tap and he said the watt numbers were the same after doing this.
Finally - remember that tire pressure plays a big role. I’ve found that if I bring it up to the same pressure before every trainer ride (120psi), I seldom have to adjust the roller setting.
I assume you do this on zero slope with zero resistance?
(I am scared to try… in being worried that I won’t be able to get it up to 25mph!)
Sounds like a great tip though - thanks.
I did a 20k trial run two weeks ago. At 230 watts with regular training wheels I went 23.6 mph. Give me race wheels and maybe 15 more watts and I can go 40kph.
I raced ~22k last weekend (loop course) with the same setup, in a howling wind, and went 22.9 mph on 229 watts.
So, I say 245 watts. I know of people that have done it on 225. I also know 275 watt guys that have never broken 1:03.
To do it at 245 watts or less, you have to get really, really low on your bike and tweak things like arm width, etc. (I’m 6’, 73 kilos).
Zero slope and no watts setting, yes. There will be resistance from the roller proportional to your speed.
Put it in the big ring in front and and haul a$$ - you just need to do it for a couple of seconds. I try to hold 25mph for at least a second or two before I stop pedaling as it tends to overshoot or undershoot that speed, but it’s all one big approximation anyway.
Rick,
Just curious,
How much faster do you think race wheels (compare for me: open pro 32h set to Zipp disc/HED3 set) are at Fiesta Island, with the variable winds?
Say I do 5:42 on the small laps with training wheels and a jersey/bib, do you think a long sleeve skinsuit, and the addition of a Zipp 900/HED3 combo would be worth 12 seconds faster per lap (small 2.5 lap)?
- Gary
I also know 275 watt guys that have never broken 1:03.
Rick,
Just curious,
How much faster …
I haven’t done any rides out there with my race wheels yet (404 front and a rear wheel cover). I figure the “standard” 60-90 seconds per 40k? That would be 6-9 seconds per short lap…? Clothing (shoe covers, etc) is claimed to be worth as much as 15-20 seconds per 40k, so you might get close to 10-12 seconds per lap total.
I raced your pal last weekend out there (5 short loops, plus to and from the parking lot off the island down past the Hilton). At 50 more watts than me, he only outsplit me by 46 seconds* – and he had race wheels.
So, I’m claiming that race wheels = 46 seconds for ~22k. 
But the real message is that riding with my nose a few inches above the front tire is really, truly faster than I imagined.
*Of course, he outran me by a mile or two… 
I guess the real test will be once I start racing again. 10-12 seconds would be great and put my speed up there. I have to do some more testing, but a calm day, and my goal avg wattage, if I can go 10-12 seconds per lap faster than I do in training, that should get me a OK time out there.
I have been twaeking my position gradually and have got as low as I can, comfortably, with a flat back. Now I just have to practice it more than once a month, to get the back and abs stronger.
We’ll see how it goes.
Thanks for the input.
- Gary
If you don’t have a picture, it isn’t happening.
On most kiwi roads, I think that you’d need to be close to 300w on the flats – the chip seal surface really sucks speed out. If you head over to my board then you can check some recent ride data from my SRMs.
The first 40K of the IMNZ course is very fast – generally about 4-6 km/h quicker out than back (on the same power). Last year, 244w got me an average of 38.7 on the first hour. 255w got me an average of 34.9 on the second hour.
My position isn’t great in a 40K sense but it works for me overall.
g
depending of the user 
.
I guess the real test will be once I start racing again. 10-12 seconds would be great and put my speed up there. I have to do some more testing, but a calm day, and my goal avg wattage, if I can go 10-12 seconds per lap faster than I do in training, that should get me a OK time out there.
I have been twaeking my position gradually and have got as low as I can, comfortably, with a flat back. Now I just have to practice it more than once a month, to get the back and abs stronger.
We’ll see how it goes.
Thanks for the input.
- Gary
it isn’t necessary to get a flat back, and indeed not everyone can. forcing yourself into a flat back position might not be great for you. The important thing in aerodynamic terms and assuming you don’t have access to a wind tunnel, is to get your front end low and try to be as low as your hips (when looking from the side an excellent rule of thumb is to have your acromion process at the same height or just above your greater trochanter - some peoples back will have a curve and some will be flat. it depends on your natural shape). not everyone can get that low though, and may not be possible with every bike.
you should definetely practice more than once a month. at least one session/week all year round should be a minimum, with at least one moderately difficult to TT effort workout.
as regards using the default on analytic cycling, it could be right for you Gary, or it could be completely wrong – depending on your bike position and equipment.
ric
Cheers Gordo, interesting data and I think your right about the Kiwi roads. A lot of overseas riders come to Taupo and complain about the slow surface but personally I think it is some of the quicker chip seal that I have ridden back home.
The Canterbury and Nelson roads often make me think I am riding with the brakes on!
I also am curious as to how to set the frontal area on analyticcycling.com. If I use the default, then I come up with 261 watts for my best 40k time. Seems like an average power production. If I use .7-the high end of the ‘typcal’ scale- because my position was probably worse than average (road bike, wide clip ons, stem kind of high), I come up with 348 wattswhich seems kind of studly. I can’t afford a power meter, but would like to know my ballpark wattage production just for giggles.
Thanks
I was able to get low enough that you can see my shoulders are slightly lower than the ‘center hump’ in my back, because I have the type of back that is not completely flat, to do this I moved my saddle slightly forward and up, and went out further on the aerobars a bit, and lowered the stem.
It is a roadie type aero position, back on the bike with a 80mm stem, 74.5 degree seat angle, nose of saddle is 4cm behind the center of the bottom bracket, short aerobars.
I also changed my TT helmet from the Louis Garneau prologue and got one with the smallest frontal profile I have seen and it lowers my overall height as well.
better to pose is to compare wattage per weight
.
I also am curious as to how to set the frontal area on analyticcycling.com. If I use the default, then I come up with 261 watts for my best 40k time. Seems like an average power production. If I use .7-the high end of the ‘typcal’ scale- because my position was probably worse than average (road bike, wide clip ons, stem kind of high), I come up with 348 wattswhich seems kind of studly. I can’t afford a power meter, but would like to know my ballpark wattage production just for giggles.
Thanks
The product of the two 0.5 numbers gives CdA; in the default case, it’s 0.25. A CdA of 0.25 is really quite aggressive and probably only applies to folks who are very serious about their aerodynamics. Most triathletes should use a value more like 0.29 to 0.33; MOP folks on road bikes with clip-ons are above 0.33. I thought I had a fairly low and aggressive position (arm pads 15 cm down from the saddle) until some trials indicated that my CdA was 0.29. I’ve now got the pads 21 cm down, and my elbows 4 cm closer together and I think I’m down closer to 0.26.
Many users of that site set one or the other input to “1.0”, and make the other one equal the CdA estimate they have in mind. It makes changes easier.
wow, thanks. Based on that, if .33 would be averageto high for a tri, my airstrykes(wide) bars only slightly below the saddle, I went with .7 for a total of .35. That put me at 347 watts for the 59 minutes. Seems high, but I turn 40 this year, so I’ll take it 