Time Trial Aerodynamics v. Power
Results 1 to 22 of 22
  1. #1
    RoadBikeReview Member
    Reputation:
    Join Date
    Dec 2005
    Posts
    3,494

    Time Trial Aerodynamics v. Power

    I raced in a small stage race recently (VOS in Phoenix) which included a 23K/14.4 mile out and back TT. Conditions were virtually the same for the field. Come to find out the guy who finished .3 (that's three tenths of a second) faster than me averaged 40W less during his run. We are very similar in build and both had dedicated TT bikes, wheels, helmets, etc...To my untrained eye our positions look similar.

    No known mechanical issues. Running Vittoria Corsa Evo CX tubulars. Assuming it's not a calibration issue I'm having a hard time understanding where my position is losing so much efficiency! I don't have video or pics so I can't really ask for suggestions specific to me. Simply wondering if anyone has run into a similar situation and was there something you missed? Was it a calibration issue? Just curious.

  2. #2
    RoadBikeReview Member
    Reputation: spade2you's Avatar
    Join Date
    May 2009
    Posts
    12,085
    He could potentially stay in position more. He may have put more effort into certain sections and coasted more in others.

    As a really slim and small dude, I tend to be ~50w lower than most people with similar times. My position is fairly relaxed compared to bigger riders with a similar time.

  3. #3
    RoadBikeReview Member
    Reputation:
    Join Date
    Dec 2005
    Posts
    3,494
    ^^^Wow! 50W! Not too sure if I'm relaxed or not? I feel comfortable with the exception of head position. Neck does get tired but, I was aware this and made conscious effort to hold head up.

  4. #4
    RoadBikeReview Member
    Reputation: spade2you's Avatar
    Join Date
    May 2009
    Posts
    12,085
    I'm probably an extreme case. There's also just enough climbing in my local TTs.

    I'm definitely a lot more upright than most TT guys. I tend to be conservative because my area tends to throw the ~40km ITT in with a really long race weekend.

  5. #5
    RoadBikeReview Member
    Reputation:
    Join Date
    Dec 2005
    Posts
    3,494
    Hmmm...thinking too much again. I understand the power to weight aspect of climbing TT's. This TT it was pretty flat (1%), straight, one turn around. Should favor those that can produce wattage. It's possible the guy misread his power but, he gave me his power for the previous year which was around 30W more (than this year) and he was a minute faster.

    Ah well. Gives me something to work on. Better position that it...

  6. #6
    RoadBikeReview Member
    Reputation: spade2you's Avatar
    Join Date
    May 2009
    Posts
    12,085
    Windy or calm?

  7. #7
    RoadBikeReview Member
    Reputation: stevesbike's Avatar
    Join Date
    Jun 2002
    Posts
    5,610
    not uncommon for people to save 25+ watts (at say 25mph) after a trip to the wind tunnel.

    chad.williamson: A Trip to the A2 Wind Tunnel

  8. #8
    Cycling Coach
    Reputation: Alex_Simmons/RST's Avatar
    Join Date
    Jan 2008
    Posts
    1,734
    Quote Originally Posted by woodys737 View Post
    I raced in a small stage race recently (VOS in Phoenix) which included a 23K/14.4 mile out and back TT. Conditions were virtually the same for the field. Come to find out the guy who finished .3 (that's three tenths of a second) faster than me averaged 40W less during his run. We are very similar in build and both had dedicated TT bikes, wheels, helmets, etc...To my untrained eye our positions look similar.

    No known mechanical issues. Running Vittoria Corsa Evo CX tubulars. Assuming it's not a calibration issue I'm having a hard time understanding where my position is losing so much efficiency! I don't have video or pics so I can't really ask for suggestions specific to me. Simply wondering if anyone has run into a similar situation and was there something you missed? Was it a calibration issue? Just curious.
    Some people are aerodynamically gifted, but everyone can improve their aerodynamics.

    I was the same height, weight and power output as one of my club mates, but he's a world level age group pursuit rider and I'd be lucky to make finals at state level. We've measured his aerodynamics, and I also did some work with him to optimise his aero.

    His Coefficient of drag x Area (CdA) is ~18-20% less than mine.

  9. #9
    RoadBikeReview Member
    Reputation:
    Join Date
    Dec 2005
    Posts
    3,494
    Quote Originally Posted by spade2you View Post
    Windy or calm?
    3-5mph

    Quote Originally Posted by stevesbike View Post
    not uncommon for people to save 25+ watts (at say 25mph) after a trip to the wind tunnel.

    chad.williamson: A Trip to the A2 Wind Tunnel
    Thanks Steve! Before this week end I never would have thought that possible.

