For two similar riders one riding a road bike, and one on a aero tri bike with deep carbon wheels how much overall time would the TT bike gain over a flat, 40k road course?
For two similar riders one riding a road bike, and one on a aero tri bike with deep carbon wheels how much overall time would the TT bike gain over a flat, 40k road course?
Here’s pretty much the same question discussed over the last couple of weeks: http://forum.slowtwitch.com/gforum.cgi?do=post_view_flat;post=4580110;page=1;sb=post_latest_reply;so=ASC;mh=25;
This may help as well: http://www.bikeradar.com/road/gear/article/how-aero-is-aero-19273/
-Dave
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5 minutes.
It could be very little, or even a loss (let the flames begin), or it could be significant. It depends on your position on each bike, the wheels on each, comfort level, etc. Also, speed of the rider will be a significant factor, as faster riders will benefit more from aerodynamics than the slowest of riders, i.e., a 28mph rider has more to gain than a 16mph rider). IMO, we’ve been privileged to read Chris Boardman’s posts / comments on this subject here on Slowtwitch regarding this subject.
Don’t misunderstand my comments to read that a TT bike and aerodynamics aren’t or can’t be faster. It’s just important to understand that there are a lot of things factoring into speed other than just riding a TT bike vs. a regular (but equipped for a TT) road bike. A blanket statement of how much faster or what is faster is just inaccurate until the rider is factored into the equation. Describe the rider, exact course and all conditions and you’ll be able to come closer to a more realistic answer.
Also, speed of the rider will be a significant factor, as faster riders will benefit more from aerodynamics than the slowest of riders, i.e., a 28mph rider has more to gain than a 16mph rider).
Nope!
150 watts, 40k, 0.01 reduction in CdA = 55 seconds savings.
1 hour 19 minutes and 35 seoconds to 1 hour 18 minutes and 40 seconds.
% Change: ~1.152%
300 watts, 40k, 0.01 reduction in CdA = 41 seconds
60 minutes 16 seconds to 59 minutes 35 seconds
% Change: ~1.154% (slightly more)
Not intuitive, but true. Hear me now, believe me later.
Nope!
150 watts, 40k, 0.01 reduction in CdA = 55 seconds savings.
300 watts, 40k, 0.01 reduction in CdA = 41 seconds
Not intuitive, but true. Hear me now, believe me later.
Jackmott, you’re also, IMO, a solid authority and contributor to Slowtwitch. We disagree on this one. Seriously, I’m hoping that CB comments on this area. The bigger point to understand that there are a lot of factors here in comparing TT bikes and aero equipment as compared to road bikes outfitted for TT’s. The rider should be considered as part of any equation before saying any bike is xxx faster.
throws physics in the trash
We disagree on this one. Seriously, I’m hoping that CB comments on this area.
Just out of curiosity, can you flip the problem around and see how much more power a rider with a 0.01 higher CdA needs to get the same time as a 150 watt and 300 watt rider?
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Nope!
150 watts, 40k, 0.01 reduction in CdA = 55 seconds savings.
300 watts, 40k, 0.01 reduction in CdA = 41 seconds
Not intuitive, but true. Hear me now, believe me later.
Jackmott, you’re also, IMO, a solid authority and contributor to Slowtwitch. We disagree on this one. Seriously, I’m hoping that CB comments on this area. The bigger point to understand that there are a lot of factors here in comparing TT bikes and aero equipment as compared to road bikes outfitted for TT’s. The rider should be considered as part of any equation before saying any bike is xxx faster.
I think you’re both right, actually.
The faster rider will always a obtain larger % savings of time.
The slower rider, despite getting a smaller % time savings, is on the course longer, so the total time saved will be slightly more.
In real world practice, the numbers are sufficiently close for amateurs that they don’t really need to worry about it, except that yes, even the slowsters will get a speed benefit from aero gear. Whether it matters to them when they’re nowhere near the podium or if they can just train a little more to get much more time savings, is a whole different issue.
Yeah it does seam weird but reductions in drag do correlate pretty closely with reductions in percentage time saved, in speeds that most of us bike at (heard between 20-60kph)
The only issue is that the 40kph guy will have a harder time finding 0.01 cda as he has likely picked most of the low hanging fruit.
Maurice
Tour magazine in Germany did an article about this last year. They went through various iterations from roadie riding on the hoods in standard kit, then on drops, then on aero bars, then on tri bikes etc etc to full blown skies limit with everything aero.
They used 42km/h as the speed.
Roadie on tops was around 458watts. Top to hoods to drops went from 458 to 439 to 415 watts
TOUR MAG thought you could drop it down to 319 watts with everything aero.(whether that position was rideable is another matter)
The frontal area went from .617m^2 to .464m^2
This was in 2012 Triathlon-Spezial pages 12-13.
…
Just out of curiosity, can you flip the problem around and see how much more power a rider with a 0.01 higher CdA needs to get the same time as a 150 watt and 300 watt rider?
The rule of thumb is that every .01 m^2 of CdA is “worth” ~10W, or 1s/km of time difference.
Tour magazine in Germany did an article about this last year. They went through various iterations from roadie riding on the hoods in standard kit, then on drops, then on aero bars, then on tri bikes etc etc to full blown skies limit with everything aero.
They used 42km/h as the speed.
Roadie on tops was around 458watts. Top to hoods to drops went from 458 to 439 to 415 watts
TOUR MAG thought you could drop it down to 319 watts with everything aero.(whether that position was rideable is another matter)
The frontal area went from .617m^2 to .464m^2
This was in 2012 Triathlon-Spezial pages 12-13.
Those numbers all seem REALLY high…even for typical triathletes 
I can tell you for sure it didn’t take ANYWHERE near 319W for me to go significantly >42km/hr (43.5km/hr) for a 40K TT…and 460W to go that on a roadie? Please…
For two similar riders one riding a road bike, and one on a aero tri bike with deep carbon wheels how much overall time would the TT bike gain over a flat, 40k road course?
You should talk in terms of watts saved, not time saved. The amount of time saved will vary based on “engine” and is not a good measure. The faster the athlete, the more the effects of air resistance are magnified as “drag”.