  10. #10
    RoadBikeReview Member
    Reputation:
    Join Date
    Apr 2003
    Posts
    3,349
    Quote Originally Posted by woodys737 View Post
    We are very similar in build and both had dedicated TT bikes, wheels, helmets, etc...To my untrained eye our positions look similar.
    Regarding equipment (rather than position), there are many things which taken alone don't seem important, but in aggregate can add up. Not all aero frames and wheels are equal and are not always set up the same. Choice of aerobar and cable routing can have an impact and tire choice can affect wheel drag and rolling resistance (tubulars are at high risk for this unless glued on properly). Also, the tire inflation pressure (too high or too low) can affect speed. Aero helmets are not all the same and what works well for one rider, might not be the best choice for another. Skin suits are the same. There is no one best skin suit for everyone. What works best for one persons body shape, might be a bad choice for another.

  11. #11
    RoadBikeReview Member
    Reputation:
    Join Date
    Dec 2005
    Posts
    3,494
    Quote Originally Posted by Alex_Simmons/RST View Post
    Some people are aerodynamically gifted, but everyone can improve their aerodynamics.

    I was the same height, weight and power output as one of my club mates, but he's a world level age group pursuit rider and I'd be lucky to make finals at state level. We've measured his aerodynamics, and I also did some work with him to optimise his aero.

    His Coefficient of drag x Area (CdA) is ~18-20% less than mine.
    Quote Originally Posted by asgelle View Post
    Regarding equipment (rather than position), there are many things which taken alone don't seem important, but in aggregate can add up. Not all aero frames and wheels are equal and are not always set up the same. Choice of aerobar and cable routing can have an impact and tire choice can affect wheel drag and rolling resistance (tubulars are at high risk for this unless glued on properly). Also, the tire inflation pressure (too high or too low) can affect speed. Aero helmets are not all the same and what works well for one rider, might not be the best choice for another. Skin suits are the same. There is no one best skin suit for everyone. What works best for one persons body shape, might be a bad choice for another.
    Thank you gentlemen. Living here in Phoenix a low speed wind tunnel exists just minutes from me in Scottsdale. It's a low speed tunnel and doesn't have the tolerance that the more established wind tunnels have in say California. I was surprised to read over on slowtwitch how hard the guys hammered them for their testing of the Dimond. IIRC it was more for their protocol than the tolerance of the facility. I know nothing of the engineering or protocol of their testing and fearful of S***T in S**t out. Maybe this was just for the Dimond? I know UHC spends time there as do various amateurs and pros. If you have any insight as to the facility I'm referring to I'd be curious to read your insight as I could probably find a way to afford a little time there...thx

  12. #12
    RoadBikeReview Member
    Reputation:
    Join Date
    Sep 2011
    Posts
    6,497
    Quote Originally Posted by Alex_Simmons/RST View Post
    Some people are aerodynamically gifted, but everyone can improve their aerodynamics.

    I was the same height, weight and power output as one of my club mates, but he's a world level age group pursuit rider and I'd be lucky to make finals at state level. We've measured his aerodynamics, and I also did some work with him to optimise his aero.

    His Coefficient of drag x Area (CdA) is ~18-20% less than mine.
    Curious as to what accounts for his superior aero?

  13. #13
    RoadBikeReview Member
    Reputation: stevesbike's Avatar
    Join Date
    Jun 2002
    Posts
    5,610
    Just use Zabriskie as an example - reputed to have the most aero position. Body proportions also count - a relatively long femur allows riders like Zabriskie to overcome the 5cm rule in the sense that they can get an effectively steeper position because of it (hint, if you want to maximize things and your tt bike isn't going to be subjected to inspection there are a lot of ways to increase aero position and power from it, such as steep effective sta, bar angle, etc.


    Dave-Zabriskie.jpg
    Quote Originally Posted by aclinjury View Post
    Curious as to what accounts for his superior aero?

  14. #14
    Cycling Coach
    Reputation: Alex_Simmons/RST's Avatar
    Join Date
    Jan 2008
    Posts
    1,734
    Quote Originally Posted by aclinjury View Post
    Curious as to what accounts for his superior aero?
    The way the air flows around his body is quite different than for me, despite the height and weight similarities. He presents a more arrow like shape than I do, which his shoulders enable.

    I was reminded recently by this great 50 year old text book picture to emphasise how air flow around an object has a massive impact to aerodynamics. Both these objects (shown as a cross-section) exhibit the same amount of drag force for a wind coming from the left (or objects moving to the right):



    IOW, it's not just about how much frontal area you present to the wind, but how that wind flows around you.

  15. #15
    ngl
    ngl is offline
    RoadBikeReview Member
    Reputation:
    Join Date
    Jan 2002
    Posts
    710
    I was given an indepth tour of this facility while vacationing in Scottsdale. The facility and people seem top notch and I was impressed. I cannot compare their equipment, testing or protocols to any other facility. I asked many questions.

    All I can say is my two freinds (who purchased a winter home in Scottsdale) frequent this facility on a regular basis and after purchasing VERY high end road bicycles their cycling has improved remarkably!!!! I can't say (and they won't either) if it's the bikes, training, bike fit, wind tunnel testing or ???? or any combination. Needless to say I am in awh. If I lived that close I would definitly give them a try.

  16. #16
    RoadBikeReview Member
    Reputation: stevesbike's Avatar
    Join Date
    Jun 2002
    Posts
    5,610
    and re the slowtwitch critique of them, it's not a real debate on slowtwitch until someone gets banned, so I wouldn't worry too much about that....

    Quote Originally Posted by ngl View Post
    I was given an indepth tour of this facility while vacationing in Scottsdale. The facility and people seem top notch and I was impressed. I cannot compare their equipment, testing or protocols to any other facility. I asked many questions.

    All I can say is my two freinds (who purchased a winter home in Scottsdale) frequent this facility on a regular basis and after purchasing VERY high end road bicycles their cycling has improved remarkably!!!! I can't say (and they won't either) if it's the bikes, training, bike fit, wind tunnel testing or ???? or any combination. Needless to say I am in awh. If I lived that close I would definitly give them a try.

  17. #17
    RoadBikeReview Member
    Reputation:
    Join Date
    Dec 2005
    Posts
    3,494
    I've always felt tunnel time for an average guy like me seemed a bit over the top and I would probably never travel out of state to do it. But considering how much time I spend evaluating my training, nutrition, equipment, etc...and the facility is a short bike ride away, perhaps it's not so silly. Hell I've spent more on race entry fees this year than the cost of an hour in the tunnel. lol!

  18. #18
    RoadBikeReview Member
    Reputation:
    Join Date
    May 2006
    Posts
    739
    Quote Originally Posted by aclinjury View Post
    Curious as to what accounts for his superior aero?
    Agree with the others. Two people the same height, weight, and frontal area will not have the same exact shape, therefore, slightly different Drag coefficients.

    Drag coefficient - Wikipedia, the free encyclopedia

    the link shows drag coefficient of different shapes. You could make all these shapes have the same exact frontal area, but resultant drag will differ a bit, due to overall shape.

    At 5'10" 160 pounds and one of the worst TTers you've ever seen, I'm sure my biceps, shoulders, and big butt produce a lot of drag. I race Cat 3s and struggle not to be DFL in the whole race amongst all male categories.
    Last edited by Poncharelli; 02-25-2014 at 10:15 AM.

  19. #19
    RoadBikeReview Member
    Reputation: serious's Avatar
    Join Date
    May 2006
    Posts
    3,493
    Can it be that the weight of the other rider is lighter (5-10 lbs) despite a similar build?
    My rides:
    Lynskey Ti Pro29 SL singlespeed
    KHS Team 29
    KHS CX 550 Cross
    S-Works Roubaix SL3 Dura Ace
    Pake French 75 track

  20. #20
    RoadBikeReview Member
    Reputation:
    Join Date
    Mar 2003
    Posts
    373
    Is he counting zero's in his Power readings. Many people choose to display power not counting zero's. Makes quite a bit of difference.

  21. #21
    RoadBikeReview Member
    Reputation: 32and3cross's Avatar
    Join Date
    Feb 2005
    Posts
    3,135
    I can relate to this story. Back when I was racing I did a TT with rolling hills as did my team mate. We both used disc covers on our power tab wheels. We both calibrated our PTs and both recorded the power in the same way. Over the course of the TT he measured avg watts that was 15-20 watts more than me and he weighed 15lbs less than me, yet I beat him by over 20 seconds. We were on course at nearly the same time so the conditions where close to the same as well. The up shot is my position was much more aero than his.

  22. #22
    RoadBikeReview Member
    Reputation:
    Join Date
    Dec 2005
    Posts
    3,494
    Quote Originally Posted by Bridgey View Post
    Is he counting zero's in his Power readings. Many people choose to display power not counting zero's. Makes quite a bit of difference.
    If you are referring to me, yes, I've always included zeros.

Similar Threads

  1. Time Trial Power - What Type of Interval?
    By Mr. Papagiorgio in forum Coaching
    Replies: 14
    Last Post: 06-26-2009, 03:38 PM
  2. First Time Trial
    By Mad_Hun in forum Racing, Training, Nutrition, Triathlons
    Replies: 2
    Last Post: 08-11-2008, 06:59 AM
  3. Optimum time trial position without time trial bars
    By the rat in forum Racing, Training, Nutrition, Triathlons
    Replies: 19
    Last Post: 04-25-2008, 11:25 AM
  4. Looking For Time Trial
    By zipp2001 in forum New England
    Replies: 1
    Last Post: 02-27-2007, 05:21 AM
  5. TIME RXR Time Trial Module
    By grimontime in forum Bikes, Frames and Forks
    Replies: 0
    Last Post: 02-11-2007, 04:02 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

THE SITE

ABOUT ROADBIKEREVIEW

VISIT US AT

© Copyright 2020 VerticalScope Inc. All rights reserved.